The Muscular System Manual: The Skeletal Muscles of the Human Body [4th ed.] 0323327702, 9780323327701

Citation preview

THE MUSCULAR SYSTEM MANUAL The Skeletal Muscles of the Human Body FOURTH EDITION

JOSEPH E. MUSCOLINO, DC, Instructor, Purchase College, State University of New York (SUNY) Purchase, New York Owner, The Art and Science of Kinesiology Stamford, Connecticut http://www.learnmuscles.com

2

Table of Contents Cover image Title page Copyright Dedication REVIEWERS FOURTH EDITION FOREWORDS THIRD EDITION FOREWORD SECOND EDITION FOREWORD PREFACE HOW TO USE THIS BOOK ACKNOWLEDGMENTS ABOUT THE AUTHOR

PART 1: The Musculoskeletal System Chapter 1: Basic Kinesiology Terminology MAJOR BODY PARTS ANATOMIC POSITION LOCATION TERMINOLOGY PLANES AXES MOVEMENT TERMINOLOGY JOINT ACTION ATLAS REVIEW QUESTIONS

3

THINK IT THROUGH

Chapter 2: The Skeletal System THE SKELETON JOINTS ATLAS OF BONY LANDMARKS AND MUSCLE ATTACHMENT SITES ON BONES REVIEW QUESTIONS THINK IT THROUGH

Chapter 3: How Muscles Function MUSCLES CREATE PULLING FORCES WHAT IS A MUSCLE CONTRACTION? NAMING A MUSCLE’s ATTACHMENTS: ORIGIN AND INSERTION VS. ATTACHMENTS ROLES OF MUSCLES SLIDING FILAMENT MECHANISM MUSCLE FIBER ARCHITECTURE LEARNING MUSCLES PALPATION GUIDELINES REVIEW QUESTIONS THINK IT THROUGH

PART 2: The Skeletal Muscles of the Upper Extremity Chapter 4: Muscles of the Shoulder Girdle Joints Posterior View of the Muscles of the Shoulder Girdle Region Anterior View of the Muscles of the Shoulder Girdle Region Right Lateral View of the Muscles of the Shoulder Girdle and Neck Region Trapezius (“Trap”) Rhomboids Major and Minor Levator Scapulae Serratus Anterior Pectoralis Minor Subclavius REVIEW QUESTIONS THINK IT THROUGH

Chapter 5: Muscles of the Glenohumeral Joint Posterior View of the Muscles of the Glenohumeral Joint and Shoulder Girdle Region Anterior View of the Muscles of the Glenohumeral Joint and Shoulder Girdle Region Posterior and Anterior Views of the Muscles of the Glenohumeral Joint Anterior View of a Frontal Plane Section through the Right Glenohumeral Joint

4

Right Lateral Views of the Muscles of the Neck, Shoulder Girdle, and Trunk Regions Deltoid Coracobrachialis Pectoralis Major Latissimus Dorsi (“Lat”) Teres Major Rotator Cuff Group Supraspinatus (of Rotator Cuff Group) Infraspinatus (of Rotator Cuff Group) Teres Minor (of Rotator Cuff Group) Subscapularis (of Rotator Cuff Group) Review Questions Think It Through

Chapter 6: Muscles of the Elbow and Radioulnar Joints Anterior Views of the Muscles of the Right Elbow Joint Posterior Views of the Muscles of the Right Elbow Joint Lateral View of the Muscles of the Right Elbow Joint Medial View of the Muscles of the Right Elbow Joint Views of the Muscles of the Right Radioulnar Joints Transverse Plane Cross Sections of the Right Arm Biceps Brachii Brachialis Brachioradialis (of Radial Group) Triceps Brachii Anconeus Pronator Teres Pronator Quadratus Supinator REVIEW QUESTIONS THINK IT THROUGH

Chapter 7: Muscles of the Wrist Joint Anterior View of the Muscles of the Right Wrist Joint—Superficial View Anterior View of the Muscles of the Right Wrist Joint— Intermediate View Anterior View of the Muscles of the Right Wrist Joint—Deep View Anterior View of the Right Wrist Flexor Group of Muscles Posterior View of the Muscles of the Right Wrist Joint—Superficial View Posterior Views of the Muscles of the Right Wrist Joint— Deep Views Posterior View of the Right Wrist Extensor Group of Muscles Medial View of the Muscles of the Right Wrist Joint Lateral View of the Muscles of the Right Wrist Joint

5

Transverse Plane Cross Sections of the Right Forearm Flexor Carpi Radialis (of Wrist Flexor Group) Palmaris Longus (of Wrist Flexor Group) Flexor Carpi Ulnaris (of Wrist Flexor Group) Extensor Carpi Radialis Longus (of Wrist Extensor and Radial Groups) Extensor Carpi Radialis Brevis (of Wrist Extensor and Radial Groups) Extensor Carpi Ulnaris (of Wrist Extensor Group) REVIEW QUESTIONS THINK IT THROUGH

Chapter 8: Extrinsic Muscles of the Finger Joints Anterior View of the Muscles of the Right Wrist Joint and Extrinsic Finger Muscles—Superficial View Anterior View of the Muscles of the Right Wrist Joint and Extrinsic Finger Muscles—Intermediate View Anterior View of the Muscles of the Right Wrist Joint and Extrinsic Finger Muscles—Deep View Posterior View of the Muscles of the Right Wrist Joint and Extrinsic Finger Muscles—Superficial View Posterior Views of the Muscles of the Right Wrist Joint and Extrinsic Finger Muscles—Intermediate and Deep Views Lateral View of the Muscles of the Right Wrist Joint and Extrinsic Finger Muscles Medial View of the Muscles of the Right Wrist Joint and Extrinsic Finger Muscles Flexor Digitorum Superficialis (FDS) Flexor Digitorum Profundus (FDP) Flexor Pollicis Longus Extensor Digitorum Extensor Digiti Minimi Deep Distal Four Group Abductor Pollicis Longus (of Deep Distal Four Group) Extensor Pollicis Brevis (of Deep Distal Four Group) Extensor Pollicis Longus (of Deep Distal Four Group) Extensor Indicis (of Deep Distal Four Group) REVIEW QUESTIONS THINK IT THROUGH

Chapter 9: Intrinsic Muscles of the Finger Joints Anterior (Palmar) View of the Musculature of the Right Hand—Superficial View with Palmar Aponeurosis Anterior (Palmar) View of the Musculature of the Right Hand—Superficial Muscular View Anterior (Palmar) View of the Musculature of the Right Hand—Intermediate Muscular View Anterior (Palmar) View of the Musculature of the Right Hand—Deep Muscular View Anterior (Palmar) View of the Musculature of the Right Hand—Deepest Muscular View Posterior (Dorsal) View of the Musculature of the Right Hand Transverse Plane Cross Section of the Right Wrist Transverse Plane Cross Section of the Right Hand through the Metacarpal Bones Dorsal Digital Expansion Thenar Eminence Group

6

Abductor Pollicis Brevis Flexor Pollicis Brevis Opponens Pollicis Hypothenar Eminence Group Abductor Digiti Minimi Manus Flexor Digiti Minimi Manus Opponens Digiti Minimi Central Compartment Group Adductor Pollicis Lumbricals Manus Palmar Interossei Dorsal Interossei Manus (DIM) Palmaris Brevis REVIEW QUESTIONS THINK IT THROUGH

PART 3: The Skeletal Muscles of the Axial Body Chapter 10: Muscles of the Spinal Joints Posterior Views of the Muscles of the Trunk—Superficial and Intermediate Views Posterior Views of the Muscles of the Trunk—Deep Views Anterior Views of the Muscles of the Trunk—Superficial and Intermediate Views Anterior Views of the Muscles of the Trunk—Deep Views Right Lateral View of the Muscles of the Trunk Transverse Plane Cross Sections of the Trunk Posterior Views of the Neck and Upper Back Region—Superficial Views Posterior Views of the Neck and Upper Back Region—Intermediate Views Posterior Views of the Neck and Upper Back Region—Deep Views Anterior Views of the Neck and Upper Chest Region—Superficial Views Anterior Views of the Neck and Upper Chest Region—Intermediate and Deep Views Right Lateral View of the Muscles of the Neck Region Cross-Sectional View of the Neck FULL SPINE Erector Spinae Group Iliocostalis (of Erector Spinae Group) Longissimus (of Erector Spinae Group) Spinalis (of Erector Spinae Group) Transversospinalis Group Semispinalis (of Transversospinalis Group) Multifidus (of Transversospinalis Group) Rotatores (of Transversospinalis Group)

7

Interspinales Intertransversarii NECK AND HEAD Sternocleidomastoid (SCM) Scalene Group Anterior Scalene (of Scalene Group) Middle Scalene (of Scalene Group) Posterior Scalene (of Scalene Group) Prevertebral Group Longus Colli (of Prevertebral Group) Longus Capitis (of Prevertebral Group) Rectus Capitis Anterior (of Prevertebral Group) Rectus Capitis Lateralis (of Prevertebral Group) Splenius Capitis Splenius Cervicis Suboccipital Group Views of the Suboccipital Group Rectus Capitis Posterior Major (of Suboccipital Group) Rectus Capitis Posterior Minor (of Suboccipital Group) Obliquus Capitis Inferior (of Suboccipital Group) Obliquus Capitis Superior (of Suboccipital Group) LOW BACK Quadratus Lumborum (QL) Anterior Abdominal Wall Muscles Anterior Abdominal Wall Muscles—Superficial View Anterior Abdominal Wall Muscles—Deep View Rectus Abdominis (of Anterior Abdominal Wall) External Abdominal Oblique (of Anterior Abdominal Wall) Internal Abdominal Oblique (of Anterior Abdominal Wall) Transversus Abdominis (of Anterior Abdominal Wall) Psoas Minor REVIEW QUESTIONS THINK IT THROUGH

Chapter 11: Muscles of the Rib Cage Joints Posterior Views of the Muscles of the Trunk—Superficial and Intermediate Views Posterior Views of the Muscles of the Trunk—Deep Views Anterior Views of the Muscles of the Trunk—Superficial and Intermediate Views Anterior Views of the Muscles of the Trunk—Deep Views Right Lateral View of the Muscles of the Trunk—Superficial View Right Lateral View of the Muscles of the Trunk—Deep View External Intercostals

8

Internal Intercostals Transversus Thoracis Diaphragm Serratus Posterior Superior Serratus Posterior Inferior Levatores Costarum Subcostales REVIEW QUESTIONS THINK IT THROUGH

Chapter 12: Muscles of the Temporomandibular Joints Superficial Right Lateral View of the Muscles of the Head Views of the Major Muscles of Mastication Anterior Views of the Neck and Upper Chest Region Temporalis Masseter Lateral Pterygoid Medial Pterygoid Hyoid Group SUPRAHYOIDS Digastric (of Hyoid Group) Mylohyoid (of Hyoid Group) Geniohyoid (of Hyoid Group) Stylohyoid (of Hyoid Group) INFRAHYOIDS Sternohyoid (of Hyoid Group) Sternothyroid (of Hyoid Group) Thyrohyoid (of Hyoid Group) Omohyoid (of Hyoid Group) REVIEW QUESTIONS THINK IT THROUGH

Chapter 13: Muscles of Facial Expression Superficial Right Lateral View of the Muscles of the Head Anterior Views of the Muscles of the Head Posterior View of the Muscles of the Head Facial Landmarks SCALP Occipitofrontalis (of Epicranius) Temporoparietalis (of Epicranius) Auricularis Group EYE

9

Orbicularis Oculi Levator Palpebrae Superioris Corrugator Supercilii NOSE Procerus Nasalis Depressor Septi Nasi MOUTH Levator Labii Superioris Alaeque Nasi Levator Labii Superioris Zygomaticus Minor Zygomaticus Major Levator Anguli Oris Risorius Depressor Anguli Oris Depressor Labii Inferioris Mentalis Buccinator Orbicularis Oris Platysma REVIEW QUESTIONS THINK IT THROUGH

PART 4: The Skeletal Muscles of the Lower Extremity Chapter 14: Muscles of the Hip Joint Anterior Views of the Muscles of the Hip Joint—Superficial and Intermediate Views Anterior Views of the Muscles of the Hip Joint—Deep Views Posterior Views of the Muscles of the Hip Joint—Superficial and Intermediate Views Posterior Views of the Muscles of the Hip Joint—Deep Views Medial View of the Muscles of the Right Hip Joint— Superficial View Medial View of the Muscles of the Right Hip Joint—Deep View Lateral View of the Muscles of the Right Hip Joint— Superficial View Lateral View of the Muscles of the Right Hip Joint—Deep View Transverse Plane Cross Sections of the Right Thigh Psoas Major (of Iliopsoas) Iliacus (of Iliopsoas) Tensor Fasciae Latae (TFL) ATTACHMENTS FUNCTIONS RELATIONSHIP TO OTHER STRUCTURES

10

MISCELLANEOUS Adductor Longus (of Adductor Group) ATTACHMENTS FUNCTIONS RELATIONSHIP TO OTHER STRUCTURES MISCELLANEOUS Adductor Brevis (of Adductor Group) ATTACHMENTS FUNCTIONS RELATIONSHIP TO OTHER STRUCTURES MISCELLANEOUS Gluteal Group Gluteus Maximus (of Gluteal Group) ATTACHMENTS FUNCTIONS RELATIONSHIP TO OTHER STRUCTURES MISCELLANEOUS Gluteus Minimus (of Gluteal Group) ATTACHMENTS FUNCTIONS RELATIONSHIP TO OTHER STRUCTURES MISCELLANEOUS Posterior Views of the Deep Lateral Rotator Group Superior Gemellus (of Deep Lateral Rotator Group) Obturator Internus (of Deep Lateral Rotator Group) Inferior Gemellus (of Deep Lateral Rotator Group) Obturator Externus (of Deep Lateral Rotator Group) Quadratus Femoris (of Deep Lateral Rotator Group) REVIEW QUESTIONS THINK IT THROUGH

Chapter 15: Muscles of the Knee Joint Anterior Views of the Muscles of the Knee Joint Posterior Views of the Muscles of the Knee Joint Lateral Views of the Muscles of the Right Knee Joint Medial Views of the Muscles of the Right Knee Joint Transverse Plane Cross Sections of the Muscles of the Right Thigh Quadriceps Femoris Group (Quads) Views of the Quadriceps Femoris Group Rectus Femoris (of Quadriceps Femoris Group) Vastus Lateralis (of Quadriceps Femoris Group) Vastus Medialis (of Quadriceps Femoris Group)

11

Vastus Intermedius (of Quadriceps Femoris Group) Articularis Genus Hamstring Group Posterior Views of the Hamstring Group Biceps Femoris (of Hamstring Group) Semimembranosus (of Hamstring Group) Popliteus REVIEW QUESTIONS THINK IT THROUGH

Chapter 16: Muscles of the Ankle and Subtalar Joints Anterior View of the Muscles of the Right Ankle and Subtalar Joints Posterior View of the Muscles of the Right Ankle and Subtalar Joints—Superficial View Posterior View of the Muscles of the Right Ankle and Subtalar Joints—Intermediate View Posterior View of the Muscles of the Right Ankle and Subtalar Joints—Deep View Lateral View of the Muscles of the Right Ankle and Subtalar Joints Medial Views of the Muscles of the Right Ankle and Subtalar Joint Transverse Plane Cross Section of the Right Leg—Compartments Transverse Plane Cross Section of the Right Leg—Muscles Tibialis Anterior Fibularis Tertius Fibularis Longus Fibularis Brevis Gastrocnemius (Gastrocs) (of Triceps Surae Group) Soleus (of Triceps Surae Group) Plantaris Tibialis Posterior (Tom of Tom, Dick, and Harry Group) REVIEW QUESTIONS THINK IT THROUGH

Chapter 17: Extrinsic Muscles of the Toe Joints Anterior View of the Extrinsic Muscles of the Toes of the Right Foot—Superficial View Anterior View of the Extrinsic Muscles of the Toes of the Right Foot—Deep View Posterior View of the Extrinsic Muscles of the Toes of the Right Foot—Superficial View Posterior Views of the Extrinsic Muscles of the Toes of the Right Foot—Intermediate and Deep Views Medial View of the Extrinsic Muscles of the Toes of the Right Foot—Superficial View Medial View of the Extrinsic Muscles of the Toes of the Right Foot—Deep View Transverse Plane Cross Section of the Right Leg Extensor Digitorum Longus Extensor Hallucis Longus Flexor Digitorum Longus (Dick of Tom, Dick, and Harry Group) Flexor Hallucis Longus (Harry of Tom, Dick, and Harry Group)

12

REVIEW QUESTIONS THINK IT THROUGH

Chapter 18: Intrinsic Muscles of the Toe Joints Plantar View of the Right Foot—Superficial Fascial View Plantar View of the Right Foot—Superficial Muscular View Plantar View of the Right Foot—Intermediate View Plantar View of the Right Foot—Deep View Dorsal View of the Muscles of the Right Foot Lateral and Medial Views of the Muscles of the Right Foot Cross Section through the Right Foot DORSAL SURFACE Extensor Digitorum Brevis Extensor Hallucis Brevis PLANTAR SURFACE: LAYER I Abductor Hallucis Abductor Digiti Minimi Pedis Flexor Digitorum Brevis PLANTAR SURFACE: LAYER II Quadratus Plantae Lumbricals Pedis PLANTAR SURFACE: LAYER III Flexor Hallucis Brevis Flexor Digiti Minimi Pedis Adductor Hallucis PLANTAR SURFACE: LAYER IV Plantar Interossei Dorsal Interossei Pedis REVIEW QUESTIONS THINK IT THROUGH

PART 5: Functional Mover Groups of Muscles Chapter 19: Functional Groups of Muscles FUNCTIONAL MOVER GROUPS: UPPER EXTREMITY Scapulocostal Joint Elevators Scapulocostal Joint Depressors Scapulocostal Joint Protractors and Retractors Scapulocostal Joint Upward and Downward Rotators Glenohumeral Joint Flexors and Extensors Glenohumeral Joint Abductors

13

Glenohumeral Joint Lateral and Medial Rotators Elbow Joint Flexors and Extensors Radioulnar Joints Pronators and Supinators Wrist Joint Flexors and Extensors Wrist Joint Radial Deviators Wrist Joint Ulnar Deviators Thumb Flexors and Extensors Thumb Abductors Thumb Medial and Lateral Rotators Finger Flexors and Extensors Finger Abductors and Adductors FUNCTIONAL MOVER GROUPS: AXIAL BODY Temporomandibular Joint (Mandible): Elevators and Depressors Temporomandibular Joint (Mandible) Protractors, Retractors, and Contralateral Deviators Hyoid Bone Elevators and Depressors Cervical Spinal Joint (Neck and Head) Flexors Cervical Spinal Joint (Neck and Head) Extensors Cervical Spinal Joint (Neck and Head) Lateral Flexors Cervical Spinal Joint (Neck and Head) Contralateral Rotators Cervical Spinal Joint (Neck and Head) Ipsilateral Rotators Thoracolumbar Spinal Joint (Trunk) Flexors Thoracolumbar Spinal Joint (Trunk) Extensors Thoracolumbar Spinal Joint (Trunk) Lateral Flexors Thoracolumbar Spinal Joint (Trunk) Contralateral Rotators Thoracolumbar Spinal Joint (Trunk) Ipsilateral Rotators FUNCTIONAL MOVER GROUPS: LOWER EXTREMITY Hip Joint Flexors and Extensors Hip Joint Abductors (Pelvic Depressors) Hip Joint Adductors (Pelvic Elevators) Hip Joint Lateral Rotators (Pelvic Contralateral Rotators) Hip Joint Medial Rotators (Pelvic Ipsilateral Rotators) Knee Joint Flexors Knee Joint Extensors Knee Joint Medial and Lateral Rotators Ankle Joint Dorsiflexors and Plantarflexors Subtalar Joint Pronators (Everters) Subtalar Joint Supinators (Inverters) Toe Flexors Toe Extensors Toe Abductors and Adductors MUSCLES OF THE PELVIC FLOOR Medial Views of the Pelvic Floor

14

Superior Views of the Pelvic Floor Inferior Views of the Pelvic Floor MYOFASCIAL MERIDIANS Superficial Back and Front Lines Lateral and Deep Front Lines Spiral Lines Arm Lines Functional Lines REVIEW QUESTIONS THINK IT THROUGH

REFERENCES INDEX Skeletal Muscles of the Body—Alphabetically

15

Copyright 3251 Riverport Lane St. Louis, Missouri 63043 THE MUSCULAR SYSTEM MANUAL:     ISBN: 978-0-323-32770-1 THE SKELETAL MUSCLES OF THE HUMAN BODY, FOURTH EDITION Copyright © 2017, Elsevier Inc. All Rights Reserved. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein).

Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. With respect to any drug or pharmaceutical products identified, readers are advised to check the most current information provided (i) on procedures featured or (ii) by the manufacturer of each product to be administered, to verify the recommended dose or formula, the method and duration of administration, and contraindications. It is the responsibility of practitioners, relying on their own experience and knowledge of their patients, to make diagnoses, to determine dosages and the best treatment for each individual patient, and to take all appropriate safety precautions. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. Previous editions copyrighted 2010, 2005, 2003. Library of Congress Cataloging-in-Publication Data Names: Muscolino, Joseph E., author. Title: The muscular system manual : the skeletal muscles of the human body / Joseph E. Muscolino. Description: Fourth edition. | St. Louis, Missouri : Elsevier, [2017] | Includes bibliographical references.

16

Identifiers: LCCN 2015039008 | ISBN 9780323327701 (pbk. : alk. paper) Subjects: | MESH: Musculoskeletal System—anatomy & histology—Atlases. | Muscles—physiology —Atlases. Classification: LCC QM151 | NLM WE 17 | DDC 612.7/4—dc23 LC record available at http://lccn.loc.gov/2015039008 Content Strategist: Shelly Stringer, Jennifer Janson Content Development Manager: Ellen Wurm-Cutter Associate Content Development Specialist: Kelly Skelton Publishing Services Manager: Julie Eddy Book Production Specialist: Celeste Clingan Manager, Art & Design: Julia Dummitt

Printed in Canada Last digit is the print number: 9 8 7 6 5 4 3 2 1

17

Dedication This book is dedicated to Simona Cipriani, my wife and angel.

18

REVIEWERS Jennifer Apodaca, LMT, Albuquerque, New Mexico Patty Berak, NCBTMB, AMTA, ABMP, Program Director for Therapeutic Massage and BHSA, Baker College of Clinton Township, Clinton Township, Michigan Jennifer Boal, M.Ed, LMT, School of Healthcare Team Leader, Pittsburgh Technical Institute, Pittsburgh, Pennsylvania Jill Burynski, LMBT, NCTMB, Massage Therapy Educator, Living Sabai Continuing Education, Asheville, North Carolina Andrea Claire Caplan, BA, LMT, Owner, The Body Politic, LLC, Chevy Chase, Maryland Michelle Carbonneau, BA Chemistry, LMT, RYT, Massage Therapy, Anatomy & Physiology Instructor, Program Director, Yogissage, LLC, Honolulu, Hawaii Denise Cugini, BBA, LMT, NCTMB, Massage Instructor, Beacon Wellness Arts Center, Petaluma, California Angelica De Geer, LMT, CA, BA, BFA, Dental Hygiene, Certificate-Sweden, Clinic Supervisor, Midwest Institute, Earth City, Missouri Jeanne deMontagnac-Hall, BS, AHI, LMT, Allied Health Instructor, Sinclair Community CollegeCourseview Campus, Mason, Ohio Gautam J. Desai, DO, FACOFP, Professor, Department of Primary Care Medicine, Kansas City University of Medicine and Biosciences, Kansas City, Missouri Karen M. Hobson, MSHE, LMT, Executive Director, The International Professional School of Bodywork, San Diego, California Jane Irving and Matt Isolampi, LMT, CNMT MMP, Massage Therapy Instructor, OCPS Wellness Representative, Orange County Schools, Westside Tech Campus, Winter Garden, Florida Kathy Lee, LMT, BS, Owner, Catalina Massage Therapy, Tuscon, Arizona David MacDougall, MA, LMT, CSHE, Director/Associate Professor of Massage Therapy, North Country Community College, Saranac Lake, New York Serenity Martinez, CPI, NCTM, ACMT, Medical Instructor, Omega Institute Inc., Pennsauken, New Jersey Patricia C. Nuovo, LMT, Naturopath, Massage Instructor, Beacon Wellness Arts Center, Petaluma, California Tracey Obeda, MS, LMBT, NCTMB, Massage Therapist, CEO/Owner, Miller Motte College, Cary, North Carolina Roger Olbrot, Director of Education, Myotherapy College of Utah, Salt Lake City, Utah Julie Onofrio http://www.massageschoolnotes.com http://www.massagepracticebuilder.com, Licensed Massage Practitioner, Author, Seattle, Washington

19

Kevin Pierce, MBA, NCBTMB and Elan Schacter, LMBT, Elan Schacter Massage Therapy, Charlotte, North Carolina Michelle Tramm, NCTM, Certified in Prenatal, Infant, Fertility, Therapeutics and KinesioTape, Instructor, Indiana Therapeutic Massage School, Indianapolis, Indiana Terri Lynn Visovatti, BS, LMT, BCTMB, RockDoc, FMT, PMT, CKTP, CES, Movement Specialist/Massage Therapist/Business Owner, Urban Wellness Chicago, Chicago, Illinois Jeffery B. Wood, LMT, COTA/L, BS, Massage Therapy Educator, Massage Smart: Education in Action, Inverness, Florida

20

FOURTH EDITION FOREWORDS Thomas Myers Every attempt to set in order the unified, mysterious, and seemingly miraculous symphony required for human movement is bound to fall short. Books are limited to a flat page, video to a linear narrative, and even the newest interactive applications, with all their ‘Wow!’ factor, can cause more confusion than enlightenment. The design of the human body is organic—we are grown from a seed, not assembled from parts. To elucidate this design, however, we must take the body apart to see how it is put together—it is a conundrum that faces every anatomist. In dissection, every concept demonstrated necessarily obscures another. My life work has been dedicated to exposing the design concepts currently going under the buzzword ‘fascia’, which have been obscured over the centuries of earnest anatomists throwing out the fascia to clarify the concepts contained in the organ of ‘muscle’. But it is the same with every choice in the design of each illustration, every book, and all our curricula—maps emphasize certain features of the terrain at the expense of others. Hence, no one book can fulfill all our needs, and thus my shelves, my wallet, and my wife all groan at the number of anatomical atlases I seem to need. The clarity of Netter, the artistry of Sobotta, the portability of Platzer, the encyclopedic inclusiveness of Gorman, the ease of use of Trail Guide—all these and many more have added to my knowledge with their unique presentation of the neuromyofascial web. Nevertheless, I am pleased to add whatever ‘endorsement’ a foreword provides to the singular effort of Dr. Joe Muscolino in the steadily improving editions of The Muscular System Manual. Joe has worked to make his anatomical explanations succinct but accurate, and the design of the book allows maximum applicability for the working manual or movement therapist without sacrificing the inevitable complexity that comes from synergetic, stabilizing, and force transmitting functions that go beyond the simple ‘bringing the two ends together’ manner in which muscles are defined in so many of these atlases. As far as I know, I am the therapist who said to Bob King, “To really develop your intuition, know your anatomy!” Science and intuition are merely two ways of knowing, and they do not oppose but rather reinforce each other. This book provides a number of services to the reader who wants to develop both in tandem. I find ‘studying’ anatomy to be an activity that is boring in the extreme, and is a good way to find elusive sleep. Exploring anatomy, however, with this book and a colleague to palpate, for instance, can be an eye-opening thrill as the flat page leaps into the palpating fingers as three-dimensional, never-to-be-lost palpatory certainty - “This is what I am on, and I know it, and I can feel what to do.” Once myofascial anatomy is generally mastered—a snowball of a process that starts slowly and painfully but soon accumulates in a rush—further motivation for deepening your anatomy usually comes from problem clients—“What was that odd thing I just felt?” Such explorations—motivated by the desire to help a particular individual—have led me to far more knowledge than my formal studies or late-night exam cramming. There is also a broader motivation for learning: We are on the threshold of a revolution in biomechanics, as models drawn from cybernetics, complexity mathematics, and tensegrity engineering include Newtonian leverage- and compression-based biomechanics in a more complex, perhaps difficult, but also more accurate picture. What we have assumed to be true about muscles and their individual actions is being revealed as only one part of a very dynamic whole-body process of adaptation to myriad flickering forces. Joe Muscolino is forthright and adroit in dealing with the controversies and uncertainties of this transitional time. The functional advantages of this book are well-catalogued on the book cover and introduction. Suffice it for me to say that its clarity, comprehension, and variety, reflect a tremendous amount of work that has resulted in a useful tool for any therapist or educator wanting more of the calm confidence that comes from thoroughly knowing your subject.

21

Thomas Myers October 13, 2014 Thomas Myers, LMT, NCTMB, ARP Thomas Myers is the author of Anatomy Trains (Elsevier 2001, 2014) and co-author of Fascial Release for Structural Balance (North Atlantic 2010), as well as numerous articles for trade magazines and journals. Tom and his faculty provide continuing education worldwide for a variety of professions. Tom studied directly with Buckminster Fuller, Ida Rolf, and Moshe Feldenkrais and has practiced integrative bodywork for 40 years. Tom lives, writes, and sails on the coast of Maine in the United States with his partner Quan and a number of animals. Joe Tatta Physical therapists, and in fact all manual and movement therapists, work primarily in the realm of neuromuscular conditions, whether they are overuse conditions, postural or movement dysfunction patterns, and/or injury or post-surgery rehabilitation. When working with our patients, a fundamental understanding of the anatomy and physiology of the musculoskeletal system in imperative. Knowing anatomy allows one to understand physiology, which leads to an understanding of pathophysiology, and by extension, assessment and treatment. Indeed, effective and incisive clinical orthopedic work, whether it is manual therapy, therapeutic exercise, or selfcare advice for the patient, relies not on memorization of cookbook recipes for treatment, but on an understanding of underlying pathologic mechanism(s) of the client’s condition. This requires critical thought that is, by necessity, based on a fundamental knowledge of the anatomy and physiology of the musculoskeletal system. This is where Dr. Joseph Muscolino’s The Muscular System Manual: The Skeletal Muscles of the Human Body, 4th edition, becomes so invaluable. Many muscle atlases are available to the student and therapist, but Joseph Muscolino has created a fully referenced, evidence-based work that is not only the most thorough atlas of muscle structure and function that exists, but also one that presents the content in a manner that invites true understanding of how the muscular system works. Instead of simply stating the attachments and actions of the muscles, The Muscular System Manual explains why each muscle has the actions that it does. In addition to the concentric joint actions, it also presents the isometric stabilization functions and the eccentric restraining functions of each muscle. Further, unique to this book, it presents a full description of not only the open-chain standard actions, but also the closed-chain reverse actions of the muscle. And new to this edition, and unique to this book, it presents and explains the distinction between a muscle’s actions and its oblique plane motion pattern. And relationships to myofascial meridians and applications to musculoskeletal conditions are given as well. All of this information is accompanied by the most beautiful and clear illustrations that can be found: photographs of a real person with the bones and muscles overlaid onto the photograph. Further, an on-line digital program accompanies the book that allows the reader/viewer to work with thirty-three figure views of the body and place into the figure, any combination of muscles that would be seen from that view. Fancier digital apps are available on the web, but none of them are as easy and clear to use. This is a tremendous feature not only for the beginning student to initially learn the muscles, but also invaluable for the seasoned therapist who desires a greater and subtler understanding of the relationships between muscles. And other digital resource that accompany The Muscular System Manual are video demonstration of the author showing and explaining the palpation for each of the muscles in the book, and a customized digital program that allows the therapist to print out full color stretches for the patient’s self-care program. For any practicing therapist who wants to be able to critically think through their patient’s condition and then creatively apply the appropriate treatment techniques, there is no stronger foundation for effective clinical orthopedic work than Joseph Muscolino’s The Muscular System Manual, 4th edition! I am more than thrilled to attest to this great work and recommend it to you. Joe Tatta June 11, 2015 Joe Tatta, PT, DPT, CNN Joe Tatta is a doctor of physical therapy and certified clinical nutritionist. He is Co-Founder of Premier Physical Therapy & Wellness, one of the largest outpatient physical therapy providers in the New York Tri-State area. He is board certified in orthopedics from the American Board of Physical Therapy Specialties and studied nutrition at the Clinical Nutrition Certification Board and

22

Functional Medicine at the Institute for Functional Medicine. His greatest success stems from the growth of his practice and the thousands of clients healed annually. He also actively lectures and mentors health and professionals on subjects pertaining to injury prevention, nutrition, and functional medicine.

23

THIRD EDITION FOREWORD Bob King Although I often wonder why some texts go through second and third editions, such was not the case with Joe Muscolino’s The Muscular System Manual! This new and spectacularly upgraded edition certainly establishes the author as the leading muscular system expert for manual therapists in this country. Indeed, the upgrades, resources, and knowledge base of this text are nothing short of brilliant. Initially, Chapters 1 to 3 provide new and innovative material on how the muscular system works with a detailed overview of the roles of bones, joints, and connective tissues. Dr. Muscolino’s valuable perspective on the muscular system, the primary user of body energy, provides a perspective and background that would be of value to any manual or movement therapy student, even the individual with a very limited knowledge base. The location terminology, color drawings, bony structure, and movement presentations provide a basic kinesiology foundation that serves as a cornerstone for the rest of the book. All of the muscles featured (yes, all of them!) are now re-ordered to their respective joints, making the flow and portability of this edition superior to other texts. Furthermore, it coincides with the way that most muscular/myology/kinesiology classes are taught in massage and other bodywork schools. This is an especially useful adjunct for today’s student of the healing arts, offering a more systematic portrayal of muscular system and body functioning. Remarkably enough, this edition is even more thorough than its predecessor in the presentation of muscle function. The author painstakingly presents not only the muscular attachments, but also expands the functional information of each muscle to include the concentric, shortening mover actions, and the reverse mover actions, as well as the eccentric lengthening and isometric stabilization actions. Incredible! These features alone are missing from other bodywork texts, and this material provides a more comprehensive understanding of muscle functioning at all levels. Reverse mover actions are important because they explain, for instance, why the tensor fasciae latae (TFL) is not only a flexor of the thigh at the hip joint and an abductor and medial rotator of the thigh at the same joint, but also how its reverse actions anteriorly tilt the pelvis and ipsilaterally rotate and depress that side of the pelvis as well. This alone marks TFL as an overlooked source of low back pain, scoliotic compensation, sacroiliac dysfunction and a vitally essential muscle to release in the classic lower crossed syndrome. Useful hands-on and palpatory insights such as this abound throughout this exciting new edition. Simply reviewing this copy generated new clinical insights for me for several clients with whom I currently provide clinical massage. It will be a primary resource in my treatment room for years to come. Consequently, not only will the student, but also the experienced manual therapist, benefit from this clinically relevant information, presented, once again, in a clear and systematic fashion. Fully expect your knowledge of challenging therapeutic cases to increase with this new edition, which is the most thorough book on muscle functioning currently available. I believe this text will also upgrade, if not revolutionize, the teaching of the muscular system, moving away from useless memorizations and dogma to functionally important information, descriptions, and solid explanations plotted out with careful reasoning. New and improved color drawings are ubiquitous throughout this edition. Full-color drawings are featured individually, within muscle or function groups and also drawn on real persons, giving learners a vivid presentation of location, palpation, and attachment points. This feature alone will clarify concepts, and stimulate the visual learner to an even deeper awareness of the spectacular movements of the human body and the intricate combination of forces that generate optimal functioning. An interactive CD is included with the textbook that is a first of its kind! Each of the base illustrations is given showing the body and the skeleton along with a list of all the muscles of that region. The student can then build the muscular system on the illustration, choosing any

24

combination of muscles to show next to each other. Do you want to see the TFL next to the sartorius? Perhaps add in the gluteus medius and/or iliopsoas? You choose. This CD alone will greatly enhance the beginner student’s ability to learn the muscles, as well as challenge seasoned therapists to better learn their anatomy. It helps students and therapists alike, not only learn the individual muscles, but also begin the incredibly important and needed clinical task of putting the muscular system back together! This along with audio files of the attachments and actions that allow the student to burn CDs and MP3 files to study on-the-go are alone worth the price of admission to the book. The newly added Chapter 19 contains functional mover groups of muscles illustrating the concentric, reverse, eccentric, and isometric stabilization functions—once again showcased with excellent new drawings. The second part of this chapter illustrates (with the gracious permission of rolfer and myofascial innovator Tom Myers) the essential myofascial meridians depicting the fascial webbings and relationships of connective tissue that assist with movement and posture. This is yet another feature of The Muscular System Manual that underlies its premier status as the most complete book available on this wondrous and vital system of the human body. The author has truly created a work of science and art masterfully blended for optimal results! Bob King August 3, 2009 Bob King, LMT, NCTMB Bob King authored manuals, books, videos, curricula, and numerous clinical articles in a massage therapy career spanning more than three decades. He was a Cortiva Educational Consultant and conducted advanced myofascial trainings throughout the country. He was the founder and past president of the Chicago School of Massage Therapy, served two terms as AMTA National President, and was widely regarded as a successful innovator, activist, and educator within the profession. In 2009, Bob was named to the Massage Therapy Hall of Fame. In 2004, he received the Distinguished Service Award for the Massage Therapy Foundation for visionary leadership.

25

SECOND EDITION FOREWORD Bob King The more than 650 muscles of the human body, when optimally stabilized and integrated, generate an elegant functioning that is truly extraordinary. The static hold of the weightlifter … the leaping twirl of the ballet dancer … the rotational decompression of the pole vaulter at eighteen feet … the stunning accuracy of a left hook … a touchdown pass … or the joyous flip of an exuberant cheerleader. Muscles in motion are the very essence of health, performance, and life itself. Unfortunately, this kinetic symphony sometimes comes to an abrupt halt when pain and injury impact the soft tissues. As a practicing massage therapist for the past 30 years, I am still often intrigued and amazed by the “stuff” of the athletic injury or the muscular system breakdown: the muscles, tendons, skin, fascia, and ligaments are both promising and puzzling to the dynamics of healing. This soft tissue “stuff” provides the physiological basis and the therapeutic significance of our hands-on clinical endeavors. In witnessing the mysterious process of healing, it would seem that the successful hands-on bodyworkers must be adept and comfortable with their right-brain skills. These skills might include postural analysis, revealing global rather than isolated segmental relationships. Therapeutic compassion and care can jump start the placebo effect. Intuitive hunches often prove more reliable than high tech testing protocols. Clinical reasoning is seldom linear. Skillful palpation includes wandering around in myofascial neighborhoods—and wandering doesn’t mean you’re lost. Novel explorations and vital discoveries within the soft tissue realm are often guided by literate palpation and three-dimensional visualization. However, the left-brain skills of anatomical knowledge and objective accuracy are equally vital for successful outcomes. The charismatic extrovert, no matter how reassuring and cheerful, requires a clear understanding of rotator cuff functioning to best serve the client with upper quarter pain. The introverted wisdom of the energy worker is more clinically effective when the attachments and function of the quadratus lumborum are clearly understood. Effective palpation is clearly an art and a science. Fortunately, compassion and competency are not mutually exclusive skills. Neither are accuracy and artistry. A noted neuromuscular therapist once told me, “To really develop your intuition, know your anatomy!” How true. So how do we creatively bring the objectivity, the detail and the accuracy of scientific anatomy into the learning process and the ongoing education of the bodywork practitioner? Some 20 years ago, a groundbreaking event occurred with the publication of Drs. Travell and Simons’ Myofascial Pain and Dysfunction, Volume I. Physical medicine, manipulative medicine, and bodywork therapies were gifted with a lavishly illustrated and referenced guide to the human muscular system. Massage school curricula began to change. Anatomical competencies were elevated and anatomically-based clinical accuracy was the foundation for many advanced trainings and specialties within the field. “Neutralizing Trigger Points!” became the battle cry for a whole generation of massage therapists. As the therapeutic quest deepened and evolved, it became apparent that trigger points were only one mechanism of pain, dysfunction, and injury … and certainly not the only clinically important aspect of the healing process. Mystery, nuance, perspective, and experimentation, all valid to the therapeutic encounter, seldom develop within rigid formulas. Inquiry, research and dialogue come together to compose a reflective landscape. In recent years, more thoughtful and inclusive bodywork approaches have emerged, encompassing muscle, fascia, function, structure, energetics, mobilization, breathwork, and self-stabilization in forming a new and clinically potent therapeutic philosophy. It became evident that a new foundational textbook, reference and muscular system manifesto was needed … one that would encompass attachments, movement, layers, synergists, palpation skills, an image bank, discussion questions, an instructor’s manual, crossword puzzles, and review questions in a

26

four color, user-friendly, and Power Point convertible format. Such a book has arrived. The newly revised The Muscular System Manual, by Dr. Joseph Muscolino, is a comprehensive, allin-one resource that scientifically and artfully introduces the student, reinforces the educator, and validates the practitioner in learning and effectively treating the muscular system. The book’s remarkable commitment to precision and detail is underscored by the author’s sense of wonder and intellectual curiosity. The use of color, layout, design, methodology, and muscle group illustration enables the learner to absorb essential information while simultaneously seeing the “big picture” of global and regional relationships. Truly, this is a text that will integratively support the education, clinical practice, and continuing education of the manual therapist. While conducting a clinical symposium on the iliopsoas complex recently, I used The Muscular System Manual as a teaching reference. The drawings, pronunciations, attachments, multiple actions, and learning methodology of this manual greatly facilitated learning outcomes, expertly organized the clinical information, and accurately supported the student learning of palpation and assessment skills. The author’s explanation of reverse actions was especially useful, given the multiple action possibilities of this muscle group. The book also documented that psoas minor is absent in 40% of the population, the lumbar plexus is located within the belly of psoas major, and the tenderloin cut of steak is actually the cow’s psoas major! I believe massage therapy education should be informative, interactive and fun. The Muscular System Manual not only supports these goals, it stands on its own as a superb teaching reference book. The author is a practicing chiropractor, massage school anatomy instructor, and an activist for professional standards of competency. He has served as a test specification expert in the fields of anatomy, physiology, and kinesiology for the National Certification Board of Therapeutic Massage and Bodywork Job Analysis Survey Task Force. He is the author of numerous anatomical and clinical features in Journal of Bodywork and Movement Therapies and Massage Therapy Journal. Perhaps equally important, Dr. Muscolino has a twinkle in his eye and a profoundly animated response whenever discussions veer into the realm of muscles and movement. I believe The Muscular System Manual reflects his vast knowledge, his creative vision, and the twinkle in his eye. The Muscular System Manual is the most current and informative reference for the human muscular system and its potential for function and creative movement. This book will last you a lifetime. Robert K. King August 11, 2004

27

PREFACE The Muscular System Manual: The Skeletal Muscles of the Human Body, 4th edition, is meant to be the most thorough atlas of muscle function that is available. Instead of simply listing muscle attachments and actions that are typically taught, The Muscular System Manual comprehensively covers all muscle functions of each muscle. Shortening action functions with their reverse actions are addressed, as well as eccentric and stabilization functions. By offering the student the full picture of muscle function, it actually makes the task of learning the muscles easier, not harder. Students can grasp the information more quickly because they understand it and do not have to memorize it.

28

WHO WILL BENEFIT FROM THIS BOOK? This book is primarily written for students and practicing therapists of manual and movement therapies, including massage therapy, physical therapy, chiropractic, osteopathy, orthopedists, athletic training, yoga, Pilates, and Feldenkrais. However, anyone who needs to learn the skeletal muscles of the body will find this book invaluable and essential. Unlike many books, you will not outgrow The Muscular System Manual. It will be your guide as you first learn the muscles of the body, and it will remain an invaluable resource on your bookshelf for as long as you are in practice.

29

CONCEPTUAL APPROACH The approach taken by The Muscular System Manual is unique. Instead of simply listing information, it teaches the information and makes it understandable, allowing for true critical thinking. The beginning chapters set the framework for how muscles work as well as give a five-step approach to learning muscles. Each individual muscle then has notes that explain how the actions can be reasoned out instead of memorized. The goal of this book is to enable the student/therapist/trainer/physician to be able to critically think through muscle functioning when working clinically with clients and patients.

30

ORGANIZATION The Muscular System Manual is organized into five Parts. Part 1 covers the basic language of kinesiology that the student needs to be able to understand muscle attachments and functions and also communicate with other members of the health care and fitness fields. Parts 2 through 4 systematically cover each of the major muscles of the body, presenting in a clear and organized manner the essential information of every muscle. The beginning of each chapter in these parts opens with large group illustrations of the muscles of the joint region. Each muscle then has an individual layout in which the muscle’s attachments, functions, innervation, arterial supply, palpation, relationship to other structures, and other miscellaneous information that is intellectually and clinically relevant are given. Part 5 presents illustrations of all the major functional joint action mover groups of muscles as well as illustrations of the muscles of the pelvic floor and myofascial meridians of the body.

31

DISTINCTIVE FEATURES OF THIS BOOK There are many features that distinguish this book: • The most thorough coverage of muscle function available. • Explanations to understand the muscle’s actions that promote critical thinking. • Full referencing for all joint actions. • Information presented in a layered à la carte approach that allows each student or instructor to determine what content is covered. • Beautiful illustrations in which the bones and muscles are placed on a photograph of a real person. • Large group illustrations for every functional group. • Myofascial meridian information for every muscle. • Bulleted clear and easy-to-follow palpations for each muscle. • An interactive digital program on Evolve that allows for any combination of muscles to be placed on the skeleton and body.

32

NEW TO THIS EDITION All features of the 3rd edition have been preserved; the 4th edition of The Muscular System Manual has many new features: • Evidence-based full referencing for all joint actions of the muscles. • Expanded coverage of muscle function to address the oblique plane motion patterns of the muscles. • A flashcard app that offers a portable resource for studying more than 250 flashcards, which include coverage of muscles, muscle locations, pronunciations, attachments, actions, and innervation information. • New illustrations for the muscle attachments and myofascial meridians, as well as for many of the muscles. • A concise review of all organ systems of the body. • Digital access to video demonstrations of the palpation of all the muscles of the body. • An interactive customized digital program that allows stretches of the individual muscles to be printed out for self-care use or for use with patients/clients.

33

LEARNING AIDS • The attachment and functions information is presented in a layered à la carte approach that allows the student to decide at what depth to learn the information. • This book is meant to be used not only as a textbook, but also as an in-class manual. For this reason, checkboxes are provided for each muscle layout as well as each piece of information. This allows the student to check off exactly what content will be learned. Instructors, having students check off content covered, allows for extremely clear expectations of what they are responsible for. • Arrows are placed over the muscle for each individual muscle illustration so that the line of pull of the muscle can be seen and visually understood. This allows for the actions of the muscle to be understood instead of memorized. • A Miscellaneous section is provided that offers interesting insights to each muscle. Many of these are clinical applications that flesh out and make learning the muscle more interesting.

34

EVOLVE ONLINE RESOURCES This book is backed up by an Evolve website that includes the following student resources: • An interactive digital program that is simple, thorough, and easy to use. A base photograph of the region of the body is presented with the skeleton drawn in. A list of every muscle of that region is given and you can choose any combination of muscles and place them onto the illustration, allowing you to not only see that muscle’s attachments, but more importantly, to be able to see the relationship between all the muscles of the region. Any combination of muscles can be chosen! • Video demonstrations by the author showing palpation of each and every muscle of the book. • An audio feature in which the author reads aloud the names, attachments, and major actions of all the muscles. This allows for studying while commuting or for use with an MP3 device. Ideal for studying and learning while on the go! • Interactive review exercises such as Drag ‘n’ Drop labeling exercises and Name That Muscle quizzes for further review of the skeletal muscles of the human body. • 200 short-answer review questions to reinforce knowledge learned in the book. • An interactive customized digital program that allows stretches of the individual muscles to be printed out for self-care use or for use with patients/clients. • A concise review of all organ systems of the body. • Supplemental appendices featuring valuable information on the following topics: soft tissue attachments, palpation guidelines, overview of innervation, overview of arterial supply, additional skeletal muscles, and mnemonics for remembering muscle names.

35

OTHER RESOURCES For instructors, the entire book is available in 50-minute PowerPoint lectures, with learning outcomes, discussion topics, and critical thinking questions. There is also an instructor’s manual that provides step-by-step approaches to leading the class through learning the muscles, as well as case studies that allow for a critical thinking application of the muscles to common musculoskeletal conditions. Further, a complete image collection that contains every figure in the book, and a test bank in ExamView containing 1,500 questions, are provided.

36

RELATED PUBLICATIONS The Muscular System Manual is also supported by an excellent coloring book and set of flash cards that can be purchased separately. Look for Musculoskeletal Anatomy Coloring Book, 2nd edition, and Musculoskeletal Anatomy Flash Cards, 2nd edition, published by Mosby/Elsevier. For more on muscle palpation, look for The Muscle and Bone Palpation Manual, With Trigger Points, Referral Patterns, and Stretching, 2nd edition (Mosby/Elsevier, 2015).

37

NOTE TO THE STUDENT This book is thick and packed with information. You can choose exactly how much you want to learn. If you are a beginner to learning muscles, the outstanding illustrations and the simple and clear explanations will make learning muscles easy. If you are an advanced student of the muscular system, the depth of information will help you reach new levels of knowledge and clinical application. You will not outgrow this book. Whether as an in-class manual or a reference text for your bookshelf, you will find this book to be an ideal and essential book now and into the future!

38

HOW TO USE THIS BOOK

Muscle and Group Name (if applicable), covered in a 2- to 3-page spread. Illustration of individual muscle, with arrows indicating lines of pull. Bony attachments are shaded in brown for easy identification. Muscle is deep to (behind) a bone from this. Figures are full color anatomic illustrations of muscles and bones drawn over photographs to help identify positions of the structures. The positions of muscles and bones in the human body are unmistakable in this overlay artwork. Checkboxes are used throughout the 2- to 3-page individual muscle spreads so you can mark information to be covered or check it off once you have learned the material. A first look at the name of the muscle to see what free information the name gives us.

39

Derivation and proper pronunciation of the muscle are provided here. Simple attachment (origin) information. (Note: For illustrations of bones, bony landmarks, and muscle attachment sites, see Chapter 2.) More detailed attachment (origin) information. Simple attachment (insertion) information. (Note: If more detailed attachment [insertion] information is present, it will follow directly after this section.) Functions section: This section covers every contraction function of the muscle. This information serves to make The Muscular System Manual more complete, giving a comprehensive presentation of musculoskeletal function. (Note: For an explanation of muscle function, see Chapter 3.) Concentric (Shortening) Mover Actions table: The actions (standard and reverse) that are usually taught at a beginning or intermediate level are in bold print within the table. The remaining actions within the table are for more advanced levels of learning. (Note: For illustrations of joint actions, see Chapter 1.) Standard Mover Action notes: Methodology information that explains the reasoning behind each of the muscle’s standard actions. Reverse Mover Action notes: Methodology information that explains the reasoning behind each of the muscle’s reverse actions.

40

Motions: The oblique plane motion(s) of the muscle is given here to better understand the true motion pattern(s) of the muscle. Eccentric and Isometric Functions and Notes: The importance of core stabilization (isometric contraction) in exercise and rehabilitation has become increasingly understood in recent years, and negative (eccentric) contractions are used more and more in exercise. Coverage of this information is unique to this book. Additional notes on the muscle’s actions are given here. Innervation section: Two levels of detail are provided, with the predominant spinal levels shown in bold print. Arterial Supply section: Two levels of detail are provided. (Note: Arterial supply to muscles is extremely variable. Although specific information is provided here, this variability must be kept in mind when learning this material.) Palpation section: Easy-to-follow numbered steps to palpate the muscle. See the Evolve website for more in-depth video palpation protocols for the muscle palpation guidelines. Relationship section: Gives information regarding the muscle’s anatomic relationship to other musculoskeletal structures. Miscellaneous section: In this section, interesting information about the muscle and clinical applications are given.

41

ACKNOWLEDGMENTS No book of this magnitude can be achieved without help. I would like to express my gratitude to so many people who aided and supported me in the production of this book. This book would not exist today if it were not for the help and support that all of you have given me. Much of the beauty and success of this book rests in the beautiful illustrations of muscles and bones drawn over photographs of models. Photography was done by Yanik Chauvin and the principle model is Audrey Van Herck, both of Montreal, Canada. The artists are Frank Forney and Dave Carlson of Colorado and Giovanni Rimasti of Canada. A big thank you is also due to Jodie Bernard of Lightbox Visuals in Canada. Many of the illustrations from Chapters 1 and 3 were artfully done by Jean Luciano of Connecticut and Jeanne Robertson of St. Louis and borrowed from my Kinesiology textbook. The art direction and layout set the tone of this book. Thank you to Julia Dummitt for making a muscle book so attractive to look at and so easy to negotiate. Putting together a book of this size is no small feat. Thank you to the Production people at Elsevier. And a special thank you to the Editorial team at Elsevier, Shelly Stringer and Kelly Skelton, who worked hand in hand with me throughout this entire project. One could not ask for a more devoted managing editor than Shelly; she was truly my partner in the creation of this edition. And Kelly skillfully attended to every detail along the way. And continuing appreciation to Jennifer Watrous, my original editor, for all her work and assistance with the earlier editions of this book. A continuing thank you to Dr. Sharon Sawitzke, Ph.D., Associate Professor, Division of Anatomical Sciences at the University of Bridgeport, College of Chiropractic, who lent her expertise to provide the information regarding the arterial supply to the muscles. I could not have simplified and organized this material without her. And continuing thanks to David Elliot, PhD of the Touro University College of Osteopathic Medicine, my content editor, who combed through the original edition of this book, ensuring that the informational content was correct. He also fielded countless questions from me, helping me organize the content, and provided needed information when the boundaries of my knowledge had been reached. Thank you also to Tom Myers of Maine who graciously lent of his knowledge and was generous with illustrations from the third edition of his book, Anatomy Trains. I would like to thank Dr. Michael Carnes, my first anatomy instructor, of Western States Chiropractic College in Portland, Oregon. He first whetted my appetite for learning, understanding, and appreciating the beauty of anatomy and physiology. I believe that textbook writing is essentially “teaching on pages.” I am so lucky to have had the best field training that anyone could ask for. Teaching at the Connecticut Center for Massage Therapy (CCMT) under the guidance of Steve Kitts shaped me as a writer. I don’t think my students realized just how much I was learning along with them. Thank you to the many teaching assistants I was lucky enough to have through the years. So many of them not only assisted in the classroom, but also improved my teaching by showing me ways of more clearly explaining and demonstrating the material to our students. And I always reserve a special acknowledgement to one student (and now a fellow instructor), William Courtland, who one day uttered the simple words, “You should write a book.” Those words began my writing career. Lastly, I must express my love and appreciation to my entire family for their unending love, support, and understanding as I sat at my computer hour after hour after hour working on this book.

42

ABOUT THE AUTHOR

Dr. Joe Muscolino has been teaching musculoskeletal and visceral anatomy and physiology, kinesiology, neurology, pathology, and hands-on manual and movement therapy courses for 30 years. Dr. Muscolino has also published the following titles with Elsevier: • Kinesiology: The Skeletal System and Muscle Function, 2nd edition. • The Muscle and Bone Palpation Manual, with Trigger Points, Referral Patterns, and Stretching • Musculoskeletal Anatomy Coloring Book • Know the Body: Muscle, Bone, and Palpation Essentials • Workbook for Know the Body: Muscle, Bone, and Palpation Essentials • Musculoskeletal Anatomy Flashcards • Flashcards for Bones, Joints, and Actions of the Human Body • Flashcards for Palpation, Trigger Points, and Referral Patterns • Mosby’s Trigger Point Flip Chart with Referral Patterns and Stretching. And he has also self published the following two titles: • Advanced Treatment Techniques for the Manual Therapist: Neck • Manual Therapy for the Low Back and Pelvis: A Clinical Orthopedic Approach In addition, Dr. Muscolino has published numerous DVDs for the manual and movement therapist on such topics as orthopedic assessment, palpation, body mechanics, soft tissue manipulation, stretching, and arthrofascial stretching (Grade IV Joint Mobilization). Dr. Muscolino writes the column article, “Body Mechanics,” in The Massage Therapy Journal (MTJ) and has written for the Journal of Bodywork and Movement Therapies (JBMT) as well as many other journals, both in the United States and overseas.

43

Dr. Muscolino teaches continuing education workshops in the world of manual and movement therapies, including a Certification in Clinical Orthopedic Manual Therapy (COMT). He teaches these workshops throughout the United States, Europe, Australia, New Zealand, and Asia. He also runs instructor in-services for kinesiology instructors. He is an approved provider of continuing education (CE); and CE credit is available through the NCBTMB for Massage Therapists and Bodyworkers toward certification renewal. Dr. Joe Muscolino holds a Bachelor of Arts degree in Biology from the State University of New York at Binghamton, Harpur College. He attained his Doctor of Chiropractic Degree from Western States Chiropractic College in Portland, Oregon, and is licensed in Connecticut, New York, and California. Dr. Muscolino has been in private practice in Connecticut for more than 30 years and incorporates soft tissue work into his chiropractic practice for all of his patients. If you would like further information regarding The Muscular System Manual: The Skeletal Muscles of the Human Body or any of Dr. Muscolino’s other Elsevier publications, or if you are an instructor and would like information regarding the many supportive materials such as PowerPoint slides, test banks of questions, or TEACH instructor’s manuals, please visit http://www.us.elsevierhealth.com. If you would like information regarding Dr. Muscolino’s other publications, DVDs, and workshops, or if you would like to contact Dr. Muscolino directly, please visit his website: www.learnmuscles.com.

44

PA R T 1

The Musculoskeletal System OUTLINE Chapter 1: Basic Kinesiology Terminology Chapter 2: The Skeletal System Chapter 3: How Muscles Function

45

CHAPTER 1

46

Basic Kinesiology Terminology OBJECTIVES After completing this chapter, the student should be able to perform the following: 1. Define the key terms of this chapter. 2. Describe the importance of clear communication using precise terminology. 3. Describe the major divisions of the body. 4. List the specific divisions of the axial and appendicular body. 5. Describe anatomic position and its role as a reference point for location and movement terminology. 6. List and define all pairs of location terminology. 7. Describe the major planes of the body. 8. Describe the axes and their relation to the planes of the body. 9. List and define all pairs of movement terminology.

10. Identify which movements occur at each of the major joints of the body.

http://evolve.elsevier.com/Muscolino/muscular It is not possible to discuss muscle function without fluency in the language of kinesiology (Box 1-1). The reason why specific kinesiology terms exist is that they help us to avoid the ambiguities of lay language. Therefore embracing and using these terms is extremely important in the health care field, where someone’s health depends on clear communication. The purpose of this chapter is to provide an overview of the basic terms of kinesiology that are needed. Further explanation of kinesiology terminology is provided on the Evolve website that accompanies this book. For an indepth and thorough discussion of the terminology of kinesiology, see Kinesiology: The Skeletal System and Muscle Function, 2nd edition (Elsevier, 2010).

BOX 1-1 The term kinesiology literally means the study of motion. Given that motion of our body occurs when bones move at joints, and that muscles are the primary creator of the forces that move the bones, kinesiology is the study of the musculoskeletal system. Because the muscles are controlled and directed by the nervous system, it might be more accurate to expand kinesiology to be the study of the neuromusculoskeletal system. And when we consider the importance of fascia to musculature and movement, perhaps the best way that we can define kinesiology is to describe it as the study of the neuro-myo-fascio-skeletal system!

47

MAJOR BODY PARTS Motions of the body involve movement of body parts. To be able to describe the body part’s motion, we must be able to accurately name it. Figure 1-1 illustrates the major divisions and body parts of the human body. The two major divisions are the axial body and the appendicular body. The appendicular body can be divided into the upper extremities and the lower extremities.

48

FIGURE 1-1 The three major divisions of the body are the axial body and the two divisions of the appendicular body. The appendicular body is composed of the upper extremities and lower extremities. Furthermore, the body parts within these major divisions are shown. A, Anterior view. B, Posterior view. C, Lateral view.

The names of most body parts are identical to the lay English names for them. However, there are a few cases in which kinesiology terms are very specific and need to be observed. For example, the term arm is used to refer to the region of the upper extremity that is located between the glenohumeral (GH) (shoulder) and elbow joints. The term forearm refers to the body part that is located between the elbow and wrist joints; the forearm is a separate body part and not considered to be part of the arm. Similarly, the term leg describes the region of the lower extremity that is located between the knee and ankle joints, whereas the term thigh is used to describe an entirely separate body part that is located between the hip and knee joints; the thigh is not part of the leg. The precise use of these terms is essential so that movements of the leg and thigh are not confused with each other, and movements of the arm and forearm are not confused with each other. Another term that should be noted is pelvis. The pelvis is a separate body part from the trunk and is located between the trunk and thighs.

49

50

ANATOMIC POSITION Anatomic position is a standard reference position used to define terms that describe the physical location of structures of the body and points on the body. In anatomic position, the person is standing erect, facing forward, with the arms at the sides, the palms facing forward, and the fingers and toes extended (Figure 1-2). Note: Given that movement terminology is based on location terminology, anatomic position is ultimately the foundation for movement terminology as well.

FIGURE 1-2 Anatomic position is a reference position of the body in which the person is standing erect, facing forward, with the arms at the sides, the palms facing forward, and the fingers and toes extended.

51

LOCATION TERMINOLOGY Now that anatomic position has been defined, it can be used as the reference position for location terms that describe the relative locations of body parts, structures, and points on the body to each other. Location terminology is composed of directional terms that come in pairs, each member of the pair being the opposite of the other.

Pairs of Terms Anterior/Posterior Anterior means farther to the front; posterior means farther to the back. These terms can be used for the entire body, axial and appendicular. Note: The term ventral is sometimes used for anterior, and the term dorsal is sometimes used for posterior. The true definition of ventral is the soft belly surface of a body part; dorsal refers to the harder surface on the other side of the body part. In the lower extremity, anterior/ventral and posterior/dorsal are not synonymous. The ventral surface of the thigh is the medial surface, of the leg is the posterior surface, and of the foot is the plantar surface.

Medial/Lateral Medial means closer to an imaginary midline that divides the body into left and right halves; lateral means farther from this imaginary midline. These terms can be used for the entire body, axial and appendicular.

Superior/Inferior Superior means above (toward the head); inferior means below (away from the head). These terms are usually used for the axial body only.

Proximal/Distal Proximal means closer (i.e., more proximity) to the axial body; distal means farther (i.e., more distance) from the axial body. These terms are used for the appendicular body only.

Superficial/Deep Superficial means closer to the surface of the body; deep means farther from the surface of the body (i.e., more internal). These terms can be used for the entire body, axial and appendicular. Note: When employing the terms superficial and deep, it is recommended to always state from which perspective you are viewing the body.

Radial/Ulnar The terms radial and ulnar can be used for the forearm and hand in place of the terms lateral and medial, respectively. The radius is the lateral bone of the forearm; the ulna is the medial bone.

Tibial/Fibular The terms tibial and fibular can be used for the leg and sometimes the foot in place of the terms medial and lateral, respectively. The tibia is the medial bone of the leg; the fibula is the lateral bone.

Palmar/Dorsal The terms palmar and dorsal can be used for the hand in place of the terms anterior and posterior, respectively.

Plantar/Dorsal The terms plantar and dorsal can be used for the foot. The plantar surface of the foot is the undersurface that is planted on the ground. The dorsal surface is the top or dorsum of the foot.

Cranial/Caudal

52

Cranial means toward the head; caudal means toward the “tail” of the body. These terms are used for the axial body only. Note: The term cephalad is often used in place of cranial.

Combining Terms of Location These terms that describe location can be combined together. Similar to combining terms such as north and west to create northwest, location terms can be combined. When doing this, the end of the first word is usually dropped and the letter o is placed to connect the two words. For example, anterior and lateral combine to become anterolateral. Although no hard-and-fast rule exists, anterior and posterior are usually placed first when combined with other terms. Figure 1-3 is an anterior view of a person, illustrating the terms of relative location as they pertain to the body.

FIGURE 1-3

Various terms of location relative to anatomic position.

53

PLANES Planes are flat surfaces that cut through and can be used to map three-dimensional space. Because space is three-dimensional, there are three major planes, known as cardinal planes. The three cardinal planes are the sagittal plane, frontal plane, and transverse plane (Box 1-2). A sagittal plane divides the body into left and right portions. A frontal plane divides the body into front and back (anterior and posterior) portions. A transverse plane divides the body into upper and lower (superior and inferior or proximal and distal) portions. Each of the three cardinal planes is perpendicular to the other two cardinal planes. Any plane that is not perfectly sagittal, frontal, or transverse is described as an oblique plane. Therefore an oblique plane has components of two or three cardinal planes. Figure 1-4 illustrates two examples each of the three cardinal planes and oblique planes.

BOX 1-2 The frontal plane is also known as the coronal plane. The transverse plane is also known as the horizontal plane.

54

FIGURE 1-4 Anterolateral views of the body, illustrating the three cardinal planes (sagittal, frontal, and transverse) and oblique planes. A, Two examples of sagittal planes. B, Two examples of frontal planes. C, Two examples of transverse planes. D, Two examples of oblique planes. (Note: The upper oblique plane has frontal and transverse components to it; the lower oblique plane has sagittal and transverse components to it.)

Motion of the Body within Planes Planes become extremely important when we describe the motion of a body part through space, because the body part moves within a plane. Hence, by defining the planes of space, we can describe the path of motion of a body part when it moves. Note that the sagittal and frontal planes are vertical and the transverse plane is horizontal. Therefore motions within the sagittal and frontal planes move vertically up and down, and motions within the transverse plane move horizontally. Figure 1-5 illustrates examples of motion within the three cardinal planes and oblique planes.

55

FIGURE 1-5 Examples of motion of body parts within planes. A, Motions of the head and neck and the forearm within the sagittal plane. B, Motions of the head and neck and the arm within the frontal plane. C, Motions of the head and neck and the arm within the transverse plane. D, Motions of the head and neck and the arm within an oblique plane.

56

AXES An axis (plural: axes) is an imaginary line around which a body part moves. If a body part moves in a circular path around an axis, it is described as an axial motion. If the body part moves in a straight line, it is described as a nonaxial motion. Both axial and nonaxial motions of a body part move within a plane. However, an axial motion moves within a plane and moves around an axis. The orientation of the axis for an axial movement is always perpendicular to the plane within which the movement is occurring. Each plane has its own corresponding axis; therefore there are three cardinal axes. The axis for sagittal plane movements is oriented side to side and described as the mediolateral axis, the axis for frontal plane movements is oriented front to back and described as anteroposterior, and the axis for transverse plane movements is oriented up and down and described as superoinferior or simply vertical. Each oblique plane also has its own corresponding axis, which is perpendicular to it. Figure 1-6 illustrates axial motions that occur within planes and around their corresponding axes.

FIGURE 1-6 A to D, Anterolateral views that illustrate the corresponding axes for the three cardinal planes and an oblique plane; the axes are shown as red tubes. A, Motion occurring in the sagittal plane around a mediolateral axis. B, Motion occurring in the frontal plane around an anteroposterior axis. C, Motion occurring in the transverse plane around a superoinferior axis, or more simply, a vertical axis. D, Motion occurring in an oblique plane; around an oblique axis.

57

MOVEMENT TERMINOLOGY Using anatomic position, we are able to define terms that describe static locations on the body. We now need to define terms that describe dynamic movements of the body. These movement terms are called joint actions (Box 1-3). Similar to location terms, they come in pairs in which each member of the pair is the opposite of the other. However, different from location terms, movement terms do not describe a static location, but rather a direction of motion. The major pairs of joint action terms are defined here.

BOX 1-3 It is extremely important to point out that joint action terms describe cardinal plane motions. For example, flexion and extension of the arm at the shoulder (glenohumeral) joint occur within the sagittal plane, abduction and adduction of the arm at the glenohumeral joint occur within the frontal plane, and right rotation and left rotation of the arm at the glenohumeral joint occur within the transverse plane. If a body part were to move in an oblique plane, then as a general rule, to describe its motion, its cardinal plane motion components must be stated. For example, if the arm moves in a straight line that is forward and toward the midline, it would be described as flexing and adducting, even though it moves in only one direction. Understanding this concept is crucial to understanding oblique plane motions created by a muscle. For example, the coracobrachialis muscle moves the arm at the glenohumeral joint forward into flexion and toward the midline into adduction as described above. Therefore, when its one “joint motion” is described in joint actions terms, it is stated that it flexes and adducts the arm at the glenohumeral joint. This is often misconstrued to mean that the coracobrachialis can create two separate joint motions; that it can either flex or adduct the arm. It cannot (or at least it cannot do pure flexion or pure adduction). When it contracts, it must bring the arm into the oblique plane movement that is comprised of the sagittal plane component of flexion and the frontal plane component of adduction. Therefore, when learning the movement that a muscle creates, it is important to discern between the actual motion that it creates and its joint actions. Because a joint action is a cardinal plane motion, if a muscle creates one motion within a cardinal plane, its motion and action are synonymous. But if it creates one motion within an oblique plane, this oblique plane motion must be described as its multiple component cardinal plane actions. It should be noted that joint actions usually describe cardinal plane motions of a body part. For example, the brachialis muscle brings the forearm anteriorly in the sagittal plane at the elbow joint, so its action is described as flexion of the forearm at the elbow joint. If a muscle creates an oblique plane motion, this motion is described by breaking it into its component cardinal plane joint action motions. An example is the coracobrachialis muscle, which moves the arm anteriorly (in the sagittal plane) and medially (in the frontal plane). When describing this motion, it is said that the coracobrachialis flexes and adducts the arm at the glenohumeral joint. It actually causes one motion, but this one motion is described as having two cardinal (sagittal and frontal) plane components. For more information on this, please go to the Evolve website that accompanies this book or see Kinesiology: The Skeletal System and Muscle Function, 2nd edition (Elsevier, 2010). Following the definitions of joint action terms is a joint action atlas with illustrations that demonstrate all the joint actions of the body.

Pairs of Terms Flexion/Extension Flexion is generally an anterior movement of a body part within the sagittal plane; extension is generally a posterior movement within the sagittal plane. Exceptions include movements of the legs, feet, toes, and thumbs. From the knee joint and further distally, flexion of a body part moves posteriorly (extension is therefore an anterior movement). The thumb moves medially within the frontal plane when it flexes, and laterally within the frontal plane when it extends.

58

The terms flexion and extension can be used for the entire body, axial and appendicular.

Abduction/Adduction Abduction is generally a lateral movement within the frontal plane that is away from the imaginary midline of the body; adduction is a medial movement toward the midline. Exceptions include the toes and fingers, including the thumbs. The toes adduct toward an imaginary line through the center of the second toe when the second toe is in anatomic position; they abduct away from this imaginary line. Toe number two can only abduct; it can do tibial abduction and fibular abduction. Fingers two through five adduct toward an imaginary line that goes through the center of the middle finger when the middle finger is in anatomic position; they abduct away from this imaginary line. The middle finger can only abduct; it can do radial abduction and ulnar abduction. The thumb abducts within the sagittal plane by moving away from the palm of the hand; it adducts within the frontal plane by moving back toward the palm. The terms abduction and adduction are used only for the appendicular body.

Right Lateral Flexion/Left Lateral Flexion Right lateral flexion is a side-bending movement of the head, neck, and/or trunk toward the right within the frontal plane. Left lateral flexion is the opposite. These terms are used only for the axial body.

Lateral Rotation/Medial Rotation Lateral rotation is a movement within the transverse plane in which the anterior surface of the body part moves to face more laterally (away from the midline); medial rotation moves the anterior surface to face more medially (toward the midline). Lateral rotation is also known as external rotation; medial rotation is also known as internal rotation. These terms are used only for the appendicular body.

Right Rotation/Left Rotation Right rotation is a movement within the transverse plane in which the anterior surface of the body part moves to face more to the right; left rotation moves the anterior surface to face more to the left. These terms are used for the axial body only. (Note: They are also used to describe rotation motions of the pelvis.) Note: The terms ipsilateral rotation and contralateral rotation are often used to describe motions created by muscles that produce right or left rotation. Ipsilateral rotation and contralateral rotation are not joint action terms. Rather, they are ways to describe that a muscle on one side of the body either produces rotation to that same (ipsilateral) side or to the opposite (contralateral) side (Box 14).

BOX 1-4 De-rotation is a term that is sometimes used to describe the function of a muscle that, when the body is in anatomic position, cannot do rotation, but when the body part to which the muscle is attached is first rotated, the muscle can then create rotation to bring the body part back to anatomic position. Hence it “de-rotates” the body part and can be described as a “de-rotator.” This occurs because in anatomic position, the muscle attaches onto the bone over the axis for transverse plane (rotation) motion; but when the bone is first rotated, the muscle’s line of pull relative to the axis changes such that it can now rotate the bone back.

Elevation/Depression Elevation is a movement wherein the body part moves superiorly; depression occurs when the body part moves inferiorly.

Protraction/Retraction Protraction is a movement wherein the body part moves anteriorly; retraction is a posterior movement of the body part (Box 1-5).

59

BOX 1-5 The term protraction of the head is often used to describe a postural dysfunctional pattern in which the head is held excessively anterior. The consequence is that the center of weight of the head is imbalanced over thin air such that posterior cervicocranial extensor musculature (e.g., upper trapezius, semispinalis capitis) must isometrically contract to maintain this posture. Although the head can protract at the atlanto-occipital joint, this postural pattern is actually a pattern of the entire cervicocranial region, involving flexion of the lower neck and extension of the head and upper neck.

Right Lateral Deviation/Left Lateral Deviation Lateral deviation is a linear movement that occurs in the lateral direction.

Pronation/Supination The terms pronation and supination can be applied to motion of the forearm at the radioulnar joints and motion of the foot at the subtalar (tarsal) joint. Pronation of the forearm results in the posterior surface of the radius facing anteriorly (when in anatomic position); supination is the opposite. Note: It is easy to confuse forearm pronation with medial rotation of the arm at the glenohumeral joint, and forearm supination with lateral rotation of the arm. Pronation of the foot at the subtalar joint is an oblique plane motion made up primarily of eversion; it also includes dorsiflexion and lateral rotation (also known as abduction) of the foot at the subtalar joint. Pronation drops the arch structure of the foot. Supination of the foot is primarily made up of inversion; it also includes foot plantarflexion and medial rotation (also known as adduction) at the subtalar joint. Supination raises the arch structure of the foot.

Inversion/Eversion The foot inverts at the subtalar (tarsal) joint when it turns its plantar surface toward the midline of the body; it everts when its plantar surface is turned outward away from the midline. Inversion is the principal component of supination of the foot; eversion is the principal component of pronation of the foot.

Dorsiflexion/Plantarflexion The foot dorsiflexes when it moves superiorly (in the direction of its dorsal surface); it plantarflexes when it moves inferiorly (in the direction of its plantar surface). Technically, dorsiflexion is extension and plantarflexion is flexion.

Opposition/Reposition The thumb opposes at the saddle (carpometacarpal) joint when its pad meets the pad of another finger; it repositions when it returns back toward anatomic position. Opposition is actually a composite of abduction, flexion, and medial rotation of the thumb; reposition is a composite of adduction, extension, and lateral rotation of the thumb. The little finger can also oppose and reposition at its carpometacarpal joint. Little finger opposition is composed of flexion, adduction, and lateral rotation of the little finger; little finger reposition is composed of extension, abduction, and medial rotation.

Upward Rotation/Downward Rotation The scapula upwardly rotates when its glenoid fossa is moved to face more superiorly; downward rotation is the opposite motion. The clavicle upwardly rotates when its inferior surface moves to face anteriorly; downward rotation is the opposite motion. Note: These actions of the scapula and clavicle cannot be isolated. Rather, they must couple with motions of the arm at the glenohumeral joint.

Lateral Tilt/Medial Tilt and Upward Tilt/Downward Tilt The scapula laterally tilts when its medial border lifts away from the body wall; medial tilt is the

60

opposite motion, wherein the medial border moves back toward the body wall. Lateral tilt of the scapula is also known as medial (internal) rotation. Medial tilt of the scapula is also known as lateral (external) rotation. The scapula upwardly tilts when its inferior angle lifts away from the body wall; downward tilt is the opposite motion, wherein the inferior angle moves back toward the body wall.

Horizontal Flexion/Horizontal Extension Horizontal flexion is a movement of the arm or thigh in which it begins in a horizontal position (i.e., abducted to 90 degrees) and then moves anteriorly toward the midline of the body. Horizontal extension is the movement in the opposite direction. Note: Horizontal flexion is also known as horizontal adduction; horizontal extension is also known as horizontal abduction. The terms horizontal flexion/extension are generally used for motion of the arm at the glenohumeral joint; the terms horizontal adduction/abduction are generally used for motion of the thigh at the hip joint.

Hyperextension and Circumduction Hyperextension The term hyperextension is often used to describe extension beyond anatomic position. This text does not use hyperextension in this manner. Extension beyond anatomic position is called extension, just as flexion and abduction beyond anatomic position are called flexion and abduction. The prefix hyper denotes excessive; therefore the term hyperextension would be better and more consistently defined as a range of extension motion that occurs beyond what is normal or beyond what is healthy.

Circumduction Circumduction is not a joint action. Rather, circumduction is a sequence of four joint actions performed one after the other. For example, if a person moves his or her arm at the glenohumeral joint into flexion, then abduction, then extension, and then adduction, and does this by rounding the corners of the four motions, it creates a circular motion pattern that is called circumduction. It should also be noted that circumduction does not contain any rotation motion. Any joint that allows motion within two or more planes (biaxial or triaxial joints) can allow circumduction to occur.

61

JOINT ACTION ATLAS Upper Extremity Scapula at the Scapulocostal Joint

FIGURE 1-7 Nonaxial actions of elevation/depression and protraction/retraction of the scapula at the scapulocostal (ScC) joint. A, Elevation of the right scapula. B, Depression of the right scapula. C, Protraction of the right scapula. D, Retraction of the right scapula. The left scapula is in anatomic position in all figures. (Note: All views are posterior.)

62

FIGURE 1-8 Upward rotation of the right scapula at the scapulocostal (ScC) joint. The left scapula is in anatomic position. (Note: The scapular action of upward rotation cannot be isolated. It must accompany humeral motion. In this case, the humerus is abducted at the glenohumeral joint.) (Note: This is a posterior view.)

FIGURE 1-9 Tilt actions of the scapula at the scapulocostal (ScC) joint. A, Upward tilt of the right scapula; the left scapula is in anatomic position. B, Lateral tilt (medial/internal rotation) of the right scapula; the left scapula is in anatomic position. (Note: Both views are posterior.)

63

Clavicle at the Sternoclavicular Joint

FIGURE 1-10 A, Elevation of the right clavicle at the sternoclavicular (SC) joint. B, Depression of the right clavicle. (Note: The left clavicle is in anatomic position. Both views are anterior.)

FIGURE 1-11

A, Protraction of the right clavicle at the sternoclavicular (SC) joint. B, Retraction of the right clavicle. (Note: Both views are anterosuperior.)

64

FIGURE 1-12 Anterior view that illustrates upward rotation of the right clavicle at the sternoclavicular (SC) joint; the left clavicle is in anatomic position. (Note: Upward rotation of the clavicle cannot be isolated. In this figure, the arm is abducted at the glenohumeral joint, resulting in the scapula upwardly rotating, which results in upward rotation of the clavicle.)

Arm at the Glenohumeral Joint

FIGURE 1-13

Sagittal plane actions of the arm at the glenohumeral (GH) joint. A, Flexion. B, Extension. (Note: Both views are lateral.)

65

FIGURE 1-14

FIGURE 1-15

Frontal plane actions of the arm at the glenohumeral (GH) joint. A, Abduction. B, Adduction. (Note: Both views are anterior.)

Transverse plane actions of the arm at the glenohumeral (GH) joint. A, Lateral rotation. B, Medial rotation. (Note: Both views are anterior.)

66

Reverse Action of the Scapula and Trunk at the Glenohumeral Joint

FIGURE 1-16 Reverse actions in which the trunk moves relative to the arm at the glenohumeral (GH) joint are also possible. In the accompanying illustrations, the trunk is seen to move relative to the arm at the GH joint. A and B illustrate neutral position and right lateral deviation of the trunk at the right GH joint, respectively. C and D illustrate neutral position and right rotation of the trunk at the right GH joint, respectively. E and F illustrate neutral position and elevation of the trunk at the right GH joint, respectively. In all three cases, note the change in angulation between the arm and trunk at the GH joint (for lateral deviation B and elevation F, the elbow joint has also flexed). (Note: All views are anterior.)

Forearm at the Elbow and Radioulnar Joints

67

FIGURE 1-17 Sagittal plane motions of the forearm at the elbow joint. A, Flexion of the forearm at the elbow joint. B, Extension of the forearm at the elbow joint. (Note: Both views are lateral.)

FIGURE 1-18 Pronation and supination of the right forearm at the radioulnar (RU) joints. A, Pronation. B, Supination, which is anatomic position for the forearm. Pronation and supination are joint actions created by a combination of motions at the proximal, middle, and distal RU joints and occur within the transverse plane. (Note: Both views are anterior.)

68

Hand at the Wrist Joint

FIGURE 1-19 Motions of the hand at the wrist joint (radiocarpal and midcarpal joints). A and B, Lateral views illustrating sagittal plane flexion and extension of the hand, respectively. C and D, Anterior views illustrating frontal plane radial deviation and ulnar deviation, respectively. Radial deviation of the hand is also known as abduction; ulnar deviation is also known as adduction.

Fingers Two through Five at the Metacarpophalangeal and Interphalangeal Joints

69

FIGURE 1-20 Actions of fingers two through five at the metacarpophalangeal (MCP) joints of the hand. A and B, Radial (i.e., lateral) views illustrating sagittal plane flexion and extension, respectively. Flexion of the fingers at the interphalangeal joints is also seen. C and D, Anterior views illustrating frontal plane abduction and adduction, respectively. E and F, Anterior views illustrating frontal plane radial abduction and ulnar abduction of the middle finger at the third MCP joint, respectively.

Thumb at the Carpometacarpal Joint

70

FIGURE 1-21 Actions of the thumb at the first carpometacarpal (CMC) joint (also known as the saddle joint of the thumb). A and B, Anterior views that illustrate oblique plane opposition and reposition of the thumb, respectively. Opposition and reposition are actually combinations of cardinal plane actions; the component actions of opposition and reposition are shown in C to F. C and D, Anterior views that illustrate flexion and extension, respectively; these actions occur within the frontal plane. E and F, Lateral views that illustrate abduction and adduction, respectively; these actions occur within the sagittal plane. Medial rotation and lateral rotation in the transverse plane are not shown separately, because these actions cannot occur in isolation; they must occur in conjunction with flexion and extension, respectively. (Note: Flexion of the phalanges of the thumb and/or little finger at the metacarpophalangeal joint is also seen in A and C; flexion of the thumb at the interphalangeal joint is also seen in C).

Axial Body Head at the Atlanto-Occipital Joint

71

FIGURE 1-22 Lateral views illustrating sagittal plane motions of the head at the atlanto-occipital joint (AOJ). A illustrates flexion; B illustrates extension. The sagittal plane actions of flexion and extension are the primary motions of the AOJ.

FIGURE 1-23 Posterior views illustrating frontal plane lateral flexion motions of the head at the atlantooccipital joint (AOJ). A illustrates left lateral flexion; B illustrates right lateral flexion.

72

FIGURE 1-24

Posterior views illustrating transverse plane rotation motions of the head at the atlantooccipital joint (AOJ). A illustrates left rotation; B illustrates right rotation.

Neck at the Cervical Spinal Joints

73

FIGURE 1-25 Motions of the neck at the cervical spinal joints. A and B are lateral views that depict sagittal plane flexion and extension, respectively. C and D are posterior views that depict frontal plane left lateral flexion and right lateral flexion, respectively. E and F are anterior views that depict transverse plane right rotation and left rotation, respectively. Note: A to F depict motions of the entire craniocervical region (i.e., the head at the atlanto-occipital joint and the neck at the cervical spinal joints).

Trunk at the Thoracolumbar Spinal Joints

FIGURE 1-26 Motions of the thoracolumbar spine (trunk) at the spinal joints. A and B are lateral views that illustrate sagittal plane flexion and extension of the trunk, respectively. C and D are anterior views that illustrate frontal plane right lateral flexion and left lateral flexion of the trunk, respectively. E and F are anterior views that illustrate transverse plane right rotation and left rotation of the trunk, respectively.

Pelvis at the Lumbosacral Joint

74

FIGURE 1-27 Motion of the pelvis at the lumbosacral (LS) joint. A and B, Lateral views illustrating sagittal plane posterior tilt and anterior tilt, respectively, of the pelvis at the LS joint. (Note: In A and B, little or no motion is occurring at the hip joints; therefore the thighs are seen to “go along for the ride,” resulting in the lower extremities changing their orientation.)

75

FIGURE 1-27 C and D, Anterior views illustrating frontal plane elevation of the right pelvis and ele– vation of the left pelvis, respectively, at the LS joint (when one side of the pelvis elevates, note that the other side depresses). (Note: In the drawn illustrations of C and D, no motion is occurring at the hip joints; therefore the thighs are seen to “go along for the ride,” resulting in the lower extremities changing their orientation.) E and F, Anterior and superior views illustrating transverse plane rotation of the pelvis to the right and rotation to the left, respectively, at the LS joint. (Note: The dashed black line represents the orientation of the spine, and the red dotted line represents the orientation of the pelvis. Given the different directions of these two lines, it is clear that the pelvis has rotated relative to the spine; this motion has occurred at the LS joint.)

Mandible at the Temporomandibular Joints

76

FIGURE 1-28 A and B, Lateral views that illustrate depression and elevation, respectively, of the mandible at the temporomandibular joints (TMJs). These are axial motions.

FIGURE 1-29 A and B, Lateral views that illustrate protraction and retraction, respectively, of the mandible at the temporomandibular joints (TMJs). These are nonaxial motions.

77

FIGURE 1-30 A and B, Anterior views that illustrate right lateral deviation and left lateral deviation, respectively, of the mandible at the temporomandibular joints (TMJs). These are nonaxial motions.

Lower Extremity Thigh at the Hip Joint

FIGURE 1-31 Motions of the thigh at the hip joint. A and B, Lateral views illustrating sagittal plane flexion and extension, respectively. C and D, Anterior views illustrating frontal plane abduction and adduction, respectively. E and F, Anterior views illustrating transverse plane lateral rotation and medial rotation, respectively.

Pelvis at the Hip Joint

78

FIGURE 1-32 Motion of the pelvis at the hip joint. (Note: In A to D, no motion is occurring at the lumbosacral joint; therefore the trunk is seen to “go along for the ride,” resulting in the upper body changing its orientation.) A and B, Lateral views illustrating sagittal plane posterior tilt and anterior tilt, respectively, of the pelvis at the hip joint.

79

FIGURE 1-32 C and D, Anterior views illustrating frontal plane depression of the right pelvis and elevation of the right pelvis, respectively, at the right hip joint. (Note: When the pelvis elevates on one side, it depresses on the other, and vice versa.) E and F, Anterior and superior views illustrating transverse plane rotations of the pelvis to the right and to the left, respectively, at the hip joints. (Note: The black dashed line represents the orientation of the thighs and the red dotted line represents the orientation of the pelvis. Given the different directions of these lines, it is clear that the pelvis has rotated relative to the thighs; this motion has occurred at the hip joints.)

Leg at the Knee Joint

80

FIGURE 1-33 Motions possible at the tibiofemoral (i.e., knee) joint. A and B, Lateral views illustrating sagittal plane flexion and extension of the leg at the knee joint, respectively. C and D, Anterior views illustrating transverse plane lateral rotation and medial rotation of the leg at the knee joint, respectively. (Note: The knee joint can only rotate if it is first flexed.)

Foot at the Ankle Joint

81

FIGURE 1-34

A and B, Lateral views illustrating sagittal plane dorsiflexion and plantarflexion of the foot at the talocrural (i.e., ankle) joint, respectively.

Foot at the Subtalar (Tarsal) Joint

FIGURE 1-35 Motions of the foot at the subtalar (tarsal) joint. A, Pronation of the foot. Pronation is an oblique plane movement composed of three cardinal plane components: (1) eversion, (2) dorsiflexion, and (3) lateral rotation (also known as abduction) of the foot. The principal component of pronation is eversion. B, Supination of the foot. Supination is an oblique plane movement composed of three cardinal plane components: (1) inversion, (2) plantarflexion, and (3) medial rotation (also known as adduction) of the foot. The principal component of supination is inversion.

82

Foot at the Subtalar and Ankle Joints

FIGURE 1-36 Cardinal plane components of foot motion at the subtalar and ankle joints. A, Frontal plane components of eversion/inversion. B, Sagittal plane components of dorsiflexion/plantarflexion. C, Transverse plane components of lateral rotation/medial rotation (abduction/adduction). (Note: The axes are represented by the red dots or red tube/dashed line.)

Toes at the Metatarsophalangeal and Interphalangeal Joints

83

FIGURE 1-37 Motion of the toes at the metatarsophalangeal (MTP) joints. A and B, Lateral views illustrating sagittal plane flexion and extension of the toes, respectively (at both the MTP and interphalangeal [IP] joints). C and D, Dorsal views illustrating frontal plane abduction and adduction of the toes at the MTP joints. E, Fibular abduction of the second toe at the MTP joint. F, Tibial abduction of the second toe at the MTP joint.

84

REVIEW QUESTIONS 1. Describe the orientation of the body in standard anatomic position. ____________________________ ____________________________ 2. _______ is a term meaning toward the head; _______ means toward the “tail” of the body. 3. The three cardinal planes are called the_______, _______, and _______ planes. A fourth plane, containing components of two or more cardinal planes is called an _______ plane. 4. True or False: The orientation of the axis for an axial movement is always parallel to the plane within which the movement is occurring._______ 5. Movement terms do not describe a static location, but instead a_______. 6. If a muscle creates an oblique plane motion, how is this motion described? ____________________________ ____________________________ 7. True or False: Ipsilateral rotation and contralateral rotation are joint action terms._______ 8. Pronation of the foot at the subtalar joint is made up of what joint actions? This motion has what effect on the arch structure of the foot? ____________________________ ____________________________ ____________________________ ____________________________ 9. The combined actions of abduction, flexion, and medial rotation of the thumb make up the composite motion known as_______. 10. Explain the concept of circumduction and give an example. ____________________________ For answers to these questions, visit http://evolve.elsevier.com/Muscolino/muscular

85

THINK IT THROUGH This chapter has introduced the concept of a standard anatomic position and has defined location and movement terminology in reference to this position. If a person is observed outside of standard anatomic position, such as during an athletic or recreational activity, how does this affect our ability to communicate information about location and movement? Think of a familiar activity and look at each position and movement in terms of what has been learned in this chapter. ____________________________ ____________________________ ____________________________ ____________________________ ____________________________

86

CHAPTER 2

87

The Skeletal System OBJECTIVES After completing this chapter, the student should be able to perform the following: 1. Define the key terms of this chapter. 2. Identify the approximate number of bones in the adult human body. 3. Define a joint. 4. Describe the structural classifications of joints. 5. Describe the functional classifications of joints. 6. Describe the types of synovial joints.

http://evolve.elsevier.com/Muscolino/muscular

88

THE SKELETON The skeletal system is composed of approximately 206 bones and can be divided into bones of the axial body and bones of the appendicular body. Figure 2-1 is an anterior view of the full skeleton. Figure 2-2 is a posterior view.

FIGURE 2-1

Full skeleton—anterior view. Green, axial skeleton; cream, appendicular skeleton. From

Muscolino JE: Kinesiology: the skeletal system and muscle function, ed 2, St Louis, 2010, Elsevier.

89

FIGURE 2-2

Full skeleton—posterior view. Green, axial skeleton; cream, appendicular skeleton. From

Muscolino JE: Kinesiology: the skeletal system and muscle function, ed 2, St Louis, 2010, Elsevier.

90

JOINTS Wherever two or more bones come together—in other words, join—a joint is formed.

Structural Classification of Joints Structurally, the definition of a joint is having the two (or more) bones united by a soft tissue. There are three structural classifications of joints: fibrous, cartilaginous, and synovial. Fibrous joints are united by dense fibrous fascial tissue, cartilaginous joints are united by fibrocartilage, and synovial joints are united by a thin fibrous capsule that is lined internally by a synovial membrane, enclosing a joint cavity that contains synovial fluid. Only synovial joints possess a joint cavity and have articular cartilage that covers the joint surfaces of the bones. Figure 2-3 illustrates the three types of structural joints.

FIGURE 2-3

Structurally, there are three types of joints: A, fibrous; B, cartilaginous; and C, synovial. From Muscolino JE: Kinesiology: the skeletal system and muscle function, ed 2, St Louis, 2010, Elsevier.

Functional Classification of Joints Functionally, a joint is defined by its ability to allow motion between two (or more) bones. There are three functional classifications of joints: synarthrotic, amphiarthrotic, and diarthrotic. Synarthrotic joints permit very little motion; amphiarthrotic joints allow limited to moderate motion; and diarthrotic joints allow a great deal of motion. Generally, a correlation exists between the structural and functional classifications of joints. Fibrous joints are usually classified as synarthrotic because they allow very little motion; cartilaginous joints are usually classified as amphiarthrotic because they allow a limited to moderate amount of motion; and synovial joints are usually classified as diarthrotic because they allow a great deal of motion.

Types of Synovial Joints Diarthrotic synovial joints can be subdivided based on the number of axes around which they permit motion to occur. The four categories are uniaxial, biaxial, triaxial, and nonaxial. These categories can be further subdivided based on the shape of the joint.

91

Uniaxial Joints There are two types of synovial uniaxial joints: hinge and pivot. Hinge joints act similar to the hinge of a door. One surface is concave and the other is spool-like in shape. Flexion and extension are allowed in the sagittal plane around a mediolateral axis. The humeroulnar (elbow) joint is a classic example of a hinge joint (Figure 2-4).

FIGURE 2-4 The humeroulnar joint of the elbow is an example of a synovial, uniaxial hinge joint. It allows flexion and extension within the sagittal plane around a mediolateral axis. From Muscolino JE: Kinesiology: the skeletal system and muscle function, ed 2, St Louis, 2010, Elsevier.

The other type of synovial uniaxial joint is the pivot joint. A pivot joint allows only rotation (pivot) motions in the transverse plane around a vertical axis. The atlantoaxial joint of the spine is a classic example of a uniaxial pivot joint (Figure 2-5).

FIGURE 2-5 The atlantoaxial (C1-C2) joint of the spine between the atlas and axis is an example of a synovial, uniaxial pivot joint. It allows right and left rotations within the transverse plane around a vertical axis. From Muscolino JE: Kinesiology: the skeletal system and muscle function, ed 2, St Louis, 2010, Elsevier.

Biaxial Joints There are two types of synovial biaxial joints: condyloid and saddle. A condyloid joint has one bone whose surface is concave, and the other bone’s surface is convex. The convex surface of one bone

92

fits into the concave surface of the other. Flexion and extension are allowed within the sagittal plane around a mediolateral axis, and abduction and adduction are allowed within the frontal plane around an anteroposterior axis. The metacarpophalangeal joint of the hand is an example of a condyloid joint (Figure 2-6).

FIGURE 2-6 The metacarpophalangeal joint of the hand is an example of a synovial, biaxial condyloid joint. It allows flexion and extension in the sagittal joint around a mediolateral axis (A), and abduction and adduction in the frontal plane around an anteroposterior axis (B). From Muscolino JE: Kinesiology: the skeletal system and muscle function, ed 2, St Louis, 2010, Elsevier.

The other type of synovial biaxial joint is the saddle joint. Both bones of a saddle joint have a convex and concave shape. The convexity of one bone fits into the concavity of the other and vice versa. Flexion and extension are allowed in one plane and abduction and adduction are allowed in a second plane. It is interesting to note that a saddle joint also allows medial rotation and lateral rotation to occur in the third plane, so some might consider a saddle joint to be triaxial. However, because these rotation actions cannot be actively isolated, a saddle joint is still considered to be biaxial. The carpometacarpal joint of the thumb is a classic example of a saddle joint (Figure 2-7; Box 2-1).

BOX 2-1 The saddle (carpometacarpal) joint of the thumb does allow rotation motions within the transverse plane around a vertical axis. However, medial rotation can only occur as the thumb flexes, and lateral rotation can only occur as the thumb extends; thus these rotation motions cannot be actively isolated—that is, they cannot be actively performed by themselves. Therefore the saddle joint of the thumb allows motion around two axes: (1) an oblique axis for oblique plane motions that are composed of flexion combined with medial rotation and extension combined with lateral rotation and (2) the mediolateral axis for the cardinal plane motions of abduction and adduction within the sagittal plane. For this reason, the saddle joint of the thumb is considered to be biaxial

93

FIGURE 2-7 The carpometacarpal joint of the thumb is an example of a synovial, biaxial saddle joint. It allows flexion and extension (as shown in A) and abduction and adduction (as shown in B). It also allows medial and lateral rotation; however, these motions cannot be actively isolated. They must be coupled with flexion and extension respectively, so the saddle joint is considered to be biaxial. From Muscolino JE: Kinesiology: the skeletal system and muscle function, ed 2, St Louis, 2010, Elsevier.

Triaxial Joints There is only one major type of synovial triaxial joint: the ball-and-socket joint. As its name implies, one bone is shaped like a ball and fits into the socket shape of the other bone. A ball-and-socket joint allows the following motions: flexion and extension in the sagittal plane around a mediolateral axis; abduction and adduction in the frontal plane around an anteroposterior axis; and medial rotation and lateral rotation in the transverse plane around a vertical axis. The hip joint is a classic example of a ball-and-socket joint (Figure 2-8).

94

FIGURE 2-8 The hip joint between the head of the femur and the acetabulum of the pelvic bone is an example of a synovial, triaxial ball-and-socket joint. It allows flexion and extension in the sagittal plane around a mediolateral axis (A), abduction and adduction in the frontal plane around an anteroposterior axis (B), and medial rotation and lateral rotation in the transverse plane around a vertical axis (C). From Muscolino JE: Kinesiology: the skeletal system and muscle function, ed 2, St Louis, 2010, Elsevier.

Nonaxial Joints Synovial nonaxial joints permit motion within a plane, but the motion is a linear gliding motion and not a circular (axial) motion around an axis. The surfaces of nonaxial joints are usually flat or curved. Intertarsal joints between individual tarsal bones of the ankle region are examples of nonaxial joints (Figure 2-9).

95

FIGURE 2-9 An intertarsal joint of the ankle region is an example of a synovial nonaxial joint. Linear gliding motion is allowed within a plane, but this motion does not occur around an axis; hence it is nonaxial.

96

ATLAS OF BONY LANDMARKS AND MUSCLE ATTACHMENT SITES ON BONES Upper Extremity

FIGURE 2-10

Anterior view of the bones and bony landmarks of the right scapula/arm.

97

FIGURE 2-11

Anterior view of muscle attachment sites on the right scapula/arm.

98

FIGURE 2-12

Posterior view of bones and bony landmarks of the right scapula/arm.

99

FIGURE 2-13

Posterior view of muscle attachment sites on the right scapula/arm.

100

FIGURE 2-14

Anterior view of bones and bony landmarks of the right forearm.

101

FIGURE 2-15

Anterior view of muscle attachment sites on the right forearm.

102

FIGURE 2-16

Posterior view of bones and bony landmarks of the right forearm.

103

FIGURE 2-17

Posterior view of muscle attachment sites on the right forearm.

104

FIGURE 2-18

Palmar view of bones and bony landmarks of the right hand.

105

FIGURE 2-19

Palmar view of muscle attachment sites on the right hand.

106

FIGURE 2-20

Dorsal view of bones and bony landmarks of the right hand.

107

FIGURE 2-21

Dorsal view of muscle attachment sites on the right hand.

Axial Body

108

FIGURE 2-22

Anterior view of bones and bony landmarks of the neck.

FIGURE 2-23

Posterolateral view of bony landmarks of the mandible.

109

FIGURE 2-24

Posterolateral view of muscle attachment sites on the mandible.

110

FIGURE 2-25

Anterior view of muscle attachment sites on the neck. AS, Anterior scalene; MS, middle scalene; PS, posterior scalene.

111

FIGURE 2-26

Posterior view of bones and bony landmarks of the neck.

112

FIGURE 2-27

Posterior view of muscle attachment sites on the neck.

113

FIGURE 2-28

Anterior view of bones and bony landmarks of the trunk.

114

FIGURE 2-29

Anterior view of muscle attachment sites on the trunk.

115

FIGURE 2-30

Posterior view of bones and bony landmarks of the trunk.

116

FIGURE 2-31

Posterior view of muscle attachment sites on the trunk.

117

FIGURE 2-32

Anterior view of bones and bony landmarks of the head.

118

FIGURE 2-33

Anterior view of muscle attachment sites on the head.

119

FIGURE 2-34

Lateral view of bones and bony landmarks of the head.

120

FIGURE 2-35

Lateral view of muscle attachment sites on the head.

121

FIGURE 2-36

Inferior view of bones and bony landmarks of the head.

122

FIGURE 2-37

Inferior view of muscle attachment sites on the head.

Lower Extremity

123

FIGURE 2-38

Anterior view of bones and bony landmarks of the right pelvis and thigh.

124

FIGURE 2-39

Anterior view of muscle attachment sites on the right pelvis and thigh.

125

FIGURE 2-40

Posterior view of bones and bony landmarks of the right pelvis and thigh.

126

FIGURE 2-41

Posterior view of muscle attachment sites on the right pelvis and thigh.

127

FIGURE 2-42

Anterior view of bones and bony landmarks of the right leg.

128

FIGURE 2-43

Anterior view of muscle attachment sites on the right leg.

129

FIGURE 2-44

Posterior view of bones and bony landmarks of the right leg.

130

FIGURE 2-45

Posterior view of muscle attachment sites on the right leg.

131

FIGURE 2-46

Dorsal view of bones and bony landmarks of the right foot.

132

FIGURE 2-47

Dorsal view of muscle attachment sites on the right foot.

133

FIGURE 2-48

Plantar view of bones and bony landmarks of the right foot.

134

FIGURE 2-49

Plantar view of muscle attachment sites on the right foot.

135

REVIEW QUESTIONS 1. Approximately how many bones make up the adult human body?_______. 2. The junction of two or more bones is called a_______. 3. What type of joint has an enclosed cavity containing a lubricating fluid?

a. Fibrous b. Cartilaginous c. Synovial d. All joint types 4. List the types of joints according to their functional classification, in order of increasing movement. ____________________________ ____________________________ ____________________________ 5. Explain the correlation between the structural and functional classifications of joints. ____________________________ ____________________________ ____________________________ 6. Diarthrotic synovial joints can be subdivided based on the number of _______ around which they permit motion to occur. 7. Name the two types of synovial uniaxial joints and give an example of each. ____________________________ ____________________________ 8. Name the two types of synovial biaxial joints and give an example of each. ____________________________ ____________________________ 9. Name the major type of synovial triaxial joint and give two examples of it. ____________________________ ____________________________ 10. Describe the motion allowed by synovial nonaxial joints and give an example of such a joint. ____________________________ ____________________________ For answers to these questions, visit http://evolve.elsevier.com/Muscolino/muscular

136

THINK IT THROUGH Knowing what we now know about joints, think about the entirety of the human body and the role joints play in how we move. What would be the effect if a few of our joints were different from what they are now? What if the elbow (humeroulnar) joint were a saddle joint? What if the knee were a triaxial ball-and-socket joint? How would these changes affect our movement patterns? ____________________________ ____________________________ ____________________________ ____________________________ ____________________________

137

CHAPTER 3

138

How Muscles Function OBJECTIVES After completing this chapter, the student should be able to perform the following: 1. Define the key terms of this chapter. 2. Explain the basic function of a muscle. 3. Explain concentric muscle contraction. 4. Explain the concepts of standard mover and reverse mover actions. 5. Explain open-chain and closed-chain actions. 6. Discuss the ways in which muscle attachments can be named. 7. Explain eccentric muscle contractions. 8. Explain isometric muscle contractions. 9. Discuss the roles that muscles can perform.

10. Explain the sliding filament mechanism. 11. Describe the structure and organization of muscle tissue. 12. Describe the two major muscle fiber arrangements. 13. Explain the five-step approach to learning muscles. 14. Describe the process of figuring out a muscle’s actions. 15. Describe the functional group approach to learning muscles. 16. Discuss the use of a rubber band as a visual and kinesthetic aid for learning muscle actions. 17. Explain the basic guidelines of muscle palpation.

http://evolve.elsevier.com/Muscolino/muscular

139

MUSCLES CREATE PULLING FORCES The essence of muscle function is that muscles create pulling forces. It is as simple as that. When a muscle contracts, it attempts to pull in toward its center. This results in a pulling force being placed on its attachments. If this pulling force is sufficiently strong, the muscle will succeed in shortening and it will move one or both of the body parts to which it is attached. It is also important to realize that this pulling force is equal on both of its attachments. A muscle does not and cannot choose to pull on one of its attachments and not the other. In effect, a muscle is nothing more than a simple “pulling machine.” When ordered to contract by the nervous system, it pulls on its attachments; when not ordered to contract, it relaxes and does not pull (Box 3-1).

BOX 3-1 To call a muscle nothing more than a simple “pulling machine” does not lessen the amazing and awe-inspiring complexity of movement patterns that the muscular system produces. Any one muscle is a simple machine that pulls. But when different aspects of various muscles are coordered to contract in concert with each other and in temporal sequence with each other, the sum of many “simple” pulling forces results in an amazingly fluid and complex array of postural and movement patterns. The director of this symphony who coordinates these pulling forces is the nervous system. It is usually extremely helpful when confronted with a new kinesiology term to see whether there is a cognate, in other words, a similar term in lay English. This helps us to intuitively understand the new kinesiology term instead of having to memorize its meaning. When it comes to the study of muscle function, the operative word is contract because that is what muscles do. However, in this case, it can be counterproductive to try to understand muscle contraction by relating it to how the term contract is defined in English. In English, the word contract means “to shorten.” This leads many students to assume that when a muscle contracts, it shortens. This is not necessarily true, and making this assumption can limit our ability to truly grasp how the muscular system functions. In fact, most muscle contractions do not result in the muscle shortening, and to look at the muscular system this way is to overlook much of how the muscular system functions.

140

WHAT IS A MUSCLE CONTRACTION? When a muscle contracts, it attempts to shorten. Whether or not it does succeed in shortening is based on the strength of its contraction compared with the resistance force it encounters that is opposed to its shortening. For a muscle to shorten, it must move one or both of its attachments. Therefore the resistance to shortening is usually the weight of the body parts to which the muscle is attached. Let’s look at the brachialis muscle that attaches from the humerus in the arm to the ulna in the forearm (Figure 3-1).

FIGURE 3-1 Brachialis muscle. The brachialis muscle attaches from the humerus in the arm to the ulna in the forearm. For the brachialis to contract and shorten, it must move the forearm toward the arm and/or move the arm toward the forearm.

For the brachialis to contract and shorten, it must move the forearm toward the arm and/or move the arm toward the forearm. The resistance to moving the forearm is the weight of the forearm, plus the weight of the hand that must move (go along for the ride) with the forearm. The resistance to moving the arm is the weight of the arm, plus the weight of much of the upper part of the body that must move (go along for the ride) when the arm moves toward the forearm. Therefore, for the brachialis to contract and shorten, it must generate a force that is greater than the weight of the forearm (and hand) or the arm (and upper body). Because the forearm and hand weigh less than the arm and upper body, when the brachialis contracts and shortens, the forearm usually moves, not the arm. Thus the minimum force that the brachialis must generate if it is to contract and shorten is the weight of its lighter attachment, the forearm. However, even if the brachialis contracts with insufficient strength to shorten, it is important to understand that it is still exerting a pulling force on its attachments. This pulling force can play an important role in musculoskeletal function. When a muscle’s function is described, it is usually stated in terms of its joint actions, which are its shortening contractions. For this reason, there is a tendency to overly focus on the shortening contraction of a muscle and overlook the importance of its contraction when it does not shorten.

Concentric Contraction Let’s first look at what happens when a muscle contracts and does shorten. A shortening

141

contraction of a muscle is called a concentric contraction. The word concentric literally means “with center.” In other words, when a concentric contraction occurs, the muscle moves toward its center. As we have said, for a muscle to contract and shorten, it must move at least one of its attachments. Let’s explore the idea of concentric contraction by looking at a “typical” muscle (Figure 3-2).

FIGURE 3-2

A “typical” muscle is shown. It attaches to bone A and bone B and crosses the joint that is located between them.

A muscle attaches to two bones and in doing so, it crosses the joint that is located between them (Box 3-2). Let’s call one of the attachments A and the other attachment B. When the muscle contracts, it creates a pulling force on both bones. If this pulling force is strong enough, a concentric contraction can occur in three possible ways: the muscle can either succeed in pulling bone A toward bone B, or it can pull bone B toward bone A, or it can pull both bones A and B toward each other (Figure 3-3). The bone that moves is described as the mobile attachment and the bone that does not move is described as the fixed attachment. For a concentric contraction to occur, at least one of the attachments must be mobile and move. Regardless of which attachment moves, when a muscle contracts and does generate sufficient force to move one or both of its attachments toward the other, it is the mover of the joint action that is occurring and called the mover or agonist. By definition, when a mover muscle contracts, it contracts concentrically.

BOX 3-2 A typical muscle attaches to two bones and crosses the joint between them. However, some muscles have attachments to more than two bones, or attach into adjacent soft tissue instead of or in addition to bone; and some muscles cross more than two joints. To help understand the underlying concept of a muscle’s contraction, we will use for our examples a typical muscle that attaches to two bones and crosses one joint.

FIGURE 3-3 Examples of concentric contraction. A muscle can concentrically contract and cause motion in one of three ways. By naming the muscle’s attachments A and B, we can describe these three scenarios. In A, bone A moves toward bone B. In B, bone B moves toward bone A. And in C, both bones A and B move toward each other.

142

If we now explore concentric contraction a little further and ask which attachment will be the mobile one that does the moving, the answer will be the one that offers the least resistance to moving. That will usually be the lighter attachment. When we are looking at muscles on the extremities of the body, the lighter attachment is usually the distal one. In the upper extremity, the hand is lighter than the forearm, the forearm is lighter than the arm, and the arm is lighter than the shoulder girdle/trunk. In the lower extremity, the foot is lighter than the leg, the leg is lighter than the thigh, and the thigh is lighter than the pelvis. Furthermore, as we have stated, for the more proximal attachment to move, the core of the body usually must move with it, which adds even more weight and resistance to moving. Therefore, when an extremity muscle concentrically contracts, it usually moves its distal attachment. For this reason, when a muscle’s joint actions are learned, they are usually presented and demonstrated with the proximal attachment fixed and the distal attachment mobile. These are what can be termed the standard mover actions of the muscle.

Reverse Actions Although the more common and typically thought of muscle action (the standard action) is one in which the proximal attachment stays fixed and the distal attachment moves, this is not always the case. In fact, it often is not. Let’s look at a concentric contraction of the brachialis muscle across the elbow joint. When the brachialis contracts, it would most likely move the distal attachment toward the proximal attachment, moving the forearm and hand toward the arm as in Figure 3-4, A. However, if the hand holds onto an immovable object such as a pull-up bar, then because the hand is fixed, the forearm is also fixed and cannot move unless the pull-up bar is ripped off the wall. Therefore the arm will now offer less resistance to moving than the forearm, and if the brachialis contracts with sufficient force to move the arm (and the weight of the trunk that must move with it), the arm will be moved toward the forearm and the person will do a pull-up (Figure 3-4, B). When the proximal attachment moves toward the distal one instead of the distal one moving toward the proximal one, it is called a reverse mover action. Hence in this scenario, flexing the forearm toward the arm at the elbow joint is the typically thought of standard action; and flexing the arm toward the forearm at the elbow joint is the reverse action. For every standard action of a muscle, a reverse action is always theoretically possible.

FIGURE 3-4 Standard and reverse mover actions. A, The standard mover action of the brachialis muscle in which the distal forearm moves toward the proximal arm. B, When the hand is fixed, the reverse mover action occurs; the proximal arm moves toward the distal forearm.

How often reverse actions occur varies across the body and is also based on what motions and activities are being performed. In the upper extremity, reverse actions usually occur whenever the hand is gripping an immovable object. A pull-up bar as illustrated in Figure 3-4 is one example of this. Many other examples in everyday life exist, such as using a banister when walking up the stairs, someone helping to pull you up from a seated to standing position, or a disabled person using a handicap bar.

143

In the lower extremity, reverse actions are extremely common. This is because much of the time when we are standing, seated, or walking, our foot is planted on the ground. Unless we are on ice or some other slick surface, our foot is at least partially fixed and resistant to moving, resulting in our leg moving toward the foot. Similarly, with the distal end fixed, the thigh would have to move toward the leg and the pelvis would have to move toward the thigh. An excellent example of this is when we use our quadriceps femoris muscle group to stand from a seated position (Figure 3-5). We usually think of the quadriceps femoris group as extending the leg at the knee joint. But in this case, it must perform the reverse action of extending the thigh at the knee joint. As the thighs extend at the knee joints, the rest of the body must also be lifted. If you palpate the quadriceps femoris in your anterior thighs as you stand up from a seated position, you will easily feel their contraction. In fact, it is because of this frequent activity of daily life that our quadriceps femoris group needs to be so large and powerful.

FIGURE 3-5 Reverse mover action of the quadriceps femoris musculature. When we stand up from a seated position, the quadriceps femoris muscles create their reverse mover action, which is extension of the thighs at the knee joints, in other words, extending the more proximal thighs toward the distal legs instead of extending the more distal legs toward the proximal thighs.

In the axial body, we do not use the terms proximal and distal. Here, the usually thought of regular muscle action moves the superior attachment toward the inferior one. This is because the upper axial body (head, neck, and upper trunk) is lighter than the lower axial body (lower trunk) and because when we are sitting or standing, our lower body is more fixed and consequently more resistant to moving. Therefore, when a muscle of the axial body moves the lower trunk toward the upper trunk, neck, and head, it is a reverse mover action. These reverse actions happen quite often when we are lying down, for example, when moving in bed or doing floor exercises.

Open-Chain and Closed-Chain The terms open-chain and closed-chain are often used to describe the concept of standard and reverse actions of a muscle. An extremity or the axial body can be considered a chain of elements. The upper extremity is composed of the shoulder girdle, arm, forearm, and hand; the lower extremity is composed of the pelvic girdle, thigh, leg, and foot; and the axial body is composed of the trunk, neck, and head. Using the upper extremity as an example, if the distal element, the hand, is free to move in the air, the upper extremity is described as being open-chain; if the hand is holding onto a fixed surface of some kind, then the upper extremity is described as being closed-chain. Open-chain scenarios usually result in standard actions. Closed-chain scenarios usually result in reverse actions. When students first study muscle system function and the specific actions of muscles, it is

144

extremely important to not develop too rigid a mindset and only think of the body as operating in open-chain posture in which a muscle is moving its distal (or superior) attachment when it concentrically contracts. Remember that a closed-chain reverse mover action is always theoretically possible. Although some occur only rarely, others occur frequently and play an integral part of everyday movement patterns and activities. Throughout this text, when a muscle is discussed, its corresponding closed-chain reverse mover actions are presented next to its open-chain standard mover actions so that the reader can better understand and appreciate the full realm of that muscle’s function.

145

NAMING A MUSCLE’s ATTACHMENTS: ORIGIN AND INSERTION VS. ATTACHMENTS The classic method to name a muscle’s attachments is to describe one attachment as the origin and the other as the insertion. Although the exact definitions have varied, the origin is usually defined as the more fixed attachment and the insertion as the more mobile attachment. Because the proximal attachment usually is the more fixed attachment and the distal attachment usually is the more mobile attachment, some medical dictionaries even define the origin as the more proximal attachment and the insertion as the more distal attachment. In recent years, use of the terms origin and insertion has been decreasing in favor. Perhaps the reason is that teaching students who are first learning muscles that one attachment of the muscle is usually fixed tends to promote the idea that it is always fixed. This can lead to less flexibility in how students view muscular function because they tend to ignore the closed-chain reverse actions of muscles wherein the insertion stays fixed and the origin moves. Given how often these closed-chain reverse actions actually occur can handicap the student as he or she begins to use and apply muscle knowledge clinically with clients. Furthermore, asking students who are first learning muscles— and who are already overwhelmed trying to remember the names, attachment sites, and actions of the muscles—to now also learn which attachment is designated as the origin and which one is designated as the insertion can be more of a burden. For these reasons, naming a muscle’s attachments by simply describing their location is gaining favor. After all, if the origin can also be defined as the proximal attachment and the insertion can also be defined as the distal attachment, why not skip use of the terms origin and insertion entirely and simply learn the names of the attachments as proximal and distal? Or, if the muscle is running superiorly and inferiorly or medially and laterally, simply name the attachments using these locational terms. This approach is not only simpler, but also has the advantage of pointing out to the student what the fiber direction of the muscle is. This helps the student to see the muscle’s line of pull, which is the most crucial step in figuring out its actions. This text does not use origin/insertion terminology. For those who would like to use these terms, the first attachment given for each muscle is the attachment usually defined as the origin, and the second attachment given is the attachment usually defined as the insertion. What is most important is that the student learns that a muscle has two attachments, that either one can potentially move, and that what determines which one actually does move in any particular scenario depends on its relative resistance to being moved.

Eccentric Contractions We have already discussed concentric contractions. They occur when a muscle contracts with a force that is greater than an attachment’s resistance force to moving. Therefore the muscle moves the attachment and succeeds in shortening. As we have stated, a muscle does not always succeed in shortening when it contracts. If a muscle contracts, attempting to pull in toward its center, but the resistance force is greater than the muscle’s contraction force, not only will the muscle not succeed in shortening, the muscle’s attachment will actually be pulled farther away from the center of the muscle. This will result in a lengthening of the muscle as it contracts. A lengthening contraction is defined as an eccentric contraction. Eccentric contractions happen most often when a muscle is working against gravity. For example, if I am holding an object and want to lower it down to a tabletop, I can let gravity bring my forearm and hand down. However, if the object is fragile, I need to lower it slowly so that it does not crash down onto the table and break. This requires me to contract musculature that opposes gravity so that the object can be lowered slowly and safely (Figure 3-6). In this instance, the muscle contraction’s purpose is not to beat gravity and raise the object; rather its purpose is to lose to gravity, but do so slowly so that the effect of the force of gravity is slowed and the object is lowered slowly. Therefore the purpose of an eccentric contraction is to slow or restrain a joint action that is caused by another force, usually gravity. Because the muscle that eccentrically contracts opposes the joint action movement that is occurring, it is called the antagonist. By definition, when an antagonist muscle contracts, it contracts eccentrically (Box 3-3).

146

BOX 3-3 By definition, when a mover muscle contracts and shortens, it contracts concentrically; and when an antagonist muscle contracts and lengthens, it contracts eccentrically. This does not mean that every muscle that is shortening is concentrically contracting or that every muscle that is lengthening is eccentrically contracting. A muscle can be relaxed as it shortens or lengthens.

FIGURE 3-6 Eccentric contraction. While the force of gravity causes extension of the forearm at the elbow joint to lower the person’s forearm and hand down toward the table, the person’s musculature (brachialis muscle is shown) contracts with an upward pull toward flexion of the forearm at the elbow joint to slow the descent of the glass of water. In this scenario, this brachialis is eccentrically contracting as an antagonist to the joint action that is occurring.

Isometric Contractions A concentric contraction occurs when the force of the muscle’s contraction is greater than the resistance force; an eccentric contraction occurs when the force of the muscle’s contraction is less than the resistance force. An isometric contraction occurs when the force of the muscle’s contraction is equal to the resistance force. Because the two forces are equal, the muscle is able neither to win and shorten nor to lose and lengthen. Instead, it stays the same length as it contracts. This is defined as an isometric contraction. In fact, the term isometric literally means “same length.” If the muscle stays the same length, its attachments do not move. The function of an isometrically contracting muscle can be critically important because it fixes, in other words, stabilizes, its bony attachment (Figure 3-7). This stabilization force can oppose an external force such as gravity or the force created by another individual, as seen in Figures 3-7, A and B, or it can oppose an internal force created by another muscle within the body, as seen in Figure 3-7, C. This concept is often described as core stabilization and is extremely prevalent in the body. Core stabilization usually involves one muscle isometrically contracting to stabilize the proximal attachment of a mover muscle while the mover muscle moves its distal attachment.

147

FIGURE 3-7 Examples of isometric contraction. A, The person’s deltoid muscle isometrically contracts with a force that is equal to the force of gravity so that the person’s arm does not move. B, The musculature of the person arm wrestling is isometrically contracting because the resistance force from the opponent is exactly equal to the muscle’s contraction force. Therefore no movement occurs. C, The rectus abdominis contracts as a core stabilizer to stop the pelvis from moving when the tensor fasciae latae (TFL) contracts to move the thigh. (C, From Muscolino JE: Kinesiology: the skeletal system and muscle function, ed 2, St Louis, 2010, Elsevier. Modeled from Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation, ed 2, St Louis, 2010, Mosby.)

148

ROLES OF MUSCLES As we have seen, muscle function can be viewed very simply: muscles contract and create pulling forces. However, muscles can contract concentrically and shorten as movers, contract eccentrically and lengthen as antagonists, or contract isometrically and stay the same length as stabilizers. All too often, students who first learn muscle function focus only on the muscle’s standard mover concentric contractions. For a deeper understanding of muscle function, we need to understand and appreciate all types of contractions and all roles that a muscle can play in our posture and movement patterns. Only this deeper understanding will allow for the critical thinking necessary for clinical application when it comes to assessment and treatment of clients.

149

SLIDING FILAMENT MECHANISM To truly understand the bigger picture of concentric, eccentric, and isometric contractions, it is helpful to examine the actual mechanism that defines muscle contraction. This mechanism occurs on a microscopic level and is known as the sliding filament mechanism. A muscle is made up of thousands of muscle cells, also known as muscle fibers. Within a muscle, these fibers are bundled together into groups called fascicles. A muscle also contains numerous layers of fibrous fascia that are identical to each other in structure but are given different names based on their location. Endomysium (plural: endomysia) surrounds each individual muscle fiber; perimysium (plural: perimysia) surrounds each fascicle; and epimysium surrounds the entire muscle (Figure 3-8, A). The endomysia, perimysia, and epimysia continue beyond each end of the muscle to create the fibrous tissue attachment of the muscle onto the bone (and/or adjacent soft tissue). If this attachment is cordlike in shape, it is called a tendon. If it is broad and flat, it is called an aponeurosis. The major purpose of the tendon/aponeurosis is to transmit the pulling force of the muscle belly to its attachment (Box 3-4). Although it is common to describe the tendon (or aponeurosis) of a muscle as if it is a separate structure, it is important to understand that the tendon is the continuation of the fibrous fascia that is wholly integral to the muscle’s structure (Figure 3-8, B). For this reason, some texts refer to muscles as muscle-tendon or myofascial units.

BOX 3-4 There are also additional layers of fibrous fascia that envelop and surround groups of muscles within a region of the body. These layers are often called intermuscular septa (singular: septum).

150

FIGURE 3-8 Cross sections of a muscle. A, A muscle is composed of fascicles, which are bundles of fibers. The fibers themselves are filled with myofibrils, which are composed of filaments. Fibrous fascial sheaths called endomysia, perimysia, and epimysium surround the fibers, fascicles, and entire muscle, respectively. B, The fascia of a muscle is integral to its structure (B, Illustrated by Giovanni Rimasti. From Muscolino JE: Reversing anatomy: from muscles to myofascial meridians, Massage Therapy Journal, Summer 2011).

If we look more closely at an individual muscle fiber, we see that it is filled with structures called myofibrils. Myofibrils run longitudinally within the muscle fiber and are composed of filaments (see Figure 3-8, A). These filaments are arranged into structures called sarcomeres. The term sarcomere literally means “unit of muscle.” To truly understand how a muscle functions, it is necessary to understand how a sarcomere functions. Sarcomeres are composed of thin and thick filaments. The thin filaments are actin and are arranged on both sides of the sarcomere and attach to the Z-lines, which are the borders of the sarcomere. The thick filament is a myosin filament and is located in the center and contains projections called heads. When a stimulus from the nervous system is sent to the muscle, binding sites on the actin filaments become exposed and the myosin heads attach onto them, creating crossbridges. The myosin heads then attempt to bend in toward the center of the sarcomere, creating a pulling force on the actin filaments. If the pulling force is sufficiently strong, the actin filaments will be pulled in toward the center of the sarcomere, sliding along the myosin filament, hence the name sliding filament mechanism. This will cause the Z-lines to be pulled in toward the center, and the sarcomere will shorten (Figure 3-9).

151

FIGURE 3-9 A sarcomere is composed of actin and myosin filaments. When the nervous system orders a muscle fiber to contract, myosin heads attach to actin filaments, attempting to pull them in toward the center of the sarcomere. If the pulling force is strong enough, the actin filaments will move and the sarcomere will shorten.

Whatever happens to one sarcomere happens to all the sarcomeres of all the myofibrils of the muscle fiber. If we extrapolate this concept, we see that if all the sarcomeres of a myofibril shorten, the myofibril itself will shorten. If all the myofibrils of a muscle fiber shorten, the muscle fiber will shorten. If enough muscle fibers shorten, the muscle itself will shorten, pulling one or both of its attachments in toward the center, causing motion of the body. This is how a concentric contraction occurs. When a muscle’s contraction was said to create a pulling force toward its center, that pulling force is the sum of the bending forces of all the myosin heads. If the sum of these forces is greater than the resistance to shortening, the actin filaments will be pulled in toward the center of the sarcomere and a concentric contraction occurs. If the sum of these forces is less than the resistance to shortening, the actin filaments will be pulled away from the center of the sarcomere and an eccentric contraction occurs. If the sum of the forces of the myosin heads is equal to the resistance force, the actin filaments will not move and an isometric contraction occurs. Therefore the definition of muscle contraction is having myosin heads creating cross-bridges and pulling on actin filaments.

152

MUSCLE FIBER ARCHITECTURE Not all muscles have their fibers arranged in the same manner. There are two major architectural types of muscle fiber arrangement. They are longitudinal and pennate. A longitudinal muscle has its fibers running along the length of the muscle. A pennate muscle has its fibers running obliquely to the length of the muscle. The major types of longitudinal muscles are demonstrated in Figure 310. The major types of pennate muscles are demonstrated in Figure 3-11. It is worth noting that individual muscle fibers do not necessarily run the entire length of the muscle from attachment to attachment. Rather, they are often shorter and linked in series, end to end.

FIGURE 3-10 Various architectural types of longitudinal muscles. A, Brachialis demonstrates a fusiformshaped (also known as spindle-shaped) muscle. B, Sartorius demonstrates a strap muscle. C, Pronator quadratus demonstrates a rectangular-shaped muscle. D, Rhomboid muscles demonstrate rhomboidalshaped muscles. E, Pectoralis major demonstrates a triangular-shaped (also known as fan-shaped) muscle.

153

FIGURE 3-11 The three architectural types of pennate muscles. Pennate muscles have one or more central tendons running along the length of the muscle from which the muscle fibers come off at an oblique angle. A, Vastus lateralis is a unipennate muscle. (Note: Central tendon is not visible in the anterior view.) B, Rectus femoris is a bipennate muscle. C, Deltoid is a multipennate muscle.

154

LEARNING MUSCLES • Essentially, when learning about muscles, two major aspects must be learned: (1) the attachments of the muscle and (2) the actions of the muscle. • Generally speaking, the attachments of a muscle must be memorized. However, times exist when clues are given about the attachments of a muscle by the muscle’s name.

• For example, the name coracobrachialis tells us that the coracobrachialis muscle has one attachment on the coracoid process of the scapula and that its other attachment is on the brachium (i.e., the humerus). • Similarly, the name zygomaticus major tells us that this muscle attaches onto the zygomatic bone (and that it is bigger than another muscle called the zygomaticus minor). • Unlike muscle attachments, muscle actions do not have to be memorized. Instead, by understanding the simple concept that a muscle pulls at its attachments to move a body part, the action or actions of a muscle can be reasoned out.

Five-Step Approach to Learning Muscles When first confronted with having to study and learn about a muscle, the following five-step approach is recommended: • Step 1: Look at the name of the muscle to see whether it gives you any “free information” that saves you from having to memorize attachments or actions of the muscle. • Step 2: Learn the general location of the muscle well enough to be able to visualize the muscle on your body. At this point, you need only know it well enough to know the following:

• What joint it crosses • Where it crosses the joint (e.g., anteriorly, medially, etc.) • How it crosses the joint (i.e., the direction in which its fibers are running, i.e., vertically or horizontally) • Step 3: Use this general knowledge of the muscle’s location (Step 2) to figure out the actions of the muscle. • Step 4: Go back and learn (memorize, if necessary) the specific attachments of the muscle. • Step 5: Now think about the relationship of this muscle to other muscles (and other soft tissue structures) of the body. Consider the following: Is this muscle superficial or deep? In addition, what other muscles (and other soft tissue structures) are located near this muscle?

Figuring Out a Muscle’s Actions (Step 3 in Detail) • Once you have a general familiarity with a muscle’s location on the body, it is time to begin the process of reasoning out the actions of the muscle. The most important thing that you must keep in mind is the following: • The direction of the muscle fibers relative to the joint that it crosses • By doing this, you can see the following: • The line of pull of the muscle relative to the joint • This line of pull determines the actions of the muscle (i.e., how the contraction of the muscle causes the body parts to move at that joint). • The best approach is to ask the following three questions: 1. What joint does the muscle cross? 2. Where does the muscle cross the joint? 3. How does the muscle cross the joint?

Question 1—What Joint Does the Muscle Cross? • The first thing to determine in figuring out the action(s) of a muscle is to simply know what joint it crosses. • The following rule applies: If a muscle crosses a joint, it can have an action at that joint. (Note: This, of course, assumes that the joint is healthy and allows movement to occur.) • For example, if we look at the coracobrachialis (see Figure 5-7), knowing that it crosses the shoulder (glenohumeral [GH]) joint tells us that it must have an action at the GH joint. • We may not know what the exact action of the coracobrachialis is yet, but at least we now know at what joint it has its actions.

155

• To figure out exactly what these actions are, we need to look at questions 2 and 3. • Note: It is worth pointing out that the converse of the rule about a muscle having the ability to create movement (i.e., an action) at a joint that it crosses is also generally true. In other words, if a muscle does not cross a joint, it cannot have an action at that joint. (There are exceptions to this rule.)

Questions 2 and 3—Where Does the Muscle Cross the Joint? How Does the Muscle Cross the Joint? • These two questions must be looked at together. • The where of a muscle crossing a joint is whether it crosses the joint anteriorly, posteriorly, medially, or laterally. • It is helpful to place a muscle into one of these broad groups because the following general rules apply: muscles that cross a joint anteriorly will usually flex a body part at that joint, and muscles that cross a joint posteriorly will usually extend a body part at that joint; muscles that cross a joint laterally will usually abduct or laterally flex a body part at that joint, and muscles that cross a joint medially will usually adduct a body part at that joint. • The how of a muscle crossing a joint is whether it crosses the joint with its fibers running vertically or horizontally. This is also very important. • To illustrate this idea, we will look at the pectoralis major muscle (see Figure 5-8). The pectoralis major has two parts: (1) a clavicular head and (2) a sternocostal head. The where of these two heads of the pectoralis major crossing the GH joint is the same (i.e., they both cross the GH joint anteriorly). However, the how of these two heads crossing the GH joint is very different. The clavicular head crosses the GH joint with its fibers running primarily vertically; therefore it flexes the arm at the GH joint (because it pulls the arm forward and upward in the sagittal plane, which is termed flexion). However, the sternocostal head crosses the GH joint with its fibers running horizontally, therefore it adducts the arm at the GH joint (because it pulls the arm from lateral to medial in the frontal plane, which is termed adduction). • With a muscle that has a horizontal direction to its fibers, another factor must be considered when looking at how this muscle crosses the joint; that is, whether the muscle attaches to the first place on the bone that it reaches or whether the muscle wraps around the bone before attaching to it. Muscles that run horizontally (in the transverse plane) and wrap around the bone before attaching to it create a rotation action when they contract and pull on the attachment. • For example, the sternocostal head of the pectoralis major does not attach to the first point on the humerus that it reaches. Instead, it continues to wrap around the shaft of the humerus to attach onto the lateral lip of the bicipital groove of the humerus. When the sternocostal head pulls, it medially rotates the arm at the GH joint (in addition to its other actions). • In essence, by asking the three questions of Step 3 of the five-step approach to learning muscles (What joint does a muscle cross? Where does the muscle cross the joint? How does the muscle cross the joint?), we are trying to determine the direction of the muscle fibers relative to the joint. Determining this will give us the line of pull of the muscle relative to the joint, and that will give us the actions of the muscle—saving us the trouble of having to memorize this information!

Functional Group Approach to Learning Muscles Once the five-step approach to learning muscles has been used a few times and learned, it is extremely helpful to begin to transition to the functional group approach to learning muscles. This approach places emphasis on seeing that muscles can be placed into a functional group, based on their common joint action. For example, if the biceps brachii has been studied and it is seen that it crosses the elbow joint anteriorly and flexes it, then it is easier to see and learn that the brachialis also flexes the elbow joint because it also crosses the elbow joint anteriorly. In fact, all muscles that cross the elbow joint anteriorly belong to the functional group of elbow joint flexors. Similarly, all muscles that cross the elbow joint posteriorly belong to the functional group of elbow joint extensors. Applying the functional group approach to the GH joint, it is seen that all muscles that cross the GH joint anteriorly with a vertical fiber direction (or at least a vertical component to their fiber direction) flex it. All muscles that cross it posteriorly with a vertical fiber direction extend it. All muscles that cross it laterally, abduct it; and all muscles that cross it medially adduct it. Functional groups of medial and lateral rotators are not as segregated location-wise, but with closer

156

inspection, it is seen that all medial rotators of the GH joint wrap in the same direction and all lateral rotators wrap in the other direction. Chapter 19 contains illustrations of all the major functional groups of muscles.

Visual and Kinesthetic Exercise for Learning a Muscle’s Actions Rubber Band Exercise • An excellent method for learning the actions of a muscle is to place a large, colorful rubber band (or large, colorful shoelace or string) on your body, or the body of a partner, in the same location that the muscle you are studying is located. • Hold one end of the rubber band at one of the attachment sites of the muscle, and hold the other end of the rubber band at the other attachment site of the muscle. • Make sure that you have the rubber band running/oriented in the same direction as the direction of the fibers of the muscle. If it is not uncomfortable, you may even loop or tie the rubber band (or shoelace) around the body parts that are the attachments of the muscle. • Once you have the rubber band in place, pull one of the ends of the rubber band toward the other attachment of the rubber band to see the action that the rubber band/muscle has on that body part’s attachment. Once done, return the attachment of the rubber band to where it began and repeat this exercise for the other end of the rubber band to see the action that the rubber band/muscle has on the other attachment of the muscle (Box 3-5).

BOX 3-5 When doing the rubber band exercise, it is extremely important that the attachment of the rubber band you are pulling on is pulled exactly toward the other attachment and in no other direction. In other words, your line of pull should be exactly the same as the line of pull of the muscle (which is essentially determined by the direction of the fibers of the muscle). When doing the rubber band exercise, the attachment of the muscle that you are pulling on would be the mobile attachment in that scenario; the end that you do not move is the fixed attachment in that scenario. Further, by doing this exercise twice (i.e., by then repeating it by reversing which attachment you hold fixed and which one you pull on and move), you are simulating the open-chain standard mover action and the closed-chain reverse mover action of the muscle. • By placing the rubber band on your body or your partner’s body, you are simulating the direction of the muscle’s fibers relative to the joint that it crosses. • By pulling either end of the rubber band toward the center, you are simulating the line of pull of the muscle relative to the joint that it crosses. The resultant movements that occur are the mover actions that the muscle would have. This is an excellent exercise both to visually see the actions of a muscle and to kinesthetically experience the actions of a muscle. • This exercise can be used to learn all muscle actions and can be especially helpful for determining actions that may be a little more challenging to visualize, such as rotation actions. • Note: The use of a large, colorful rubber band is more helpful than a shoelace or string, because when you stretch out a rubber band and place it in the location where a muscle would be, the natural elasticity of a rubber band creates a pull on the attachment sites that nicely simulates the pull of a muscle on its attachments when it contracts. • If you can, you should work with a partner to do this exercise. Have your partner hold one of the “attachments” of the rubber band while you hold the other “attachment.” This leaves one of your hands free to pull the rubber band attachment sites toward the center. • A further note of caution: If you are using a rubber band, be careful that you do not accidentally let go and have the rubber band hit you or your partner. For this reason, it would be preferable to use a shoelace or string instead of a rubber band when working near the face.

157

158

PALPATION GUIDELINES Learning to palpate muscles is both a science and an art. The science is based on knowing the attachments and actions of the target muscle that you want to palpate. By knowing its attachments, you know where to place your palpating fingers. By knowing its actions, you know what action to ask the client to perform so that the target muscle contracts and hardens, thereby standing out among the adjacent soft tissues. Also knowing the actions of the adjacent muscles is important so that you can choose the best action of the target muscle when asking it to engage and contract so that ideally an isolated contraction of the target muscle is achieved. The art of muscle palpation involves many other guidelines. For more on muscle palpation, see the Evolve website. For a much fuller discussion of muscle and bone palpation, see The Muscle and Bone Palpation Manual, with Trigger Points, Referral Patterns, and Stretching, 2nd ed (Elsevier, 2015).

159

REVIEW QUESTIONS 1. When the nervous system signals a muscle to contract, what happens? ____________________________ 2. A shortening contraction of a muscle is called a/an _______ contraction. In this contraction, which attachment will be the mobile one that does the moving? ____________________________ ____________________________ 3. What is a reverse mover action? Give an example of when such an action may occur. ____________________________ ____________________________ 4. What is the relationship between muscle actions and open- and closed-chain scenarios? ____________________________ ____________________________ 5. A lengthening contraction of a muscle is called a/an _______ contraction. What causes this type of contraction to occur? ____________________________ ____________________________ 6. A type of muscle contraction in which there is no movement is called a/an _______ contraction. What important function does this type of contraction perform? ____________________________ 7. A tendon is composed of the continuation of what fascial layers surrounding muscle tissue? ____________________________ ____________________________ 8. Sarcomeres are composed of _______ and _______ filaments. When these two filaments interact during a muscle contraction, they form_______. 9. What is the line of thought behind the assertion that muscle actions do not have to be memorized? ____________________________ ____________________________ 10. During muscle palpation, why would it be important to know the actions of muscles adjacent to your target muscle? ____________________________ ____________________________ ____________________________ For answers to these questions, visit http://evolve.elsevier.com/Muscolino/muscular

160

THINK IT THROUGH You open up your favorite news source one day and see this headline: “New Muscle Discovered in the Human Body.” Upon further reading, this yet-to-be-named muscle attaches superiorly at the inferior surface of the medial clavicle and travels inferiorly and posteriorly to attach onto the posterior iliac crest and posterior sacrum (on the same side of the body). Without being given any further information, could you figure out what actions this muscle would have at the joints it crosses? Use Step 3 of the five-step approach to learning muscles as a guide. ____________________________ ____________________________ ____________________________ ____________________________ ____________________________

161

PA R T 2

The Skeletal Muscles of the Upper Extremity OUTLINE Chapter 4: Muscles of the Shoulder Girdle Joints Chapter 5: Muscles of the Glenohumeral Joint Chapter 6: Muscles of the Elbow and Radioulnar Joints Chapter 7: Muscles of the Wrist Joint Chapter 8: Extrinsic Muscles of the Finger Joints Chapter 9: Intrinsic Muscles of the Finger Joints

162

CHAPTER 4

163

Muscles of the Shoulder Girdle Joints CHAPTER OUTLINE Trapezius Rhomboids major and minor Levator scapulae Serratus anterior Pectoralis minor Subclavius

OBJECTIVES After completing this chapter, the student should be able to perform the following for each of the muscles covered in the chapter: 1. Explain the general structure. 2. Explain the general function. 3. State the attachments. 4. State the standard mover actions. 5. State the reverse mover actions. 6. Discuss the line(s) of pull the muscle has and the motion(s) created. 7. State the eccentric antagonist functions. 8. State the isometric stabilization functions. 9. State the nervous innervation.

10. State the arterial supply. 11. Describe the starting position for palpation. 12. Describe the steps for palpation. 13. Discuss the muscle’s relationship to other body structures. 14. Discuss additional information that may help with palpation, assessment, and clinical decision making. CHAPTER OVERVIEW The muscles addressed in this chapter are the muscles whose principal function is usually considered to be movement of the shoulder girdle (scapula and clavicle at the scapulocostal and sternoclavicular joints). Other muscles in the body can also move the shoulder girdle, but they are placed in different chapters because their primary function is usually considered to be at another joint. These muscles cross and move the glenohumeral joint and are covered in Chapter 5. Overview of STRUCTURE Structurally, muscles that move the shoulder girdle attach from the trunk to the scapula and/or clavicle. The bellies of these muscles may be located posteriorly, such as the trapezius, rhomboids, and levator scapulae; or they may be located anteriorly, such as the serratus anterior, pectoralis minor, and subclavius.

164

Overview of FUNCTION The following general rules regarding actions can be stated for the functional groups of muscles of the shoulder girdle: If a muscle attaches to the scapula and its other attachment is superior to the scapula, it can elevate the scapula at the scapulocostal joint. If a muscle attaches to the scapula and its other attachment is inferior to the scapula, it can depress the scapula at the scapulocostal joint. If a muscle attaches to the scapula and its other attachment is medial to the scapula on the posterior side (i.e., closer to the spine), it can retract (adduct) the scapula at the scapulocostal joint. If a muscle attaches to the scapula and its other attachment is lateral to the scapula (i.e., closer to the anterior surface of the body), it can protract (abduct) the scapula at the scapulocostal joint. If a muscle attaches to the scapula away from the axis of scapular rotation (off-axis), it can either upwardly rotate or downwardly rotate the scapula at the scapulocostal joint. Which rotation it performs depends on its line of pull relative to the axis. Any muscle that moves the scapula at the scapulocostal joint can do the same motion of the clavicle at the sternoclavicular joint (and vice versa). Reverse actions of these standard mover actions involve the scapula being fixed and the other attachment (i.e., the trunk) moving toward the scapula at the scapulocostal joint. Note: Motion of the scapula at the scapulocostal joint is largely due to motion of the clavicle at the sternoclavicular joint.

http://evolve.elsevier.com/Muscolino/muscular

165

Posterior View of the Muscles of the Shoulder Girdle Region

FIGURE 4-1 The left side is superficial. The right side is deep (the deltoid, trapezius, sternocleidomastoid, and infraspinatus fascia have been removed).

166

Anterior View of the Muscles of the Shoulder Girdle Region

FIGURE 4-2 The right side is superficial. The left side is deep (the deltoid, pectoralis major, trapezius, scalenes, omohyoid, and muscles of the arm have been removed; the sternocleidomastoid has been cut).

167

Right Lateral View of the Muscles of the Shoulder Girdle and Neck Region

FIGURE 4-3

168

Trapezius (“Trap”) The name, trapezius, tells us that the trapezius is shaped like a trapezoid (

).

Derivation trapezius: Gr. a little table (or trapezoid shape) Pronunciation tra-PEE-zee-us

ATTACHMENTS Entire Muscle: External Occipital Protuberance, Medial ⅓ of the Superior Nuchal Line of the Occiput, Nuchal Ligament, and Spinous Processes of C7-T12 to the Entire Muscle: Lateral ⅓ of the Clavicle, Acromion Process, and the Spine of the Scapula UPPER: the external occipital protuberance, the medial ⅓ of the superior nuchal line of the occiput, the nuchal ligament, and the spinous process of C7 to the UPPER: lateral ⅓ of the clavicle and the acromion process of the scapula MIDDLE: the spinous processes of T1-T5 to the MIDDLE: acromion process and spine of the scapula LOWER: the tubercle at the root of the spine of the scapula to the LOWER: the spinous processes of T6-T12

FUNCTIONS Concentric (Shortening) Mover Actions

ScC joint = scapulocostal joint

Standard Mover Action Notes • The upper trapezius attaches from the scapula inferiorly, to the spine and the occiput superiorly. When the spinal/occipital attachment is fixed and the upper trapezius contracts, it pulls the scapula superiorly toward the head and neck. Therefore the upper trapezius elevates the scapula at the scapulocostal joint. (action 1) • The entire trapezius attaches from the scapula laterally to the spine medially (with its fibers running horizontally in the frontal plane). When the spinal attachment is fixed and the trapezius

169

contracts, it pulls the scapula medially toward the spine. Therefore the entire trapezius retracts (adducts) the scapula at the scapulocostal joint. Of the three parts, the middle trapezius is best at this action because its fibers are oriented most horizontally in the frontal plane. (actions 2, 4, 6) • When the upper trapezius pulls at the acromion process and the lower trapezius pulls at the tubercle of the root of the spine of the scapula, both pull on the scapula in such a manner that the scapula rotates, orienting the glenoid fossa superiorly (both upper and lower trapezius rotate the right scapula counter-clockwise in Figure 4-4 above). Therefore the upper and lower trapezius upwardly rotate the scapula at the scapulocostal joint. (actions 3, 7)

FIGURE 4-4

Posterior view of the right trapezius.

• The lower trapezius attaches from the scapula superiorly to the spine inferiorly. When the spinal attachment is fixed and the lower trapezius contracts, it pulls the scapula inferiorly toward the spine. Therefore the lower trapezius depresses the scapula at the scapulocostal joint. (action 5) • Via the direct pull of the upper trapezius on the clavicle and the indirect pull of the entire trapezius via its attachment to the scapula, the trapezius can create the same actions of the clavicle (at the sternoclavicular joint) as its actions of the scapula (at the scapulocostal joint). (actions 1, 2, 3, 4, 5, 6, 7) • If the lower trapezius pulls the scapula inferiorly toward the spine, and the scapula is fixed to the

170

trunk, the upper trunk (with the scapula fixed to it) will extend in the sagittal plane toward the lower spinal attachment. (action 5)

Reverse Mover Action Notes • The upper trapezius crosses the joints of the cervical spine and the atlanto-occipital joint posteriorly (with fibers running vertically in the sagittal plane). Therefore the upper trapezius extends the neck at the cervical spinal joints and the head at the atlanto-occipital joint. (reverse action 1) • The upper trapezius crosses the joints of the cervical spine and the atlanto-occipital joint posteriorly (with fibers running somewhat horizontally in the transverse plane). When the upper trapezius contracts, it pulls the more medial attachment (the spinal/occipital attachment) toward the lateral attachment (the scapula/clavicle), causing the anterior surface of the neck and/or head to face the opposite side of the body from the side of the body to which the trapezius is attached. Therefore the upper trapezius contralaterally rotates the neck at the cervical spinal joints and the head at the atlanto-occipital joint. (reverse action 2) • The upper trapezius crosses the joints of the cervical spine and the atlanto-occipital joint laterally (with fibers running vertically in the frontal plane). Therefore the upper trapezius laterally flexes the neck at the cervical spinal joints and the head at the atlanto-occipital joint. (reverse action 3) • If the scapula is fixed and the middle and lower trapezius pull on their spinal attachments, the spinous processes will be pulled toward the scapula. This causes the anterior bodies of the vertebrae to come to face the opposite side of the body. Therefore the middle and lower trapezius contralaterally rotate the trunk at the spinal joints. (reverse actions 4, 6) • The lower trapezius crosses the joints of the thoracic spine posteriorly (with its fibers running vertically in the sagittal plane). If the scapula is fixed and the inferior spinal attachment is pulled superiorly toward the scapula, the trunk will extend at the thoracic spinal joints. (reverse action 5)

Motions Because the trapezius has more than one line of pull, it can create more than one motion. 1. The upper trapezius has one line of pull upon the scapula in an oblique plane and therefore creates one motion, which is a combination of elevation, retraction, and upward rotation at the scapulocostal joint. 2. The middle trapezius has one line of pull upon the scapula and therefore creates one motion, which is its action of retraction at the scapulocostal joint. 3. The lower trapezius has one line of pull upon the scapula in an oblique plane and therefore creates one motion, which is a combination of depression, retraction, and upward rotation at the scapulocostal joint. 4. The upper trapezius has one line of pull upon the neck and head in an oblique plane and therefore creates one motion, which is a combination of extension, lateral flexion, and contralateral rotation at the spinal joints.

Eccentric Antagonist Functions Upper 1. Restrains/slows depression, protraction, and downward rotation of the scapula at the scapulocostal joint 2. Restrains/slows flexion, opposite-side lateral flexion, and ipsilateral rotation of the head and neck at the spinal joints

Middle 1. Restrains/slows protraction of the scapula at the scapulocostal joint 2. Restrains/slows ipsilateral rotation of the trunk at the spinal joints

Lower 1. Restrains/slows elevation, protraction, and downward rotation of the scapula at the scapulocostal joint 2. Restrains/slows flexion, ipsilateral rotation, and opposite-side lateral flexion of the trunk at the

171

spinal joints

Isometric Stabilization Functions 1. Stabilizes the scapula and clavicle 2. Stabilizes the head, neck, and trunk at the spinal joints

Additional Notes on Actions 1. In addition to its other actions, the scapula can also tilt. If the medial border of the scapula were to move away from the body wall, contraction of the middle and lower trapezius would pull it back to its position against the body wall. The medial border of the scapula moving toward the body wall is called medial tilt; therefore the middle trapezius and lower trapezius medially tilt the scapula. The action of medial tilt of the scapula is particularly important when the scapula is protracted because the scapula tends to laterally tilt (i.e., wing out) when it protracts. Muscles that medially tilt the scapula prevent the scapula from laterally tilting (winging out). Note: Lateral tilt of the scapula is also referred to as medial rotation of the scapula; medial tilt is also referred to as lateral rotation. 2. The trapezius also attaches to the clavicle. Therefore it acts upon the clavicle as well as the scapula. For each action of the scapula at the scapulocostal joint, the clavicle also moves at the sternoclavicular joint. 3. The muscle actions of the upper trapezius are often written stating that bilateral contraction of the upper trapezius creates extension of the head and neck at the spinal joints. This is certainly true. However, this should not be interpreted to mean that unilateral contraction of the upper trapezius does not cause extension; it does (because of its line of pull being posterior to the spinal joints in the sagittal plane). In fact, unilateral contraction of the upper trapezius will cause extension, same-side (ipsilateral) lateral flexion, and contralateral rotation of the head and neck because its line of pull is across all three planes. So, even though bilateral contraction of the upper trapezius causes pure extension of the head and neck (the opposite lateral flexions cancel each other out and the opposite rotations cancel each other out), unilateral contraction can cause extension too. Note: This concept is true for extension and flexion for all spinal muscles.

I N N E RVAT I O N Spinal Accessory Nerve (CN XI) and C3, C4

A R T E R I A L S U P P LY The Transverse Cervical Artery (a branch of the Thyrocervical Trunk) and the Dorsal Scapular Artery (a branch of the Subclavian Artery)

PA L PAT I O N 1. With the client prone, place palpating hand over the trapezius. 2. Ask the client to actively abduct the arm at the glenohumeral joint and slightly retract the scapula at the scapulocostal joint. 3. Palpate all three parts of the trapezius, lower, middle, and upper, by strumming perpendicular to the fibers. 4. To further bring out the upper trapezius, have the client perform slight extension of the head and neck at the spinal joints.

RELATIONSHIP TO OTHER STRUCTURES The entire trapezius is superficial in the neck and the back (except for the most anterior portion, which is deep to the platysma). Directly deep to the trapezius in the neck are the semispinalis capitis, the splenius capitis, and the levator scapulae. Directly deep to the trapezius in the trunk are the supraspinatus, the rhomboids, and the most superior part of the latissimus dorsi. Directly anterior to the anterior border of the trapezius are the splenius capitis, the levator scapulae, and the scalenes (in the posterior triangle of the neck).

172

The trapezius is located within the superficial back arm line myofascial meridian.

MISCELLANEOUS 1. The trapezius is usually considered to have three functional parts: upper, middle, and lower. 2. The trapezius’ lateral attachments are the same as the proximal attachments of the deltoid— namely, the lateral clavicle, the acromion process, and the spine of the scapula. 3. The upper trapezius is actually quite narrow and thin. Pain in the upper neck that is ascribed to the upper trapezius is often due to the deeper semispinalis capitis. 4. When a person has his or her head inclined anteriorly, the center of gravity of the head is such that it would fall into flexion if it were not for the isometric contraction of head and neck extensor musculature. Because this type of posture is so often assumed, posterior cervical muscles, including the upper trapezius, are probably the most commonly found tight muscles in the human body. 5. Whenever a purse or any type of bag is carried on the shoulder (regardless of the weight), the bag should slide off given the downward slope of the shoulder. However, people usually prevent this by subconsciously elevating the scapula on the side on which the bag is being carried. This posture causes elevators of the scapula (including the upper trapezius) to isometrically contract for long periods of time and therefore become tight and painful. This is a common posture that may cause tightness of the upper trapezius. 6. Whenever a phone is crimped between the head and the shoulder instead of being held by the hand, lateral flexors of the neck and/or elevators of the scapula (including the upper trapezius) on that side of the body must isometrically contract to hold the phone in place. This posture, if held for prolonged periods of time, will cause tension and pain in the muscles involved. This is a common posture that may cause tightness of the upper trapezius. 7. Rounded shoulders is a common postural condition in which the scapulae are protracted (abducted) and depressed (at the scapulocostal joints) and the humeri are medially rotated (at the glenohumeral joints). Given the trapezius’ action of retraction of the scapulae (especially the middle trapezius), when the trapezius muscles are weak, they can contribute to this condition because they are unable to efficiently oppose protraction of the scapulae. This is especially true if the protractors of the scapulae (often the pectoralis minor and major muscles) are tight. 8. The greater occipital nerve, which innervates the posterior half of the scalp, pierces through the upper trapezius (and the semispinalis capitis of the transversospinalis group). When the upper trapezius is tight, the greater occipital nerve can be compressed, causing a tension headache that is felt in the posterior head. (This condition is also known as greater occipital neuralgia.) 9. Whenever a heavy weight is held in the hand, a downward force is exerted on the scapula and clavicle. Another important function of the trapezius is to isometrically contract to support the distal clavicle and the scapula from being pulled inferiorly by this downward force. Therefore long periods of carrying a heavy weight in the hand can result in tension and soreness in the upper trapezius. 10. Whenever the arm is abducted at the glenohumeral joint, the abductor musculature (most likely the deltoid) will create a downward rotation force on the scapula (at the glenohumeral and scapulocostal joints). Upward rotator muscles such as the upper trapezius must contract to fix (stabilize) the scapula from downwardly rotating. Therefore holding the arm in a position of abduction is another common posture that may cause tightness of the upper trapezius. If the arm is abducted approximately 30 degrees or more, the upward rotator muscles must contract to create upward rotation of the scapula as a coupled action to accompany the arm abduction.

173

Rhomboids Major and Minor The name, rhomboids, tells us that these muscles have the geometric shape of a rhombus (a parallelogram or diamond shape). Major tells us that the rhomboid major is the larger muscle of the two; minor tells us that the rhomboid minor is smaller. Derivation rhomb: Gr. rhombos (the geometric shape) oid: Gr. shape, resemblance major: L. larger minor: L. smaller Pronunciation ROM-boyd MAY-jor MY-nor

ATTACHMENTS THE RHOMBOIDS: Spinous Processes of C7-T5 to the THE RHOMBOIDS: Medial Border of the Scapula From the Root of the Spine to the Inferior Angle of the Scapula MINOR: spinous processes of C7-T1 and the inferior nuchal ligament to the MINOR: at the root of the spine of the scapula MAJOR: between the root of the spine and the inferior angle of the scapula to the MAJOR: spinous processes of T2-T5

FUNCTIONS Concentric (Shortening) Mover Actions

ScC joint = scapulocostal joint

Standard Mover Action Notes • The rhomboids attach from the spine medially, to the scapula laterally (with their fibers running somewhat horizontally). When the rhomboids contract, they pull the scapula medially toward the spine; therefore the rhomboids retract (adduct) the scapula at the scapulocostal joint. (action 1)

174

FIGURE 4-5

Posterior view of the right rhomboids major and minor. The levator scapulae has been ghosted in.

• The rhomboids attach from the spine superiorly, to the scapula inferiorly (with their fibers running somewhat vertically). When the rhomboids contract, they pull the scapula superiorly toward the spine; therefore the rhomboids elevate the scapula at the scapulocostal joint. (action 2) • When the rhomboids contract, they pull on the scapula, causing the inferior angle of the scapula to swing up toward the spine. This will cause the glenoid fossa to orient downward; therefore the rhomboids downwardly rotate the scapula at the scapulocostal joint. The rhomboid major is more powerful than the rhomboid minor at downward rotation because its attachment on the scapula is more inferior. From there it has better leverage to rotate the scapula because it attaches farther from the axis of scapular rotation. (action 3) • Downward rotation of the scapula at the scapulocostal joint is the best joint action to engage and palpate the rhomboids. (action 3) • Medial tilt is a motion of the scapula that brings its medial border back against the body wall (medial tilt of the scapula is also known as lateral rotation). In anatomic position, the scapula should be fully medially tilted. The action of medial tilt of the scapula is particularly important when the scapula is protracted because the scapula tends to laterally tilt (i.e., wing out) when it protracts. Therefore muscles that medially tilt the scapula keep the scapula from laterally tilting, or winging out. (action 4)

Reverse Mover Action Notes • When the scapula is fixed and the rhomboids contract, they pull the spinous processes of the vertebrae toward the scapula. This will cause the anterior bodies of these vertebrae to rotate to the opposite side of the body. Therefore the rhomboids can contralaterally rotate the trunk at the spinal joints. (reverse actions 1, 3) • The rhomboids cross the spinal joints posteriorly with a vertical direction to their fibers. If the

175

scapula is fixed, the spinal attachment is pulled inferiorly toward the scapula. Therefore, the rhomboids can extend the trunk at the spinal joints. (reverse action 2)

Motion 1. The rhomboids have one line of pull in an oblique plane and therefore create one motion, which is a combination of retraction, elevation, and downward rotation of the scapula at the scapulocostal joint (as well as medial tilt of the scapula).

Eccentric Antagonist Functions 1. Restrains/slows scapular protraction, depression, upward rotation, and lateral tilt 2. Restrains/slows flexion and ipsilateral rotation of the trunk

Isometric Stabilization Functions 1. Stabilizes the scapula 2. Stabilizes C7-T5 vertebrae

Additional Note on Actions 1. The pull of the rhomboids upon the scapula at the scapulocostal joint is also exerted upon the clavicle at the sternoclavicular joint.

I N N E RVAT I O N The Dorsal Scapular Nerve C4, C5

A R T E R I A L S U P P LY The Dorsal Scapular Artery (a branch of the Subclavian Artery)

PA L PAT I O N 1. With the client seated or prone and the hand placed in the small of the back, place palpating hand between the scapula (at a level that is between the inferior angle and the root of the spine of the scapula) and the spine. 2. Ask the client to move the hand away from the back and feel for the contraction of the rhomboids. 3. Palpate the entirety of the rhomboids.

RELATIONSHIP TO OTHER STRUCTURES The rhomboids are deep to the trapezius. The rhomboid minor is directly superior to the rhomboid major. The rhomboid minor attaches onto the scapula, inferior to the levator scapulae’s attachment onto the scapula. Deep to the rhomboids are the splenius capitis, the splenius cervicis, the serratus posterior superior, and the erector spinae and transversospinalis groups. The rhomboids are located within the spiral line and deep back arm line myofascial meridians.

MISCELLANEOUS 1. The rhomboids major and minor are considered together because they have identical fiber direction and therefore identical lines of pull and identical actions (except for the greater downward rotation force of the rhomboid major). 2. Sometimes there is a small interval of space between the two rhomboids, but often there is not. These two muscles may even blend together. 3. The inferior border of the rhomboids is more easily visualized and palpated than the superior border. 4. The rhomboids blend into the serratus anterior on the anterior side of the scapula (as part of the

176

spiral line myofascial meridian). Because of this blending, the rhomboids and serratus anterior are sometimes referred to as the rhomboserratus muscle. The rhomboserratus musculature acts as a sling that holds and balances the posture of the scapula. 5. The rhomboid muscles are sometimes called the Christmas tree muscles. When you look at the rhomboids bilaterally with the spinal column between them, they look like a Christmas tree in shape. 6. Rounded shoulders is a common postural condition in which the scapulae are protracted (abducted) and depressed at the scapulocostal joints and the humeri are medially rotated at the glenohumeral joints. Given the rhomboids’ actions of both retraction and elevation of the scapulae, when the rhomboid muscles are weak, they can contribute to this condition because they are unable to efficiently oppose protraction and depression of the scapulae. This is especially true if the protractors and/or depressors of the scapulae (often the pectoralis minor and major muscles) are tight.

177

Levator Scapulae The name, levator scapulae, tells us that this muscle elevates the scapula. Derivation levator: L. lifter scapulae: L. of the scapula Pronunciation le-VAY-tor SKAP-you-lee

ATTACHMENTS Transverse Processes of C1-C4 the Posterior Tubercles of the Transverse Processes of C3 and C4 to the Medial Border of the Scapula, from the Superior Angle to the Root of the Spine of the Scapula

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Elevates the scapula at the ScC joint 2. Downwardly rotates the scapula at the ScC joint 3. Retracts the scapula at the ScC joint

Reverse Mover Actions 1. Extends the neck at the spinal joints 2. Laterally flexes the neck at the spinal joints 3. Ipsilaterally rotates the neck at the spinal joints

ScC joint = scapulocostal joint

Standard Mover Action Notes • The levator scapulae attaches from the scapula inferiorly, to the cervical spine superiorly (with its fibers running vertically). When the cervical spine is fixed and the levator scapulae contracts, it pulls the scapula superiorly toward the cervical spine. Therefore the levator scapulae elevates the scapula at the scapulocostal joint. (action 1) • When the cervical spine is fixed and the levator scapulae contracts, it pulls the superior angle of the scapula superiorly and the inferior angle moves superiorly and medially. This causes the glenoid fossa to orient inferiorly. Therefore the levator scapulae downwardly rotates the scapula at the scapulocostal joint. (action 2) • The levator scapulae attaches from the spine medially to the scapula laterally (with its fibers running somewhat horizontally). When the levator scapulae contracts, it pulls the scapula medially toward the spine. Therefore the levator scapulae retracts (adducts) the scapula at the scapulocostal joint. (action 3)

Reverse Mover Action Notes • The levator scapulae crosses the cervical spine posteriorly (with its fibers running vertically in the sagittal plane). When the scapula is fixed and the levator scapulae contracts, it pulls the cervical spine posteriorly and inferiorly toward the scapula. Therefore it extends the neck at the cervical spinal joints. (reverse action 1)

178

FIGURE 4-6

Posterior view of the right levator scapulae. The trapezius has been ghosted in.

• The levator scapulae crosses the cervical spine laterally (with its fibers running vertically in the frontal plane). When the scapula is fixed and the levator scapulae contracts, it pulls the cervical spine laterally and inferiorly toward the scapula. Therefore the levator scapulae laterally flexes the neck at the cervical spinal joints. (reverse action 2) • The levator scapulae’s fibers wrap around the cervical spine to attach onto the transverse processes (with its fibers oriented somewhat horizontally, from posterior to anterior, in the transverse plane). When the levator scapulae contracts, it pulls the transverse processes posteromedially, causing the anterior surface of the neck to face the same side of the body to which the levator scapulae is attached. Therefore the levator scapulae ipsilaterally rotates the neck at the cervical spinal joints. Note the similar line of pull to the adjacent splenius capitis and cervicis muscles, which are also ipsilateral rotators. (reverse action 3)

Motions 1. The levator scapulae has one line of pull in an oblique plane and therefore creates one motion, which is a combination of elevation, downward rotation, and retraction of the scapula at the scapulocostal joint. 2. Regarding its reverse action pull on the neck, the levator scapulae has one line of pull in an oblique plane and therefore creates one motion, which is a combination of extension, lateral flexion,

179

and ipsilateral rotation at the spinal joints.

Eccentric Antagonist Functions 1. Restrains/slows scapular depression, upward rotation, and protraction 2. Restrains flexion, opposite-side lateral flexion, and contralateral rotation of the neck

Isometric Stabilization Functions 1. Stabilizes the scapula 2. Stabilizes the upper cervical spinal joints

Additional Notes on Actions 1. In addition to its other actions, the scapula can also tilt. When the levator scapulae pulls on the scapula, it can pull the scapula in such a manner that the scapula is pulled superiorly and the inferior angle moves superiorly and away from the posterior body wall. The inferior angle of the scapula coming away from the body wall is called upward tilt; therefore the levator scapulae upwardly tilts the scapula at the scapulocostal joint. 2. The pull of the levator scapulae upon the scapula at the scapulocostal joint is also exerted upon the clavicle at the sternoclavicular joint.

I N N E RVAT I O N Dorsal Scapular Nerve C3, C4, C5

A R T E R I A L S U P P LY The Dorsal Scapular Artery (a branch of the Subclavian Artery)

PA L PAT I O N 1. With the client seated and the hand in the small of the back (to relax the trapezius), place palpating hand just superior to the superior angle of the scapula. 2. Ask the client to perform a short, gentle range of motion of elevation of the scapula and feel for the contraction of the levator scapulae. 3. Continue palpating the levator scapulae superiorly into the posterior triangle of the neck (the area between the sternocleidomastoid and the upper trapezius). When palpating in the posterior triangle of the neck, the client’s hand does not need to be in the small of the back and the client can contract more forcefully, and against resistance if desired.

RELATIONSHIP TO OTHER STRUCTURES Inferiorly, the levator scapulae is deep to the trapezius. Superiorly, the levator scapulae is deep to the sternocleidomastoid. There is a part of the middle to upper levator scapulae that is superficial between the trapezius and splenius capitis posteriorly, and the sternocleidomastoid and scalenes anteriorly, in the posterior triangle of the neck. The scapular attachment of the levator scapulae is superior to the attachment of the rhomboids. The transverse process attachment of the levator scapulae is directly deep (anterior) to the transverse process attachment of the splenius cervicis and directly superficial (posterior) to the transverse process attachment of the scalenes. The levator scapulae is located within the deep back arm line myofascial meridian.

MISCELLANEOUS 1. At approximately the midpoint of the levator scapulae, there is a twist in the fibers that creates an increased density in the middle of the muscle. This increased density may be mistaken for a trigger point. (Of course, it is possible that a trigger point may be present at this location.) 2. Because the cervical transverse process attachment of the levator scapulae is more anterior than

180

the scapular attachment, some sources state that the levator scapulae has the ability to pull the scapula anteriorly. Therefore the levator scapulae is able to protract (abduct) the scapula at the scapulocostal joint. Whether the levator scapulae retracts or protracts the scapula is due to the posture of the individual. The more posturally protracted the client is—in other words, the more rounded the client’s shoulders are—the more likely that the levator scapulae can protract the scapula. 3. Many students/therapists have a hard time palpating the superior aspect of the levator scapulae because they do not have a good sense of where the transverse process of the atlas (C1) is located. The transverse process of the atlas is easily palpable just posterior to the posterior border of the ramus of the mandible, directly inferior to the ear, and directly anterior to the mastoid process of the temporal bone.

181

Serratus Anterior The name, serratus anterior, tells us that this muscle has a serrated appearance and is anterior (anterior to the serratus posterior superior and serratus posterior inferior). Derivation serratus: L. a notching anterior: L. in front Pronunciation ser-A-tus an-TEE-ri-or

ATTACHMENTS Ribs one through nine anterolaterally to the Anterior Surface of the Entire Medial Border of the Scapula

FUNCTIONS Concentric (Shortening) Mover Actions

ScC joint = scapulocostal joint

Standard Mover Action Notes • The costal (i.e., rib) attachment of the serratus anterior is more anterior than the scapular attachment. When the serratus anterior contracts, it pulls the scapula anteriorly toward the ribs; therefore the serratus anterior protracts (i.e., abducts) the scapula at the scapulocostal joint. (action 1) • Scapular protraction is important when pushing, punching, and reaching forward with the upper extremity. (action 1) • When the serratus anterior contracts, it pulls on the scapula, causing the inferior angle of the scapula to swing anteriorly and superiorly toward the rib attachment of the serratus anterior (this is especially true of the fibers attaching to the inferior angle of the scapula). This causes the glenoid fossa to orient upward; therefore the serratus anterior upwardly rotates the scapula at the scapulocostal joint. (action 2)

182

FIGURE 4-7

Lateral view of the right serratus anterior.

• Upward rotation of the scapula is a coupled motion that must accompany any abduction and/or flexion of the arm at the glenohumeral joint. The serratus anterior is especially engaged to upwardly rotate the scapula when the arm is flexed at the glenohumeral joint. (action 2) • The serratus anterior is the prime mover of scapular protraction, upward rotation, and medial tilt. (actions 1, 2, 5) • Only the upper fibers of the serratus anterior can elevate the scapula. (action 3) • Only the lower fibers of the serratus anterior can depress the scapula. (action 4) • When the scapula moves at the scapulocostal joint, the clavicle also moves at the sternoclavicular joint. (actions 1, 2, 3, 4) • Medial tilt (also known as lateral rotation) is a motion of the scapula that brings its medial border back against the body wall. In anatomic position, the scapula should be fully medially tilted. If the serratus anterior muscles are weak, the client may have a posture of winged scapulae (laterally tilted scapulae). The fact that the serratus anterior is a strong protractor and medial tilter is especially important because the scapula tends to laterally tilt when it protracts. (action 5) • Downward tilt of the scapula is a motion wherein the inferior angle of the scapula is pulled back against the body wall. In anatomic position, the scapula should be fully downwardly tilted. (action 6)

183

Reverse Mover Action Notes • The reverse action of retracting the trunk (i.e., moving it posteriorly) relative to the scapula at the scapulocostal joint is best seen when performing a push-up. At the point in a push-up when the body has been pushed up away from the ground and the elbow joints are fully extended, there is a small additional degree of upward movement of the body. This motion is created by the serratus anterior pulling the trunk up (posteriorly) toward the scapulae, which are now fixed due to the hands being placed on the floor. (reverse action 1) • The reverse action of depression of the trunk relative to the scapula at the scapulocostal joint might occur if the arms are flexed 180 degrees overhead with the hands fixed to an immovable object when lying down and the body is pulled downward away from the immovable object. (reverse action 2) • The reverse action of elevation of the trunk relative to the scapula at the scapulocostal joint is not very likely to occur. (reverse action 3)

Motion 1. The serratus anterior has one line of pull in an oblique plane and therefore creates one motion, which is a combination of protraction, upward rotation, medial tilt, and downward tilt of the scapula at the scapulocostal joint. (Note: Its upper fibers also elevate the scapula and its lower fibers also depress the scapula.)

Eccentric Antagonist Functions 1. Restrains/slows scapular retraction, downward rotation, depression, elevation, lateral tilt, and upward tilt 2. Restrains/slows protraction, elevation, and depression of the trunk

Isometric Stabilization Functions 1. Stabilizes the scapula 2. Stabilizes the rib cage

Isometric Stabilization Function Note • The stabilization of the scapula function of the serratus anterior is particularly important for maintaining a healthy posture of the scapula. The serratus anterior is the most important muscle for preventing lateral tilt (winging) and upward tilt of the scapula.

Additional Notes on Actions 1. Some sources state that the uppermost fibers of the serratus anterior can downwardly rotate and laterally tilt the scapula. 2. There is controversy regarding whether or not the serratus anterior is involved with respiration by moving the ribcage. Given its attachments onto the ribs, an accessory respiratory action seems likely. 3. The pull of the serratus anterior upon the scapula at the scapulocostal joint is also exerted upon the clavicle at the sternoclavicular joint.

I N N E RVAT I O N The Long Thoracic Nerve C5, C6, C7

A R T E R I A L S U P P LY The Dorsal Scapular Artery (a branch of the Subclavian Artery) and the Lateral Thoracic Artery (a branch of the Axillary Artery) and the Superior Thoracic Artery (a branch of the Axillary Artery)

PA L PAT I O N 1. With the client supine and the arm flexed to 90 degrees at the shoulder joint (hand pointed

184

toward the ceiling), place palpating hand on the rib cage on the lateral trunk between the anterior and posterior axillary folds of tissue. 2. Have the client protract the scapula by pushing the hand toward the ceiling and feel for the contraction of the serratus anterior. Resistance may be added. 3. Once located, try to follow the serratus anterior as far anterior as possible (deep to the pectoralis major) and as far posterior as possible (deep to the latissimus dorsi and the scapula).

RELATIONSHIP TO OTHER STRUCTURES From the posterior perspective, the majority of the serratus anterior lies deep to the scapula and the latissimus dorsi. From the anterior perspective, much of the muscle lies deep to the pectoralis major and minor. The serratus anterior is superficial anterolaterally on the trunk where it meets the external abdominal oblique. The lowest four to five slips of the costal (i.e., rib) attachments of the serratus anterior interdigitate with the external abdominal oblique. The serratus anterior lies next to (anterior to) the subscapularis. The serratus anterior is located within the spiral line myofascial meridian.

MISCELLANEOUS 1. The serrated appearance comes from attaching onto separate ribs, which creates the notched look of a serrated knife. 2. In very well-developed individuals, the serratus anterior looks like ribs standing out in the anterolateral trunk. 3. The serratus anterior can be considered to have three parts: the first part attaching from ribs one and two to the superior angle of the scapula, the second part from ribs two and three to the length of the medial border of the scapula, and the third part from ribs four through nine to the inferior angle of the scapula. The third part (most inferior part) of the serratus anterior is the strongest. 4. The serratus anterior blends into the rhomboids on the anterior side of the scapula (as part of the spiral line myofascial meridian). Because of this blending, the rhomboids and serratus anterior are sometimes referred to as the rhomboserratus muscle. The rhomboserratus musculature acts as a sling that holds and balances the posture of the scapula.

185

Pectoralis Minor The name, pectoralis minor, tells us that this muscle is located in the pectoral (chest) region and is small (smaller than the pectoralis major). Derivation pectoralis: L. refers to the chest minor: L. smaller Pronunciation PEK-to-ra-lis MY-nor

ATTACHMENTS Ribs three through five to the Coracoid Process of the Scapula

the medial aspect

FUNCTIONS Concentric (Shortening) Mover Actions

ScC joint = scapulocostal joint

Standard Mover Action Notes • The pectoralis minor attaches from the scapula posteriorly, to the ribs anteriorly (with its fibers running horizontally). When the pectoralis minor contracts, it pulls the scapula anteriorly toward the rib cage attachment. Therefore the pectoralis minor protracts (abducts) the scapula at the scapulocostal joint. (action 1) • The pectoralis minor attaches from the scapula superiorly, to the ribs inferiorly (with its fibers running vertically). When the pectoralis minor contracts, it pulls the scapula inferiorly toward the rib cage attachment. Therefore the pectoralis minor depresses the scapula at the scapulocostal joint. (action 2) • When the pectoralis minor contracts and pulls on the coracoid process of the scapula, it rotates the scapula in such a manner that the coracoid process is pulled inferiorly and laterally, and the inferior angle of the scapula elevates and moves medially. This rotation causes the glenoid fossa of the scapula to orient downward; therefore the pectoralis minor downwardly rotates the scapula at the scapulocostal joint. (action 3)

186

FIGURE 4-8

Anterior view of the right pectoralis minor. The coracobrachialis and cut pectoralis major have been ghosted in.

• Downward rotation of the scapula at the scapulocostal joint is the best joint action to engage and palpate the pectoralis minor. (action 3) • Lateral tilt is a motion of the scapula that brings its medial border away from the body wall. In anatomic position, the scapula should be fully medially tilted. When the pectoralis minor contracts and pulls on the scapula, it pulls the coracoid process medially in front, which pulls the medial border of the scapula away from the posterior body wall. A tight pectoralis minor can result in a laterally tilted scapula, known in lay terms as a winged scapula. Note: Lateral tilt of the scapula is also known as medial rotation of the scapula. (action 4) • Upward tilt is a motion of the scapula that brings its inferior angle away from the body wall. In anatomic position, the scapula should be fully downwardly tilted. When the pectoralis minor contracts and pulls on the scapula, it pulls the coracoid process down in front, which lifts the inferior angle of the scapula up and away from the posterior body wall. (action 5)

Reverse Mover Action Notes • The pectoralis minor attaches from the scapula superiorly, to the ribs inferiorly (with its fibers running vertically). When the scapula is fixed and the pectoralis minor contracts, it pulls the ribs superiorly toward the scapula. Therefore the pectoralis minor elevates ribs three through five at the sternocostal and costospinal joints. Even though the pectoralis minor can perform five actions of the scapula, only one reverse action of the ribs (elevation) is possible. (reverse action 1) • Elevation of ribs helps to increase the volume of the thoracic cavity and therefore the lungs. Hence the pectoralis minor is a muscle of inspiration. (reverse action 1)

Motion 1. The pectoralis minor has one line of pull in an oblique plane and therefore creates one motion, which is a combination of protraction, depression, downward rotation, lateral tilt, and upward tilt

187

of the scapula at the scapulocostal joint.

Eccentric Antagonist Functions 1. Restrains/slows scapular retraction, elevation, upward rotation, medial tilt, and downward tilt 2. Restrains/slows depression of ribs three through five

Isometric Stabilization Functions 1. Stabilizes the scapula 2. Stabilizes ribs three through five

Additional Note on Actions 1. The pull of the pectoralis minor upon the scapula at the scapulocostal joint is also exerted upon the clavicle at the sternoclavicular joint.

I N N E RVAT I O N The Medial and Lateral Pectoral Nerves C5, C6, C7, C8, T1

A R T E R I A L S U P P LY The Pectoral Branches of the Thoracoacromial Trunk (a branch of the Axillary Artery) and the Posterior Intercostal Arteries (branches of the Aorta) and the Lateral Thoracic Artery (a branch of the Axillary Artery)

PA L PAT I O N 1. With the client seated and the hand relaxed in the small of the back, place palpating fingers just inferior to the coracoid process of the scapula. 2. Have the client lift the hand away from the back and feel for the contraction of the pectoralis minor. 3. Palpate the entirety of the muscle.

RELATIONSHIP TO OTHER STRUCTURES The pectoralis minor is deep to the pectoralis major. Deep to the pectoralis minor are the serratus anterior and the rib cage. The superior attachment of the pectoralis minor is the coracoid process. The short head of the biceps brachii and the coracobrachialis also attach onto the coracoid process of the scapula. The pectoral minor is located within the deep front arm line myofascial meridian.

MISCELLANEOUS 1. The pectoralis minor often attaches to the second rib. 2. The brachial plexus of nerves and the subclavian artery and vein are sandwiched between the pectoralis minor and the rib cage. Therefore this is a common entrapment site for these nerves and blood vessels. If the pectoralis minor is tight, these vessels and nerves may be compressed and the condition is called pectoralis minor syndrome (one of four types of thoracic outlet syndrome). 3. Rounded shoulders is a common postural condition in which the scapulae are protracted (abducted) and depressed (at the scapulocostal joints) and the humeri are medially rotated (at the glenohumeral joints). Given the pectoralis minor’s actions of both protraction and depression of the scapula, when the pectoralis minor muscles are tight, they can significantly contribute to this condition. Note: Rounded shoulders is part of a broader postural distortion pattern that is known as upper crossed syndrome. Upper crossed syndrome also involves increased thoracic kyphosis and an anteriorly held (protracted) head. 4. A tight pectoralis minor, by rounding the shoulders, can also contribute to the clavicle dropping toward the first rib, decreasing the space between these two bones (costoclavicular space). Given that the brachial plexus of nerves and subclavian artery and vein travel in this space, they may be

188

impinged. When this occurs, it is called costoclavicular syndrome (one of the four types of thoracic outlet syndrome).

189

Subclavius The name, subclavius, tells us that this muscle is “under” (i.e., inferior to) the clavicle. Derivation sub: L. under clavius: L. key Pronunciation sub-KLAY-vee-us

ATTACHMENTS First Rib at the junction with its costal cartilage to the Clavicle the middle ⅓ of the inferior surface

FUNCTIONS Concentric (Shortening) Mover Actions

SC joint = sternoclavicular joint

Standard Mover Action Notes • The subclavius attaches from the first rib inferiorly to the clavicle superiorly (with its fibers running somewhat vertically). When the first rib is fixed and the subclavius contracts, it pulls the clavicle inferiorly toward the first rib. Therefore the subclavius depresses the clavicle at the SC joint. (action 1) • The clavicular attachment is also slightly posterior to the first rib attachment, so when the subclavius contracts, it pulls the clavicle anteriorly toward the first rib attachment. Therefore the subclavius protracts the clavicle at the SC joint. (action 2) • When the subclavius contracts, it pulls the clavicle in an anteroinferior direction, causing the anterior surface of the clavicle to face inferiorly (because its pull is anterior to the axis about which the clavicle rotates). Therefore the subclavius downwardly rotates the clavicle at the SC joint. Note: The clavicle is fully downwardly rotated in anatomic position, so the subclavius must downwardly rotate a clavicle that is first upwardly rotated. (action 3) • Given that the clavicle and scapula often move as a unit, when the subclavius moves the clavicle at the SC joint, it can also create the same movement of the scapula at the scapulocostal joint. (actions 1, 2, 3)

190

FIGURE 4-9

Anterior view of the right subclavius. The pectoralis major has been ghosted in.

Reverse Mover Action Notes • The subclavius attaches to the first rib inferiorly, from the clavicle superiorly. When the clavicle is fixed and the subclavius contracts, it pulls the first rib superiorly toward the clavicle. Therefore the subclavius elevates the first rib at the sternocostal and costospinal joints. (reverse action 1) • Elevation of ribs helps to increase the volume of the thoracic cavity and therefore the lungs. Hence the subclavius can assist with inspiration. (reverse action 1)

Motion 1. The subclavius has one line of pull in an oblique plane and therefore creates one motion, which is a combination of depression, protraction, and downward rotation of the clavicle at the SC joint.

Eccentric Antagonist Functions 1. Restrains/slows clavicular elevation, retraction, and upward rotation 2. Restrains/slows depression of the first rib

Isometric Stabilization Functions 1. Stabilizes the clavicle and first rib 2. Indirectly, stabilizes the scapula

Isometric Stabilization Function Note • Many sources state that the major function of the subclavius is to stabilize the clavicle during motions of the arm at the glenohumeral joint. Its medial to lateral horizontal line of pull helps to hold the medial end of the clavicle into the manubrium of the sternum.

Additional Notes on Actions 1. The actions listed here for the subclavius are posited based on the lines of pull of this muscle on the bones to which it attaches. Electromyographic evidence as to when the subclavius is and is not recruited to contract is contradictory and unclear. Therefore considerable controversy exists regarding exactly which actions this muscle performs and when it performs them. 2. The pull of the subclavius upon the clavicle at the sternoclavicular joint is also exerted upon the scapula at the scapulocostal joint.

191

I N N E RVAT I O N A Nerve from the Brachial Plexus C5, C6

A R T E R I A L S U P P LY The Clavicular Branch of the Thoracoacromial Trunk (a branch of the Axillary Artery) and the Suprascapular Artery (a branch of the Thyrocervical Trunk)

PA L PAT I O N 1. With the client supine and the arm medially rotated (to relax and slacken the pectoralis major) and resting at the side of the body, place palpating fingers slightly inferior to the middle ⅓ of the clavicle. 2. Now curl your fingers under the clavicle and feel for the subclavius against the inferior surface of the clavicle. 3. To engage the subclavius, have the client depress the shoulder girdle and feel for its contraction.

RELATIONSHIP TO OTHER STRUCTURES The subclavius is located between the clavicle and the first rib. The subclavius is deep to the pectoralis major. Deep to the subclavius are the brachial plexus of nerves and the subclavian artery and vein. The subclavius is located within the deep front arm line myofascial meridian.

MISCELLANEOUS 1. A somewhat common anomaly is for the subclavius to attach to the coracoid process of the scapula in addition to, or instead of, attaching to the clavicle. 2. The brachial plexus of nerves and the subclavian artery and vein are located deep to the subclavius, between the clavicle and the first rib. If the subclavius is tight, it can pull the clavicle and first rib toward each other, lessening the space between these two bones (costoclavicular space) and possibly compressing these neurovascular structures. When entrapment of these nerves and/or vessels occurs in this location, it is called costoclavicular syndrome (one of four types of thoracic outlet syndrome).

192

REVIEW QUESTIONS 1. What is the rotation action at the head and neck of the upper trapezius? ____________________________ 2. What nerve pierces through the upper trapezius? If this nerve were to be compressed, what symptoms might be experienced? ____________________________ ____________________________ 3. What joint action is optimal for engaging the rhomboids during palpation? ____________________________ 4. Describe the role of the rhomboids in the common postural condition of rounded shoulders. ____________________________ ____________________________ ____________________________ 5. Describe upward tilt of the scapula. What muscle(s) contribute(s) to this motion? ____________________________ ____________________________ ____________________________ 6. What scapular muscle contains a twist of fibers approximately midbelly that may be mistaken for a trigger point? ____________________________ 7. Onto what ribs does the serratus anterior attach? ____________________________ 8. Explain the importance of the serratus anterior as it relates to its action of medial tilt (lateral rotation) of the scapula. ____________________________ ____________________________ ____________________________ 9. What role, if any, does the pectoralis minor play in breathing? ____________________________ ____________________________ 10. What are the attachments of the subclavius? Given this information, what potential problem could be caused by excessive tightness of this muscle? ____________________________ ____________________________ ____________________________ For answers to these questions, visit http://evolve.elsevier.com/Muscolino/muscular

193

THINK IT THROUGH The muscles of this chapter are all listed as scapular stabilizers. What might be the reason that so many muscles can function as scapular stabilizers? ____________________________ ____________________________ ____________________________ ____________________________ ____________________________

194

CHAPTER 5

195

Muscles of the Glenohumeral Joint CHAPTER OUTLINE Deltoid Coracobrachialis Pectoralis major Latissimus dorsi Teres major Rotator cuff group Supraspinatus Infraspinatus Teres minor Subscapularis

OBJECTIVES After completing this chapter, the student should be able to perform the following for each of the muscles covered in the chapter: 1. Explain the general structure. 2. Explain the general function. 3. State the attachments. 4. State the standard mover actions. 5. State the reverse mover actions. 6. Discuss the line(s) of pull the muscle has and the motion(s) created. 7. State the eccentric antagonist functions. 8. State the isometric stabilization functions. 9. State the nervous innervation.

10. State the arterial supply. 11. Describe the starting position for palpation. 12. Describe the steps for palpation. 13. Discuss the muscle’s relationship to other body structures. 14. Discuss additional information that may help with palpation, assessment, and clinical decision making. CHAPTER OVERVIEW The muscles addressed in this chapter are the muscles whose principal function is usually considered to be movement of the glenohumeral (GH) joint. Other muscles in the body can also move the GH joint, but they are placed in different chapters because their primary function is usually considered to be at another joint. These muscles are the biceps brachii and triceps brachii covered in Chapter 6. Overview of STRUCTURE Structurally, muscles of the GH joint are varied. Two of them are large, expansive muscles that

196

arise proximally on the trunk and make their way to attach onto the humerus, crossing the GH joint along the way. One of these two is the pectoralis major, which is anterior; the other is the latissimus dorsi, which is posterior. The rest of the GH joint muscles travel from the scapula (and perhaps the clavicle) to attach to the humerus. These muscles include the deltoid, the coracobrachialis, the teres major, and the rotator cuff group. The larger, more superficial muscles are primarily important for creating motion. The deeper, smaller ones, especially the rotator cuff group muscles, function primarily to stabilize the head of the humerus at the GH joint. Overview of FUNCTION The following general rules regarding actions can be stated for the functional groups of muscles of the GH joint: If a muscle crosses the GH joint anteriorly with a vertical direction to its fibers, it can flex the arm at the GH joint by moving the anterior surface of the arm toward the scapula. If a muscle crosses the GH joint posteriorly with a vertical direction to its fibers, it can extend the arm at the GH joint by moving the posterior surface of the arm toward the scapula. If a muscle crosses the GH joint laterally (superiorly, over the top of the joint), it can abduct the arm at the GH joint by moving the lateral surface of the arm toward the scapula. If a muscle crosses the GH joint medially (inferiorly, below the center of the joint), it can adduct the arm at the GH joint by moving the medial surface of the arm toward the scapula. Medial rotators of the arm wrap around the humerus from medial to lateral, anterior to the GH joint. Lateral rotators of the arm wrap around the humerus from medial to lateral, posterior to the GH joint. Reverse actions of these standard mover actions involve the scapula being moved relative to the humerus at the GH joint (the scapula will also be moved relative to the ribcage at the scapulocostal joint [ScC]). These reverse actions are usually either rotation or tilt actions of the scapula.

http://evolve.elsevier.com/Muscolino/muscular

197

Posterior View of the Muscles of the Glenohumeral Joint and Shoulder Girdle Region

FIGURE 5-1 The left side is superficial. The right side is deep (the deltoid, trapezius, sternocleidomastoid, and infraspinatus fascia have been removed).

198

Anterior View of the Muscles of the Glenohumeral Joint and Shoulder Girdle Region

FIGURE 5-2 The right side is superficial. The left side is deep (the deltoid, pectoralis major, trapezius, sternocleidomastoid, scalenes, omohyoid, and muscles of the arm have been removed).

199

Posterior and Anterior Views of the Muscles of the Glenohumeral Joint

FIGURE 5-3 A, Posterior view. The deltoid, triceps brachii, and latissimus dorsi have been ghosted in. B, Anterior view. The rib cage has been cut. The coracobrachialis has been ghosted in.

200

Anterior View of a Frontal Plane Section through the Right Glenohumeral Joint

FIGURE 5-4

201

Right Lateral Views of the Muscles of the Neck, Shoulder Girdle, and Trunk Regions

FIGURE 5-5

A, Anatomic position. B, The arm is abducted. The triceps brachii has been ghosted in.

202

Deltoid The name, deltoid, tells us that this muscle has a triangular shape similar to the Greek letter delta (Δ). Derivation delta: Gr. the letter delta (Δ) oid: Gr. resemblance Pronunciation DEL-toid

ATTACHMENTS Lateral Clavicle, Acromion Process, and the Spine of the Scapula the lateral ⅓ of the clavicle to the Deltoid Tuberosity of the Humerus

FUNCTIONS Concentric (Shortening) Mover Actions

GH joint = glenohumeral joint

203

FIGURE 5-6 The right deltoid. A, Lateral view. The proximal end of the brachialis has been ghosted in. B, Anterior view. The proximal ends of the pectoralis major and brachialis have been ghosted in. C, Posterior view. The proximal end of the triceps brachii has been ghosted in.

Standard Mover Action Notes • The deltoid crosses over the top of the GH joint on the lateral side (with its fibers running vertically in the frontal plane); therefore it abducts the arm at the GH joint. The anterior and posterior parts of the deltoid can abduct the arm at the GH joint, but the fibers of the middle deltoid have the best line of pull for this action. (action 1) • Although the deltoid can abduct the arm at the GH joint throughout its entire range of motion, the deltoid’s activity is strongest between 90 degrees and 120 degrees. (action 1) • The lowest fibers of the anterior deltoid and posterior deltoid can adduct the arm at the GH joint because they pass inferior to the axis of motion of the GH joint. (action 1) • The anterior deltoid crosses the GH joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the arm at the GH joint. The anterior deltoid is considered to be the prime mover of flexion of the arm at the GH joint. (action 2) • The middle deltoid also has a component of flexion of the arm because the scapula is oriented approximately 30–35 degrees off the frontal plane toward the sagittal plane. (action 2) • The anterior deltoid crosses the GH joint anteriorly from medial on the clavicle to more lateral on the humerus (with its fibers running somewhat horizontally in the transverse plane). However, it does not attach onto the first aspect of the humerus that it reaches, but rather it wraps around the humerus to attach onto the deltoid tuberosity. Therefore when the anterior deltoid contracts, the anterior surface of the humerus rotates medially. This movement is called medial rotation of the arm at the GH joint. (action 3) • When the arm is first abducted 90 degrees, the fibers of the anterior deltoid are lined up horizontally in front of the GH joint. When the humeral attachment is pulled toward the clavicular attachment, the arm is moved horizontally and anteriorly, toward the midline of the body; this motion is called horizontal flexion (or horizontal adduction) of the arm at the GH joint. (action 4) • The anterior deltoid is a powerful horizontal flexor of the arm at the GH joint. In fact, this is the best action to engage and isolate the anterior deltoid from the middle and posterior deltoid when palpating it. (action 4) • The posterior deltoid crosses the GH joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it extends the arm at the GH joint. (action 5) • The posterior deltoid crosses the GH joint posteriorly from medial on the scapula to more lateral on the humerus (with its fibers running somewhat horizontally in the transverse plane).

204

However, it does not attach onto the first aspect of the humerus that it reaches, but rather it wraps around the humerus to attach onto the deltoid tuberosity. Therefore when the posterior deltoid contracts, the anterior surface of the humerus rotates laterally. This movement is called lateral rotation of the arm at the GH joint. (action 6) • When the arm is first abducted 90 degrees, the fibers of the posterior deltoid are lined up horizontally in back of the GH joint. When the humeral attachment is pulled toward the attachment on the spine of the scapula, the arm is moved horizontally and posteriorly, away from the midline of the body; this motion is called horizontal extension (or horizontal abduction) of the arm at the GH joint. (action 7) • The posterior deltoid is a powerful horizontal extensor of the arm at the GH joint. In fact, this is the best action to engage and isolate the posterior deltoid from the middle and anterior deltoid when palpating it. (action 7)

Reverse Mover Action Notes • When the arm is fixed and the deltoid contracts, the deltoid pulls directly on the scapula (and indirectly on the scapula by pulling on the lateral clavicle), pulling the acromion process inferiorly toward the humerus. This causes the inferior angle of the scapula to swing up toward the vertebral column and causes the glenoid fossa to orient downward. Therefore the deltoid downwardly rotates the scapula relative to the humerus at the GH joint and relative to the rib cage at the scapulocostal joint. (reverse action 1) • The reverse action of downward rotation of the scapula by the deltoid is extremely important. If this action is not opposed by an upward rotator muscle (usually the upper trapezius) when the deltoid contracts to abduct the humerus, the humeral head and acromion process of the scapula will approximate each other, pinching the rotator cuff tendon and subacromial bursa between them. (reverse action 1) • If the arm is fixed and the anterior deltoid pulls on the clavicle, the clavicle would normally be moved at the sternoclavicular joint (into depression, downward rotation, and protraction). However, if the clavicle and scapula are fixed to the trunk, the trunk will be pulled with the clavicle and scapula and will be rotated such that it faces the same side of the body on which the anterior deltoid is located. This action may be called ipsilateral rotation of the trunk at the GH joint (in reality, it is a scapular motion relative to the humerus at the GH joint, and the trunk, being fixed to the clavicle and scapula, goes along for the ride, rotating such that it comes to face the same side of the body). (reverse action 2) • If the arm is fixed and the posterior deltoid pulls on the scapula, the scapula would normally be moved at the GH and scapulocostal joints (into downward rotation and downward tilt). However, if the scapula is fixed to the trunk, the trunk will be pulled with the scapula and will be rotated such that it faces the opposite side of the body from where the posterior deltoid is located. This action may be called contralateral rotation of the trunk at the GH joint (in reality, it is a scapular motion relative to the humerus at the GH joint, and the trunk, being fixed to the scapula, goes along for the ride, rotating such that it comes to face the other side of the body). (reverse action 3)

Motions Because the deltoid has more than one line of pull, it can create more than one motion. 1. The anterior deltoid has one line of pull in an oblique plane and therefore creates one motion, which is a combination of flexion, abduction, and medial rotation of the arm at the GH joint. 2. The posterior deltoid has one line of pull in an oblique plane and creates one motion, which is a combination of extension, abduction, and lateral rotation of the arm at the GH joint. 3. The middle deltoid has one line of pull, essentially in one cardinal plane (the frontal plane) and therefore has one motion, which is a cardinal plane action, abduction of the arm at the GH joint.

Eccentric Antagonist Functions 1. Restrains/slows arm adduction, extension, horizontal extension, flexion, horizontal flexion, lateral rotation, and medial rotation 2. Restrains/slows contralateral rotation and ipsilateral rotation of the trunk 3. Restrains/slows clavicular elevation, upward rotation, and retraction 4. Restrains/slows scapular upward rotation and upward tilt

205

Eccentric Antagonist Function Note • Upward tilt of the scapula is a motion in which the inferior angle of the scapula lifts away from the rib cage wall.

Isometric Stabilization Functions 1. Stabilizes the GH joint 2. Stabilizes the scapula and clavicle

Additional Notes on Actions 1. The middle deltoid is not perfectly in the frontal plane; rather it is in the plane of the scapula, which is ideally approximately 30 to 35 degrees anterior to the frontal plane (toward the sagittal plane). Therefore it actually moves the arm into abduction with some flexion, not pure abduction. If a person has “rounded shoulder” posture, the middle deltoid would be further oriented toward the sagittal plane and its motion would be even more biased toward flexion and less toward pure abduction. 2. The most inferior fibers of the anterior and posterior deltoid cross below the (anteroposterior) axis for frontal plane motion of the GH joint; therefore these lowest fibers can adduct the arm at the GH joint.

I N N E RVAT I O N The Axillary Nerve C5, C6

A R T E R I A L S U P P LY The Anterior and Posterior Circumflex Humeral Arteries (branches of the Axillary Artery) and the Pectoral and Deltoid branches of the Thoracoacromial Trunk (a branch of the Axillary Artery)

PA L PAT I O N 1. With the client seated, place palpating hand just distal to the acromion process of the scapula. 2. Have the client abduct the arm at the GH joint and feel for the contraction of the deltoid. Resistance can be added. 3. Continue palpating the deltoid anteriorly for the anterior fibers and posteriorly for the posterior fibers. Palpate all fibers distally to the deltoid tuberosity of the humerus. 4. Note: Horizontal flexion can be used for the anterior fibers; horizontal extension can be used for the posterior fibers.

RELATIONSHIP TO OTHER STRUCTURES The deltoid is superficial and found at the anterior, lateral, and posterior shoulder. It gives the shoulder its characteristic shape. The anterior deltoid lies next to the clavicular head of the pectoralis major. There is usually a small but visually apparent gap between these two muscles. Inferior to the posterior deltoid are the infraspinatus, the teres minor, the teres major, and the triceps brachii. The following muscles all have tendons that are deep to the deltoid: the pectoralis minor, the coracobrachialis, and the short head of the biceps brachii (all attaching to the coracoid process of the scapula); the supraspinatus, the infraspinatus, the teres minor, and the subscapularis (rotator cuff muscles attaching to the greater and lesser tubercles of the humerus); and the pectoralis major, the long head of the biceps brachii, and the long and lateral heads of the triceps brachii. The deltoid is located within the superficial back arm line myofascial meridian.

MISCELLANEOUS 1. The deltoid is considered to have three parts: anterior, middle, and posterior.

206

2. The anterior deltoid crosses the GH joint anteriorly and attaches to the lateral clavicle proximally. The middle deltoid crosses the GH joint laterally and attaches to the acromion process of the scapula proximally. The posterior deltoid crosses the GH joint posteriorly and attaches to the spine of the scapula proximally. 3. The proximal attachments of the deltoid are the same as the lateral attachments of the trapezius— namely, the lateral clavicle, the acromion process, and the spine of the scapula. 4. Note how the deltoid fans around the GH joint. It crosses the GH joint anteriorly, laterally, and posteriorly. This orientation is similar to the orientation of the gluteus medius to the hip joint. Therefore both of these muscles can do the same actions at their respective joints. The deltoid abducts, flexes, extends, medially rotates, and laterally rotates the arm at the GH joint. The gluteus medius abducts, flexes, extends, medially rotates, and laterally rotates the thigh at the hip joint. 5. The anterior and posterior fibers of the deltoid are longitudinal (nonpennate). The middle fibers are multipennate. 6. Because it is pennate, the middle deltoid functions more for stabilization (in the frontal plane). The anterior and posterior fibers, being longitudinal (nonpennate), function more for movement (in the sagittal plane).

207

Coracobrachialis The name, coracobrachialis, tells us that this muscle is related to the coracoid process and the brachium (the arm), hence its attachments onto the coracoid process of the scapula and the humerus. Derivation coraco: Gr. refers to the coracoid process of the scapula brachialis: L. refers to the arm Pronunciation KOR-a-ko-BRA-key-AL-is

ATTACHMENTS Coracoid Process of the Scapula the apex to the Medial Shaft of the Humerus the middle ⅓

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes the arm at the GH joint 2. Adducts the arm at the GH joint 3. Horizontally flexes the arm at the GH joint

Reverse Mover Actions 1. Upwardly tilts the scapula at the GH and ScC joints 2. Downwardly rotates the scapula at the GH and ScC joints 3. Protracts the scapula at the GH and ScC joints

GH joint = glenohumeral joint; ScC joint = scapulocostal joint

Standard Mover Action Notes • The coracobrachialis crosses the GH joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the arm at the GH joint. (action 1) • The coracobrachialis crosses the GH joint medially (with its fibers running vertically in the frontal plane); therefore it adducts the arm at the GH joint. (action 2) • The coracobrachialis is a strong horizontal flexor of the arm at the GH joint. In fact, horizontally flexing the arm against resistance is probably the most effective way to engage and palpate the coracobrachialis. (action 3)

Reverse Mover Action Notes • When the scapula moves relative to the arm at the GH joint, it also moves relative to the rib cage at the scapulocostal joint. (reverse actions 1, 2, 3) • Pulling the coracoid process anteriorly and down causes the inferior angle to lift up and posteriorly away from the rib cage wall. Lifting the inferior angle of the scapula away from the rib cage is called upward tilt. (reverse action 1) • Pulling the coracoid process in front down and laterally causes the inferior angle in back to lift up and medially. This causes the glenoid fossa to orient downward. Therefore the coracobrachialis downwardly rotates the scapula at the scapulocostal joint. (reverse action 2)

208

FIGURE 5-7

Anterior view of the right coracobrachialis. The deltoid and proximal end of the pectoralis minor have been ghosted in.

• If the arm is fixed and in a flexed position, the scapula would be pulled anteriorly toward the arm; therefore it protracts. However, its range of motion will be severely limited because the head of the humerus will obstruct its path of motion. (reverse action 3)

Motion 1. The coracobrachialis has one line of pull in an oblique plane and therefore creates one motion, which is a combination of flexion and adduction of the arm at the GH joint.

Eccentric Antagonist Functions 1. Restrains/slows arm extension, abduction, and horizontal extension 2. Restrains/slows scapular upward rotation, retraction, and downward tilt

Isometric Stabilization Functions 1. Stabilizes the GH joint 2. Stabilizes the scapula

Additional Note on Actions 1. When in anatomic position, the coracobrachialis attaches onto the humerus over the (vertical) axis for transverse plane rotation motions of the arm at the GH joint; therefore when the GH is in anatomic position, the coracobrachialis cannot do rotation. But if the arm is first rotated, the line of pull of the coracobrachialis changes relative to the axis for transverse plane motions. If the arm is laterally rotated, the coracobrachialis can medially rotate the arm back to anatomic position; if the

209

arm is medially rotated, the coracobrachialis can laterally rotate the arm back to anatomic position. Therefore the coracobrachialis can do rotation depending on the position of the arm at the GH joint. In each case it rotates the arm back to anatomic position. Muscles that have this function are sometimes referred to as de-rotators

I N N E RVAT I O N The Musculocutaneous Nerve C5, C6, C7

A R T E R I A L S U P P LY The muscular branches of the Brachial Artery (the continuation of the Axillary Artery) and the Anterior Circumflex Humeral Artery (a branch of the Axillary Artery)

PA L PAT I O N 1. With the client seated with the arm abducted to 90 degrees and laterally rotated, and the forearm flexed at the elbow joint to 90 degrees, place palpating fingers on the medial side of the humerus, approximately halfway down the shaft. 2. Have the client horizontally flex the arm at the GH joint against resistance and feel for the contraction of the coracobrachialis. (Note: It can be challenging to discern the coracobrachialis from the short head of the biceps brachii; the biceps brachii also contracts with flexion of the forearm at the elbow joint.) 3. Note: Be careful with palpation in the medial arm because the median and ulnar nerves and brachial artery are superficial here.

RELATIONSHIP TO OTHER STRUCTURES From an anterior perspective, the coracobrachialis lies deep to the deltoid and the pectoralis major. Proximally, the coracobrachialis lies medial to the short head of the biceps brachii. More distally, the coracobrachialis is deep to the short head of the biceps brachii. The coracobrachialis attaches onto the shaft of the humerus on the medial side between the attachments of the brachialis and the triceps brachii (medial head). The proximal attachment of the coracobrachialis is the coracoid process of the scapula. The short head of the biceps brachii and the pectoralis minor also attach to the coracoid process. The coracobrachialis is located within the deep front arm line myofascial meridian.

MISCELLANEOUS 1. The proximal attachment of the coracobrachialis blends with the proximal attachment of the short head of the biceps brachii. 2. The musculocutaneous nerve pierces through the coracobrachialis.

210

Pectoralis Major The name, pectoralis major, tells us that this muscle is located in the pectoral (chest) region and is large (larger than the pectoralis minor). Derivation pectoralis: L. refers to the chest major: L. larger Pronunciation PEK-to-ra-lis MAY-jor

ATTACHMENTS Medial Clavicle, Sternum, and the Costal Cartilages of Ribs One through Seven the medial ½ of the clavicle, and the aponeurosis of the external abdominal oblique to the Lateral Lip of the Bicipital Groove of the Humerus

FUNCTIONS Concentric (Shortening) Mover Actions

GH joint = glenohumeral joint; ScC joint = scapulocostal joint

Standard Mover Action Notes • The pectoralis major crosses the GH joint anteriorly, from medial on the trunk to lateral on the humerus (with the fibers running horizontally in the frontal plane and crossing below the center of the GH joint). When the pectoralis major contracts, it pulls the humerus medially toward the trunk; therefore the pectoralis major adducts the arm at the GH joint. Adduction is performed primarily by the sternocostal head whose fibers are more horizontal in orientation and located within the frontal plane. (action 1)

211

FIGURE 5-8

Anterior view of the right pectoralis major. The deltoid has been ghosted in.

• The pectoralis major crosses the GH joint anteriorly from the trunk to the humerus. However, the pectoralis major does not attach to the most medial aspect of the humerus but rather wraps around the humerus to attach onto the lateral lip of the bicipital groove (with its fibers running horizontally in the transverse plane). When the pectoralis major contracts, it pulls the humeral attachment posteromedially, causing the anterior surface of the arm to face medially. Therefore the pectoralis major medially rotates the arm at the GH joint. Medial rotation is performed primarily by the sternocostal head, whose fibers are more horizontal in orientation and located in the transverse plane. (action 2) • The clavicular head of the pectoralis major crosses the GH joint anteriorly with the fibers running somewhat vertically (in the sagittal plane); therefore it flexes the arm at the GH joint. The clavicular head of the pectoralis major can only flex the arm up to a position of approximately 60 degrees. (action 3) • The sternocostal head of the pectoralis major crosses the GH joint in such a way (with its fibers running in the sagittal plane) that if the arm is already in a position of flexion, these fibers can pull the arm, which is more anterior, posteriorly back toward the chest. Therefore the pectoralis major can extend the arm at the GH joint. The pectoralis major cannot extend the arm at the GH joint beyond anatomic position. (action 4) • If the arm is in a position of approximately 100 degrees of abduction or more, the line of pull of the clavicular head of the pectoralis major relative to the GH joint shifts from being below the center of the joint to being above it, changing its action from adduction to abduction of the arm at the GH joint. (action 5) • When the arm is first abducted 90 degrees, the fibers of the pectoralis major are lined up in front of the GH joint and can create a powerful horizontal flexion (horizontal adduction) force on the arm at the GH joint. (action 6) • When the pectoralis major pulls on the arm, if the scapula is fixed to the humerus, the scapula will also be moved and will move at the scapulocostal joint. A pulling force of flexion and medial rotation on the arm can result in protraction of the scapula. A pulling force of extension on the arm can result in retraction of the scapula. If the arm is overhead, pulling the humerus and scapula toward the chest will cause depression of the scapula. Note: This will also result in the clavicle performing the same movement at the sternoclavicular joint. (actions 7, 8, 9)

212

• Protraction of the scapula is especially important when performing pushing and throwing actions. Retraction of the scapula is important with pulling motions. (actions 7, 8)

Reverse Mover Action Notes • Reverse actions of the trunk moving relative to the arm can occur at the GH joint if the scapula is fixed to the trunk (so that the trunk and scapula move as a unit relative to the arm) or at the scapulocostal joint if the scapula is fixed to the humerus (so that the trunk moves relative to the scapula/arm as a unit). (reverse actions 1, 2, 3, 5, 6) • The reverse actions of the trunk moving relative to the arm are often performed by people using handicap bars to pull themselves up from a seated position, or by people pulling themselves up stairs using a banister. (reverse actions 1, 2, 3, 5, 6) • If the arm is in an abducted position and fixed, the pectoralis major can pull the trunk laterally toward the arm in the frontal plane. This will result in the trunk laterally deviating toward the same-side arm. (reverse action 1) • If the arm is fixed, the clavicular head of the pectoralis major can pull the trunk down toward the humerus. This will result in flexion of the trunk at the spinal joints (as well as moving the scapula (with the trunk) relative to the humerus at the GH joint). (reverse action 2) • If the arm is in a position of flexion and fixed, the sternocostal head can pull the trunk anteriorly toward the humeral attachment. (reverse action 3) • When the arm is fixed and the pectoralis major contracts, it pulls indirectly on the scapula by pulling on the clavicle, pulling the acromion process inferiorly toward the humerus. This causes the glenoid fossa to orient downward. Therefore the pectoralis major downwardly rotates the scapula relative to the humerus at the GH joint and relative to the rib cage at the scapulocostal joint. (reverse action 4) • When the humerus is fixed, the pectoralis major can pull the trunk toward the arm in the transverse plane. This will result in the trunk ipsilaterally rotating toward the humeral attachment. (reverse action 5) • The reverse action of depressing the scapula (via the pectoralis major’s pull on the humerus) relative to a fixed trunk is to pull the trunk up toward the scapula. (reverse action 6)

Motions Because the pectoralis major has more than one line of pull, it can create more than one motion. 1. The sternocostal head of the pectoralis major has one line of pull in an oblique plane and therefore creates one motion, which is a combination of adduction and medial rotation of the arm at the GH joint (and extension if the arm is first flexed). 2. The clavicular head of the pectoralis major has one line of pull in an oblique plane and therefore creates one motion, which is a combination of adduction, medial rotation, and flexion of the arm at the GH joint.

Eccentric Antagonist Functions 1. Restrains/slows arm abduction, lateral rotation, extension, horizontal extension, flexion, and adduction 2. Restrains/slows scapular retraction, protraction, elevation, and upward rotation 3. Restrains/slows contralateral rotation. Extension, opposite-side lateral deviation, posterior translation, and depression of the trunk

Isometric Stabilization Functions 1. Stabilizes the GH joint 2. Stabilizes the clavicle and scapula

Additional Note on Actions 1. The pectoralis major and the latissimus dorsi are both large, powerful muscles that attach from the trunk to the arm. These two muscles are synergistic to each other with respect to their arm actions in that they both adduct and medially rotate the arm at the GH joint. They are both synergistic and antagonistic to each other with respect to their sagittal plane arm actions; the sternocostal head of the pectoralis major extends the arm at the GH joint and the clavicular head

213

flexes the arm at the GH joint, and the latissimus dorsi extends the arm at the GH joint.

I N N E RVAT I O N The Medial and Lateral Pectoral Nerves C5, C6, C7, C8, T1

A R T E R I A L S U P P LY The Pectoral branches of the Thoracoacromial Trunk (a branch of the Axillary Artery) and the Posterior Intercostal Arteries (branches of the Aorta) and the Lateral Thoracic Artery (a branch of the Axillary Artery)

PA L PAT I O N 1. With the client seated with the arm raised to 90 degrees of abduction at the GH joint, place palpating hand on the belly of the pectoralis major. 2. Have the client horizontally flex the arm against resistance and feel for the contraction of the pectoralis major. 3. Continue palpating the pectoralis major medially and superiorly toward its attachments on the trunk and distally toward its humeral attachment. 4. Note: The anterior axillary fold of tissue is created by the pectoralis major.

RELATIONSHIP TO OTHER STRUCTURES The pectoralis major is superficial in the chest. The pectoralis minor and the subclavius, as well as the proximal attachments of the coracobrachialis and the short and long heads of the biceps brachii, are deep to the pectoralis major. Lateral to the clavicular head of the pectoralis major is the anterior deltoid. The pectoralis major is located within the superficial front arm line and front functional line myofascial meridians.

MISCELLANEOUS 1. Sources differ on how the pectoralis major is divided into parts. Some say that it has clavicular, sternal, costal, and abdominal heads; others lump the sternal and costal heads into a sternocostal head; others omit the abdominal head altogether. Regardless of how it is divided, what is most important to realize is that the pectoralis major has upper fibers and lower fibers that cross the shoulder joint differently and therefore have different actions at the GH joint. 2. Toward its humeral attachment, the pectoralis major has layers: the clavicular fibers are the most superficial (anterior); the sternal fibers are deep to the clavicular fibers; and the costal and abdominal fibers are the deepest (most posterior). 3. The clavicular fibers attach more distally on the humerus; the sternocostal fibers attach more proximally on the humerus. 4. The fibers of the sternocostal head of the pectoralis major twist so that the more superior fibers attach further distally on the humerus; the more inferior fibers attach more proximally on the humerus. Note: The fibers of the latissimus dorsi also twist so that the superior fibers attach distally on the humerus and the inferior fibers attach proximally on the humerus. 5. If the arm is abducted 180 degrees so that the hand is up in the air, the twist in the pectoralis major’s fibers disappears. The higher fibers on the trunk that attach most distally on the humerus are now attaching “higher” on the humerus; and the lower fibers on the trunk that attach most proximally on the humerus are now attaching “lower” on the humerus. 6. The pectoralis major makes up the vast majority of the anterior axillary fold of tissue, which borders the axilla (the armpit) anteriorly.

214

215

Latissimus Dorsi (“Lat”) The name, latissimus dorsi, tells us that this muscle is a wide muscle of the back. Derivation latissimus: L. wide dorsi: L. of the back Pronunciation la-TIS-i-mus DOOR-si

ATTACHMENTS Spinous processes of T7-L5, Posterior Sacrum, and the Posterior Iliac Crest all via the thoracolumbar fascia and the lowest three to four ribs and the inferior angle of the scapula to the Medial Lip of the Bicipital Groove of the Humerus

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Medially rotates the arm at the GH joint

Reverse Mover Actions 1. Contralaterally rotates the pelvis and trunk at the spinal joints

2. Adducts the arm at the GH joint

2. Elevates the same-side pelvis at the LS joint

3. Extends the arm at the GH joint 4. Depresses the scapula at the scapulocostal joint

3. Anteriorly tilts the pelvis at the LS joint and extends the trunk at the spinal joints 4. Elevates the trunk

GH joint = glenohumeral joint; LS joint = lumbosacral joint

Standard Mover Actions Notes • The latissimus dorsi crosses the GH joint from medial on the pelvis and trunk to lateral on the humerus (with its fibers oriented somewhat horizontally in the transverse plane). However, it does not attach onto the first aspect on the humerus that it reaches but rather wraps around to the anterior side of the humerus to attach onto the medial lip of the bicipital groove of the humerus. When the latissimus dorsi contracts, it pulls the medial lip of the bicipital groove posteromedially, causing the anterior surface of the humerus to face medially. Therefore the latissimus dorsi medially rotates the arm at the GH joint. (action 1) • The latissimus dorsi crosses the GH joint posteriorly from medial on the trunk to lateral on the humerus (with fibers running horizontally in the frontal plane). Therefore when the lateral attachment, the humerus, is pulled toward the medial attachment, the trunk, the humerus is pulled toward the midline. Therefore the latissimus dorsi adducts the arm at the GH joint. (action 2)

216

FIGURE 5-9

Posterior view of the right latissimus dorsi.

• The latissimus dorsi crosses the GH joint posteriorly (with the fibers running vertically in the sagittal plane); therefore it extends the arm at the GH joint. (action 3) • The latissimus dorsi attaches from inferiorly on the trunk to superiorly on the humerus (with its fibers running vertically). When the humerus is fixed to the scapula and the latissimus dorsi contracts, it pulls the humerus and the scapula inferiorly. Therefore when the humerus is fixed to the scapula, the latissimus dorsi depresses the scapula at the scapulocostal joint. (action 4) • Because the latissimus dorsi often has an attachment onto the inferior angle of the scapula, it can have the ability to act directly on the scapula. When the trunk is fixed, the fibers between the spine and scapula may depress, retract (i.e., adduct), and/or downwardly rotate the scapula at the scapulocostal joint. When the arm is fixed, the fibers between the arm and scapula may elevate, protract (i.e., abduct), and/or upwardly rotate the scapula at the scapulocostal joint. (action 4)

Reverse Mover Action Notes • With the humeral attachment fixed, the latissimus dorsi—especially the higher more horizontally oriented fibers—will pull the trunk toward the arm, causing the anterior trunk to face the opposite side of the body from which the latissimus dorsi is attached. Therefore the latissimus dorsi contralaterally rotates the trunk at the spinal joints. (reverse action 1) • With the humeral attachment fixed, the latissimus dorsi, by pulling superiorly on the lateral

217

pelvis (because the fibers are running vertically), elevates the pelvis on that side at the LS joint. Note: Elevation of one side of the pelvis causes the other side to depress. (reverse action 2) • When the pelvis elevates, because the LS joint does not allow a great deal of motion, the lower lumbar spine will move with the pelvis, causing the lower lumbar spine to laterally flex under the upper lumbar and thoracic spine. Moving the trunk toward a fixed upper extremity is the type of motion that is performed by people using handicap bars. This motion can occur at the GH joint if the scapula is fixed to the trunk, or at the scapulocostal joint if the scapula is fixed to the humerus. (reverse action 2) • With the humeral attachment fixed, the latissimus dorsi, by crossing the LS joint posteriorly and pulling superiorly on the posterior pelvis, anteriorly tilts the pelvis at the LS joint. (reverse action 3) • Regarding spinal extension, the latissimus dorsi primarily extends the lumbar spine because its fibers are oriented more vertically in the lumbar region (they are more horizontally oriented in the thoracic region). Further, when the pelvis anteriorly tilts, because the LS joint does not allow a great deal of motion, the lower lumbar spine will move with the pelvis, causing the lower lumbar spine to extend under the upper lumbar and thoracic spine. (reverse action 3) • If the arm is first in an elevated position (whether it is flexed, extended, abducted, or adducted) above the trunk and the humeral attachment of the latissimus dorsi is fixed, then, when the latissimus dorsi contracts, it pulls the trunk superiorly toward the humerus (because the fibers are running vertically). Therefore the latissimus dorsi elevates the trunk at the scapulocostal joint. This movement of the trunk relative to the scapula at the scapulocostal joint requires the scapula to be fixed to the arm. This type of motion is performed by people using handicap bars, doing pull-ups, or mountain climbing. This motion can occur at the GH joint if the scapula is fixed to the trunk. (reverse action 4)

Motion 1. The latissimus dorsi has one line of pull upon the arm in an oblique plane and therefore creates one motion, which is a combination of extension, adduction, and medial rotation of the arm at the GH joint. 2. Regarding its reverse action pull on the pelvis, the latissimus dorsi has one line of pull in an oblique plane and therefore creates one motion, which is a combination of elevation, anterior tilt, and contralateral rotation of the pelvis.

Eccentric Antagonist Functions 1. Restrains/slows arm lateral rotation, abduction, and flexion 2. Restrains/slows ipsilateral rotation, same-side depression, and posterior tilt of the pelvis 3. Restrains/slows ipsilateral rotation, flexion, and depression of the trunk 4. Restrains/slows elevation of the scapula

Isometric Stabilization Functions 1. Stabilizes the GH joint 2. Stabilizes the spinal joints 3. Stabilizes the scapula

Additional Notes on Actions 1. The latissimus dorsi does all three GH joint actions necessary to swim the crawl (i.e., freestyle stroke): namely, extension, adduction, and medial rotation of the arm at the GH joint. For this reason, it is sometimes called the swimmer’s muscle. 2. Some sources credit the latissimus dorsi with other actions, including elevation of the lower ribs, ipsilateral rotation of the trunk if the inferior attachment is fixed, retraction of the scapula, and extension of the thoracic spine. Given the direction of fibers of this muscle, it would seem likely that the latissimus dorsi can contribute to these joint actions. 3. Note the similarity of the direction of fibers of the latissimus dorsi to the direction of fibers of the teres major. They have the same actions of the arm at the GH joint. 4. The latissimus dorsi and the pectoralis major are both large, powerful muscles that attach from the trunk to the arm. These two muscles are synergistic to each other with respect to their arm

218

actions in that they both adduct and medially rotate the arm at the GH joint. They are both synergistic and antagonistic to each other with respect to their sagittal plane arm actions; the latissimus dorsi extends the arm at the GH joint; the sternocostal head of the pectoralis major also extends the arm, but the clavicular head flexes the arm at the GH joint.

I N N E RVAT I O N The Thoracodorsal Nerve C6, C7, C8

A R T E R I A L S U P P LY The Thoracodorsal Artery (a branch of the Subscapular Artery) and the dorsal branches of the Posterior Intercostal Arteries (branches of the Aorta)

PA L PAT I O N 1. Both the client and therapist are standing; the therapist is standing to the front and side of the client. 2. Have the client place his or her arm on your shoulder and place your palpating hand on the client’s posterior axillary fold. 3. Have the client attempt to adduct and extend the arm at the GH joint with your shoulder providing resistance, and feel for the contraction of the latissimus dorsi. 4. Continue palpating the latissimus dorsi distally into the axilla toward the humeral attachment and inferiorly toward the lumbar/pelvic attachment.

RELATIONSHIP TO OTHER STRUCTURES The latissimus dorsi is superficial except for a small portion that is deep to the lower trapezius. The distal tendon of the latissimus dorsi runs parallel to the distal tendon of the teres major. The teres major and the latissimus dorsi both attach onto the medial lip of the bicipital groove of the humerus. On the medial lip, the latissimus dorsi attaches more anteriorly, with the teres major attaching directly posterior to it. The latissimus dorsi’s attachments onto the ribs meet with and are approximately perpendicular to the external abdominal oblique’s attachments onto the ribs (inferior to the interdigitation of the serratus anterior with the external abdominal oblique). Deep to the latissimus dorsi in the lumbar region are the serratus posterior inferior, the most posterior attachments of the external and internal abdominal obliques, the erector spinae, and the quadratus lumborum. From the posterior perspective, the serratus anterior is deep to the latissimus dorsi in the axillary region. From the anterior perspective, the humeral attachment of the latissimus dorsi is deep to the pectoralis major, the short head of the biceps brachii, and the coracobrachialis. The attachment of the distal tendon of the latissimus dorsi onto the humerus is between the teres major’s humeral attachment (which is posterior to it) and the pectoralis major’s humeral attachment (which is anterior to it). A saying to help one remember this is “the lady between two majors.” The lady (pronounce it laty) refers to the latissimus dorsi; the two majors refer to the teres major and the pectoralis major. The latissimus dorsi is located within the superficial front arm line and back functional line myofascial meridians.

MISCELLANEOUS 1. The fibers of the latissimus dorsi twist in such a way that the superior fibers attach distally on the humerus and the inferior fibers attach proximally on the humerus (the distal fibers of the sternocostal head of the pectoralis major also twist so that the superior fibers attach most distally at the humeral attachment and the inferior fibers attach most proximally at the humeral attachment). Similar to the pectoralis major, this twist would disappear if the arm were abducted to 180 degrees with the hand up in the air.

219

2. The latissimus dorsi and the teres major make up the vast majority of the posterior axillary fold of tissue, which borders the axilla (armpit) posteriorly. 3. Sometimes the latissimus dorsi blends with the teres major. 4. The scapular attachment of the latissimus dorsi is often absent. 5. Because the humeral attachment of the latissimus dorsi is on the inside of the medial lip at the bicipital groove, it is often described as being in the bicipital groove of the humerus instead of being on the medial lip. 6. The spinal and pelvic attachments of the latissimus dorsi are all via the thoracolumbar fascia, a layer of fascia that covers the deeper muscles of the thoracic and lumbar regions. The thoracolumbar fascia is especially thick in the lumbar region, where it divides into three layers, investing and enveloping the deep muscles of the lumbar region and eventually attaching onto the posterior iliac crest and the spinous processes and transverse processes of the lumbar vertebrae.

220

Teres Major The name, teres major, tells us that this muscle is round and large (larger than the teres minor). Derivation teres: L. round major: L. larger Pronunciation TE-reez MAY-jor

ATTACHMENTS Inferior Angle and Inferior Lateral Border of the Scapula the inferior ⅓ on the dorsal surface to the Medial Lip of the Bicipital Groove of the Humerus

FUNCTIONS Concentric (Shortening) Mover Actions

GH joint = glenohumeral joint; ScC joint = scapulocostal joint

Standard Mover Action Notes • The teres major crosses the GH joint from medial on the scapula to lateral on the humerus (with its fibers oriented somewhat horizontally in the transverse plane). However, it does not attach onto the first aspect on the humerus that it reaches, but rather it wraps around to the anterior side of the humerus to attach onto the medial lip of the bicipital groove of the humerus. Therefore when the teres major contracts and the humeral attachment is pulled toward the scapular attachment, the anterior side of the humerus orients medially. This movement is called medial rotation of the arm at the GH joint, because the anterior side of the humerus rotates medially. (action 1) • The teres major crosses the GH joint posteriorly, from medial on the scapula to lateral on the humerus (with fibers running horizontally in the frontal plane). Therefore when the lateral humeral attachment is pulled toward the medial scapular attachment, the humerus is pulled toward the midline. Therefore the teres major adducts the arm at the GH joint. (action 2) • The teres major crosses the GH joint posteriorly (with the fibers running somewhat vertically in the sagittal plane); therefore it extends the arm at the GH joint. (action 3)

221

FIGURE 5-10

Views of the right teres major. A, Posterior view. The deltoid and teres minor have been ghosted in. B, Anterior view.

Reverse Mover Actions Notes • If the arm is fixed and the teres major contracts, the inferior angle of the scapula is pulled up toward the humerus, resulting in upward rotation of the scapula at the GH joint. When the scapula moves relative to the arm at the GH joint, it also moves relative to the rib cage at the scapulocostal joint. (reverse action 1) • Because the humeral attachment is anterior to the scapular attachment, when the humeral attachment is fixed, the teres major can pull the inferior angle of the scapula anteriorly against the rib cage wall. This motion is called downward tilt of the scapula. (reverse action 2)

Motion 1. The teres major has one line of pull in an oblique plane and therefore creates one motion, which is a combination of extension, adduction, and medial rotation of the arm at the GH joint.

Eccentric Antagonist Functions 1. Restrains/slows arm lateral rotation, abduction, and flexion

222

2. Restrains/slows scapular downward rotation and upward tilt

Eccentric Antagonist Function Note • Upward tilt of the scapula is a motion in which the inferior angle of the scapula lifts posteriorly away from the rib cage wall.

Isometric Stabilization Functions 1. Stabilizes the GH joint 2. Stabilizes the scapula

Additional Note on Actions 1. The teres major is sometimes called the little brother or the little helper of the latissimus dorsi, because they run together between the scapula and the humerus, they attach together onto the medial lip of the bicipital groove of the humerus, and they have the same direction of muscle fibers and therefore the same actions of the arm at the GH joint (medial rotation, adduction, and extension). Perhaps a better name for the teres major would be the big little brother or big little helper, because this muscle is extremely thick (hence the name teres major).

I N N E RVAT I O N The Lower Subscapular Nerve C5, C6, C7

A R T E R I A L S U P P LY The Circumflex Scapular Artery (a branch of the Subscapular Artery) and the Thoracodorsal Artery (a continuation of the Subscapular Artery)

PA L PAT I O N 1. With the client prone with the arm on the table and the forearm hanging off the table, place palpating hand just lateral to the inferior lateral border of the scapula. 2. Have the client medially rotate the arm at the GH joint (this requires the client’s hand to swing posteriorly and up) and feel for the contraction of the teres major. Resistance can be added. 3. Continue palpating the teres major distally into the axilla toward the medial lip of the bicipital groove on the anterior surface of the humerus.

RELATIONSHIP TO OTHER STRUCTURES The teres major lies inferior to the teres minor. The long head of the triceps brachii runs between the teres minor and the teres major. The distal tendon of the teres major runs parallel to the distal tendon of the latissimus dorsi. The teres major and the latissimus dorsi both attach onto the medial lip of the bicipital groove of the humerus. On the medial lip, the teres major attaches posterior to the latissimus dorsi. Deep to the teres major is the scapula. The teres major is located within the superficial front arm line and involved with the deep back arm line myofascial meridians.

MISCELLANEOUS 1. Although the teres major and the teres minor share the word teres in their name (because they are both round in shape) and sit next to each other, they wrap around the humerus in opposite directions and therefore have opposite rotary actions. The teres major wraps around to the anterior side of the GH joint to attach onto the humerus and therefore medially rotates the arm at the GH joint; the teres minor wraps around to the posterior side of the GH joint to attach onto the humerus and therefore laterally rotates the arm at the GH joint. 2. The teres major and the teres minor, because of their different rotary actions of the arm, are in different functional groups. These two muscles are also innervated by different nerves.

223

3. The latissimus dorsi and the teres major make up the vast majority of the posterior axillary fold of tissue that borders the axilla (armpit) posteriorly. 4. The belly and/or distal tendon of the teres major sometimes blend with the latissimus dorsi.

224

Rotator Cuff Group The rotator cuff is a group of four muscles that attach from the scapula to the humerus. The four rotator cuff muscles are the supraspinatus, infraspinatus, teres minor, and subscapularis.

ATTACHMENTS These four muscles are grouped together as the rotator cuff group, because their distal tendons all conjoin to form a cuff across the greater and lesser tubercles of the humerus. The supraspinatus, infraspinatus, and teres minor all attach to the greater tubercle of the humerus. The subscapularis attaches to the lesser tubercle of the humerus.

FUNCTIONS These four muscles are designated as the rotator cuff group, because when they act as movers of the humerus, three of the four muscles rotate the humerus. Even the fourth muscle, the supraspinatus, does a rotary motion in the sense that abduction (and flexion) is considered to be an axial/rotary motion. Functionally, as a group, the rotator cuff muscles are extremely important, because they act to fix (stabilize) the head of the humerus into the glenoid fossa of the scapula whenever the distal end of the humerus is elevated from anatomic position (which can occur with flexion, extension, abduction, and adduction of the arm). When elevating the humerus, it is desirable to elevate only the distal end, so that the hand can be brought to a higher position. When this occurs, the proximal end of the humerus, the head of the humerus, must be stabilized down into the glenoid fossa of the scapula. This is accomplished principally by the rotator cuff group. Given that flexion, extension, abduction, and adduction of the humerus may all involve elevation of the distal humerus, the rotator cuff muscles are more active as stabilizers of the humerus than as movers. Of the four rotator cuff muscles, the two most active in this regard are the infraspinatus and the subscapularis. Their role as fixators (stabilizers) is especially important and necessary, because the ligamentous structure of the shoulder joint is very lax, and the bony shape with the glenoid fossa being so shallow create a very mobile, less stable joint, so stability must be principally provided by the muscles.

MISCELLANEOUS 1. There is a bursa located between the supraspinatus portion of the rotator cuff tendon and the acromion process of the scapula and deltoid muscle superior to it. This bursa is known as the subacromial bursa and/or the subdeltoid bursa.

I N N E RVAT I O N The rotator cuff muscles are innervated by the suprascapular, axillary, and upper and lower subscapular nerves.

A R T E R I A L S U P P LY The rotator cuff muscles receive their arterial supply almost entirely from the suprascapular and circumflex scapular arteries.

225

226

FIGURE 5-11 Views of the right rotator cuff group of muscles. A, Superior view of the right scapula. B, Posterior view showing the supraspinatus, infraspinatus, and teres minor. C, Anterior view showing the subscapularis. The coracobrachialis and cut deltoid and pectoralis major have been ghosted in.

227

Supraspinatus (of Rotator Cuff Group) The name, supraspinatus, tells us that one of this muscle’s attachments is the supraspinous fossa of the scapula. Derivation supraspinatus: L. above the spine (of the scapula) Pronunciation SOO-pra-spy-NAY-tus

ATTACHMENTS Supraspinous Fossa of the Scapula the medial ⅔ to the Greater Tubercle of the Humerus the superior facet

FUNCTIONS Concentric (Shortening) Mover Actions

GH joint = glenohumeral joint; ScC joint = scapulocostal joint

Standard Mover Action Notes • The supraspinatus crosses the GH joint over the top of the joint (with its fibers running first horizontally and then vertically in the frontal plane); therefore it abducts the arm at the GH joint. Note the similarity of the direction of fibers of the supraspinatus to the direction of fibers of the middle deltoid. For quite some time it was believed that the supraspinatus could only initiate abduction of the arm at the GH joint and that the deltoid would have to complete this motion. However, recent research has shown that the supraspinatus is capable of moving the arm through the entire range of motion of abduction at the GH joint. Of course, the supraspinatus does not have the strength of the deltoid. (action 1) • The supraspinatus pulls the arm up into the plane of the scapula. Given that the scapula is approximately 30–35 degrees off the frontal plane toward the sagittal plane, the arm is not pulled purely into abduction in the frontal plane, but somewhat into flexion in the sagittal plane. It is worth noting that if a person has rounded shoulders, the scapulae lie even farther from the frontal plane and closer to the sagittal plane, increasing the component of flexion action by the supraspinatus (and commensurately decreasing the amount of pure abduction in the frontal plane). Some texts refer to the action of the supraspinatus not as abduction, but as scaption to describe the fact that the arm is moved in the plane of the scapula, which is a combination of abduction and flexion. (action 2)

228

FIGURE 5-12

Posterior view of the right supraspinatus. The trapezius and levator scapulae have been ghosted in.

Reverse Mover Action Notes • If the supraspinatus contracts and the humerus is fixed, it pulls on the scapula, causing the glenoid fossa to orient downward. Therefore it downwardly rotates the scapula relative to the humerus at the GH joint. When the scapula moves relative to the arm at the GH joint, it also moves relative to the rib cage at the scapulocostal joint. (reverse action 1)

Motion 1. The supraspinatus has one line of pull in an oblique plane and therefore creates one motion, which is a combination of abduction and flexion of the arm at the GH joint.

Eccentric Antagonist Functions 1. Restrains/slows arm adduction and extension 2. Restrains/slows scapular upward rotation

Isometric Stabilization Function 1. Stabilizes the GH joint 2. Stabilizes the scapula

Isometric Stabilization Function Note • The rotator cuff muscles (supraspinatus, infraspinatus, teres minor, and subscapularis) are extremely important as stabilizers of the humeral head at the GH joint.

Additional Notes on Actions

229

1. Some sources state that the supraspinatus can also contribute to horizontal extension (horizontal abduction) of the arm at the GH joint. 2. When in anatomic position, the supraspinatus cannot create transverse plane rotation of the arm at the GH joint. However, many sources state that when the humerus is first rotated, the supraspinatus can contribute to rotation. Most likely, this rotation function will be to “de-rotate” the humerus back to anatomic position. Therefore the supraspinatus could be considered to be a derotater muscle. 3. The supraspinatus is the only one of the four rotator cuff muscles that does not contribute to a transverse plane rotation action of the arm at the GH joint (from anatomic position).

I N N E RVAT I O N The Suprascapular Nerve C5, C6

A R T E R I A L S U P P LY The Suprascapular Artery (a branch of the Thyrocervical Artery)

PA L PAT I O N 1. With the client seated and the arm hanging at the side, place palpating hand just superior to the spine of the scapula. 2. Have the client perform a short, gentle range of motion of the arm at the GH joint that is approximately 30–35 degrees anterior to pure abduction (i.e., an oblique motion that is a combination of abduction and flexion) and feel for the contraction of the supraspinatus. (Note: If the client is prone, a short, gentle range of pure abduction of the arm can be done.) 3. Palpate the entirety of the belly in the supraspinous fossa and then palpate the distal tendon on the greater tubercle of the humerus (note: the portion deep to the acromion process cannot be palpated).

RELATIONSHIP TO OTHER STRUCTURES The supraspinatus is superior to the spine of the scapula. The proximal attachment of the supraspinatus is deep to the trapezius. The distal tendon of the supraspinatus courses deep to the acromion process of the scapula to then attach distally onto the greater tubercle of the humerus, deep to the deltoid. The supraspinatus is located within the deep back arm line and may be involved with the deep front arm line myofascial meridians.

MISCELLANEOUS 1. The supraspinatus is one of the four rotator cuff muscles. The rotator cuff muscles are the supraspinatus, infraspinatus, teres minor, and subscapularis. Sometimes the rotator cuff muscles are called the SITS muscles; each of the four letters stands for the first letter of the four rotator cuff muscles. Supraspinatus is the first S of SITS. 2. The supraspinatus is one of three muscles that attach onto the greater tubercle of the humerus. The two other muscles that attach here are the infraspinatus and the teres minor. 3. The distal tendon of the supraspinatus adheres to the capsule of the glenohumeral joint, which is deep to the supraspinatus. 4. The acromion process and the deltoid are superior to the supraspinatus. There is a bursa called the subacromial and/or subdeltoid bursa that is located between the supraspinatus and these two other structures. 5. Because of its location between the acromion process of the scapula and the greater tubercle of the humerus, the supraspinatus’s distal tendon is the most commonly injured tendon of the rotator cuff musculature. In fact, the distal tendon of the supraspinatus is sometimes referred to as the critical zone of the rotator cuff tendon. 6. The supraspinatus distal tendon is most often impinged between the greater tubercle and acromion process and therefore injured when the medially rotated arm is abducted approximately

230

90 degrees or more. Whenever abducting the arm, it is important for it to be first laterally rotated. 7. The supraspinatus muscle fiber architecture is pennate.

231

Infraspinatus (of Rotator Cuff Group) The name, infraspinatus, tells us that one of this muscle’s attachments is the infraspinous fossa of the scapula. Derivation infraspinatus: L. below the spine (of the scapula) Pronunciation IN-fra-spy-NAY-tus

ATTACHMENTS Infraspinous Fossa of the Scapula the medial ⅔ to the Greater Tubercle of the Humerus the middle facet

FUNCTIONS Concentric (Shortening) Mover Actions

GH joint = glenohumeral joint; ScC joint = scapulocostal joint

Standard Mover Action Notes • The infraspinatus crosses the GH joint posteriorly from medial to lateral (with its fibers running horizontally in the transverse plane). However, it does not attach onto the first aspect of the humerus that it reaches, but rather it wraps around the humerus to attach onto the greater tubercle. Therefore when the infraspinatus contracts and the humeral attachment is pulled toward the scapular attachment, the posterior side of the humerus moves medially. This movement is called lateral rotation of the arm at the GH joint, because the anterior side of the humerus rotates laterally. Note the similarity of the direction of fibers of the infraspinatus to the direction of fibers of the teres minor. (action 1) • The infraspinatus is a very active muscle because so many arm movements also involve lateral rotation of the arm at the GH joint. (action 1) • When the arm is in a position of 90 degrees of abduction, the infraspinatus’s line of pull is horizontal and can pull the arm directly posteriorly. This motion is called horizontal extension (or horizontal abduction) of the arm at the GH joint. (action 2)

Reverse Mover Action Notes • When the infraspinatus contracts and the humerus is fixed, the scapula is pulled toward the humerus. This causes the medial border of the scapula to lift away from the rib cage wall. This motion is called lateral tilt (or medial rotation) of the scapula. (reverse action 1)

232

FIGURE 5-13

Posterior view of the right infraspinatus. The deltoid has been ghosted in.

• When the scapula moves relative to the arm at the GH joint, it also moves relative to the rib cage at the scapulocostal joint. (reverse action 1)

Motion 1. The infraspinatus has one line of pull in the transverse plane and therefore its motion is its cardinal plane joint action, lateral rotation of the arm at the GH joint.

Eccentric Antagonist Functions 1. Restrains/slows arm medial rotation and horizontal flexion 2. Restrains/slows scapular medial tilt

Eccentric Antagonist Action Note • Medial tilt of the scapula is a motion in which the medial border of the scapula moves toward the rib cage wall (it is also known as lateral rotation of the scapula).

Isometric Stabilization Functions 1. Stabilizes the GH joint

233

2. Stabilizes the scapula

Isometric Stabilization Function Note • The rotator cuff muscles (supraspinatus, infraspinatus, teres minor, and subscapularis) are extremely important as stabilizers of the head of the humerus at the GH joint.

Additional Note on Actions 1. There is controversy regarding whether the infraspinatus can abduct or adduct the arm at the GH joint. Some sources state that the upper fibers can abduct the arm and the lower fibers can adduct the arm. Other sources state that whether one or the other occurs is due to the position of the GH joint at the time. In either case, because of the poor lever arm, the infraspinatus has little strength as an abductor or adductor of the arm at the GH joint.

I N N E RVAT I O N The Suprascapular Nerve C5, C6

A R T E R I A L S U P P LY The Suprascapular Artery (a branch of the Thyrocervical Artery) and the Circumflex Scapular Artery (a branch of the Subscapular Artery)

PA L PAT I O N 1. With the client prone with the arm on the table and the forearm hanging off the table, place palpating hand on the infraspinous fossa. (Make sure you are inferior to the deltoid.) 2. Have the client laterally rotate the arm at the GH joint (this requires the client’s hand to swing anteriorly and up) through a small range of motion and feel for the contraction of the infraspinatus. Resistance can be given. (Note: It can be challenging to discern the infraspinatus from the teres minor.) 3. Palpate the infraspinatus in the infraspinous fossa and then follow it distally to the greater tubercle of the humerus.

RELATIONSHIP TO OTHER STRUCTURES The infraspinatus is inferior to the spine of the scapula. Inferior to the infraspinatus are the teres minor and teres major. Much or most of the infraspinatus is superficial in the infraspinous fossa. Medially, a small portion of the infraspinatus lies deep to the trapezius. Distally, the infraspinatus is deep to the deltoid. The infraspinatus is located within the deep back arm line myofascial meridian.

MISCELLANEOUS 1. The infraspinatus is one of the four rotator cuff muscles. The rotator cuff muscles are the supraspinatus, infraspinatus, teres minor, and subscapularis. Sometimes the rotator cuff muscles are called the SITS muscles; each of the four letters stands for the first letter of the four rotator cuff muscles. Infraspinatus is the I of SITS. 2. The infraspinatus is one of three muscles that attach onto the greater tubercle of the humerus. The two other muscles that attach here are the supraspinatus and the teres minor. 3. The distal tendon of the infraspinatus adheres to the capsule of the glenohumeral joint, which is deep to the infraspinatus. 4. Sometimes there is a bursa located between the infraspinatus and the glenohumeral joint capsule. 5. There is usually a thick layer of fascia overlying the infraspinatus muscle. 6. Sometimes the infraspinatus blends with the teres minor. 7. The infraspinatus muscle fiber architecture is pennate.

234

235

Teres Minor (of Rotator Cuff Group) The name, teres minor, tells us that this muscle is round and small (smaller than the teres major). Derivation teres: L. round minor: L. smaller Pronunciation TE-reez MY-nor

ATTACHMENTS Superior Lateral Border of the Scapula the superior ⅔ of the dorsal surface to the Greater Tubercle of the Humerus the inferior facet

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Laterally rotates the arm at the GH joint 2. Adducts the arm at the GH joint 3. Horizontally extends the arm at the GH joint

Reverse Mover Actions 1. Laterally tilts the scapula at the GH and ScC joints 2. Upwardly rotates the scapula at the GH and ScC joints 3. Laterally tilts the scapula at the GH and ScC joints

GH joint = glenohumeral joint; ScC joint = scapulocostal joint

Standard Mover Action Notes • The teres minor crosses the GH joint posteriorly from medial to lateral (with its fibers running horizontally in the transverse plane). However, it does not attach onto the first aspect of the humerus that it reaches; rather it wraps around the humerus to attach onto the greater tubercle. Therefore when the teres minor contracts and the humeral attachment is pulled toward the scapular attachment, the posterior side of the humerus moves medially. This movement is called lateral rotation of the arm at the GH joint, because the anterior side of the humerus rotates laterally. Note the similarity of the direction of fibers of the teres minor to the direction of fibers of the infraspinatus. (action 1) • The teres minor is a very active muscle because so many arm movements also involve lateral rotation of the arm at the GH joint. (action 1) • There is some controversy regarding whether or not the teres minor can adduct the arm at the GH joint. However, the humeral attachment seems clearly distal enough for it to be below the center of the joint and therefore perform adduction. (action 2) • When the arm is in a position of 90 degrees of abduction, the teres minor’s line of pull is horizontal and can pull the arm directly posteriorly. This motion is called horizontal extension (or horizontal abduction) of the arm at the GH joint. (action 3)

236

FIGURE 5-14

Posterior view of the right teres minor. The teres major has been ghosted in.

Reverse Mover Action Notes • If the arm is fixed and the teres minor contracts, the scapula is pulled toward the humerus, causing the medial border to lift away from the rib cage wall. This motion is called lateral tilt (or medial rotation) of the scapula and occurs at the GH joint. (reverse actions 1, 3) • If the arm is fixed and the teres minor contracts, the inferior angle of the scapula is pulled up toward the humerus, resulting in upward rotation of the scapula at the GH joint. (reverse action 2) • When the scapula moves relative to the arm at the GH joint, it also moves relative to the rib cage at the scapulocostal joint. (reverse actions 1, 2, 3)

Motion 1. The teres minor has one line of pull in an oblique plane and therefore creates one motion, which is a combination of lateral rotation and adduction of the arm at the GH joint.

Eccentric Antagonist Functions 1. Restrains/slows arm medial rotation, abduction, and horizontal flexion

237

2. Restrains/slows scapular medial tilt and downward rotation

Eccentric Antagonist Function Note • Medial tilt of the scapula is a motion in which the medial border of the scapula moves toward the rib cage wall (it is also known as lateral rotation of the scapula).

Isometric Stabilization Functions 1. Stabilizes the GH joint 2. Stabilizes the scapula

Isometric Stabilization Function Note • The rotator cuff muscles (supraspinatus, infraspinatus, teres minor, and subscapularis) are extremely important as stabilizers of the head of the humerus at the GH joint. However, some sources claim that the stabilization function of the teres minor is not as important as that of the other rotator cuff muscles. Perhaps this is because the teres minor has an adduction action that would oppose any abduction movement, and its posterior location would oppose flexion movements as well. However, its vertical direction of fibers makes it ideal to hold the head of the humerus down into the glenoid fossa as the distal end elevates.

Additional Note on Actions 1. Some sources state that the teres minor can assist with extension of the arm at the GH joint. If so, this would most likely occur when the arm is first in a position of flexion.

I N N E RVAT I O N The Axillary Nerve C5, C6

A R T E R I A L S U P P LY The Circumflex Scapular Artery (a branch of the Subscapular Artery) and the Posterior Circumflex Humeral Artery (a branch of the Axillary Artery)

PA L PAT I O N 1. With the client prone with the arm on the table and the forearm hanging off the table, place palpating hand just lateral to the superior lateral border of the scapula and feel for the round belly of the teres minor. 2. Have the client laterally rotate the arm at the GH joint (this requires the client’s hand to swing anteriorly and up) and feel for its contraction. Resistance can be given. (Note: It can be challenging to discern the teres minor from the infraspinatus.) 3. Palpate the teres minor distally to the greater tubercle of the humerus.

RELATIONSHIP TO OTHER STRUCTURES The medial portion of the teres minor is superficial and is located at the lateral border of the scapula. The lateral portion of the teres minor is deep to the deltoid. On the scapula the teres minor attaches just superior to the attachment of the teres major. The teres minor lies between the infraspinatus (which is superior to it) and the teres major (which is inferior to it). The long head of the triceps brachii runs between the teres minor and the teres major. The teres minor is located within the deep back arm line myofascial meridian.

MISCELLANEOUS 1. The teres minor is one of the four rotator cuff muscles. The rotator cuff muscles are the supraspinatus, infraspinatus, teres minor, and subscapularis. Sometimes the rotator cuff muscles are called the SITS muscles; each of the four letters stands for the first letter of the four rotator cuff

238

muscles. Teres minor is the T of SITS. 2. The teres minor is one of three muscles that attach onto the greater tubercle of the humerus. The other two muscles that attach here are the supraspinatus and the infraspinatus. 3. Although the teres minor and the teres major share the word teres in their name (because they are both round in shape) and sit next to each other, they wrap around the humerus in opposite directions and therefore have opposite rotary actions. The teres minor wraps around to the posterior side of the GH joint to attach onto the humerus and therefore laterally rotates the arm at the GH joint; the teres major wraps around to the anterior side of the shoulder joint to attach onto the humerus and therefore medially rotates the arm at the GH joint. 4. The teres major and the teres minor, because of their different rotary actions of the arm, are in different functional groups. These two muscles are also innervated by different nerves. 5. The distal tendon of the teres minor adheres to the capsule of the glenohumeral joint, which is deep to the teres minor. 6. Sometimes the teres minor blends with the infraspinatus. 7. The teres minor muscle fiber architecture is longitudinal (nonpennate).

239

Subscapularis (of Rotator Cuff Group) The name, subscapularis, tells us that one of this muscle’s attachments is the subscapular fossa of the scapula. Derivation subscapularis: L. refers to the subscapular fossa Pronunciation sub-skap-u-LA-ris

ATTACHMENTS Subscapular Fossa of the Scapula to the Lesser Tubercle of the Humerus

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Medially rotates the arm at the GH joint

Reverse Mover Actions 1. Medially tilts the scapula at the GH and ScC joints

GH joint = glenohumeral joint; ScC joint = scapulocostal joint

Standard Mover Action Note • The subscapularis crosses the GH joint anteriorly from medial to lateral (with its fibers running horizontally in the transverse plane). However, it does not attach onto the first aspect of the humerus that it reaches, but rather wraps around the humerus to attach onto the lesser tubercle. Therefore when the subscapularis contracts and the humeral attachment is pulled toward the scapular attachment, the anterior side of the humerus moves medially. This movement is called medial rotation of the arm at the GH joint, because the anterior side of the humerus rotates medially. Note the similarity of the direction of fibers of the subscapularis to the direction of fibers of the latissimus dorsi and teres major. (action 1)

Reverse Mover Action Note • If the subscapularis contracts and the humerus is fixed, the subscapularis pulls the medial border of the scapula against the rib cage wall. This is called medial tilt (or lateral rotation) of the scapula and occurs relative to the humerus at the GH joint. When the scapula moves relative to the arm at the GH joint, it also moves relative to the rib cage at the scapulocostal joint. (reverse action 1)

Motion 1. The subscapularis has one line of pull in the transverse plane and therefore its motion is its cardinal plane joint action, medial rotation of the arm at the GH joint.

Eccentric Antagonist Functions 1. Restrains/slows arm lateral rotation and scapular lateral tilt

240

FIGURE 5-15 Anterior view of the right subscapularis. Most of the rib cage has been removed. The coracobrachialis has been ghosted in. The pectoralis major and deltoid have been cut and ghosted in.

Eccentric Antagonist Function Note • Lateral tilt of the scapula is a motion in which the medial border of the scapula lifts away from the rib cage wall (it is also known as medial rotation of the scapula).

Isometric Stabilization Functions 1. Stabilizes the GH joint 2. Stabilizes the scapula

Isometric Stabilization Function Note • The rotator cuff muscles (supraspinatus, infraspinatus, teres minor, and subscapularis) are extremely important as stabilizers of the head of the humerus at the GH joint.

Additional Notes on Actions 1. There is controversy regarding whether or not the subscapularis can perform other actions of the arm at the GH joint. Some sources state that depending on the position of the arm, the subscapularis adducts, abducts, flexes, extends, or horizontally flexes the arm. However, given that its attachment site is so far proximal on the humerus, its lever arm would be poor. If these actions did occur, they would be very weak. 2. Because the lower fibers of the subscapularis are below the axis of motion of the GH joint, they may contribute to the reverse action of upward rotation of the scapula at the GH and scapulocostal joints.

I N N E RVAT I O N

241

The Upper and Lower Subscapular Nerves C5, C6

A R T E R I A L S U P P LY The Circumflex Scapular Artery (a branch of the Subscapular Artery) and the Dorsal Scapular and Suprascapular Arteries (both either direct or indirect branches of the Subclavian Artery) and the Lateral Thoracic Artery (a branch of the Axillary Artery)

PA L PAT I O N 1. Have the client supine with the arm that is on the side of the target muscle being palpated crossed on the chest such that the elbow is lying on the abdomen and the hand is holding onto the opposite-side shoulder (the arm will be slightly flexed and adducted at the GH joint, and the forearm will be flexed at the elbow joint). Further, have the client place the opposite-side hand on top of the elbow of the arm that is crossed on the chest, gently holding the elbow down. 2. Place your superior (cephalad) hand under the scapula, grasping the medial border of the scapula and pulling the scapula laterally (protracting the scapula at the scapulocostal joint). 3. With your inferior (palpating) hand, press in between the scapula and the ribcage of the client and then press with your finger pads oriented posteriorly against the anterior surface of the scapula for the subscapularis. 4. To engage the subscapularis, have the client medially rotate the arm at the GH joint by simply pressing the forearm against the chest. 5. Palpate as much of the subscapularis as possible.

RELATIONSHIP TO OTHER STRUCTURES From the posterior perspective, the subscapularis is deep to the scapula and superficial to the rib cage. From the anterior perspective, the subscapularis is deep to the entire rib cage and superficial to the scapula. The anterior wall of the subscapularis faces the serratus anterior. Both the subscapularis and the serratus anterior are located between the scapula and the rib cage. From the anterior perspective, the distal tendon of the subscapularis is deep to the proximal tendons of the short head of the biceps brachii and the coracobrachialis. The distal tendon of the subscapularis attaches onto the humerus directly proximal to the distal tendons of the latissimus dorsi and teres major. The subscapularis is involved with the deep back arm line myofascial meridian.

MISCELLANEOUS 1. The subscapularis is one of the four rotator cuff muscles. The rotator cuff muscles are the supraspinatus, infraspinatus, teres minor, and subscapularis. Sometimes the rotator cuff muscles are called the SITS muscles; each of the four letters stands for the first letter of the four rotator cuff muscles. Subscapularis is the last S of SITS. 2. The subscapularis (along with the latissimus dorsi and teres major) is located in the posterior axillary fold of tissue, which borders the axilla (armpit) posteriorly. 3. The distal tendon of the subscapularis adheres to the capsule of the glenohumeral joint, which is deep to the subscapularis. 4. There is a bursa located between the subscapularis muscle and the scapula called the subscapular bursa. 5. The subscapularis muscle fiber architecture is pennate.

242

Review Questions 1. Abduction of the arm at the GH joint by the deltoid is strongest between _______ and _______ degrees of motion. 2. The deltoid is considered to have _______ parts. Which part(s) is (are) pennate/nonpennate? How does this structure relate to muscle function? ____________________________ ____________________________ ____________________________ 3. The most effective way to engage and palpate the coracobrachialis is to _______ the _______ at the _______ joint against resistance. 4. What nerve pierces through the coracobrachialis? ____________________________ 5. If the arm is placed in approximately 100 degrees or more or abduction, what is the effect on the pectoralis major? ____________________________ 6. What muscle is sometimes called the swimmer’s muscle? Why is this nickname appropriate? ____________________________ ____________________________ 7. What structure runs between the teres minor and the teres major? ____________________________ 8. What four muscles make up the rotator cuff group? What is the major function of the group as a whole? ____________________________ ____________________________ ____________________________ 9. Define the term scaption. ____________________________ ____________________________ 10. What muscle of the rotator cuff group does NOT contribute to a transverse plane rotary action of the arm at the GH joint? ____________________________ For answers to these questions, visit http://evolve.elsevier.com/Muscolino/muscular

243

Think It Through When palpating the adjacent teres major and minor, the set up for palpation is nearly identical. Using the information on muscle locations, attachments, and actions provided in this chapter, explain how a therapist could go about differentiating between these two muscles. ____________________________ ____________________________ ____________________________ ____________________________ ____________________________

244

CHAPTER 6

245

Muscles of the Elbow and Radioulnar Joints CHAPTER OUTLINE Elbow joint: Biceps brachii Brachialis Brachioradialis Triceps brachii Anconeus Radioulnar joints: Pronator teres Pronator quadratus Supinator

OBJECTIVES After completing this chapter, the student should be able to perform the following for each of the muscles covered in the chapter: 1. Explain the general structure. 2. Explain the general function. 3. State the attachments. 4. State the standard mover actions. 5. State the reverse mover actions. 6. Discuss the line(s) of pull the muscle has and the motion(s) created. 7. State the eccentric antagonist functions. 8. State the isometric stabilization functions. 9. State the nervous innervation.

10. State the arterial supply. 11. Describe the starting position for palpation. 12. Describe the steps for palpation. 13. Discuss the muscle’s relationship to other body structures. 14. Discuss additional information that may help with palpation, assessment, and clinical decision making. CHAPTER OVERVIEW The muscles addressed in this chapter are the muscles whose principal function is usually considered to be movement of the elbow and radioulnar joints. Other muscles in the body can also move the elbow and radioulnar joints, but they are placed in different chapters because their primary function is usually considered to be at another joint. These muscles cross the wrist joint and/or finger joints and are covered in Chapters 7 and 8. Overview of STRUCTURE Structurally, muscles that flex the elbow joint are located anteriorly. The biceps brachii and

246

brachialis have their bellies in the arm; the brachioradialis has its belly in the forearm. In all cases, they cross the elbow joint anteriorly. The muscles that extend the elbow joint are located posteriorly. The triceps brachii has its belly in the arm and the anconeus has its belly in the forearm; they both cross the elbow joint posteriorly. Structurally, the pronator teres and pronator quadratus are located anteriorly and the supinator is located posteriorly. Note: Some muscles covered in this chapter cross and move both the elbow and radioulnar joints.

Compartments of the Arm: Arm musculature is usually divided into anterior and posterior compartments. • The anterior compartment contains the biceps brachii superficially and the brachialis and coracobrachialis deeper. • The posterior compartment contains the triceps brachii. Overview of FUNCTION The following general rules regarding actions can be stated for the functional groups of muscles of the elbow and radioulnar joints: If a muscle crosses the elbow joint anteriorly with a vertical direction to its fibers, it can flex the forearm at the elbow joint by moving the anterior surface of the forearm toward the anterior surface of the arm. If a muscle crosses the elbow joint posteriorly with a vertical direction to its fibers, it can extend the forearm at the elbow joint by moving the posterior surface of the forearm toward the posterior surface of the arm. Reverse actions at the elbow joint involve moving the arm toward the forearm at the elbow joint. This usually occurs when the hand (and therefore the forearm) is fixed by holding onto an immovable object. If a muscle crosses the radioulnar joints anteriorly with a horizontal orientation to its fibers, it will pronate the forearm at the radioulnar joints. If a muscle crosses the radioulnar joints posteriorly with a horizontal direction to its fibers, it will supinate the forearm at the radioulnar joints. Reverse actions of these standard mover actions at the radioulnar joints involve moving the ulna toward the radius at the radioulnar joints. This usually occurs when the hand (and therefore the radius) is fixed by holding onto an immovable object.

http://evolve.elsevier.com/Muscolino/muscular

247

Anterior Views of the Muscles of the Right Elbow Joint

FIGURE 6-1

A, Superficial view. B, Deep view with the pectoralis major, deltoid, and biceps brachii cut and/or removed.

248

Posterior Views of the Muscles of the Right Elbow Joint

FIGURE 6-2

A, Superficial view. B, Deep view with deltoid ghosted in.

249

Lateral View of the Muscles of the Right Elbow Joint

FIGURE 6-3

250

Medial View of the Muscles of the Right Elbow Joint

FIGURE 6-4

251

Views of the Muscles of the Right Radioulnar Joints

FIGURE 6-5

A, Anterior view. The biceps brachii and brachialis have been cut and ghosted in. B, Posterior view.

252

Transverse Plane Cross Sections of the Right Arm

FIGURE 6-6

Transverse plane cross sections of the right arm. Perspective: Right is lateral and left is medial. Top is anterior and bottom is posterior.

253

Biceps Brachii The name, biceps brachii, tells us that this muscle has two heads and lies over the brachium (the arm). Derivation biceps: L. two heads brachii: L. Pronunciation BY-seps BRAY-key-eye

ATTACHMENTS LONG HEAD: Supraglenoid Tubercle of the Scapula SHORT HEAD: Coracoid Process of the Scapula

the apex to the Radial Tuberosity and the bicipital aponeurosis into deep fascia overlying the common flexor belly/tendon

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes the forearm at the elbow joint

Reverse Mover Actions 1. Flexes the arm at the elbow joint

2. Supinates the forearm at the RU joints

2. Supinates the ulna at the RU joints and medially rotates the arm at the GH joint

3. Flexes the arm at the GH joint 4. Abducts the arm at the GH joint (long head)

3. Upwardly tilts the scapula at the GH and ScC joints

5. Adducts the arm at the GH joint (short head)

5. Downwardly rotates and laterally tilts the scapula at the GH and ScC joints

6. Horizontally flexes the arm at the GH joint

6. Protracts the scapula at the GH and ScC joints

4. Downwardly rotates the scapula at the GH and ScC joints

RU joints = radioulnar joints; GH joint = glenohumeral joint; ScC joint = scapulocostal joint

Standard Mover Action Notes • The biceps brachii crosses the elbow joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the forearm at the elbow joint. (action 1) • When the forearm is pronated, the biceps brachii attachment onto the radial tuberosity is deep between the radius and the ulna. Thus the fibers wrap around the medial side of the proximal radius. When the biceps brachii pulls at the radial tuberosity, the head of the radius will laterally rotate and the distal radius will move around the distal ulna. This movement of the radius is called supination. Therefore the biceps brachii supinates the forearm at the RU joints. (action 2)

254

FIGURE 6-7

Anterior view of the right biceps brachii. The coracobrachialis and distal end of the brachialis have been ghosted in.

• The biceps brachii is a supinator in addition to being a flexor of the forearm. For this reason, engaging and palpating the biceps brachii is best accomplished by having the client flex the forearm when it is fully supinated. The biceps brachii can supinate the forearm at the RU joints regardless of the position of flexion/extension of the elbow joint. However, the biceps brachii is strongest with regard to supination of the forearm when the forearm is partially flexed. (actions 1, 2) • The biceps brachii crosses the shoulder joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the arm at the shoulder joint. (action 3) • Similar to the middle deltoid, the long head of the biceps brachii crosses over the top of the GH joint. Therefore it abducts the arm at the GH joint. Its ability to abduct increases if the arm is in a position of lateral rotation. Laterally rotating the arm places the long head’s tendon more in the frontal plane for abduction. (action 4) • The short head of the biceps brachii crosses the GH joint from medial to lateral (with its fibers running horizontally in the frontal plane) below the center of the joint. Therefore it adducts the arm at the GH joint. It makes sense that the short head of the biceps brachii can adduct the arm at the GH joint because it has the same line of pull relative to the GH joint as the coracobrachialis. (action 5) • If the arm is first abducted to 90 degrees, the biceps brachii fibers are oriented horizontally across the anterior GH joint so they can pull the arm horizontally toward the midline. This action is called horizontal flexion (horizontal adduction) of the arm at the GH joint. Horizontal flexion of

255

the arm by the biceps brachii is primarily due to the short head. The more the arm is medially rotated, the more the long head can contribute to this action. (action 6)

Reverse Mover Action Notes • If the forearm is fixed, the biceps brachii pulls the anterior surface of the arm toward the anterior surface of the forearm. This action is flexion of the arm at the elbow joint. Flexion of the arm at the elbow joint is extremely important and occurs whenever a person grasps an immovable object and pulls his or her body toward it (examples include using a handicap bar or using a handrail when going up stairs). (reverse action 1) • Supination and pronation are usually thought of as having a mobile radius move around a fixed ulna. However, if the hand is held fixed (perhaps by holding onto an immovable object), the radius will also be fixed with regard to rotation motions because the wrist joint does not allow rotation. Therefore the reverse action of supination of the radius at the RU joints involves a mobile ulna supinating around a fixed radius. This motion of the ulna is effectively medial rotation. However, when the ulna medially rotates around the radius, because the elbow joint also does not allow rotation motions, the humerus moves with the ulna; this results in medial rotation of the arm at the GH joint. (reverse action 2) • If the biceps brachii contracts and the arm and forearm are fixed, the scapula is pulled forward in the sagittal plane toward the arm. This causes the scapula to upwardly tilt relative to the arm at the GH joint by lifting its inferior angle away from the rib cage wall. When the scapula moves relative to the arm at the GH joint, it also moves relative to the rib cage at the scapulocostal joint. (reverse action 3) • The reverse action of the long head moving the arm into abduction relative to the scapula in the frontal plane is to move the scapula into downward rotation relative to the arm in the frontal plane. This motion occurs at the GH joint. When the scapula moves at the GH joint, it also moves relative to the rib cage at the scapulocostal joint. (reverse action 4) • The reverse action of adduction of the arm at the GH joint is also to downwardly rotate the scapula at the GH and scapulocostal joints because the line of pull of the short head is on the same side of the axis for scapular rotation as is the long head’s line of pull. (reverse action 5) • Because the short head crosses the GH joint more anteriorly than the long head, it will also tend to pull the medial border of the scapula away from the rib cage wall. This is known as lateral tilt (medial rotation) of the scapula. (reverse action 5) • Protraction of the scapula relative to the humerus is not a very likely reverse action. (reverse action 6)

Motions Because the biceps brachii has more than one line of pull, it can create more than one motion. 1. The long head of the biceps brachii has one line of pull in an oblique plane and therefore creates one motion, which is a combination of flexion and supination of the forearm at the elbow and RU joints, respectively (assuming that the forearm starts in a position of extension and pronation), and flexion and abduction of the arm at the GH joint. 2. The short head of the biceps brachii has one line of pull in an oblique plane and therefore creates one motion, which is a combination of flexion and supination of the forearm at the elbow and RU joints, respectively (assuming that the forearm starts in a position of extension and pronation), and flexion and adduction of the arm at the GH joint.

Eccentric Antagonist Functions 1. Restrains/slows elbow joint extension 2. Restrains/slows RU joint pronation 3. Restrains/slows arm extension, horizontal extension, adduction, abduction, and lateral rotation 4. Restrains/slows scapular upward rotation, downward tilt, medial tilt, and retraction.

Eccentric Antagonist Function Notes • Restraining/slowing extension of the forearm at the elbow joint is extremely important when lowering an object in a careful and controlled manner. • Restraining/slowing reverse actions occur when the distal attachment of the biceps brachii is

256

fixed, usually by the hand holding onto an immovable object (closed-chain kinematics).

Isometric Stabilization Functions 1. Stabilizes the elbow, RU, and GH joints 2. Stabilizes the scapula

Additional Note on Actions 1. Some sources state that the biceps brachii can medially rotate the arm at the GH joint. This would require the forearm to be fixed at the radioulnar and elbow joints so that the muscle’s pull on the forearm is transferred to the arm.

I N N E RVAT I O N The Musculocutaneous Nerve C5, C6

A R T E R I A L S U P P LY The muscular branches of the Brachial Artery (the continuation of the Axillary Artery) and the Anterior Circumflex Humeral Artery (a branch of the Axillary Artery)

PA L PAT I O N 1. With the client seated or supine and the forearm supinated, place palpating hand on the anterior arm and feel for the biceps brachii. 2. Have the client flex the forearm at the elbow joint and feel for the contraction of the biceps brachii. Resistance can be added. 3. Continue palpating the biceps brachii proximally and distally toward its attachments. 4. Note: Be careful with palpation in the medial arm, because the median and ulnar nerves and brachial artery are superficial here.

RELATIONSHIP TO OTHER STRUCTURES Proximally, the biceps brachii is deep to the deltoid and deep to the distal tendon of the pectoralis major. The remainder of the biceps brachii is superficial. From an anterior perspective, the brachialis lies deep to the biceps brachii. The short head of the biceps brachii lies lateral to the coracobrachialis. The proximal attachment of the short head of the biceps brachii is the coracoid process of the scapula. The coracobrachialis and the pectoralis minor also attach to the coracoid process. The long head of the biceps brachii courses through the bicipital groove of the humerus. The long head of the biceps brachii then courses through the joint cavity of the glenohumeral joint; therefore it is intra-articular. Directly medial to the belly and distal tendon of the biceps brachii are the brachial artery and the median nerve. The bicipital aponeurosis is superficial to the common flexor belly/tendon and does not attach into bone. The biceps brachii is located within the deep front arm line and involved with the superficial front arm line myofascial meridians.

MISCELLANEOUS 1. The bicipital groove of the humerus is named the bicipital groove, because the long head of the biceps brachii courses through it. (The bicipital groove of the humerus is also known as the intertubercular groove, because it is located between the two tubercles of the humerus.) 2. The proximal attachment of the short head of the biceps brachii blends with the proximal attachment of the coracobrachialis at the coracoid process of the scapula. 3. The bicipital aponeurosis is also known as the lacertus fibrosis.

257

258

Brachialis The name, brachialis, tells us that this muscle attaches to the brachium (the arm). Derivation brachialis: L. refers to the arm Pronunciation BRAY-key-AL-is

ATTACHMENTS Distal ½ of the Anterior Shaft of the Humerus to the Ulnar Tuberosity

and the coronoid process of the ulna

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes the forearm at the elbow joint

Reverse Mover Actions 1. Flexes the arm at the elbow joint

Standard Mover Action Notes • The brachialis crosses the elbow joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the forearm at the elbow joint. (action 1) • Even though the biceps brachii is more well known for flexing the elbow joint, the brachialis is actually the prime mover (most powerful mover) of flexion of the elbow joint. (action 1) • The brachialis is especially engaged with elbow joint flexion if the forearm is fully pronated (because the biceps brachii and brachioradialis would supinate a fully pronated forearm in addition to flexing it). For this reason, the brachialis is best engaged and palpated by asking the client to flex the forearm when it is fully pronated. (action 1)

Reverse Mover Action Note • If the forearm is fixed, the brachialis pulls the anterior surface of the arm toward the anterior surface of the forearm. This action is flexion of the arm at the elbow joint. The reverse action of flexion of the arm at the elbow joint is extremely important and occurs whenever a person grasps an immovable object and pulls his or her body toward it. Examples include using a handicap bar or using a handrail when going up stairs. (reverse action 1)

259

FIGURE 6-8

Anterior view of the right brachialis; the coracobrachialis and distal end of the deltoid have been ghosted in.

Motion 1. The brachialis has one line of pull in the sagittal plane, and therefore its motion is its cardinal plane joint action, flexion of the elbow joint.

Eccentric Antagonist Function 1. Restrains/slows elbow joint extension

Eccentric Antagonist Function Note • Restraining/slowing extension of the forearm at the elbow joint is extremely important when lowering an object in a careful and controlled manner.

Isometric Stabilization Function 1. Stabilizes the elbow joint

I N N E RVAT I O N The Musculocutaneous Nerve

260

C5, C6, C7

A R T E R I A L S U P P LY Muscular branches of the Brachial Artery (the continuation of the Axillary Artery)

PA L PAT I O N 1. With the client seated or supine and the forearm fully pronated at the radioulnar joints, place palpating hand on the distal lateral arm. 2. Have the client flex the forearm further with a short, gentle range of motion and feel for the contraction of the brachialis. If resistance is added, add only gentle resistance. 3. The brachialis can be palpated on the lateral side of the arm and the medial side of the arm. It can also be palpated anteriorly through the biceps brachii. 4. Note: Be careful with palpation in the distal medial arm, because the median and ulnar nerves and brachial artery are superficial here.

RELATIONSHIP TO OTHER STRUCTURES Although most of the brachialis is deep to the biceps brachii, the lateral margin of the brachialis is superficial between the biceps brachii and the triceps brachii. More distally, the brachialis is superficial on both sides of the biceps brachii’s distal tendon. Deep to the brachialis is the shaft of the humerus. The proximal attachment of the brachialis forms a V shape and surrounds the distal attachment of the deltoid. On the medial side, the triceps brachii is posterior to the brachialis. On the lateral side, the triceps brachii is posterior to the brachialis proximally; the brachioradialis is posterior to the brachialis distally. The brachialis is located within the deep front arm line myofascial meridian.

MISCELLANEOUS 1. The brachialis is a strong and fairly large muscle, which accounts for much of the contour of the biceps brachii being so visible. (“Behind every great biceps brachii is a great brachialis.” ) 2. The biceps brachii attaches to the radial tuberosity whereas the brachialis attaches to the ulnar tuberosity.

261

Brachioradialis (of Radial Group) The name, brachioradialis, tells us that this muscle attaches onto the brachium (the arm) and the radius. Derivation brachio: L. refers to the arm radialis: L. refers to the radius Pronunciation BRAY-key-o-RAY-dee-AL-is

ATTACHMENTS Lateral Supracondylar Ridge of the Humerus the proximal ⅔ to the Styloid Process of the Radius the lateral side

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes the forearm at the elbow joint

Reverse Mover Actions 1. Flexes the arm at the elbow joint

2. Supinates the forearm at the RU joints

2. Supinates the ulna at the RU joints and medially rotates the arm at the GH joint

3. Pronates the forearm at the RU joints

3. Pronates the ulna at the RU joints and laterally rotates the arm at the GH joint

RU joints = radioulnar joints; GH joint = glenohumeral joint

Standard Mover Action Notes • The brachioradialis crosses the elbow joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the forearm at the elbow joint. (action 1) • The brachioradialis is most effective as a forearm flexor when the forearm is in a position that is halfway between full pronation and full supination. (action 1) • The brachioradialis is unusual in that it can both supinate and pronate the forearm at the RU joints. If the forearm is fully supinated, the brachioradialis can pronate the forearm to a position that is approximately halfway between full pronation and full supination because that position will have the two attachments of the brachioradialis, the styloid process of the radius and the lateral supracondylar ridge of the humerus, as close to each other as possible. Similarly, if the forearm is fully pronated, the brachioradialis can supinate the forearm to a position that is halfway between full pronation and full supination for the same reason. The brachioradialis is an excellent example of a muscle in the human body that has one line of pull but can have two opposite actions at the same joint (pronation and supination at the radioulnar joints) based on the position that the joint is in when the muscle contracts.

262

FIGURE 6-9

Anterior view of the right brachioradialis. The biceps brachii and brachialis have been ghosted in.

Reverse Mover Action Notes • If the forearm is fixed, the brachioradialis pulls the anterior surface of the arm toward the anterior surface of the forearm. This action is flexion of the arm at the elbow joint. The reverse action of flexion of the arm at the elbow joint is extremely important and occurs whenever a person grasps an immovable object and pulls his or her body toward it. Examples include using a handicap bar or using a handrail when going up stairs. (reverse action 1) • Supination and pronation are usually thought of as having a mobile radius move around a fixed ulna. However, if the hand is held fixed (perhaps by holding onto an immovable object), the radius will also be fixed with regard to rotation motions because the wrist joint does not allow rotation. Therefore the reverse action of supination of the forearm at the RU joints involves a mobile ulna supinating around a fixed radius. This supination motion of the ulna is effectively medial rotation. When the ulna medially rotates around the radius, because the elbow joint also does not allow rotation motions, the humerus moves with the ulna; this results in medial rotation of the arm at the GH joint. Similarly, the reverse action of pronation of the forearm at the RU joints involves a mobile ulna pronating around a fixed radius. This pronation motion of the ulna is effectively lateral rotation. This results in lateral rotation of the arm at the GH joint. (reverse

263

actions 2, 3)

Motions 1. In anatomic position, the brachioradialis has one line of pull in an oblique plane and therefore creates one motion, which is a combination of flexion and pronation of the forearm. 2. Note: If the forearm begins in a position of full pronation, its line of pull changes and its one motion is a combination of flexion and supination of the forearm.

Eccentric Antagonist Functions 1. Restrains/slows elbow joint extension 2. Restrains/slows RU joints pronation and supination

Eccentric Antagonist Function Notes • Restraining/slowing extension of the forearm at the elbow joint is extremely important when lowering an object in a careful and controlled manner. • The brachioradialis can only restrain/slow pronation when the forearm is between a fully supinated position and the position that is halfway between full supination and full pronation. Similarly, it can only restrain/slow supination when the forearm is between a fully pronated position and the position that is halfway between full supination and full pronation.

Isometric Stabilization Functions 1. Stabilizes the elbow and RU joints

Additional Note on Actions 1. The brachioradialis being able to both pronate and supinate is similar to other muscles that have been described in this text as de-rotaters. If we consider the position of the forearm being halfway between full pronation and full supination as being the neutral position, then the brachioradialis could be looked at as de-rotating the forearm back to that position when the forearm is first pronated or supinated beyond that position (although not pure, pronation and supination are essentially rotation motions of the forearm). It should be noted that this analogy does not consider anatomic position as the neutral position for the forearm.

I N N E RVAT I O N The Radial Nerve C5, C6

A R T E R I A L S U P P LY Branches of the Brachial Artery (the continuation of the Axillary Artery) and the Radial Artery (a terminal branch of the Brachial Artery)

PA L PAT I O N 1. With the client seated or supine and the forearm flexed at the elbow joint to 90 degrees and in a position halfway between full pronation and full supination, place palpating hand on the lateral anterior forearm. 2. Resist the client from further flexing the forearm and look and feel for the contraction of the brachioradialis. 3. Continue palpating the brachioradialis proximally toward the lateral supracondylar ridge of the humerus and distally toward the styloid process of the radius.

RELATIONSHIP TO OTHER STRUCTURES The brachioradialis is superficial in the lateral forearm, except at its distal end, where the abductor pollicis longus and the extensor pollicis brevis cross over it superficially. The proximal tendon of the brachioradialis is found between the brachialis and the triceps brachii. The belly of the brachioradialis is directly anterior to the extensor carpi radialis longus.

264

The radial attachment of the pronator teres lies deep to the brachioradialis. The brachioradialis is involved with the superficial back arm line and the deep back arm line myofascial meridians.

MISCELLANEOUS 1. The brachioradialis, the extensor carpi radialis longus, and the extensor carpi radialis brevis are often grouped together as the radial group of forearm muscles. They are also sometimes known as the wad of three. 2. The brachioradialis and extensor carpi radialis longus both attach to the lateral supracondylar ridge of the humerus, immediately proximal to the lateral epicondyle of the humerus. 3. The brachioradialis is located in the superficial layer of the anterior compartment of the forearm (along with the pronator teres and the muscles of the wrist flexor group). 4. The brachioradialis is sometimes nicknamed the hitchhiker muscle for the characteristic action of flexing the forearm in a position halfway between full pronation and full supination (with the thumb up) when hitchhiking. (Keep in mind that the brachioradialis has no action on the thumb itself.) 5. The brachioradialis is a flexor of the forearm at the elbow joint, but it is innervated by the radial nerve, which innervates all the forearm extensors.

265

Triceps Brachii The name, triceps brachii, tells us that this muscle has three heads and attaches to the brachium (the arm). Derivation triceps: L. three heads brachii: L. of the arm Pronunciation TRY-seps BRAY-key-eye

ATTACHMENTS LONG HEAD: Infraglenoid Tubercle of the Scapula LATERAL HEAD: Posterior Shaft of the Humerus

the proximal ⅓ MEDIAL HEAD: Posterior Shaft of the Humerus the distal ⅔ to the Olecranon Process of the Ulna

FUNCTIONS Concentric (Shortening) Mover Actions

GH joint = glenohumeral joint; ScC joint = scapulocostal joint

266

FIGURE 6-10 Posterior views of the right triceps brachii. A, Superficial view. The deltoid has been ghosted in. B, Deeper view. The lateral head has been cut to better show the medial head. The anconeus has been ghosted in.

Standard Mover Action Notes • The triceps brachii crosses the elbow joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it extends the forearm at the elbow joint. (action 1) • The triceps brachii is the prime mover (most powerful mover) of elbow joint extension. (action 1) • The long head of the triceps brachii crosses the shoulder joint posteriorly (with the fibers running vertically in the sagittal plane); therefore it extends the arm at the GH joint. (action 2) • The long head of the triceps brachii crosses the shoulder joint medially (with the fibers running horizontally in the frontal plane); therefore it adducts the arm at the GH joint. Note: the horizontal component to its fiber direction increases as the arm is abducted in the frontal plane. Therefore if the arm is first abducted, the adduction action of the triceps brachii becomes more prominent. (action 3) • If the arm is abducted to 90 degrees, the triceps brachii’s long head is oriented horizontally across the GH joint posteriorly. Therefore it can horizontally extend (horizontally abduct) the arm at the GH joint. (action 4)

Reverse Mover Action Notes • If the distal attachment of the triceps brachii is fixed, the posterior surface of the arm will be pulled toward the posterior surface of the forearm. Therefore the triceps brachii extends the arm at the elbow joint. (reverse action 1) • When the long head of the triceps brachii pulls downward on the scapula, the glenoid fossa will be oriented downward. Therefore the long head downwardly rotates the scapula at the GH joint. (reverse action 2) • When the scapula moves relative to the arm at the GH joint, it also moves relative to the rib cage at the scapulocostal joint. (reverse actions 2, 3) • Pulling the scapula laterally toward the abducted arm results in protraction of the scapula. (reverse action 3) • The long head of the triceps brachii can only laterally tilt (medially rotate) the scapula (pulling the medial border of the scapula away from the rib cage wall) when horizontally extending the arm if the arm is in front of the body. (reverse action 3)

Motions

267

1. The lateral and medial (deep) heads of the triceps brachii have one line of pull in the sagittal plane and therefore their motion is their cardinal plane joint action, extension of the elbow joint. 2. The long head of the triceps brachii has one line of pull in an oblique plane and therefore creates one motion, which is a combination of extension of the forearm, and extension and adduction of the arm at the GH joint.

Eccentric Antagonist Functions 1. Restrains/slows elbow joint flexion 2. Restrains/slows arm flexion, abduction, and horizontal flexion 3. Restrains/slows scapular upward rotation, retraction, and medial tilt

Eccentric Antagonist Function Note • Medial tilt (also known as lateral rotation) of the scapula is a motion in which the medial border of the scapula moves toward the rib cage wall. Given that the long head of the triceps brachii can only laterally tilt the scapula if the arm is in front of the body, it can only restrain/slow medial tilt if the arm is in front of the body.

Isometric Stabilization Functions 1. Stabilizes the elbow and GH joints 2. Stabilizes the scapula

I N N E RVAT I O N The Radial Nerve C7, C8

A R T E R I A L S U P P LY The Deep Brachial Artery (a branch of the Brachial Artery) and the Circumflex Scapular Artery (a branch of the Subscapular Artery)

PA L PAT I O N 1. With the client seated, place palpating hand on the distal, posterior arm, just proximal to the olecranon process of the ulna. 2. Have the client extend the forearm at the elbow joint against resistance and feel for the contraction of the triceps brachii. 3. Continue palpating the triceps brachii proximally toward the infraglenoid tubercle of the scapula, deep to the posterior deltoid.

RELATIONSHIP TO OTHER STRUCTURES The triceps brachii is superficial in the posterior arm except for the proximal attachments of the long head and the lateral head, which are deep to the deltoid. On the lateral side, the triceps brachii borders the brachialis proximally and the brachioradialis and extensor carpi radialis longus distally. On the medial side, the triceps brachii borders the coracobrachialis and the brachialis. The long head of the triceps brachii runs between the teres minor and the teres major. The triceps brachii is located within the deep back arm line myofascial meridian.

MISCELLANEOUS 1. From the posterior perspective, the medial head of the triceps brachii lies deep to the other two heads. For this reason, the medial head of the triceps brachii is sometimes known as the deep head (which probably is a better name for this head of the triceps brachii). 2. If the medial head is referred to as the deep head, then the triceps brachii would have a “deep head” without a “superficial head,” a “lateral head” without a “medial head,” and a “long head” without a “short head.”

268

3. At its proximal end, the medial head of the triceps brachii attaches to the medial proximal humerus. However, more distally, the medial head crosses over to also attach to the lateral shaft of the humerus. 4. The medial head of the triceps brachii is the most active of the three heads, meaning it is engaged most often by the nervous system; but the lateral head is the strongest. 5. The radial nerve runs between the medial and lateral heads of the triceps brachii. Because of its location here, the radial nerve is often injured.

269

Anconeus The name, anconeus, tells us that this muscle is involved with the elbow. Derivation anconeus: Gr. elbow Pronunciation an-KO-nee-us

ATTACHMENTS Lateral Epicondyle of the Humerus to the Posterior Proximal Ulna

the lateral side of the olecranon process of the ulna and the proximal ⅓ of the posterior ulna

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extends the forearm at the elbow joint

Reverse Mover Actions 1. Extends the arm at the elbow joint

Standard Mover Action Note • The anconeus crosses the elbow joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it extends the forearm at the elbow joint. (action 1)

Reverse Mover Action Note • If the distal attachment of the anconeus is fixed, the posterior surface of the arm will be pulled toward the posterior surface of the forearm. Therefore the anconeus extends the arm at the elbow joint. (reverse action 1)

Motion 1. The anconeus has one line of pull and therefore creates one motion. This line of pull is in an oblique plane, but crosses the elbow joint, which is uniaxial and only allows expression of that oblique plane pull in the sagittal (cardinal) plane. Therefore its motion is its joint action, extension of the elbow joint.

Eccentric Antagonist Function 1. Restrains/slows elbow joint flexion

Isometric Stabilization Function 1. Stabilizes the ulna and elbow joint

270

FIGURE 6-11

Posterior view of the right anconeus. The triceps brachii has been cut and ghosted in.

Isometric Stabilization Function Note • Some sources state that the major function of the anconeus is to stabilize the ulna from being moved medially (adducted) at the elbow joint during pronation of the forearm at the radioulnar joints.

Additional Note on Actions 1. Some sources state that the anconeus can move the ulna laterally at the elbow joint, in other words, abduct the forearm at the elbow joint (sometimes referred to as lateral deviation of the ulna). Given that its fibers are somewhat oriented in the frontal plane, attaching from laterally on the humerus to medially on the ulna, this would make sense because the ulnar attachment would be pulled laterally toward the humeral attachment. Abducting the ulna would increase the cubitus valgus (carrying) angle at the elbow joint.

I N N E RVAT I O N The Radial Nerve C6, C7, C8

A R T E R I A L S U P P LY The Deep Brachial Artery (a branch of the Brachial Artery)

271

PA L PAT I O N 1. With the client seated, locate the point halfway between the olecranon process of the ulna and the lateral epicondyle of the humerus, and then place your palpating finger approximately ⅓ inch (1 cm) distal to that point. 2. Have the client actively extend the forearm at the elbow joint against resistance and feel for the contraction of the anconeus. 3. Palpate the entirety of the anconeus.

RELATIONSHIP TO OTHER STRUCTURES The anconeus is superficial and located in the proximal posterior forearm on the lateral side. The anconeus is proximal to the extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris. The anconeus is located within the deep back arm line myofascial meridian.

MISCELLANEOUS 1. Besides the anconeus, the supinator attaches proximally to the lateral epicondyle of the humerus. Also arising from the lateral epicondyle are four other muscles that share the common extensor belly/tendon attachment onto the lateral epicondyle of the humerus (the extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris). 2. The anconeus is located in the superficial layer of the posterior compartment of the forearm (along with the muscles of the wrist extensor group and the extensors digitorum and digiti minimi). 3. The anconeus often blends with the triceps brachii. 4. Irritation and/or inflammation of the lateral epicondyle and/or the common extensor belly/tendon is known as lateral epicondylitis, lateral epicondylosis, or tennis elbow.

272

Pronator Teres The name, pronator teres, tells us that this muscle pronates the forearm and is round in shape. Derivation pronator: L. a muscle that pronates a body part teres: L. round Pronunciation pro-NAY-tor TE-reez

ATTACHMENTS HUMERAL HEAD: Medial Epicondyle of the Humerus (via the Common Flexor Belly/Tendon) and the medial supracondylar ridge of the humerus ULNAR HEAD: Coronoid Process of the Ulna the medial surface to the Lateral Radius the middle ⅓

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Pronates the forearm at the RU joints 2. Flexes the forearm at the elbow joint

Reverse Mover Actions 1. Pronates the ulna at the RU joints and laterally rotates the arm at the GH joint 2. Flexes the arm at the elbow joint

RU joints = radioulnar joints; GH joint = glenohumeral joint

Standard Mover Action Notes • The pronator teres crosses from the medial elbow region to the lateral (radial) side of the forearm onto the radius (with its fibers running somewhat horizontally in the transverse plane), crossing the radioulnar joints anteriorly. When it contracts, it pulls the radial attachment anteromedially. This causes the head of the radius to medially rotate and the distal radius to cross in front of the ulna. This movement of the radius is called pronation. Therefore the pronator teres pronates the forearm at the RU joints. (action 1) • Pronation of the forearm at the RU joints usually involves motion of the radius around a fixed ulna. (action 1) • The pronator teres crosses the elbow joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the forearm at the elbow joint. (action 2)

Reverse Mover Action Notes • Pronation is usually thought of as having a mobile radius move around a fixed ulna. However, if the hand is held fixed (perhaps by holding onto an immovable object), the radius will also be fixed with regard to rotation motions because the wrist joint does not allow rotation. Therefore the reverse action of pronation of the forearm at the RU joints involves a mobile ulna pronating around a fixed radius. This pronation motion of the ulna is effectively lateral rotation. When the ulna laterally rotates around the radius, because the elbow joint also does not allow rotation motions, the humerus moves with the ulna; this results in lateral rotation of the arm at the GH joint. (reverse action 1)

273

FIGURE 6-12

Anterior view of the right pronator teres. The brachioradialis has been ghosted in.

• If the forearm is fixed, the pronator teres pulls the anterior surface of the arm toward the anterior surface of the forearm. This action is flexion of the arm at the elbow joint. The reverse action of flexion of the arm at the elbow joint is extremely important and occurs whenever a person grasps an immovable object and pulls his or her body toward it. Examples include using a handicap bar or using a handrail when going up stairs. (reverse action 2)

Motion 1. The pronator teres has one line of pull in an oblique plane and therefore creates one motion, which is a combination of flexion and pronation of the forearm at the elbow and RU joints respectively.

Eccentric Antagonist Functions 1. Restrains/slows RU joints supination 2. Restrains/slows elbow joint extension

Eccentric Antagonist Function Note • Restraining/slowing extension of the forearm at the elbow joint is extremely important when

274

lowering an object in a careful and controlled manner.

Isometric Stabilization Functions 1. Stabilizes the RU joints 2. Stabilizes the elbow joint

I N N E RVAT I O N The Median Nerve C6, C7

A R T E R I A L S U P P LY The Ulnar Artery (a terminal branch of the Brachial Artery) and the Radial Artery (a terminal branch of the Brachial Artery)

PA L PAT I O N 1. With the client seated and the forearm partially flexed at the elbow joint and pronated at the radioulnar joints to a midpoint between full pronation and full supination, place palpating hand on the proximal anterior forearm and place resistance hand on the distal anterior forearm. 2. Have the client further pronate the forearm against resistance and feel for the contraction of the pronator teres. 3. Continue palpating the pronator teres proximally toward the medial epicondyle of the humerus and distally toward the lateral radius.

RELATIONSHIP TO OTHER STRUCTURES The proximal part of the pronator teres is superficial in the proximal anterior forearm, but the distal attachment is deep to the brachioradialis. The ulnar head of the pronator teres is entirely deep or nearly entirely deep to the humeral head of the pronator teres. The pronator teres is lateral to the flexor carpi radialis. The pronator teres is largely superficial to the flexor digitorum superficialis. The pronator teres is involved with the deep front arm line and superficial back arm line myofascial meridians.

MISCELLANEOUS 1. The humeral head of the pronator teres arises proximally from the medial epicondyle of the humerus via the common flexor belly/tendon. The common flexor belly/tendon is the common proximal attachment of five muscles: the pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris, and flexor digitorum superficialis. 2. The common flexor belly/tendon is usually referred to simply as the common flexor tendon. However, the bellies of these muscles usually blend long before the tendons of the muscles blend. 3. Although the humeral head of the pronator teres is part of the common flexor belly/tendon, the attachment site of the humeral head onto the medial epicondyle of the humerus is slightly more proximal than the attachment of the other four muscles of the common flexor belly/tendon. 4. The pronator teres is located in the superficial layer of the anterior compartment of the forearm (along with the muscles of the wrist flexor group and the brachioradialis). 5. The humeral head of the pronator teres is by far the larger of the two heads. 6. The median nerve courses between the humeral head and the ulnar head of the pronator teres, making it a possible entrapment site of the median nerve. When the median nerve is entrapped there, it is termed pronator teres syndrome (and may mimic symptoms of carpal tunnel syndrome or a pathologic cervical disc). 7. Overuse of the pronator teres can cause irritation and/or inflammation of the medial epicondyle and/or the common flexor belly/tendon. This is known as medial epicondylitis, medial epicondylosis, or golfer’s elbow.

275

276

Pronator Quadratus The name, pronator quadratus, tells us that this muscle pronates the forearm and has a square shape. Derivation pronator: L. a muscle that pronates a body part quadratus: L. squared Pronunciation pro-NAY-tor kwod-RAY-tus

ATTACHMENTS Anterior Distal Ulna the distal ¼ to the Anterior Distal Radius the distal ¼

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Pronates the forearm at the RU joints

Reverse Mover Actions 1. Pronates the ulna at the RU joints and laterally rotates the arm at the GH joint

RU joints = radioulnar joints; GH joint = glenohumeral joint

Standard Mover Action Notes • The pronator quadratus crosses the distal anterior forearm from the ulna to the radius (with its fibers running horizontally in the transverse plane). When the pronator quadratus contracts, it pulls the distal radius anteromedially. This causes the distal radius to cross in front of the distal ulna (and the head of the radius to medially rotate). This movement of the radius is called pronation. Therefore the pronator quadratus pronates the forearm at the RU joints. (action 1) • Pronation of the forearm at the RU joints usually involves motion of the radius around a fixed ulna. (action 1) • According to most sources, the pronator quadratus is the prime mover of forearm pronation at the RU joints even though the pronator teres is much larger. This is due to the pronator quadratus’ excellent leverage at the distal radius. (action 1)

Reverse Mover Action Notes • Pronation is usually thought of as having a mobile radius move around a fixed ulna. However, if the hand is held fixed (perhaps by holding onto an immovable object), the radius will also be fixed with regard to rotation motions because the wrist joint does not allow rotation. Therefore the reverse action of pronation of the forearm at the RU joints involves a mobile ulna pronating around a fixed radius. This pronation motion of the ulna is effectively lateral rotation. When the ulna laterally rotates around the radius, because the elbow joint also does not allow rotation motions, the humerus moves with the ulna; this results in lateral rotation of the arm at the GH joint.

277

FIGURE 6-13

Anterior view of the right pronator quadratus. The pronator teres has been ghosted in.

Motion 1. The pronator quadratus has one line of pull, which is essentially in the transverse plane. Therefore its motion is its cardinal plane joint action, pronation of the forearm at the RU joints.

Eccentric Antagonist Function 1. Restrains/slows RU joints supination

Isometric Stabilization Function 1. Stabilizes the RU joints

Isometric Stabilization Function Note • The pronator quadratus is especially important for preventing separation of the distal radius and ulna.

I N N E RVAT I O N

278

The Median Nerve anterior interosseus nerve, C7, C8

A R T E R I A L S U P P LY The Anterior Interosseus Artery (a branch of the Ulnar Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating hand distally on the distal anterolateral forearm. 2. Find the radial pulse to locate the radial artery and then palpate on either side of it to locate the pronator quadratus. The pronator quadratus is very deep and can be difficult to palpate and discern. 3. Resist the client from actively pronating the forearm at the radioulnar joints and feel for the contraction of the pronator quadratus.

RELATIONSHIP TO OTHER STRUCTURES The pronator quadratus is the deepest muscle in the anterior forearm. Every structure that crosses the wrist on the anterior side is superficial to the pronator quadratus. Deep to the pronator quadratus are the radius, the ulna, and the interosseus membrane. The pronator quadratus is involved with the deep front arm line and deep back arm line myofascial meridians.

MISCELLANEOUS 1. The pronator quadratus is located in the deep layer of the anterior compartment of the forearm (along with the flexor digitorum profundus and flexor pollicis longus).

279

Supinator The name, supinator, tells us that this muscle supinates the forearm. Derivation supinator: L. a muscle that supinates a body part Pronunciation SUE-pin-AY-tor

ATTACHMENTS Lateral Epicondyle of the Humerus and the Proximal Ulna the supinator crest of the ulna to the Proximal Radius the proximal ⅓ of the posterior, lateral, and anterior sides

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Supinates the forearm at the RU joints 2. Flexes the forearm at the elbow joint

Reverse Mover Actions 1. Supinates the ulna at the RU joints and medially rotates the arm at the GH joint 2. Flexes the arm at the elbow joint

RU joints = radioulnar joints; GH joint = glenohumeral joint

Standard Mover Action Notes • The supinator crosses from the proximal posterior ulna to the proximal posterolateral radius; thus it wraps around the posterior forearm. When the supinator pulls the radius toward the ulna on the posterior side, it causes the head of the radius to laterally rotate and the distal radius to move posterolaterally around the distal ulna. This movement of the radius is called supination. Therefore the supinator supinates the forearm at the RU joints. (action 1) • The supinator has a few fibers that run vertically and are located anterior to the elbow joint; therefore the supinator can flex the elbow joint. However, given how few fibers are oriented in this manner, this action of the supinator is very weak. (action 2)

Reverse Mover Action Notes • Supination and pronation are usually thought of as having a mobile radius move around a fixed ulna. However, if the hand is held fixed (perhaps by holding onto an immovable object), the radius will also be fixed with regard to rotation motions because the wrist joint does not allow rotation. Therefore the reverse action of supination of the forearm at the RU joints involves a mobile ulna supinating around a fixed radius. This supination motion of the ulna is effectively medial rotation. When the ulna medially rotates around the radius, because the elbow joint also does not allow rotation motions, the humerus moves with the ulna; this results in medial rotation of the arm at the GH joint. (reverse action 1)

280

FIGURE 6-14 Posterior view of the right supinator. The anconeus has been ghosted in. The extensor carpi radialis longus (ECRL) and extensor carpi radialis brevis (ECRB) have been cut and ghosted in.

• The reverse action of flexing the forearm toward the arm at the elbow joint is flexing the arm toward the forearm at the elbow joint. (reverse action 2)

Motions 1. The supinator has one line of pull, which is essentially in the transverse plane. Therefore its motion is its cardinal plane joint action, supination of the forearm at the RU. 2. Note: If the few anterior fibers that are oriented more vertically are considered, then the supinator has a second motion, which is its second cardinal plane joint action of flexion of the elbow joint.

Eccentric Antagonist Functions 1. Restrains/slows RU joint pronation 2. Restrains/slows elbow joint extension

Isometric Stabilization Functions 1. Stabilizes the RU joints 2. Stabilizes the elbow joint

281

I N N E RVAT I O N The Radial Nerve C6, C7

A R T E R I A L S U P P LY Branches of the Radial Artery (a terminal branch of the Brachial Artery) and the Interosseus Recurrent and Posterior Interosseus Arteries (branches of the Ulnar Artery)

PA L PAT I O N 1. With the client seated and the forearm passively flexed, pronated, and resting comfortably on the lap, pinch the radial group of the forearm muscles (brachioradialis, extensor carpi radialis longus, and extensor carpi radialis brevis) with your thumb on one side and your index and middle fingers on the other side, and move it anteriorly away from the posterior musculature of the forearm. 2. Sink in and palpate deeper against the radius (between the radial group of the forearm and the extensor digitorum) to locate the radial attachment of the supinator. Have the client slowly supinate the forearm at the radioulnar joints and feel for the contraction of the supinator. 3. Continue palpating the supinator proximally toward the lateral epicondyle and ulnar attachment.

RELATIONSHIP TO OTHER STRUCTURES The supinator is a deep muscle in the proximal posterior forearm. The supinator lies deep to the anconeus, extensor digitorum, extensor digiti minimi, extensor carpi radialis brevis, extensor carpi radialis longus, and brachioradialis. The distal tendon of the supinator attaches onto the radius next to the distal attachment of the pronator teres. The supinator is located within the deep front arm line myofascial meridian.

MISCELLANEOUS 1. Besides the supinator, the anconeus attaches proximally to the lateral epicondyle of the humerus. Also arising from the lateral epicondyle are four other muscles that share the common extensor belly/tendon attachment onto the lateral epicondyle of the humerus (the extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris). 2. The supinator is located in the deep layer of the posterior compartment of the forearm (along with the deep distal four group of muscles composed of the abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis). 3. Proximally, the supinator muscle has two layers: a superficial layer and a deep layer. 4. The posterior interosseus nerve, a deep branch of the radial nerve, runs between the two layers of the supinator and may be entrapped there. (Most sources state that the posterior interosseus nerve can also be called the deep branch of the radial nerve. However, other sources state that the posterior interosseus nerve is the continuation of the deep branch of the radial nerve after it has emerged from the supinator muscle.) 5. The supinator crest is located deep between the two bones of the forearm on the lateral side of the ulna. 6. Irritation and/or inflammation of the lateral epicondyle and/or the common extensor belly/tendon is known as lateral epicondylitis, lateral epicondylosis, or tennis elbow.

282

REVIEW QUESTIONS 1. What structures must a therapist be aware of when palpating the medial arm? ____________________________ ____________________________ 2. What muscle has an attachment that runs through the glenohumeral joint cavity?

a. Biceps brachii b. Brachioradialis c. Brachialis d. Triceps brachii 3. The _______ muscle of this chapter is an example of a muscle that can have two opposite actions at the same joint. What are those actions, and how is this possible? ____________________________ ____________________________ ____________________________ 4. What is the prime mover of flexion of the elbow joint? ____________________________ 5. What is the optimal position of the forearm when palpating the brachialis? ____________________________ ____________________________ 6. The radial group of forearm muscles, sometimes known as the_______, is made up of the following muscles:_______ ____________________________ 7. Which head of the triceps brachii is most often engaged by the nervous system? Which head is the strongest? What structure runs between these two heads of the triceps brachii? ____________________________ ____________________________ ____________________________ 8. Irritation and/or inflammation of the lateral epicondyle and/or the common extensor belly/tendon are best known as_______. ____________________________ 9. What muscles compose the common flexor belly/tendon? ____________________________ ____________________________ 10. The median nerve may be entrapped in the forearm by what structures? What is this condition called? ____________________________ ____________________________ For answers to these questions, visit http://evolve.elsevier.com/Muscolino/muscular

283

THINK IT THROUGH How do muscles like the pronator teres and the supinator cause actions at the glenohumeral joint even though they do not cross that joint? ____________________________ ____________________________ ____________________________ ____________________________ ____________________________

284

CHAPTER 7

285

Muscles of the Wrist Joint CHAPTER OUTLINE Wrist flexor group: Flexor carpi radialis Palmaris longus Flexor carpi ulnaris Wrist extensor group: Extensor carpi radialis longus Extensor carpi radialis brevis Extensor carpi ulnaris

OBJECTIVES After completing this chapter, the student should be able to perform the following for each of the muscles covered in the chapter: 1. Explain the general structure. 2. Explain the general function. 3. State the attachments. 4. State the standard mover actions. 5. State the reverse mover actions. 6. Discuss the line(s) of pull the muscle has and the motion(s) created. 7. State the eccentric antagonist functions. 8. State the isometric stabilization functions. 9. State the nervous innervation.

10. State the arterial supply. 11. Describe the starting position for palpation. 12. Describe the steps for palpation. 13. Discuss the muscle’s relationship to other body structures. 14. Discuss additional information that may help with palpation, assessment, and clinical decision making. CHAPTER OVERVIEW The muscles addressed in this chapter are the muscles whose principal function is usually considered to be movement of the wrist joint. Other muscles in the body can also move the wrist joint, but they are placed in different chapters because their primary function is usually considered to be at another joint. These muscles are the extrinsic finger joint muscles and are covered in Chapter 8. Overview of STRUCTURE Structurally, muscles of the wrist joint are divided into two superficial groups, each one containing three muscles. The wrist flexor group is located anteriorly and attaches proximally to the medial epicondyle of

286

the humerus via the common flexor belly/tendon. The wrist extensor group is located posteriorly and two of the three muscles in this group attach proximally to the lateral epicondyle of the humerus via the common extensor belly/tendon. The third one attaches proximally to the lateral supracondylar ridge of the humerus, just proximal to the lateral epicondyle. The wrist flexor group is composed of the flexor carpi radialis, palmaris longus, and flexor carpi ulnaris. The wrist extensor group is composed of the extensor carpi radialis longus, extensor carpi radialis brevis, and extensor carpi ulnaris. The extensors carpi radialis longus and brevis (along with the brachioradialis) are also part of the radial group of forearm muscles, sometimes referred to as the wad of three. Note: The common flexor belly/tendon is usually referred to simply as the common flexor tendon. However, the bellies of these muscles usually blend long before the tendons of the muscles blend. Similarly, the common extensor belly/tendon is usually referred to simply as the common extensor tendon. However, the bellies of these muscles also usually blend long before the tendons of the muscles blend.

Compartments of the Forearm: Forearm musculature is usually divided into anterior and posterior compartments. • The anterior compartment is composed of three layers: superficial, intermediate, and deep.

• The superficial layer contains the pronator teres, wrist flexor group (flexor carpi radialis, palmaris longus, flexor carpi ulnaris), and brachioradialis. • The intermediate layer contains the flexor digitorum superficialis. • The deep layer contains the flexor digitorum profundus, flexor pollicis longus, and pronator quadratus. • The posterior compartment is composed of two layers: superficial and deep.

• The superficial layer contains the wrist extensor group (extensor carpi radialis longus, extensor carpi radialis brevis, and extensor carpi ulnaris), extensor digitorum, extensor digiti minimi, and anconeus. • The deep layer contains the supinator and the deep distal four group (abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis). • Note: Some sources describe a radial group that is composed of the brachioradialis (of the anterior compartment) and the extensors carpi radialis longus and brevis (of the posterior compartment). Overview of FUNCTION The following general rules regarding actions can be stated for the functional groups of muscles of the wrist joint: If a muscle crosses the wrist joint anteriorly with a vertical direction to its fibers, it can flex the hand at the wrist joint by moving the palmar (anterior) surface of the hand toward the anterior surface of the forearm. If a muscle crosses the wrist joint posteriorly with a vertical direction to its fibers, it can extend the hand at the wrist joint by moving the dorsal (posterior) surface of the hand toward the posterior surface of the forearm. If a muscle crosses the wrist joint on the radial side (laterally) with a vertical direction to its fibers, it can radially deviate (abduct) the hand at the wrist joint by moving the radial side of the hand toward the radial side of the forearm. If a muscle crosses the wrist joint on the ulnar side (medially) with a vertical direction to its fibers, it can ulnar deviate (adduct) the hand at the wrist joint by moving the ulnar side of the

287

hand toward the ulnar side of the forearm. Reverse actions of these standard mover actions involve the forearm being moved toward the hand at the wrist joint. These reverse actions usually occur when the hand is fixed such as when holding onto an immovable object (in other words the upper extremity is in closed-chain position).

http://evolve.elsevier.com/Muscolino/muscular

288

Anterior View of the Muscles of the Right Wrist Joint— Superficial View

FIGURE 7-1

Anterior views of the muscles of the right wrist joint. A, Superficial view.

289

Anterior View of the Muscles of the Right Wrist Joint— Intermediate View

FIGURE 7-1

B, Intermediate view.

290

Anterior View of the Muscles of the Right Wrist Joint— Deep View

FIGURE 7-1

C, Deep view. The (cut) brachialis has been ghosted in.

291

Anterior View of the Right Wrist Flexor Group of Muscles

FIGURE 7-2

Anterior view of the right wrist flexor group of muscles.

292

Posterior View of the Muscles of the Right Wrist Joint —Superficial View

FIGURE 7-3

Posterior views of the muscles of the right wrist joint. A, Superficial view.

293

Posterior Views of the Muscles of the Right Wrist Joint — Deep Views

FIGURE 7-3

B and C, Deep views.

294

Posterior View of the Right Wrist Extensor Group of Muscles

FIGURE 7-4

Posterior view of the right wrist extensor group of muscles.

295

Medial View of the Muscles of the Right Wrist Joint

FIGURE 7-5

Medial and lateral views of the muscles of the right wrist joint. A, Medial view.

296

Lateral View of the Muscles of the Right Wrist Joint

FIGURE 7-5

B, Lateral view with the elbow joint fully extended.

297

FIGURE 7-5 C, Lateral view with the elbow joint flexed. The three muscles of the radial group are shown. ECRL = extensor carpi radialis longus, ECRB = extensor carpi radialis brevis.

298

Transverse Plane Cross Sections of the Right Forearm

FIGURE 7-6

A, Proximal. B, Middle. C, Distal.

299

Flexor Carpi Radialis (of Wrist Flexor Group) The name, flexor carpi radialis, tells us two of its actions: flexor tells us that this muscle performs flexion, and radialis tells us that this muscle performs radial deviation (abduction). Both of these actions occur at the wrist joint; carpi refers to the wrist. Derivation flexor: L. a muscle that flexes a body part carpi: L. of the wrist radialis: L. refers to the radial side (of the forearm) Pronunciation FLEKS-or KAR-pie RAY-dee-A-lis

ATTACHMENTS Medial Epicondyle of the Humerus via the Common Flexor Belly/Tendon to the Anterior Hand on the Radial Side

the anterior side of the bases of the second and third metacarpals

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes the hand at the wrist joint

Reverse Mover Actions 1. Flexes the forearm at the wrist joint

2. Radially deviates the hand at the wrist joint 3. Flexes the forearm at the elbow joint

2. Radially deviates the forearm at the wrist joint

4. Pronates the forearm at the RU joints

4. Pronates the ulna at the RU joints and laterally rotates the arm at the GH joint

3. Flexes the arm at the elbow joint

RU joints = radioulnar joints; GH joint = glenohumeral joint

Standard Mover Action Notes • The flexor carpi radialis crosses the wrist joint on the anterior side to attach onto the hand (with its fibers running vertically in the sagittal plane); therefore it flexes the hand at the wrist joint. (action 1) • The flexor carpi radialis crosses the wrist joint on the radial (lateral) side (with its fibers running vertically in the frontal plane); therefore it radially deviates (abducts) the hand at the wrist joint. (action 2) • Motion at the wrist joint occurs at the radiocarpal and midcarpal joints. (actions 1, 2) • All three members of the wrist flexor group (flexor carpi radialis, palmaris longus, and flexor carpi ulnaris) can flex the forearm at the elbow joint because they cross it anteriorly (with their fibers running vertically in the sagittal plane). (action 3)

300

FIGURE 7-7

Anterior view of the right flexor carpi radialis. The pronator teres and palmaris longus have been ghosted in.

• Pronation of the forearm at the RU joints usually involves motion of the radius around a fixed ulna. The flexor carpi radialis crosses the RU joints anteriorly in such a way that when it pulls at the lateral hand attachment, it pulls the radial side of the hand anteromedially, thereby pulling the distal radius around the distal ulna. Therefore the flexor carpi radialis pronates the forearm at the RU joints. Note the similar line of pull to the pronator teres. (action 4)

Reverse Mover Action Notes • Reverse actions at the wrist joint occur when the hand is fixed by holding onto an immovable object and the forearm moves relative to the fixed hand. The wrist joint reverse action in the sagittal plane of the flexor carpi radialis causes the anterior forearm to be pulled toward the anterior hand, in other words, flexion of the forearm at the wrist joint. The wrist joint reverse action in the frontal plane of the flexor carpi radialis causes the radial side of the forearm to be pulled toward the radial side of the hand, in other words, radial deviation of the forearm at the wrist joint. (reverse actions 1, 2) • The reverse action of flexion of the arm at the elbow joint is extremely important and occurs whenever a person grasps an immovable object and pulls his or her body toward it (examples include using a handicap bar or using a handrail when going up stairs). (reverse action 3)

301

• Pronation is usually thought of as having a mobile radius move around a fixed ulna. However, if the hand is held fixed (perhaps by holding onto an immovable object), the radius will also be fixed with regard to rotation motions because the wrist joint does not allow rotation. Therefore the reverse action of pronation of the forearm at the RU joints involves a mobile ulna pronating around a fixed radius. This pronation motion of the ulna is effectively lateral rotation. When the ulna laterally rotates around the radius, because the elbow joint also does not allow rotation motions, the humerus moves with the ulna; this results in lateral rotation of the arm at the GH joint. (reverse action 4)

Motion 1. The flexor carpi radialis has one line of pull in an oblique plane and therefore creates one motion, which is a combination of flexion and radial deviation of the hand at the wrist joint, and flexion of the forearm at the elbow joint (as well as pronation of the forearm at the RU joints).

Eccentric Antagonist Functions 1. Restrains/slows wrist joint extension and ulnar deviation 2. Restrains/slows elbow joint extension 3. Restrains/slows radioulnar joints supination

Eccentric Antagonist Function Note • Restraining/slowing extension of the forearm at the elbow joint is extremely important when lowering an object in a careful and controlled manner.

Isometric Stabilization Functions 1. Stabilizes the wrist joint 2. Stabilizes the elbow joint 3. Stabilizes the RU joints

I N N E RVAT I O N The Median Nerve C6, C7

A R T E R I A L S U P P LY The Ulnar and Radial Arteries (terminal branches of the Brachial Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating hand across the anterior wrist. 2. Have the client actively flex and/or radially deviate (abduct) the hand at the wrist joint and look and feel for the distal tendon of the flexor carpi radialis on the radial (lateral) side (slightly lateral to the distal tendon of the palmaris longus, which is located dead center in the anterior wrist). Resistance can be added. 3. Continue palpating the flexor carpi radialis proximally toward the medial epicondyle of the humerus. 4. To distinguish the flexor carpi radialis from the palmaris longus and the other muscles of the common flexor belly/tendon, radial deviation of the hand at the wrist joint is the best action to ask the client to perform.

RELATIONSHIP TO OTHER STRUCTURES The flexor carpi radialis is superficial in the anterior forearm. Proximally, the flexor carpi radialis is medial to the pronator teres. More distally, the flexor carpi radialis is medial to the brachioradialis. The flexor carpi radialis is lateral to the palmaris longus. The flexor carpi radialis is superficial to the flexor digitorum superficialis. The flexor carpi radialis is located within the superficial front arm line myofascial meridian.

302

MISCELLANEOUS 1. The flexor carpi radialis, palmaris longus, and flexor carpi ulnaris are often grouped together as the wrist flexor group of the forearm. 2. The flexor carpi radialis arises proximally from the medial epicondyle of the humerus via the common flexor belly/tendon. The common flexor belly/tendon is the common proximal attachment of five muscles: the pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris, and the flexor digitorum superficialis. 3. Overuse of the flexor carpi radialis can cause irritation and/or inflammation of the medial epicondyle and/or the common flexor belly/tendon. This is known as medial epicondylitis, medial epicondylosis, or golfer’s elbow.

303

Palmaris Longus (of Wrist Flexor Group) The name, palmaris longus, tells us that this muscle attaches into the palm of the hand and is long (longer than the palmaris brevis). Derivation palmaris: L. refers to the palm longus: L. longer Pronunciation pall-MA-ris LONG-us

ATTACHMENTS Medial Epicondyle of the Humerus via the Common Flexor Belly/Tendon to the Palm of the Hand

the palmar aponeurosis and the flexor retinaculum

FUNCTIONS Concentric (Shortening) Mover Actions

RU joints = radioulnar joints; GH joint = glenohumeral joint

Standard Mover Action Notes • The palmaris longus crosses the wrist on the anterior side to attach onto the hand (with its fibers running vertically in the sagittal plane); therefore it flexes the hand at the wrist joint. (action 1) • When the palmaris longus pulls on its distal attachment, if the wrist joint does not flex (perhaps because it is stabilized by a wrist joint extensor muscle), it pulls on the palmar aponeurosis, causing the skin of the palm to wrinkle. This helps to cup the hand, creating a slightly stronger grip on an object that is being held. (action 2) • All three members of the wrist flexor group (flexor carpi radialis, palmaris longus, and flexor carpi ulnaris) can flex the forearm at the elbow joint because they cross it anteriorly (with their fibers running vertically in the sagittal plane). (action 3)

304

FIGURE 7-8

Anterior view of the right palmaris longus. The flexor carpi radialis and flexor carpi ulnaris have been ghosted in.

• Pronation of the forearm at the RU joints usually involves motion of the radius around a fixed ulna. The palmaris longus crosses from the medial elbow region to attach more laterally into the palm of the hand. It crosses the RU joints anteriorly in such a way that when it pulls at the more lateral hand attachment, it pulls the radial side of the hand anteromedially, thereby pulling the distal radius around the distal ulna, in other words, pronation of the forearm at the RU joints. (action 4) • The palmaris longus can only radially deviate (abduct) the wrist joint if it is first in ulnar deviation. The palmaris longus can only ulnar deviate (adduct) the wrist joint if it is first in radial deviation. In either case, it “rotates” (using the term “rotation” more generally to describe any axial rotatory motion) the hand back to anatomic position. Therefore the palmaris longus can be considered to be a de-rotator muscle. (actions 5, 6) • Motion at the wrist joint occurs at the radiocarpal and midcarpal joints. (actions 1, 5, 6)

Reverse Mover Action Notes • Reverse actions at the wrist joint occur when the hand is fixed by holding onto an immovable object and the forearm moves relative to the fixed hand. The names for these reverse actions are the same as for the standard mover actions. (reverse actions 1, 4, 5)

305

• The reverse action of flexion of the arm at the elbow joint is extremely important and occurs whenever a person grasps an immovable object and pulls his or her body toward it (examples include using a handicap bar or using a handrail when going up stairs). (reverse action 2) • Pronation is usually thought of as having a mobile radius move around a fixed ulna. However, if the hand is held fixed (perhaps by holding onto an immovable object), the radius will also be fixed with regard to rotation motions because the wrist joint does not allow rotation. Therefore the reverse action of pronation of the forearm at the RU joints involves a mobile ulna pronating around a fixed radius. This pronation motion of the ulna is effectively lateral rotation. When the ulna laterally rotates around the radius, because the elbow joint also does not allow rotation motions, the humerus moves with the ulna; this results in lateral rotation of the arm at the GH joint. (reverse action 3)

Motions 1. The palmaris longus has one line of pull in the sagittal (cardinal) plane across the wrist and elbow joints; therefore it creates one motion, which is a combination of flexion of the hand at the wrist joint and flexion of the forearm at the elbow joint. 2. Note: If the forearm is in a position of radial deviation, it also creates ulnar deviation of the hand at the wrist joint; if the forearm is in a position of ulnar deviation, it also creates radial deviation of the hand at the wrist joint. 3. Once the palmaris longus enters the hand, it spreads out in the radial and ulnar directions to attach into the fascia of the palm of the hand; therefore as it is creating its other motion, it also wrinkles the skin of the palm by pulling in the palmar fascia toward the center of the hand.

Eccentric Antagonist Functions 1. Restrains/slows wrist joint extension, radial deviation, and ulnar deviation 2. Restrains/slows elbow joint extension 3. Restrains/slows RU joints supination

Eccentric Antagonist Function Note • Restraining/slowing extension of the forearm at the elbow joint is extremely important when lowering an object in a careful and controlled manner.

Isometric Stabilization Functions 1. Stabilizes the wrist joint 2. Stabilizes the elbow joint 3. Stabilizes the RU joints

I N N E RVAT I O N The Median Nerve C7, C8

A R T E R I A L S U P P LY The Ulnar Artery (a terminal branch of the Brachial Artery)

PA L PAT I O N 1. The palmaris longus is superficial and easy to palpate. 2. With the client seated or supine, place palpating hand on the anterior wrist. 3. Ask the client to cup the hand (by bringing the thenar eminence toward the hypothenar eminence) and/or flex the hand at the wrist joint against resistance with the fingers fully extended. Look and feel for the distal tendon of the palmaris longus in the center of the anterior wrist. Resistance can be added. 4. Continue palpating the palmaris longus distally into the palmar fascia and proximally toward the medial epicondyle of the humerus. It is difficult to distinguish the proximal tendon of the palmaris longus from the proximal tendons of the other muscles of the common flexor belly/tendon.

306

RELATIONSHIP TO OTHER STRUCTURES The palmaris longus is superficial in the anteromedial forearm. The palmaris longus is medial to the flexor carpi radialis. Proximally, the palmaris longus is lateral to the flexor carpi ulnaris. More distally, the palmaris longus is lateral to the flexor digitorum superficialis. The palmaris longus is located within the superficial front arm line myofascial meridian.

MISCELLANEOUS 1. The flexor carpi radialis, palmaris longus, and flexor carpi ulnaris are often grouped together as the wrist flexor group of the forearm. 2. The palmaris longus arises proximally from the medial epicondyle of the humerus via the common flexor belly/tendon. The common flexor belly/tendon is the common proximal attachment of five muscles: the pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris, and flexor digitorum superficialis. 3. The palmaris longus is the only muscle of the anterior forearm with a tendon that is superficial to the flexor retinaculum. 4. Irritation and/or inflammation of the medial epicondyle and/or the common flexor belly/tendon is known as medial epicondylitis, medial epicondylosis, or golfer’s elbow. 5. In many individuals (approximately 10%-20%), the palmaris longus is bilaterally or unilaterally absent.

307

Flexor Carpi Ulnaris (of Wrist Flexor Group) The name, flexor carpi ulnaris, tells us two of its actions: flexor tells us that this muscle performs flexion, and ulnaris tells us that this muscle performs ulnar deviation (adduction). Both of these actions occur at the wrist joint; carpi refers to the wrist. Derivation flexor: L. a muscle that flexes a body part carpi: L. of the wrist ulnaris: L. refers to the ulnar side (of the forearm) Pronunciation FLEKS-or KAR-pie ul-NA-ris

ATTACHMENTS Medial Epicondyle of the Humerus via the Common Flexor Belly/Tendon, and the Ulna the medial margin of the olecranon and the posterior proximal 2/3 of the ulna to the Anterior Hand on the Ulnar Side the pisiform, the hook of the hamate, and the base of the fifth metacarpal

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes the hand at the wrist joint 2. Ulnar deviates the hand at the wrist joint 3. Flexes the forearm at the elbow joint

Reverse Mover Actions 1. Flexes the forearm at the wrist joint 2. Ulnar deviates the forearm at the wrist joint 3. Flexes the arm at the elbow joint

Standard Mover Action Notes • The flexor carpi ulnaris crosses the wrist joint on the anterior side to attach onto the hand (with its fibers running vertically in the sagittal plane); therefore it flexes the hand at the wrist joint. (action 1) • The flexor carpi ulnaris crosses the wrist joint on the ulnar (medial) side (with its fibers running vertically in the frontal plane); therefore it ulnar deviates (adducts) the hand at the wrist joint. (action 2) • Motion at the wrist joint occurs at the radiocarpal and midcarpal joints. (actions 1, 2) • All three members of the wrist flexor group (flexor carpi radialis, palmaris longus, and flexor carpi ulnaris) can flex the forearm at the elbow joint because they cross it anteriorly (with their fibers running vertically in the sagittal plane). (action 3)

308

FIGURE 7-9

Anterior view of the right flexor carpi ulnaris.

Reverse Mover Action Notes • Reverse actions at the wrist joint occur when the hand is fixed by holding onto an immovable object and the forearm moves relative to the fixed hand. The flexor carpi ulnaris’ sagittal plane reverse action is flexion of the forearm at the wrist joint. Its frontal plane reverse action is ulnar deviation of the forearm at the wrist joint. (reverse actions 1, 2) • The reverse action of flexion of the arm at the elbow joint is extremely important and occurs whenever a person grasps an immovable object and pulls his or her body toward it (examples include using a handicap bar or using a handrail when going up stairs). (reverse action 3)

Motion 1. The flexor carpi ulnaris has one line of pull in an oblique plane and therefore creates one motion, which is a combination of flexion and ulnar deviation of the hand at the wrist joint, and flexion of the forearm at the elbow joint.

Eccentric Antagonist Functions 1. Restrains/slows wrist joint extension and radial deviation

309

2. Restrains/slows elbow joint extension

Eccentric Antagonist Function Note • Restraining/slowing extension of the forearm at the elbow joint is extremely important when lowering an object in a careful and controlled manner.

Isometric Stabilization Functions 1. Stabilizes the wrist joint 2. Stabilizes the elbow joint

Isometric Stabilization Function Note • In addition to stabilizing the wrist joint itself, the flexor carpi ulnaris also stabilizes the pisiform bone of the carpal group. This is important when the abductor digiti minimi manus (intrinsic muscle of the hand) contracts because the pisiform is its proximal attachment and the pisiform must be stabilized/fixed so that this muscle can efficiently abduct the little finger.

I N N E RVAT I O N The Ulnar Nerve C7, C8

A R T E R I A L S U P P LY The Ulnar Artery (a terminal branch of the Brachial Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating hand across the anterior wrist. 2. Have the client actively flex and/or ulnar deviate (adduct) the hand at the wrist joint and feel for the distal tendon of the flexor carpi ulnaris on the ulnar (medial) side of the anterior wrist. Resistance can be added. 3. Continue palpating the flexor carpi ulnaris distally toward the pisiform, and proximally toward the medial epicondyle of the humerus and the posterior ulna. 4. To distinguish the flexor carpi ulnaris from the palmaris longus and the other muscles of the common flexor belly/tendon, ulnar deviation of the hand at the wrist joint is the best action to ask the client to perform.

RELATIONSHIP TO OTHER STRUCTURES The flexor carpi ulnaris is superficial in the medial forearm. The flexor carpi ulnaris is anterior to the extensor carpi ulnaris. Proximally, the flexor carpi ulnaris is medial to the palmaris longus. More distally, the flexor carpi ulnaris is medial to the flexor digitorum superficialis. From the medial perspective, the flexor carpi ulnaris is superficial to the flexor digitorum superficialis and the flexor digitorum profundus. The flexor carpi ulnaris is located within the superficial front arm line myofascial meridian.

MISCELLANEOUS 1. The flexor carpi radialis, palmaris longus, and flexor carpi ulnaris are often grouped together as the wrist flexor group of the forearm. 2. The flexor carpi ulnaris arises proximally from the medial epicondyle of the humerus via the common flexor belly/tendon. The common flexor belly/tendon is the common proximal attachment of five muscles: the pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris, and flexor digitorum superficialis. 3. The flexor carpi ulnaris has two heads: a humeral head and an ulnar head. The humeral head is much larger in mass than the ulnar head (the ulnar head is very thin). 4. The ulnar head attachment of the flexor carpi ulnaris blends with the ulnar attachments of the

310

extensor carpi ulnaris and the flexor digitorum profundus. 5. Some sources describe the distal tendon of the flexor carpi ulnaris ending at the pisiform, with the pull of its contraction passing onto the hamate and the fifth metacarpal via the pisohamate and pisometacarpal ligaments. 6. The ulnar nerve passes between the two heads of the flexor carpi ulnaris. Compression of the ulnar nerve between the two heads of the flexor carpi ulnaris is called cubital tunnel syndrome. 7. The flexor carpi ulnaris is the only muscle of the anterior forearm that is innervated by the ulnar nerve instead of the median nerve. (The flexor digitorum profundus is innervated by both the median and ulnar nerves [and the brachioradialis is innervated by the radial nerve].) 8. Overuse of the flexor carpi ulnaris can cause irritation and/or inflammation of the medial epicondyle and/or the common flexor belly/tendon. This is known as medial epicondylitis, medial epicondylosis, or golfer’s elbow. 9. The flexor carpi ulnaris can be engaged by contracting the abductor digiti minimi manus (ADMM) muscle. Both muscles share a pisiform attachment. When the ADMM contracts to abduct the little finger, the flexor carpi ulnaris isometrically contracts to stabilize the pisiform so that contractile force of the ADMM is more efficiently focused on the little finger.

311

Extensor Carpi Radialis Longus (of Wrist Extensor and Radial Groups) The name, extensor carpi radialis longus, tells us two of its actions: extensor tells us that this muscle performs extension, and radialis tells us that this muscle performs radial deviation (abduction). Both of these actions occur at the wrist joint; carpi refers to the wrist. Longus tells us that this muscle is long (longer than the extensor carpi radialis brevis). Derivation extensor: L. a muscle that extends a body part carpi: L. of the wrist radialis: L. refers to the radial side (of the forearm) longus: L. longer Pronunciation eks-TEN-sor KAR-pie RAY-dee-A-lis LONG-us

ATTACHMENTS Lateral Supracondylar Ridge of the Humerus the distal 1/3 to the Posterior Hand on the Radial Side the posterior side of the base of the second metacarpal

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extends the hand at the wrist joint

Reverse Mover Actions 1. Extends the forearm at the wrist joint

2. Radially deviates the hand at the wrist joint 3. Flexes the forearm at the elbow joint

2. Radially deviates the forearm at the wrist joint

4. Pronates the forearm at the RU joints

4. Pronates the ulna at the RU joints and laterally rotates the arm at the GH joint

5. Supinates the forearm at the RU joints

5. Supinates the ulna at the RU joints and medially rotates the arm at the GH joint

3. Flexes the arm at the elbow joint

RU joints = radioulnar joints; GH joint = glenohumeral joint

Standard Mover Action Notes • The extensor carpi radialis longus crosses the wrist joint posteriorly to attach onto the hand (with its fibers running vertically in the sagittal plane); therefore it extends the hand at the wrist joint. (action 1) • The extensor carpi radialis longus crosses the wrist joint on the radial (lateral) side (with its fibers running vertically in the frontal plane). Therefore the extensor carpi radialis longus radially deviates (abducts) the hand at the wrist joint. (action 2) • The extensor carpi radialis longus crosses the wrist joint posteriorly, so it is an extensor of the wrist joint. However, it crosses the elbow joint anteriorly, so it flexes the elbow joint. (actions 1, 3)

312

FIGURE 7-10

Posterior view of the right extensor carpi radialis longus.

• Similar to the nearby brachioradialis, the extensor carpi radialis longus can both pronate and supinate the forearm at the RU joints. However, it can only pronate a supinated forearm to a position that is approximately halfway between full supination and full pronation; and it can only supinate a pronated forearm to a position that is approximately halfway between full supination and full pronation. This halfway position is the position that has its attachments closest to each other. This is an example of a muscle that has one line of pull but can have two opposite actions at the same joint based on the position of the joint when the muscle contracts. (actions 4, 5) • Pronation/supination of the forearm at the radioulnar joints usually involves motion of the radius around a fixed ulna. (actions 4, 5) • Motion at the wrist joint occurs at the radiocarpal and midcarpal joints. (actions 1, 2)

Reverse Mover Action Notes • Reverse actions at the wrist joint occur when the hand is fixed by holding onto an immovable object and the forearm moves relative to the fixed hand. The extensor carpi radialis longus’ sagittal plane reverse action is extension of the forearm at the wrist joint. Its frontal plane reverse action is radial deviation of the forearm at the wrist joint. (reverse actions 1, 2) • The reverse action of flexion of the arm at the elbow joint is extremely important and occurs

313

whenever a person grasps an immovable object and pulls his or her body toward it (examples include using a handicap bar or using a handrail when going up stairs). (reverse action 3) • The reverse actions of pronation/supination of the ulna around a fixed radius usually occurs only if the hand is fixed by holding onto an immovable object and the ulna moves relative to the fixed radius. Pronation of the ulna is effectively lateral rotation; supination of the ulna is effectively medial rotation. Because the elbow joint does not allow rotation, the humerus will have to move with the ulna. For this reason, the reverse action of forearm pronation causes the arm to laterally rotate at the GH joint; and the reverse action of forearm supination causes the arm to medially rotate at the GH joint. (reverse actions 4, 5)

Motions 1. The extensor carpi radialis longus has one line of pull in an oblique plane and therefore creates one motion, which is a combination of extension and radial deviation of the hand at the wrist joint, and flexion of the forearm at the elbow joint. 2. Note: If the forearm is in a position of full supination, it also creates pronation of the forearm at the RU joints; if the forearm is in a position of full pronation, it also creates supination of the forearm at the RU joints.

Eccentric Antagonist Functions 1. Restrains/slows wrist joint flexion and ulnar deviation 2. Restrains/slows elbow joint extension 3. Restrains/slows RU joints supination and pronation

Eccentric Antagonist Function Note • Restraining/slowing extension of the forearm at the elbow joint is extremely important when lowering an object in a careful and controlled manner.

Isometric Stabilization Functions 1. Stabilizes the wrist joint 2. Stabilizes the elbow joint 3. Stabilizes the RU joints

Isometric Stabilization Function Note • Stabilizing the wrist joint is an important action of the extensor carpi radialis longus. Whenever the flexors digitorum superficialis and profundus contract to make a fist, wrist joint extensor muscles such as the extensor carpi radialis longus must contract to prevent these finger flexor muscles from also flexing the hand at the wrist joint.

I N N E RVAT I O N The Radial Nerve C5, C6

A R T E R I A L S U P P LY Branches of the Brachial Artery (the continuation of the Axillary Artery) and the Radial Artery (a terminal branch of the Brachial Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating hand posterior to the belly of the brachioradialis. 2. Ask the client to radially deviate the hand at the wrist joint and feel for the contraction of the extensor carpi radialis longus. 3. Continue palpating the extensor carpi radialis longus proximally toward the lateral supracondylar ridge of the humerus and distally to the second metacarpal. (Note: Discerning between the extensor carpi radialis longus and extensor carpi radialis brevis is challenging.)

314

RELATIONSHIP TO OTHER STRUCTURES The extensor carpi radialis longus lies directly posterior to the brachioradialis and directly anterior to the extensor carpi radialis brevis. The extensor carpi radialis longus is superficial, except for a small part that is deep to the brachioradialis proximally and a portion of its distal tendon that is deep to the abductor pollicis longus, extensor pollicis brevis, and extensor pollicis longus. The extensor carpi radialis longus is located within the superficial back arm line myofascial meridian.

MISCELLANEOUS 1. The extensor carpi radialis longus, extensor carpi radialis brevis, and extensor carpi ulnaris are often grouped together as the wrist extensor group of the forearm. 2. The extensor carpi radialis longus, the extensor carpi radialis brevis, and the brachioradialis are often grouped together as the radial group of forearm muscles. This group is also known as the wad of three.

315

Extensor Carpi Radialis Brevis (of Wrist Extensor and Radial Groups) The name, extensor carpi radialis brevis, tells us two of its actions: extensor tells us that this muscle performs extension, and radialis tells us that this muscle performs radial deviation (abduction). Both of these actions occur at the wrist joint; carpi refers to the wrist. Brevis tells us that this muscle is short (shorter than the extensor carpi radialis longus). Derivation extensor: L. a muscle that extends a body part carpi: L. of the wrist radialis: L. refers to the radial side (of the forearm) brevis: L. shorter Pronunciation eks-TEN-sor KAR-pie RAY-dee-A-lis BRE-vis

ATTACHMENTS Lateral Epicondyle of the Humerus via the Common Extensor Belly/Tendon to the Posterior Hand on the Radial Side

the posterior side of the base of the third metacarpal

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extends the hand at the wrist joint

Reverse Mover Actions 1. Extends the forearm at the wrist joint

2. Radially deviates the hand at the wrist joint 3. Flexes the forearm at the elbow joint

2. Radially deviates the forearm at the wrist joint

4. Pronates the forearm at the RU joints

4. Pronates the ulna at the RU joints and laterally rotates the arm at the GH joint

5. Supinates the forearm at the RU joints

5. Supinates the ulna at the RU joints and medially rotates the arm at the GH joint

3. Flexes the arm at the elbow joint

RU joints = radioulnar joints; GH joint = glenohumeral joint

Standard Mover Action Notes • The extensor carpi radialis brevis crosses the wrist joint posteriorly to attach onto the hand (with its fibers running vertically in the sagittal plane); therefore it extends the hand at the wrist joint. (action 1) • The extensor carpi radialis brevis crosses the wrist joint on the radial (lateral) side (with its fibers running vertically in the frontal plane); therefore it radially deviates (abducts) the hand at the wrist joint. (action 2)

316

FIGURE 7-11

Posterior view of the right extensor carpi radialis brevis. The extensor carpi radialis longus (ECRL) has been ghosted in.

• Motion at the wrist joint occurs at the radiocarpal and midcarpal joints. (actions 1, 2) • The extensor carpi radialis brevis crosses the wrist joint posteriorly, so it is an extensor of the wrist joint. However, it crosses the elbow joint anteriorly, so it flexes the elbow joint. (actions 1, 3) • Similar to the nearby brachioradialis, the extensor carpi radialis brevis can both pronate and supinate the forearm at the RU joints. However, it can only pronate a supinated forearm to a position that is approximately halfway between full supination and full pronation; and it can only supinate a pronated forearm to a position that is approximately halfway between full supination and full pronation. This halfway position is the position that has its attachments closest to each other. This is an example of a muscle that has one line of pull but can have two opposite actions at the same joint based on the position of the joint when the muscle contracts. (actions 4, 5) • Pronation/supination of the forearm at the RU joints usually involves motion of the radius around a fixed ulna. (actions 4, 5)

Reverse Mover Action Notes • Reverse actions at the wrist joint occur when the hand is fixed by holding onto an immovable object and the forearm moves relative to the fixed hand. The extensor carpi radialis brevis’

317

sagittal plane reverse action is extension of the forearm at the wrist joint. Its frontal plane reverse action is radial deviation of the forearm at the wrist joint. (reverse actions 1, 2) • The reverse action of flexion of the arm at the elbow joint is extremely important and occurs whenever a person grasps an immovable object and pulls his or her body toward it (examples include using a handicap bar or using a handrail when going up stairs). (reverse action 3) • The reverse actions of pronation/supination of the ulna around a fixed radius usually occur only if the hand is fixed by holding onto an immovable object and the ulna moves relative to the fixed radius. Pronation of the ulna is effectively lateral rotation; supination of the ulna is effectively medial rotation. Because the elbow joint does not allow rotation, the humerus will have to move with the ulna. For this reason, the reverse action of forearm pronation causes the arm to laterally rotate at the GH joint; and the reverse action of forearm supination causes the arm to medially rotate at the GH joint. (reverse actions 4, 5)

Motions 1. The extensor carpi radialis brevis has one line of pull in an oblique plane and therefore creates one motion, which is a combination of extension and radial deviation of the hand at the wrist joint, and flexion of the forearm at the elbow joint. 2. Note: If the forearm is in a position of full supination, it also creates pronation of the forearm at the RU joints; if the forearm is in a position of full pronation, it also creates supination of the forearm at the RU joints.

Eccentric Antagonist Functions 1. Restrains/slows wrist joint flexion and ulnar deviation 2. Restrains/slows elbow joint extension 3. Restrains/slows RU joints supination and pronation

Eccentric Antagonist Function Note • Restraining/slowing extension of the forearm at the elbow joint is extremely important when lowering an object in a careful and controlled manner.

Isometric Stabilization Functions 1. Stabilizes the wrist joint 2. Stabilizes the elbow joint 3. Stabilizes the RU joints

Isometric Stabilization Function Note • Stabilizing the wrist joint is an important action of the extensor carpi radialis brevis. Whenever the flexors digitorum superficialis and profundus contract to make a fist, wrist joint extensor muscles such as the extensor carpi radialis brevis must contract to prevent these finger flexor muscles from also flexing the hand at the wrist joint. Of all wrist joint extensors, the extensor carpi radialis brevis is usually the most active with regard to stabilizing and thereby preventing flexion of the hand at the wrist joint.

I N N E RVAT I O N The Radial Nerve posterior interosseus nerve, C7, C8

A R T E R I A L S U P P LY Branches of the Brachial Artery (the continuation of the Axillary Artery) and the Radial Artery (a terminal branch of the Brachial Artery)

PA L PAT I O N 1. With the client seated or supine, pinch the radial group of the forearm muscles (brachioradialis, extensor carpi radialis longus, and extensor carpi radialis brevis) with your thumb on one side and your index and middle fingers on the other side and pull it slightly away from the forearm.

318

The fingers on the posterior aspect of the radial group are on the extensor carpi radialis brevis. 2. Have the client radially deviate the hand at the wrist joint and feel for the contraction of the extensor carpi radialis brevis. (Note: Discerning between the extensor carpi radialis brevis and extensor carpi radialis longus is challenging.) 3. The distal tendon of the extensor carpi radialis brevis can be visualized and easily palpated on the radial side of the posterior wrist when the client makes a fist (flexes the fingers) with the wrist in neutral position (or in slight extension).

RELATIONSHIP TO OTHER STRUCTURES The extensor carpi radialis brevis is superficial, except for a small part that is deep to the brachioradialis and the extensor carpi radialis longus proximally and a portion of its distal tendon, which is deep to the abductor pollicis longus, extensor pollicis brevis, and extensor pollicis longus. The actual distal attachment onto the third metacarpal is deep to the distal tendon of the extensor indicis. The extensor carpi radialis brevis lies directly posterior to the extensor carpi radialis longus and directly anterior to the extensor digitorum. The extensor carpi radialis brevis is located within the superficial back arm line myofascial meridian.

MISCELLANEOUS 1. The extensor carpi radialis longus, extensor carpi radialis brevis, and extensor carpi ulnaris are often grouped together as the wrist extensor group of the forearm. 2. The extensor carpi radialis brevis, the extensor carpi radialis longus, and the brachioradialis are often grouped together as the radial group of forearm muscles. This group is also known as the wad of three. 3. The extensor carpi radialis brevis arises proximally from the lateral epicondyle of the humerus via the common extensor belly/tendon. The common extensor belly/tendon is the common proximal attachment of four muscles: the extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris. (The anconeus and the supinator also arise from the lateral epicondyle of the humerus, but not from the common extensor belly/tendon.) 4. Overuse of the extensor carpi radialis brevis can cause irritation and/or inflammation of the lateral epicondyle and/or the common extensor belly/tendon. This is known as lateral epicondylitis, lateral epicondylosis, or tennis elbow.

319

Extensor Carpi Ulnaris (of Wrist Extensor Group) The name, extensor carpi ulnaris, tells us two of its actions: extensor tells us that this muscle performs extension, and ulnaris tells us that this muscle performs ulnar deviation (adduction). Both of these actions occur at the wrist joint; carpi refers to the wrist. Derivation extensor: L. a muscle that extends a body part carpi: L. of the wrist ulnaris: L. refers to the ulnar side (of the forearm) Pronunciation eks-TEN-sor KAR-pie ul-NA-ris

ATTACHMENTS Lateral Epicondyle of the Humerus via the Common Extensor Belly/Tendon, and the Ulna the posterior middle 1/3 of the ulna to the Posterior Hand on the Ulnar Side the posterior side of the base of the fifth metacarpal

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extends the hand at the wrist joint

Reverse Mover Actions 1. Extends the forearm at the wrist joint

2. Ulnar deviates the hand at the wrist joint 3. Extends the forearm at the elbow joint

2. Ulnar deviates the forearm at the wrist joint

4. Pronates the forearm at the RU joints

4. Pronates the ulna at the RU joints and laterally rotates the arm at the GH joint

3. Extends the arm at the elbow joint

RU joints = radioulnar joints; GH joint = glenohumeral joint

Standard Mover Action Notes • The extensor carpi ulnaris crosses the wrist joint posteriorly to attach onto the hand (with its fibers running vertically in the sagittal plane); therefore it extends the hand at the wrist joint. (action 1) • The extensor carpi ulnaris crosses the wrist joint on the ulnar (medial) side (with its fibers running vertically in the frontal plane); therefore it ulnar deviates (adducts) the hand at the wrist joint. (action 2) • Motion at the wrist joint occurs at the radiocarpal and midcarpal joints. (actions 1, 2) • The extensor carpi ulnaris crosses the elbow joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it extends the forearm at the elbow joint. (action 3)

320

FIGURE 7-12

Posterior view of the right extensor carpi ulnaris. The extensor digiti minimi has been ghosted in.

• The extensor carpi ulnaris can only pronate a supinated forearm to a position that is halfway between full supination and full pronation. Pronation of the forearm at the RU joints usually involves motion of the radius around a fixed ulna. (action 4)

Reverse Mover Action Notes • Reverse actions at the wrist joint occur when the hand is fixed by holding onto an immovable object and the forearm moves relative to the fixed hand. The extensor carpi ulnaris’ sagittal plane reverse action is extension of the forearm at the wrist joint. Its frontal plane reverse action is ulnar deviation of the forearm at the wrist joint. (reverse actions 1, 2) • Reverse actions at the elbow joint occur when the forearm is fixed (usually when the hand is holding onto an immovable object) and the arm moves relative to the fixed forearm. The extensor carpi ulnaris’ sagittal plane reverse action is extension of the arm at the elbow joint. • The reverse action of pronation of the ulna around a fixed radius usually occurs only if the hand is fixed by holding onto an immovable object and the ulna moves relative to the fixed radius. Pronation of the ulna is effectively lateral rotation. Because the elbow joint does not allow rotation, the humerus will have to move with the ulna. For this reason, the reverse action of forearm pronation causes the arm to laterally rotate at the GH joint. (reverse action 4)

321

Motion 1. The extensor carpi ulnaris has one line of pull in an oblique plane and therefore creates one motion, which is a combination of extension and ulnar deviation of the hand at the wrist joint, and extension of the forearm at the elbow joint (as well as pronation of the forearm at the RU joints).

Eccentric Antagonist Functions 1. Restrains/slows wrist joint flexion and radial deviation 2. Restrains/slows elbow joint flexion 3. Restrains/slows RU joints supination

Isometric Stabilization Functions 1. Stabilizes the wrist joint 2. Stabilizes the elbow joint 3. Stabilizes the RU joints

Isometric Stabilization Function Note • Stabilizing the wrist joint is an important action of the extensor carpi ulnaris. Whenever the flexors digitorum superficialis and profundus contract to make a fist, wrist joint extensor muscles such as the extensor carpi ulnaris must contract to prevent these finger flexor muscles from also flexing the hand at the wrist joint.

I N N E RVAT I O N The Radial Nerve posterior interosseus nerve, C7, C8

A R T E R I A L S U P P LY The Posterior Interosseus Artery (a branch of the Ulnar Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating hand directly posterior to the shaft of the ulna and feel for the belly of the extensor carpi ulnaris. 2. Continue palpating the extensor carpi ulnaris proximally toward the lateral epicondyle of the humerus and distally toward the fifth metacarpal. 3. To further bring out the extensor carpi ulnaris, have the client ulnar deviate (adduct) the hand at the wrist joint.

RELATIONSHIP TO OTHER STRUCTURES The extensor carpi ulnaris is superficial in the posterior forearm and is medial to the extensor digiti minimi and lateral (posterior) to the medial border of the ulna and the flexor carpi ulnaris. The anconeus is proximal to the extensor carpi ulnaris. The extensor carpi ulnaris is superficial to the shaft of the ulna and the deeper layer of posterior forearm muscles, which includes the supinator, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis. The extensor carpi ulnaris is located within the superficial back arm line myofascial meridian.

MISCELLANEOUS 1. The extensor carpi radialis longus, extensor carpi radialis brevis, and extensor carpi ulnaris are often grouped together as the wrist extensor group of the forearm. 2. The extensor carpi ulnaris arises proximally from the lateral epicondyle of the humerus via the common extensor belly/tendon. The common extensor belly/tendon is the common proximal attachment of four muscles: the extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris. (The anconeus and the supinator also arise from the lateral epicondyle of the humerus, but not from the common extensor belly/tendon.)

322

3. The extensor carpi ulnaris has two heads: a humeral head and an ulnar head. The humeral head is much larger in mass than the ulnar head (the ulnar head is very thin). 4. The attachment of the extensor carpi ulnaris onto the ulna blends with the ulnar attachment of the flexor carpi ulnaris and the flexor digitorum profundus. 5. Overuse of the extensor carpi ulnaris can cause irritation and/or inflammation of the lateral epicondyle and/or the common extensor belly/tendon. This is known as lateral epicondylitis, lateral epicondylosis, or tennis elbow.

323

REVIEW QUESTIONS 1. What muscles make up the radial group of forearm muscles? What is a common name for this group? ____________________________ ____________________________ ____________________________ 2. Motion of the wrist occurs at what two joints? ____________________________ ____________________________ 3. What is the functional significance of the palmaris longus’s action of wrinkling the skin of the palm? ____________________________ ____________________________ 4. What carpal bone is stabilized by the flexor carpi ulnaris? When would this isometric stability function be utilized? ____________________________ ____________________________ 5. Cubital tunnel syndrome is a name given to compression of which nerve? ____________________________ 6. When the extrinsic flexors of the fingers contract to make a fist, there must be a force of extension to prevent flexion of the hand at the wrist joint. Of all the wrist joint extensors, which muscle is the most active with regards to stabilizing, and thereby preventing, flexion of the hand at the wrist joint? ____________________________ 7. Overuse of the wrist/finger joint flexors or extensors can result in inflammation or injury to their common belly/tendon attachments. What are these conditions commonly called? ____________________________ ____________________________ ____________________________ ____________________________ 8. When palpating the flexor carpi radialis, what motion is best used to distinguish it from the palmaris longus and/or the other muscles of the common flexor belly/tendon? ____________________________ 9. What is the relationship of the extensor carpi radialis longus to its neighboring structures? ____________________________ ____________________________ ____________________________ 10. What muscles make up the wrist extensor group? ____________________________ ____________________________ ____________________________ For answers to these questions, visit http://evolve.elsevier.com/Muscolino/muscular

324

THINK IT THROUGH Is it possible for a muscle such as the flexor carpi radialis to cause motion at the glenohumeral joint? If so, how? ____________________________ ____________________________ ____________________________ ____________________________ ____________________________

325

CHAPTER 8

326

Extrinsic Muscles of the Finger Joints CHAPTER OUTLINE Flexor digitorum superficialis Flexor digitorum profundus Flexor pollicis longus Extensor digitorum Extensor digiti minimi Deep distal four group Abductor pollicis longus Extensor pollicis brevis Extensor pollicis longus Extensor indicis

OBJECTIVES After completing this chapter, the student should be able to perform the following for each of the muscles covered in the chapter: 1. Explain the general structure. 2. Explain the general function 3. State the attachments. 4. State the standard mover actions. 5. State the reverse mover actions. 6. Discuss the line(s) of pull the muscle has and the motion(s) created. 7. State the eccentric antagonist functions. 8. State the isometric stabilization functions. 9. State the nervous innervation.

10. State the arterial supply. 11. Describe the starting position for palpation. 12. Describe the steps for palpation. 13. Discuss the muscle’s relationship to other body structures. 14. Discuss additional information that may help with palpation, assessment, and clinical decision-making. CHAPTER OVERVIEW The muscles addressed in this chapter are the extrinsic muscles of the hand that move the fingers, including the thumb. Extrinsic muscles of the hand attach proximally to the arm or forearm and then travel distally to enter and attach to the hand. Intrinsic muscles of the hand that also move the fingers are addressed in Chapter 9 (intrinsic muscles of the hand are wholly located within the hand; in other words, they begin and end in the hand). Note: For cross-sectional views of the forearm, wrist, and hand, see Figures 7-6, 9-3A, and 93B, respectively.

327

Overview of STRUCTURE Structurally, extrinsic muscles of the hand that move the fingers can be divided into three groups: flexors, superficial extensors, and the deep extensors of the deep distal four group. The flexors are the flexor digitorum superficialis, flexor digitorum profundus, and flexor pollicis longus. The superficial extensors are the extensor digitorum and extensor digiti minimi. The deep distal four group is composed of the abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis. Three of the four muscles of this group have the word pollicis in their name because they move the thumb (pollicis means thumb); the extensor indicis moves the index finger. The finger flexors are located in the anterior forearm, and the superficial finger extensors are located in the posterior forearm. The deep distal four muscles are located deep in the distal posterior forearm. Note: The common flexor belly/tendon is usually referred to simply as the common flexor tendon. However, the bellies of these muscles usually blend long before the tendons of the muscles blend. Similarly, the common extensor belly/tendon is usually referred to simply as the common extensor tendon. However, the bellies of these muscles also usually blend long before the tendons of the muscles blend.

Compartments of the Forearm: Forearm musculature is usually divided into anterior and posterior compartments. • The anterior compartment is composed of three layers: superficial, intermediate, and deep.

• The superficial layer contains the pronator teres, wrist flexor group (flexor carpi radialis, palmaris longus, flexor carpi ulnaris), and brachioradialis. • The intermediate layer contains the flexor digitorum superficialis. • The deep layer contains the flexor digitorum profundus, flexor pollicis longus, and pronator quadratus. • The posterior compartment is composed of two layers: superficial and deep.

• The superficial layer contains the wrist extensor group (extensor carpi radialis longus, extensor carpi radialis brevis, and extensor carpi ulnaris), extensor digitorum, extensor digiti minimi, and anconeus. • The deep layer contains the supinator and the deep distal four group (abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis). • Note: Some sources describe a radial group that is composed of the brachioradialis (of the anterior compartment) and the extensors carpi radialis longus and brevis (of the posterior compartment). Overview of FUNCTION The following general rules regarding actions can be stated for the functional groups of extrinsic finger muscles: Fingers two through five can move at three joints: the metacarpophalangeal (MCP), proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints. If a muscle crosses only the MCP joint, it can move the finger only at the MCP joint. If the muscle crosses the MCP and PIP joints, it can move the finger at both of these joints. If the muscle crosses the MCP, PIP, and DIP joints, it can move the finger at all three joints. Note: The little finger can also move at the carpometacarpal (CMC) joint. The thumb (finger one) can move at three joints: the carpometacarpal (CMC), metacarpophalangeal (MCP), and interphalangeal (IP) joints. Similarly, a muscle can only move

328

the thumb at a joint or joints that it crosses. If a muscle crosses the MCP, PIP, or DIP joints of fingers two through five on the anterior side, it can flex the finger at the joint(s) crossed; if a muscle crosses the MCP, PIP, or DIP joints of fingers two through five on the posterior side, it can extend the finger at the joint(s) crossed. If a muscle crosses the MCP joint of fingers two, three, four, or five on the side that faces the middle finger, it can adduct the finger at the MCP joint by bringing the finger toward the middle finger; if a muscle crosses the MCP joint of fingers two, three, or four on the side that is away from the middle-finger side, it can abduct the finger at the MCP joint by bringing the finger away from the middle finger (the middle finger abducts in both directions, radial and ulnar abduction). Muscles that cross the CMC, MCP, and IP joints of the thumb on the medial side can flex the thumb at the joint(s) crossed; muscles that cross the CMC, MCP, and IP joints of the thumb on the lateral side can extend the thumb at the joint(s) crossed. Muscles that cross the CMC joint of the thumb on the anterior side can abduct the thumb at the CMC joint; muscles that cross the CMC joint of the thumb on the posterior side can adduct the thumb at the CMC joint. Reverse actions involve the proximal attachment moving toward the distal one. This would occur when the fingers are holding onto a fixed, immovable object. Because extrinsic finger/thumb muscles attach proximally to the arm or forearm, they can also move the wrist, elbow, and/or radioulnar joints. If a muscle crosses the elbow or wrist joint anteriorly, it can flex them; if it crosses these joints posteriorly, it can extend. If a muscle crosses the wrist joint on the lateral (radial) side, it can radially deviate (abduct) the hand at the wrist joint; if it crosses it on the medial (ulnar) side, it can ulnar deviate (adduct). If the muscle crosses the radioulnar joints, it can pronate or supinate the forearm at the radioulnar joints.

http://evolve.elsevier.com/Muscolino/muscular

329

Anterior View of the Muscles of the Right Wrist Joint and Extrinsic Finger Muscles—Superficial View

FIGURE 8-1

Anterior views of the muscles of the right wrist joint and extrinsic finger muscles. A, Superficial view.

330

Anterior View of the Muscles of the Right Wrist Joint and Extrinsic Finger Muscles—Intermediate View

FIGURE 8-1

B, Intermediate view.

331

Anterior View of the Muscles of the Right Wrist Joint and Extrinsic Finger Muscles—Deep View

FIGURE 8-1

C, Deep view. The brachialis has been cut and ghosted in.

332

Posterior View of the Muscles of the Right Wrist Joint and Extrinsic Finger Muscles—Superficial View

FIGURE 8-2 Posterior views of the muscles of the right wrist joint and extrinsic finger muscles. A, Superficial view. The triceps brachii and flexor carpi ulnaris have been ghosted in.

333

Posterior Views of the Muscles of the Right Wrist Joint and Extrinsic Finger Muscles—Intermediate and Deep Views

FIGURE 8-2

B, Intermediate view. C, Deep view.

334

Lateral View of the Muscles of the Right Wrist Joint and Extrinsic Finger Muscles

FIGURE 8-3

Lateral and medial views of the muscles of the right wrist joint and extrinsic finger muscles. A, Lateral view.

335

Medial View of the Muscles of the Right Wrist Joint and Extrinsic Finger Muscles

FIGURE 8-3

B, Medial view.

336

Flexor Digitorum Superficialis (FDS) The name, flexor digitorum superficialis, tells us that this muscle flexes the digits (i.e., fingers) and is superficial (superficial to the flexor digitorum profundus). Derivation flexor: L. a muscle that flexes a body part digitorum: L. refers to a digit (finger) superficialis: L. superficial (near the surface) Pronunciation FLEKS-or dij-i-TOE-rum SOO-per-fish-ee-A-lis

ATTACHMENTS Medial Epicondyle of the Humerus via the Common Flexor Belly/Tendon, and the Anterior Ulna and Radius HUMEROULNAR HEAD: medial epicondyle of the humerus (via the common flexor belly/tendon) and the coronoid process of the ulna RADIAL HEAD: proximal 1/2 of the anterior shaft of the radius (starting just distal to the radial tuberosity) to the Anterior Surfaces of Fingers Two through Five each of the four tendons divides into two slips that attach onto the sides of the anterior surface of the middle phalanx

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes fingers two through five at the MCP and PIP joints 2. Flexes the hand at the wrist joint 3. Flexes the forearm at the elbow joint

Reverse Mover Actions 1. Flexes the metacarpals at the MCP joints and flexes the proximal phalanges at the PIP joints 2. Flexes the forearm at the wrist joint 3. Flexes the arm at the elbow joint

MCP joints = metacarpophalangeal joints; PIP joints = proximal interphalangeal joints

Standard Mover Action Notes • The flexor digitorum superficialis (FDS) crosses the MCP and PIP joints of fingers two through five on the anterior side (with its fibers running vertically in the sagittal plane). Therefore the FDS flexes fingers two through five at the MCP and PIP joints. (action 1) • More specifically, the FDS flexes the proximal phalanx of each finger at the MCP joint and flexes the middle phalanx of each finger at the PIP joint. (action 1)

337

FIGURE 8-4

Anterior view of the right flexor digitorum superficialis. The distal ends of the biceps brachii and brachialis have been ghosted in.

• The FDS does not cross and therefore cannot move the fingers at the distal interphalangeal (DIP) joints; only the flexor digitorum profundus crosses and can flex the DIP joints. Because so many other (intrinsic hand) muscles cross and can flex the MCP joints, the major action of the FDS is flexion of the middle phalanx of fingers two through five at the PIP joint. (action 1) • The FDS crosses the wrist joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the hand at the wrist joint. Motion at the wrist joint occurs at the radiocarpal and midcarpal joints. (action 2) • The FDS crosses the elbow joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the forearm at the elbow joint. (action 3)

Reverse Mover Action Notes • Reverse actions at the MCP and PIP joints usually occur when the distal bones of the fingers are fixed, usually by holding onto an immovable object, requiring the proximal bone at each joint to move instead. (reverse action 1) • Reverse actions at the wrist joint occur when the hand is fixed by holding onto an immovable object and the forearm moves relative to the fixed hand. (reverse action 2) • The reverse action of flexion of the arm at the elbow joint is extremely important and occurs whenever a person grasps an immovable object and pulls his or her body toward it (examples include using a handicap bar or using a handrail when going up stairs). (reverse action 3)

Motions

338

1. Because the flexor digitorum superficialis splits into four separate tendons, depending on which fibers/motor units contract, flexion of each finger (two through five) at the MCP and PIP joints can be performed separately. 2. Regarding the rest of the actions that the flexor digitorum superficialis can create, it has one line of pull in the sagittal plane. Therefore, while finger flexion is occurring, it must also flex the hand at the wrist joint and flex the forearm at the elbow joint.

Eccentric Antagonist Functions 1. Restrains/slows MCP and PIP joint extension 2. Restrains/slows wrist joint extension 3. Restrains/slows elbow joint extension

Eccentric Antagonist Function Note • Restraining/slowing extension of the forearm at the elbow joint is extremely important when lowering an object in a careful and controlled manner.

Isometric Stabilization Functions 1. Stabilizes the MCP and PIP joints 2. Stabilizes the wrist joint 3. Stabilizes the elbow joint 4. Stabilizes the RU joints

Isometric Stabilization Function Note • Even though the FDS has little or no action across the radioulnar (RU) joints because the direction of its fibers is vertical, given that it does cross the RU joints, it can help stabilize these joints.

Additional Notes on Actions 1. Some sources state that both the flexors digitorum superficialis and profundus can also contribute to adduction of fingers two, four, and five at the MCP joints. 2. Some sources state that the flexor digitorum superficialis can contribute to ulnar deviation of the hand at the wrist joint. Given that the more medial fibers cross into the hand on the ulnar side, they could contribute to ulnar deviation of the wrist joint.

I N N E RVAT I O N The Median Nerve C7, C8, T1

A R T E R I A L S U P P LY The Ulnar and Radial Arteries (terminal branches of the Brachial Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating hand on the medial side of the proximal anterior forearm approximately 1/2 inch (1 cm) anterior to the medial border of the shaft of the ulna. 2. Have the client actively flex fingers two through five at the metacarpophalangeal joints (keep the fingers extended at the interphalangeal joints) and feel for the contraction of the flexor digitorum superficialis (FDS). 3. Continue palpating the FDS proximally toward the humeral attachment and distally toward the fingers.

RELATIONSHIP TO OTHER STRUCTURES The flexor digitorum superficialis (FDS) is located in the anterior forearm, directly deep to the flexor carpi radialis, palmaris longus, and flexor carpi ulnaris. From the medial perspective, the FDS is deep to the ulnar head of the flexor carpi ulnaris. Deep to the flexor FDS are the flexor digitorum profundus and flexor pollicis longus.

339

The four tendons of the FDS travel through the carpal tunnel medial to the median nerve and superficial to the four tendons of the flexor digitorum profundus. The flexor digitorum superficialis is located within the superficial front arm line myofascial meridian.

MISCELLANEOUS 1. The flexor digitorum superficialis (FDS) is also known as the flexor digitorum sublimis. 2. The humeral attachment of the FDS arises from the medial epicondyle of the humerus via the common flexor belly/tendon. The common flexor belly/tendon is the common proximal attachment of five muscles: the pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris, and the FDS. 3. The four distal tendons of the FDS are arranged in two layers, with the tendons going to the middle and ring fingers superficially and the tendons going to the little finger and index finger deeply. (If you take your own little finger and index finger and you make them touch behind the middle and ring fingers, you will have the arrangement that these tendons are in when they travel through the carpal tunnel.) 4. The distal tendons of the FDS attach onto the middle phalanges in an unusual manner. Because the distal tendons of the flexor digitorum profundus are deeper and yet they must ultimately attach further distally onto the distal phalanges, the tendons of the FDS must split to allow passage of the tendons of the flexor digitorum profundus through to the distal phalanges. Each one of the split distal tendons of the FDS then attaches onto both sides of the anterior surface of the middle phalanx. (This arrangement is essentially identical to that of the splitting of each of the distal tendons of the flexor digitorum brevis’ distal tendon to allow passage of the flexor digitorum longus’ distal tendon onto the distal phalanx of toes two through five in the lower extremity.) 5. The median nerve and ulnar artery travel between the two heads of the FDS. 6. Irritation of the synovial sheaths of the FDS and/or the flexor digitorum profundus in the carpal tunnel can press on the median nerve and cause carpal tunnel syndrome. 7. Irritation and/or inflammation of the medial epicondyle and/or the common flexor belly/tendon is known as medial epicondylitis, medial epicondylosis, or golfer’s elbow.

340

Flexor Digitorum Profundus (FDP) The name, flexor digitorum profundus, tells us that this muscle flexes the digits (i.e., fingers) and is deep (deep to the flexor digitorum superficialis). Derivation flexor: L. a muscle that flexes a body part digitorum: L. refers to a digit (finger) profundus: L. deep Pronunciation FLEKS-or dij-i-TOE-rum pro-FUN-dus

ATTACHMENTS Medial and Anterior Ulna the proximal 1/2 (starting just distal to the ulnar tuberosity) and the interosseus membrane to the Anterior Surfaces of Fingers Two through Five the distal phalanges

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes fingers two through five at the MCP, PIP, and DIP joints 2. Flexes the hand at the wrist joint

Reverse Mover Actions 1. Flexes the metacarpals at the MCP joints, flexes the proximal phalanges at the PIP joints, and flexes the middle phalanges at the DIP joints 2. Flexes the forearm at the wrist joint

MCP joints = metacarpophalangeal joints; PIP joints = proximal interphalangeal joints; DIP joints = distal interphalangeal joints

Standard Mover Action Notes • The flexor digitorum profundus (FDP) crosses the MCP and the PIP and DIP joints of fingers two through five on the anterior side (with its fibers running vertically in the sagittal plane). Therefore the FDP flexes fingers two through five at the MCP and the PIP and DIP joints. (action 1) • More specifically, the FDP flexes the proximal phalanx of each finger at the MCP joint, flexes the middle phalanx of each finger at the PIP joint, and flexes the distal phalanx of each finger at the DIP joint. (action 1) • The FDP crosses and can flex fingers two through five at the MCP, PIP, and DIP joints. However, because it is the only muscle that can flex the DIP joints, it is especially important for this action. (action 1) • The tautness (passive elastic recoil force) of the FDP is responsible for the partially flexed position of fingers two through five at the MCP, PIP, and DIP joints.

341

FIGURE 8-5

Anterior view of the right flexor digitorum profundus. The pronator quadratus and distal end of the brachialis have been ghosted in.

• The muscle bellies for each individual finger of the FDP are not well separated (except for the index finger). Therefore it is difficult to isolate DIP joint flexion of just one finger. (action 1) • The FDP crosses the wrist joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the hand at the wrist joint. Motion at the wrist joint occurs at the radiocarpal and midcarpal joints. (action 2)

Reverse Mover Action Notes • Reverse actions at the MCP and interphalangeal joints usually occur when the distal bones of the fingers are fixed, usually by holding onto an immovable object, requiring the proximal bone at each joint to move instead. (reverse action 1) • Reverse actions at the wrist joint occur when the hand is fixed by holding onto an immovable object and the forearm moves relative to the fixed hand. (reverse action 2)

Motions 1. Because the flexor digitorum profundus splits into four separate tendons, depending on which fibers/motor units contract, flexion of each finger (two through five) at the MCP, PIP, and DIP joints can be performed separately.

342

2. Regarding the rest of the actions that the flexor digitorum profundus can create, it has one line of pull in an oblique plane. Therefore, while finger flexion is occurring, it must also flex the forearm at the wrist joint.

Eccentric Antagonist Functions 1. Restrains/slows MCP, PIP, and DIP joint extension 2. Restrains/slows wrist joint extension

Isometric Stabilization Functions 1. Stabilizes the MCP, PIP, and DIP joints 2. Stabilizes the wrist joint

Additional Notes on Actions 1. Some sources state that both the flexors digitorum superficialis and profundus can also contribute to adduction of fingers two, four, and five at the MCP joints. 2. Some sources state that the flexor digitorum profundus can contribute to ulnar deviation of the hand at the wrist joint. Given that the more medial fibers cross into the hand on the ulnar side, they could contribute to ulnar deviation of the wrist joint.

I N N E RVAT I O N The Median and the Ulnar Nerves C8, T1 the anterior interosseus branch of the median nerve

A R T E R I A L S U P P LY The Ulnar and Radial Arteries (terminal branches of the Brachial Artery) and the Anterior Interosseus Artery (a branch of the Ulnar Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating hand on the medial side of the proximal forearm immediately anterior to the medial border of the shaft of the ulna. 2. Have the client flex the fingers at the interphalangeal joints (keep the metacarpophalangeal joints extended) and feel for the contraction of the flexor digitorum profundus. 3. Continue palpating the flexor digitorum profundus as far proximally and distally as possible.

RELATIONSHIP TO OTHER STRUCTURES From the anterior perspective, the FDP is deep to the flexor digitorum superficialis. From the medial perspective, the FDP is deep to the ulnar head of the flexor carpi ulnaris. The FDP is medial to the flexor pollicis longus. Deep to the FDP are the ulna and the interosseus membrane. The flexor digitorum profundus is located within the superficial front arm line myofascial meridian.

MISCELLANEOUS 1. The distal tendons of the FDP reach their attachment site on the distal phalanges in an unusual manner. The tendons of the flexor digitorum superficialis are superficial and split; the tendons of the FDP then pass through these splits to continue onto the distal phalanges. (This is essentially identical to the arrangement of the flexor digitorum longus and the flexor digitorum brevis of the lower extremity.) 2. Irritation of the synovial sheaths of the flexor digitorum superficialis and/or the FDP in the carpal tunnel can press on the median nerve and cause carpal tunnel syndrome.

343

344

Flexor Pollicis Longus The name, flexor pollicis longus, tells us that this muscle flexes the thumb and is long (longer than the flexor pollicis brevis). Derivation flexor: L. a muscle that flexes a body part pollicis: L. thumb longus: L. long Pronunciation FLEKS-or POL-i-sis LONG-us

ATTACHMENTS Anterior Surface of the Radius and the interosseus membrane, the medial epicondyle of the humerus, and the coronoid process of the ulna to the Thumb the anterior aspect of the base of the distal phalanx

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes the thumb at the CMC, MCP, and IP joints

Reverse Mover Actions 1. Flexes the metacarpal at the MCP joint and flexes the proximal phalanx at the IP joint

2. Flexes the hand at the wrist joint 3. Radially deviates the hand at the wrist joint

2. Flexes the forearm at the wrist joint

4. Flexes the forearm at the elbow joint

4. Flexes the arm at the elbow joint

5. Pronates the forearm at the RU joints

5. Pronates the ulna at the RU joints and laterally rotates the arm at the GH joint

3. Radially deviates the forearm at the wrist joint

CMC joint = carpometacarpal joint; MCP joint = metacarpophalangeal joint; IP joint = interphalangeal joint; RU joints = radioulnar joints; GH joint = glenohumeral joint

Standard Mover Action Notes • The flexor pollicis longus crosses the CMC joint of the thumb medially (on the ulnar side) to attach onto the distal phalanx of the thumb (with its fibers running vertically in the frontal plane). When the flexor pollicis longus contracts, it pulls the thumb medially (in an ulnar direction) within the plane of the palm of the hand (frontal plane) toward the index finger. This action is called flexion of the thumb. Therefore the flexor pollicis longus flexes the thumb by flexing the metacarpal of the thumb at the first CMC joint. Given that thumb flexion is a component of thumb opposition, the flexor pollicis longus does contribute to opposition. The flexor pollicis longus also crosses the MCP and the IP joints of the thumb medially (on the ulnar side) to attach onto the distal phalanx of the thumb. Therefore the flexor pollicis longus also flexes the proximal and distal phalanges of the thumb at these joints as well. Because of the rotational development of the thumb embryologically, the named actions of flexion and extension of the thumb occur within the frontal plane. (action 1)

345

FIGURE 8-6

Anterior view of the right flexor pollicis longus. The pronator quadratus and distal end of the brachialis have been ghosted in.

• The flexor pollicis longus is the only muscle that can flex the thumb at the IP joint; therefore this action best engages it (especially when looking to palpate and discern it from other muscles of the thumb). (action 1) • The flexor pollicis longus crosses the wrist joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the hand at the wrist joint. Motion at the wrist joint occurs at the radiocarpal and midcarpal joints. (action 2) • The flexor pollicis longus crosses the wrist joint on the radial (lateral) side to attach onto the hand (with its fibers running vertically in the frontal plane); therefore it radially deviates (abducts) the hand at the wrist joint. (action 3) • Because the humeroulnar head of the flexor pollicis longus is small or even absent, the actions of elbow joint flexion and pronation of the radioulnar joints are weak or absent. (actions 4, 5) • Pronation of the forearm at the RU joints usually involves motion of the radius around a fixed ulna. (action 5)

Reverse Mover Action Notes • Reverse actions involve moving the proximal attachment toward the distal one. This usually occurs when the distal attachment is fixed, perhaps because it is holding onto an immovable

346

object. (reverse actions 1, 2, 3, 4) • Another reverse action would be to move (flex) the trapezium toward the metacarpal of the thumb at the CMC joint; this would occur if the distal end (the metacarpal) is fixed, perhaps because the thumb is gripping an immovable object. Movement of the trapezium would likely involve movement of the entire carpus (wrist) and forearm relative to the hand. (reverse action 1) • Reverse actions at the wrist joint occur when the hand is fixed by holding onto an immovable object and the forearm moves relative to the fixed hand. (reverse actions 2, 3) • The reverse action, flexion of the arm at the elbow joint, is extremely important and occurs whenever a person grasps an immovable object and pulls his or her body toward it (examples include using a handicap bar or using a handrail when going up stairs). However, because the humeroulnar head of the flexor pollicis longus is very small or even absent, this function would be very weak or absent. (reverse action 4) • The reverse action of pronation of the ulna around a fixed radius usually occurs only if the hand is fixed by holding onto an immovable object and the ulna moves relative to the fixed radius. Because the elbow joint does not allow rotation, this will cause the arm to laterally rotate at the GH joint. However, because the humeroulnar head of the flexor pollicis longus is very small or even absent, this function would be very weak or absent. (reverse action 5)

Motion 1. The flexor pollicis longus has one line of pull in an oblique plane and therefore creates one motion, which is a combination of flexion of the thumb at the CMC, MCP, and PIP joints, flexion of the hand at the wrist joint, and flexion of the forearm at the elbow joint (as well as pronation of the forearm at the RU joints and radial deviation of the hand at the wrist joint).

Eccentric Antagonist Functions 1. Restrains/slows CMC, MCP, and IP joint extension 2. Restrains/slows wrist joint extension 3. Restrains/slows wrist joint ulnar deviation 4. Restrains/slows elbow joint extension 5. Restrains/slows supination of RU joints

Eccentric Antagonist Function Note • Restraining/slowing extension of the forearm at the elbow joint is extremely important when lowering an object in a careful and controlled manner.

Isometric Stabilization Functions 1. Stabilizes the CMC, MCP, and IP joints of the thumb 2. Stabilizes the wrist joint 3. Stabilizes the elbow joint 4. Stabilizes the RU joints

Isometric Stabilization Function Note • Because the humeroulnar head of the flexor pollicis longus is small or even absent, the stabilization force across the elbow and RU joints would be weak or absent.

Additional Note on Actions 1. Some sources state that the flexor pollicis longus can also contribute to adduction of the thumb at the carpometacarpal joint (in the sagittal plane).

I N N E RVAT I O N The Median Nerve the anterior interosseus branch of the median nerve; C7, C8

A R T E R I A L S U P P LY The Radial Artery (a terminal branch of the Brachial Artery) and the Anterior Interosseus Artery (a

347

branch of the Ulnar Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating fingers on the distal anterolateral (anteroradial) forearm. 2. Have the client actively flex the distal phalanx of the thumb at the interphalangeal joint and feel for the contraction of the flexor pollicis longus. Note: It is important that the client isolates thumb motion at the interphalangeal joint so that the flexor pollicis longus can be discerned from adjacent musculature. 3. Continue palpating the flexor pollicis longus as far proximally and distally as possible.

RELATIONSHIP TO OTHER STRUCTURES The flexor pollicis longus is a deep muscle of the anterior forearm. The majority of it is directly deep to the flexor digitorum superficialis. However, a small part of the flexor pollicis longus is superficial in the distal forearm on the medial side (and to a lesser extent, the lateral side) of the distal tendon of the flexor carpi radialis. The flexor pollicis longus is found lateral to the flexor digitorum profundus. Deep to the flexor pollicis longus are the radius and the interosseus membrane. The flexor pollicis longus is located within the superficial front arm line myofascial meridian.

MISCELLANEOUS 1. The distal tendon of the flexor pollicis longus travels through the carpal tunnel lateral to the median nerve. 2. Irritation of the synovial sheath of the flexor pollicis longus in the carpal tunnel can press on the median nerve and cause/contribute to carpal tunnel syndrome. 3. The proximal attachments of the flexor pollicis longus are variable. The medial epicondylar attachment is often missing. Sometimes the coronoid process attachment is on the medial side of the coronoid process; sometimes it is on the lateral side, and other times it is missing altogether. 4. The flexor pollicis longus often blends with the adjacent flexor digitorum profundus, resulting in an inability to isolate flexion of the interphalangeal joint of the thumb from flexion of the distal phalanx of the index finger at the DIP joint.

348

Extensor Digitorum The name, extensor digitorum, tells us that this muscle extends the digits (i.e., fingers). Derivation extensor: L. a muscle that extends a body part digitorum: L. refers to a digit (finger) Pronunciation eks-TEN-sor dij-i-TOE-rum

ATTACHMENTS Lateral Epicondyle of the Humerus via the Common Extensor Belly/Tendon to the Phalanges of Fingers Two through Five

via its dorsal digital expansion onto the posterior surfaces of the middle and distal phalanges

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extends fingers two through five at the MCP, PIP, and DIP joints 2. Extends the hand at the wrist joint 3. Medially rotates the little finger at the CMC joint

Reverse Mover Actions 1. Extends the metacarpals at the MCP joints, extends the proximal phalanges at the PIP joints, and extends the middle phalanges at the DIP joints 2. Extends the forearm at the wrist joint

4. Extends the forearm at the elbow joint

3. Lateral rotation of the hamate (carpus) at the CMC joint 4. Extends the arm at the elbow joint

MCP joints = metacarpophalangeal joints; PIP joints = proximal interphalangeal joints; DIP joints = distal interphalangeal joints; CMC joint = carpometacarpal joint

Standard Mover Action Notes • The extensor digitorum crosses the MCP joint and the PIP and DIP joints posteriorly to finally attach onto the distal phalanges of fingers two through five (with its fibers running vertically in the sagittal plane). Therefore the extensor digitorum extends fingers two through five at the MCP, PIP, and DIP joints. (action 1) • More specifically, the extensor digitorum extends the proximal phalanx of each finger at the MCP joint, extends the middle phalanx of each finger at the PIP joint, and extends the distal phalanx of each finger at the DIP joint. (action 1) • Distally, the tendons of the extensor digitorum are somewhat tied together by intertendinous connections, making independent movement of an individual finger more difficult. (action 1)

349

FIGURE 8-7 Posterior view of the right extensor digitorum. The extensor digiti minimi (EDM) and the cut extensor carpi ulnaris (ECU) and cut extensor carpi radialis brevis (ECRB) have been ghosted in.

• The extensor digitorum crosses the wrist joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it extends the hand at the wrist (radiocarpal and midcarpal) joint. (action 2) • The tendon of the extensor digitorum that goes to the little finger (finger five) crosses the fifth CMC joint posteriorly from lateral on the lateral epicondyle to attach more medially onto the phalanges of the little finger (with its fibers running slightly horizontally in the transverse plane). When the extensor digitorum contracts, it pulls the posterior side of the little finger laterally. This is medial rotation of the little finger, because the anterior surface of the little finger rotates medially. Therefore the extensor digitorum medially rotates the metacarpal of the little finger at the fifth CMC joint. (action 3) • Medial rotation of the little finger at the CMC joint is an important part of repositioning the little finger back to anatomic position from a position of opposition to the thumb. (action 3) • The extensor digitorum crosses the elbow joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it extends the forearm at the elbow joint. (action 4)

Reverse Mover Action Notes • Reverse actions at the MCP, PIP, and DIP joints usually occur when the distal bones of the fingers are fixed, usually by holding onto an immovable object, requiring the proximal bone at each joint to move instead of the distal bone. (reverse action 1) • Reverse actions at the wrist joint occur when the hand is fixed by holding onto an immovable object and the forearm moves relative to the fixed hand. (reverse action 2) • Lateral rotation of the hamate bone of the carpus (wrist) at the CMC joint only occurs if the metacarpal of the little finger is stabilized and the hamate (and entire carpus and radius) moves relative to the fifth metacarpal. This causes supination of the radius at the radioulnar joints.

350

(reverse action 3) • The extensor digitorum crosses the elbow joint posteriorly; therefore it extends the elbow joint. If the distal attachment is fixed, the arm will extend toward the forearm instead of the forearm extending toward the arm. (reverse action 4)

Motions 1. Because the extensor digitorum splits into four separate tendons, depending on which fibers/motor units contract, extension of each finger (two through five) at the MCP, PIP, and DIP joints can be performed separately. 2. Regarding the rest of the actions that the extensor digitorum can create, it has one line of pull in an oblique plane. Therefore, while finger extension is occurring, it must also do extension of the hand at the wrist joint and extension of the forearm at the elbow joint (as well as medial rotation of the little finger at the CMC joint).

Eccentric Antagonist Functions 1. Restrains/slows MCP, PIP, and DIP joint flexion 2. Restrains/slows wrist joint flexion 3. Restrains/slows lateral rotation of the little finger 4. Restrains/slows elbow joint flexion

Eccentric Antagonist Function Note • The extensor digitorum also restrains/slows medial rotation of the hamate (carpus and radius) at the fifth CMC joint, and pronation of the radius at the radioulnar joints.

Isometric Stabilization Functions 1. Stabilizes the MCP, PIP, and DIP joints 2. Stabilizes the wrist joint 3. Stabilizes the fifth CMC and radioulnar joints 4. Stabilizes the elbow joint

Additional Notes on Actions 1. Some sources state that the extensor digitorum can contribute to ulnar deviation of the hand at the wrist joint. Given that the more medial fibers cross into the hand on the ulnar side, they could contribute to ulnar deviation of the wrist joint. Similarly, some sources state that the extensor digitorum can contribute to radial deviation of the hand at the wrist joint. Given that the more lateral fibers cross into the hand on the radial side, they could contribute to radial deviation of the wrist joint. As the position of the hand changes in the frontal plane (in other words, it is in greater ulnar or radial deviation), the line of the pull of the extensor digitorum could change by increasing the number of fibers that are one side of the joint, as well as increasing the leverage force of the fibers by being farther from the center of the joint; therefore the frontal plane action of this muscle when the hand is out of anatomic position can become amplified. 2. Whenever the extensor digitorum contracts forcefully to extend the fingers at the MCP and IP joints, the wrist flexors also contract, creating a force of flexion of the hand at the wrist joint to fix (stabilize) the hand so that the extensor digitorum does not cause extension of the hand at the wrist joint. This can be easily felt by palpating the common flexor belly/tendon at the medial epicondyle of the humerus while forcefully extending the fingers.

I N N E RVAT I O N The Radial Nerve posterior interosseus nerve, C7, C8

A R T E R I A L S U P P LY The Posterior Interosseus Artery (a branch of the Ulnar Artery)

351

PA L PAT I O N 1. With the client seated or supine, place palpating hand in the middle of the posterior forearm. 2. Have the client actively extend fingers two through five (at the metacarpophalangeal and interphalangeal joints) and feel for the contraction of the extensor digitorum. Resistance can be added. 3. Palpate the extensor digitorum proximally and distally as far as possible.

RELATIONSHIP TO OTHER STRUCTURES The extensor digitorum is located medial to the extensors carpi radialis brevis and longus, and lateral to the extensor digiti minimi and extensor carpi ulnaris. The extensor digitorum is superficial. Deep to the extensor digitorum is the deeper layer of posterior forearm muscles, which includes the supinator, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis. The extensor digitorum is located within the superficial back arm line myofascial meridian.

MISCELLANEOUS 1. The extensor digitorum is sometimes called the extensor digitorum communis. 2. The extensor digitorum arises proximally from the lateral epicondyle of the humerus via the common extensor belly/tendon. The common extensor belly/tendon is the common proximal attachment of four muscles: the extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and the extensor carpi ulnaris. (The anconeus and the supinator also arise from the lateral epicondyle of the humerus, but not from the common extensor belly/tendon.) 3. The distal attachment of the extensor digitorum spreads out to become a fibrous aponeurotic expansion that covers the posterior, medial, and lateral sides of the proximal phalanx. It then continues distally to attach onto the posterior sides of the middle and distal phalanges. This structure is called the dorsal digital expansion. 4. The dorsal digital expansion is also known as the extensor expansion and/or the dorsal hood. The term dorsal hood is used because one of its purposes is to serve as a movable hood of tissue when the fingers flex and extend. 5. The dorsal digital expansion also serves as an attachment site for the lumbricals manus, palmar interossei, dorsal interossei manus, and abductor digiti minimi manus muscles. Given that the dorsal digital expansion crosses the proximal and distal interphalangeal joints posteriorly, these muscles can extend the middle and distal phalanges at these joints. 6. Irritation and/or inflammation of the lateral epicondyle and/or the common extensor belly/tendon is known as lateral epicondylitis, lateral epicondylosis, or tennis elbow.

352

Extensor Digiti Minimi The name, extensor digiti minimi, tells us that this muscle extends the little finger. Derivation extensor: L. a muscle that extends a body part digiti: L. refers to a digit (finger) minimi: L. least Pronunciation eks-TEN-sor DIJ-i-tee MIN-i-mee

ATTACHMENTS Lateral Epicondyle of the Humerus via the Common Extensor Belly/Tendon to the Phalanges of the Little Finger (Finger Five)

attaches into the ulnar side of the tendon of the extensor digitorum muscle (to attach onto the posterior surface of the middle and distal phalanges of the little finger via the dorsal digital expansion)

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions

Reverse Mover Actions 1. Extends the fifth metacarpal at the MCP joint, extends the fifth proximal phalanx at the PIP joint, and extends the fifth 1. Extends the little finger (finger five) at the MCP, PIP, and DIP joints middle phalanx at the DIP joint 2. Extends the forearm at the wrist joint 2. Extends the hand at the wrist joint 3. Medially rotates the little finger at the CMC joint

3. Lateral rotation of the hamate (carpus) at the CMC joint

4. Extends the forearm at the elbow joint

4. Extends the arm at the elbow joint

5. Ulnar deviates the hand at the wrist joint

5. Ulnar deviates the forearm at the wrist joint

MCP joint = metacarpophalangeal joint; PIP joint = proximal interphalangeal joint; DIP joint = distal interphalangeal joint; CMC joint = carpometacarpal joint

Standard Mover Action Notes • The extensor digiti minimi crosses the fifth MCP joint (of the little finger) before it attaches into the distal tendon of the extensor digitorum muscle of the little finger. Because the extensor digiti minimi crosses this joint posteriorly (with its fibers running vertically in the sagittal plane), it extends the little finger at the fifth MCP joint. Further, by attaching into the distal tendon of the extensor digitorum, the extensor digiti minimi pulls on that tendon the same as if the belly of the extensor digitorum muscle itself had contracted and pulled on its own tendon. Therefore the extensor digiti minimi has the same actions at the little finger as the extensor digitorum muscle has, namely, extension of the little finger at the PIP and DIP joints. (action 1)

353

FIGURE 8-8 Posterior view of the right extensor digiti minimi. The extensor digitorum (ED) and the cut extensor carpi ulnaris (ECU) and cut extensor carpi radialis brevis (ECRB) have been ghosted in.

• More specifically, the extensor digiti minimi extends the proximal phalanx of the little finger at the MCP joint, extends the middle phalanx of the little finger at the PIP joint, and extends the distal phalanx of the little finger at the DIP joint. (action 1) • The extensor digiti minimi crosses the wrist joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it extends the hand at the wrist (radiocarpal and midcarpal) joint. (action 2) • The extensor digiti minimi crosses the fifth CMC joint posteriorly from lateral on the lateral epicondyle of the humerus to attach more medially onto the little finger (with its fibers running slightly horizontally in the transverse plane). When the extensor digiti minimi contracts, it pulls the posterior side of the little finger laterally. This is medial rotation of the little finger, because the anterior surface of the little finger rotates medially. Therefore the extensor digiti minimi medially rotates the metacarpal of the little finger at the fifth CMC joint. (action 3) • Medial rotation of the little finger at the CMC joint is an important part of repositioning the little finger back to anatomic position from a position of opposition to the thumb. (action 3) • The extensor digiti minimi crosses the elbow joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it extends the forearm at the elbow joint. (action 4) • The extensor digiti minimi crosses the wrist joint on the ulnar (medial) side (with its fibers

354

running vertically in the frontal plane); therefore it ulnar deviates (adducts) the hand at the wrist joint. (action 5)

Reverse Mover Action Notes • Reverse actions at the MCP, PIP, and DIP joints occur when the distal bones of the fingers are fixed, usually by holding onto an immovable object, requiring the proximal bone at each joint to move instead. (reverse action 1) • Reverse actions at the wrist joint occur when the hand is fixed by holding onto an immovable object and the forearm moves relative to the fixed hand. (reverse action 2) • Lateral rotation of the hamate bone of the carpus (wrist) at the CMC joint occurs only if the metacarpal of the little finger is stabilized and the hamate (and entire carpus and radius) moves relative to the fifth metacarpal. This causes supination of the radius at the radioulnar joints. (reverse action 3) • The extensor digiti minimi crosses the elbow joint posteriorly; therefore it extends the elbow joint. If the distal attachment is fixed, the arm will extend toward the forearm instead of the forearm extending toward the arm. (reverse action 4) • The wrist joint reverse action in the frontal plane of the extensor digiti minimi causes the ulnar side of the forearm to be pulled toward the ulnar side of the hand, in other words, ulnar deviation of the forearm at the wrist joint. (reverse action 5)

Motion 1. The extensor digiti minimi has one line of pull in an oblique plane, and therefore creates one motion, which is a combination of extension of the little finger at the MCP, PIP, and DIP joints, extension of the hand at the wrist joint, and extension of the forearm at the elbow joint (as well as medial rotation of the little finger at the CMC joint and ulnar deviation of the hand at the wrist joint).

Eccentric Antagonist Functions 1. Restrains/slows fifth MCP, PIP, and DIP joint flexion 2. Restrains/slows wrist joint flexion 3. Restrains/slows lateral rotation of the little finger 4. Restrains/slows elbow joint flexion

Eccentric Antagonist Function Note • The extensor digiti minimi also restrains/slows medial rotation of the hamate (carpus and radius) at the fifth CMC joint, and pronation of the radius at the radioulnar joints.

Isometric Stabilization Functions 1. Stabilizes the fifth MCP, PIP, and DIP joints 2. Stabilizes the wrist joint 3. Stabilizes the fifth CMC and radioulnar joints 4. Stabilizes the elbow joint

Additional Notes on Actions 1. Given that the extensor digiti minimi also crosses the carpometacarpal joint, it should also be able to contribute to extension of the metacarpal of the little finger at that joint as well. 2. Some sources state that the extensor digiti minimi attaches far enough on the ulnar side of the MCP joint of the little finger that it can pull the little finger away from the middle finger. Therefore it can abduct the little finger at the MCP joint. 3. The extensor digiti minimi, by attaching into the distal tendon of the extensor digitorum, exerts a pull on the dorsal digital expansion of the little finger.

I N N E RVAT I O N The Radial Nerve posterior interosseus nerve; C7, C8

355

A R T E R I A L S U P P LY The Posterior Interosseus Artery (a branch of the Ulnar Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating hand on the posterior forearm toward the ulnar side. 2. Have the client actively extend the little finger at the fifth metacarpophalangeal and interphalangeal joints and feel for the contraction of the extensor digiti minimi. Resistance can be added. 3. Note: It is challenging to discern the extensor digiti minimi from the extensor digitorum fibers that go to the little finger. These extensor digitorum fibers are located more laterally (radially); the extensor digiti minimi fibers are located more medially (ulnar side).

RELATIONSHIP TO OTHER STRUCTURES The extensor digiti minimi is superficial and located between the extensor digitorum (which is lateral to it) and the extensor carpi ulnaris (which is medial to it). The extensor digiti minimi is superficial to the deeper layer of posterior forearm muscles, which includes the supinator, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis. The extensor digiti minimi is located within the superficial back arm line myofascial meridian.

MISCELLANEOUS 1. The extensor digiti minimi arises proximally from the lateral epicondyle of the humerus via the common extensor belly/tendon. The common extensor belly/tendon is the common proximal attachment of four muscles: the extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris. (The anconeus and the supinator also arise from the lateral epicondyle of the humerus, but not from the common extensor belly/tendon.) 2. The belly of the extensor digiti minimi sometimes blends with the belly of the extensor digitorum. 3. Both the extensor digiti minimi and extensor indicis attach into the ulnar side of the extensor digitorum tendon to which they attach. 4. Other than the little finger and the thumb, only the index finger has a second extensor muscle (the extensor indicis). 5. Irritation and inflammation of the lateral epicondyle and/or the common extensor belly/tendon is known as lateral epicondylitis, lateral epicondylosis, or tennis elbow.

356

Deep Distal Four Group The deep distal four group is a group of four muscles whose bellies lie deep in the distal posterior forearm. Three of them move the thumb and therefore have the word pollicis in their name (pollicis means thumb). These are the abductor pollicis longus and extensor pollicis brevis that border the anatomic snuffbox on the lateral (radial) side, and the extensor pollicis longus that borders the anatomic snuffbox on the medial (ulnar) side. The fourth muscle in the group is the extensor indicis, which extends the index finger, as its name implies. Although the bellies lie deep to superficial extensor musculature of the fingers, the distal tendons of the three pollicis muscles pass superficial to the muscles of the radial group (brachioradialis and extensors carpi radialis and brevis) in the distal quarter of the forearm and wrist region. It is interesting to note the pattern of the distal attachments on the thumb of the three pollicis muscles. The abductor pollicis longus attaches to the metacarpal, the extensor pollicis brevis attaches to the proximal phalanx, and the extensor pollicis longus attaches to the distal phalanx.

FIGURE 8-9 Posterior views of the muscles of the right deep distal four group. A, All four muscles, with the supinator ghosted in. B, Same illustration with the abductor pollicis longus and extensor pollicis longus ghosted in.

357

Abductor Pollicis Longus (of Deep Distal Four Group) The name, abductor pollicis longus, tells us that this muscle abducts the thumb and is long (longer than the abductor pollicis brevis). Derivation abductor: L. a muscle that abducts a body part pollicis: L. thumb longus: L. longer Pronunciation ab-DUK-tor POL-i-sis LONG-us

ATTACHMENTS Posterior Radius and Ulna approximately the middle 1/3 of the radius, ulna, and interosseus membrane to the Thumb the lateral side of the base of the first metacarpal

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Abducts the thumb at the CMC joint

Reverse Mover Actions 1. Abducts the carpal bone (trapezium) at the CMC joint

2. Extends the thumb at the CMC joint 3. Laterally rotates the thumb at the CMC joint

2. Extends the carpal bone (trapezium) at the CMC joint

4. Radially deviates the hand at the wrist joint

4. Radially deviates the forearm at the wrist joint

5. Flexes the hand at the wrist joint

5. Flexes the forearm at the wrist joint

6. Supinates the forearm at the radioulnar joints

6. Supinates the ulna at the radioulnar joints and medially rotates the arm at the glenohumeral joint

3. Medially rotates the carpal bone (trapezium) at the CMC joint

CMC joint = carpometacarpal joint (of the thumb; saddle joint of the thumb)

Standard Mover Action Notes • The abductor pollicis longus crosses the first CMC joint anteriorly to attach onto the metacarpal of the thumb (with its fibers running vertically in the sagittal plane). When the abductor pollicis longus contracts, it pulls the metacarpal of the thumb anteriorly (in the sagittal plane, in a direction that is perpendicular to, and away from the plane of the palm of the hand). This action is called abduction of the thumb. Therefore the abductor pollicis longus abducts the thumb by abducting the metacarpal of the thumb at the first CMC joint. (Note: Because of the rotational development of the thumb embryologically, the named actions of abduction and adduction of the thumb occur within the sagittal plane.) (action 1)

358

FIGURE 8-10

Posterior view of the abductor pollicis longus. The extensor pollicis brevis (EPB) has been ghosted in.

• The abductor pollicis longus crosses the first CMC joint laterally (radially) to attach onto the metacarpal of the thumb (with its fibers running vertically in the frontal plane). When the abductor pollicis longus contracts, it pulls the metacarpal of the thumb laterally (i.e., radially, in the frontal plane, within the plane of the palm of the hand away from the index finger). This action is called extension of the thumb. Therefore the abductor pollicis longus extends the thumb by extending the metacarpal of the thumb at the first CMC joint. (Note: Because of the rotational development of the thumb embryologically, the named actions of flexion and extension of the thumb occur within the frontal plane.) (action 2) • The abductor pollicis longus crosses the first CMC joint posteriorly from medial in the forearm to attach more laterally onto the thumb (with its fibers running slightly horizontally in the transverse plane). When the abductor pollicis longus contracts, it pulls the thumb posterolaterally. This is lateral rotation of the thumb, because the anterior side of the thumb rotates laterally. Therefore the abductor pollicis longus laterally rotates the thumb at the first CMC joint. (action 3) • The abductor pollicis longus crosses the wrist joint on the radial (lateral) side (with it fibers running vertically in the frontal plane); therefore it radially deviates (abducts) the hand at the wrist joint. (action 4)

359

• The abductor pollicis longus crosses the wrist joint slightly anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the hand at the wrist joint. (action 5) • The abductor pollicis longus crosses the ulna and radius in the posterior forearm with an ulnar-toradial orientation to its fibers (hence its fibers are running somewhat horizontally in the transverse plane). When the thumb and the hand are fixed to the radius of the forearm, and the abductor pollicis longus pulls at its distal attachment, the distal radius moves. If the forearm is in a position of pronation, the abductor pollicis longus’ line of pull causes the distal radius to be pulled in a posterolateral direction around the distal ulna (and the head of the radius to laterally rotate). This movement of the radius is called supination. Therefore the abductor pollicis longus supinates the forearm at the radioulnar joints. (action 6)

Reverse Mover Action Notes • The reverse action of movement of the metacarpal of the thumb at the first CMC joint is to move the carpal bone (trapezium) toward the metacarpal of the thumb at the CMC joint; this would occur if the distal end (the metacarpal) is fixed, perhaps because the thumb is gripping an immovable object. Movement of the trapezium would likely involve movement of the entire carpus (wrist) and forearm relative to the hand. (reverse actions 1, 2, 3) • Reverse actions at the wrist joint occur when the hand is fixed by holding onto an immovable object and the forearm moves relative to the fixed hand. (reverse actions 4, 5) • Supination of the forearm usually involves a mobile radius moving around a fixed ulna. The reverse action in which the ulna supinates around a fixed radius usually occurs if the hand is fixed by holding onto an immovable object. Because the elbow joint does not allow rotation, supination of the ulna causes the arm to move with it, causing medial rotation of the arm at the glenohumeral joint. (reverse action 6)

Motion 1. The abductor pollicis longus has one line of pull in an oblique plane, and therefore creates one motion, which is a combination of abduction, extension, and lateral rotation of the thumb at the CMC joint, radial deviation and flexion of the hand at the wrist joint, and supination of the forearm at the RU joints.

Eccentric Antagonist Functions 1. Restrains/slows adduction, flexion, and medial rotation of the metacarpal at the CMC joint of the thumb 2. Restrains/slows adduction, flexion, and lateral rotation of the carpal bone (trapezium) at the CMC joint of the thumb 3. Restrains/slows wrist joint ulnar deviation and extension 4. Restrains/slows pronation of the radioulnar joints

Isometric Stabilization Functions 1. Stabilizes the first CMC joint 2. Stabilizes the wrist joint 3. Stabilizes the radioulnar joints

Additional Notes on Actions 1. Given that the abductor pollicis longus extends the thumb at the CMC joint, and that this action is a component motion of reposition of the thumb (and that extension couples with lateral rotation, which is another component motion of reposition), the abductor pollicis longus can be said to contribute to reposition the thumb at the CMC joint. 2. Whenever the abductor pollicis longus contracts quickly or powerfully to perform extension of the thumb at the CMC joint, it would also radially deviate the hand at the wrist joint. To prevent this, an ulnar deviator of the hand at the wrist joint (i.e., flexor carpi ulnaris or extensor carpi ulnaris) must contract to create an ulnar deviation force, stabilizing the hand so that it does not radially deviate. Palpate the ulnar side of the forearm when extending the thumb and this can be felt. 3. All three deep distal muscles of the posterior forearm that move the thumb (abductor pollicis

360

longus, extensor pollicis brevis, and extensor pollicis longus) can do radial deviation (abduction) of the hand at the wrist joint.

I N N E RVAT I O N The Radial Nerve the posterior interosseus nerve, C7, C8

A R T E R I A L S U P P LY The Posterior Interosseus Artery (a branch of the Ulnar Artery) and the perforating branches of the Anterior Interosseus Artery (a branch of the Ulnar Artery)

PA L PAT I O N 1. With the client seated and the forearm in a position halfway between full pronation and full supination, place palpating hand on the lateral wrist. 2. Have the client actively abduct and extend the thumb at the first carpometacarpal joint and feel for the distal tendons of the abductor pollicis longus and extensor pollicis brevis. (They are usually visible bordering the anatomic snuffbox on the radial [lateral] side, but may appear as one tendon because they are right next to each other.) 3. Continue palpating the abductor pollicis longus proximally and distally as far as possible.

RELATIONSHIP TO OTHER STRUCTURES The abductor pollicis longus is one of four deep muscles found in the distal posterior forearm (the abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis). Most of the belly of the abductor pollicis longus is deep to the extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris. The belly of the abductor pollicis longus is directly lateral to the extensor pollicis longus and the extensor pollicis brevis. The belly of the abductor pollicis longus overlies some of the belly of the extensor pollicis brevis. The distal belly and tendon of the abductor pollicis longus become superficial (along with the extensor pollicis brevis) in the distal posterolateral forearm and lie superficial to the radial group of muscles (the brachioradialis and extensors carpi radialis longus and brevis). The abductor pollicis longus and extensor pollicis brevis pass immediately anterior to the styloid process of the radius. The abductor pollicis longus is involved with the superficial back arm line and deep front arm line myofascial meridians.

MISCELLANEOUS 1. The abductor pollicis longus is one of the four muscles that make up the deep distal four group of the posterior forearm (the four muscles of this group are the abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis). 2. The distal tendon of the abductor pollicis longus and the distal tendon of the extensor pollicis brevis make up the lateral border of the anatomic snuffbox. These two tendons are very close together and can be difficult to distinguish from each other. The abductor pollicis longus is the more anterolateral of the two. (Note: The anatomic snuffbox is bordered on the medial side by the extensor pollicis longus.) 3. The distal tendon of the abductor pollicis longus often splits to also attach onto the trapezium. 4. The abductor pollicis longus and the extensor pollicis brevis share a common synovial sheath. With excessive movements of the thumb, the friction between the tendons of the abductor pollicis longus and/or extensor pollicis brevis and the styloid process of the radius can cause a tenosynovitis (inflammation of the synovial sheath). This condition is known as de Quervain’s disease or de Quervain’s stenosing tenosynovitis.

361

362

Extensor Pollicis Brevis (of Deep Distal Four Group) The name, extensor pollicis brevis, tells us that this muscle extends the thumb and is short (shorter than the extensor pollicis longus). Derivation extensor: L. a muscle that extends a body part pollicis: L. thumb brevis: L. shorter Pronunciation eks-TEN-sor POL-i-sis BRE-vis

ATTACHMENTS Posterior Radius the distal 1/3 and the adjacent interosseus membrane to the Thumb the posterolateral base of the proximal phalanx

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extends the thumb at the CMC and MCP joints

Reverse Mover Actions 1. Extends the carpal bone (trapezium) at the CMC joint and extends the first metacarpal at the MCP joint

2. Abducts the thumb at the CMC joint 3. Laterally rotates the thumb at the CMC joint

2. Abducts the carpal bone (trapezium) at the CMC joint

4. Radially deviates the hand at the wrist joint

4. Radially deviates the forearm at the wrist joint

3. Medially rotates the carpal bone (trapezium) at the CMC joint

CMC joint = carpometacarpal joint (of the thumb; saddle joint of the thumb); MCP joint = metacarpophalangeal joint

Standard Mover Action Notes • The extensor pollicis brevis crosses the first CMC joint of the thumb laterally (radially) to attach onto the proximal phalanx of the thumb (with its fibers running vertically in the frontal plane). When the extensor pollicis brevis contracts, it pulls the proximal phalanx of the thumb laterally (radially) within the plane of the palm of the hand (frontal plane), away from the index finger. This action is called extension of the thumb. Therefore the extensor pollicis brevis extends the thumb by extending the metacarpal of the thumb at the first CMC joint. Additionally, the extensor pollicis brevis also crosses the first MCP joint of the thumb laterally (radially). Therefore it extends the proximal phalanx of the thumb at this joint as well. (Note: Because of the rotational development of the thumb embryologically, the named actions of flexion and extension of the thumb occur within the frontal plane.) (action 1)

363

FIGURE 8-11

Posterior view of the extensor pollicis brevis. The abductor pollicis longus (APL) has been ghosted in.

• The extensor pollicis brevis crosses the first CMC joint of the thumb anteriorly to attach onto the proximal phalanx of the thumb (with its fibers running vertically in the sagittal plane). When the extensor pollicis brevis contracts, it pulls the proximal phalanx of the thumb in a direction that is perpendicular to, and away from the plane of the palm of the hand (moving it within the sagittal plane). This action is called abduction of the thumb. Therefore the extensor pollicis brevis abducts the thumb by abducting the metacarpal of the thumb at the first CMC joint. (Note: Because of the rotational development of the thumb embryologically, the named actions of abduction and adduction of the thumb occur within the sagittal plane.) The extensor pollicis brevis also crosses the first MCP joint of the thumb anteriorly; however, this joint does not allow abduction. (action 2) • The extensor pollicis brevis crosses the first CMC joint posteriorly from medial in the forearm to attach more laterally onto the thumb (with its fibers running slightly horizontally in the transverse plane). When the extensor pollicis brevis contracts, it pulls the thumb posterolaterally. This is lateral rotation of the thumb, because the anterior side of the thumb rotates laterally. Therefore the extensor pollicis brevis laterally rotates the thumb at the first CMC joint. (action 3) • The extensor pollicis brevis crosses the wrist joint on the radial (lateral) side (with its fibers running vertically in the frontal plane); therefore it radially deviates (abducts) the hand at the

364

wrist joint. (action 4)

Reverse Mover Action Notes • The reverse action of movement of the metacarpal of the thumb at the first CMC joint is to move the carpal bone (trapezium) toward the metacarpal of the thumb at the CMC joint; this would occur if the distal end (the metacarpal) is fixed, perhaps because the thumb is gripping an immovable object. Movement of the trapezium would likely involve movement of the entire carpus (wrist) and forearm relative to the hand. (reverse actions 1, 2, 3) • The reverse action of movement of the proximal phalanx of the thumb at the MCP joint is to move the metacarpal of the thumb toward the proximal phalanx at the MCP joint; this would occur if the distal end (the proximal phalanx) is fixed, perhaps because the thumb is gripping an immovable object. (reverse action 1) • Reverse actions at the wrist joint occur when the hand is fixed by holding onto an immovable object and the forearm moves relative to the fixed hand. (reverse action 4)

Motion 1. The extensor pollicis brevis has one line of pull in an oblique plane, and therefore creates one motion, which is a combination of extension, lateral rotation, and abduction of the thumb at the CMC joint, extension of the thumb at the MCP joint, and radial deviation of the hand at the wrist joint.

Eccentric Antagonist Functions 1. Restrains/slows flexion of the CMC and MCP joints of the thumb 2. Restrains/slows adduction of the CMC joint of the thumb 3. Restrains/slows medial rotation of the metacarpal and lateral rotation of the carpal bone (trapezium) at the CMC joint of the thumb 4. Restrains/slows wrist joint ulnar deviation

Isometric Stabilization Functions 1. Stabilizes the CMC and MCP joints of the thumb 2. Stabilizes the wrist joint

Additional Notes on Actions 1. Some sources state that the extensor pollicis brevis can flex the hand at the wrist joint. Given that the abductor pollicis longus is far enough anterior to flex the wrist joint, and that the extensor pollicis brevis crosses the wrist joint directly next to the abductor pollicis longus, it would seem that the line of pull of the extensor pollicis brevis would allow it to flex the hand at the wrist joint. The leverage force to flex the wrist would likely increase as the wrist joint is further flexed. 2. Given that the extensor pollicis brevis extends the thumb at the CMC joint, and that this motion is a component motion of reposition of the thumb (and that extension couples with lateral rotation, which is another component motion of reposition), the extensor pollicis brevis can be said to contribute to reposition the thumb at the CMC joint. 3. Whenever the extensor pollicis brevis contracts quickly or powerfully to perform extension and/or abduction of the thumb at the CMC joint, it would also radially deviate the hand at the wrist joint. To prevent this, an ulnar deviator of the hand at the wrist joint (i.e., flexor carpi ulnaris or extensor carpi ulnaris) must contract to create an ulnar deviation force, stabilizing the hand so that it does not radially deviate. Palpate the ulnar side of the forearm when extending and/or abducting the thumb and this can be felt. 4. The extensor pollicis brevis is the only muscle of the deep distal four group that cannot supinate the forearm at the radioulnar joints because it does not cross the radioulnar joints. 5. All three deep distal muscles of the posterior forearm that move the thumb (abductor pollicis longus, extensor pollicis brevis, and extensor pollicis longus) can do radial deviation (abduction) of the hand at the wrist joint.

I N N E RVAT I O N The Radial Nerve

365

the posterior interosseus nerve, C7, C8

A R T E R I A L S U P P LY The Posterior Interosseus Artery (a branch of the Ulnar Artery) and the perforating branches of the Anterior Interosseus Artery (a branch of the Ulnar Artery)

PA L PAT I O N 1. With the client seated and the forearm in a position halfway between full pronation and full supination, place palpating hand on the lateral wrist. 2. Have the client actively abduct and extend the thumb at the first carpometacarpal joint and feel for the distal tendons of the extensor pollicis brevis and abductor pollicis longus. (They are usually visible bordering the anatomic snuffbox on the radial [lateral] side, but may appear as one tendon because they are right next to each other.) 3. Continue palpating the extensor pollicis brevis proximally and distally as far as possible.

RELATIONSHIP TO OTHER STRUCTURES The extensor pollicis brevis is one of four deep muscles found in the distal posterior forearm (the abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis). Most of the belly of the extensor pollicis brevis is deep to the extensor digitorum. The extensor pollicis brevis lies directly medial to the abductor pollicis longus and directly lateral to the extensor pollicis longus. Much of the belly of the extensor pollicis brevis lies deep to the bellies of the abductor pollicis longus and extensor pollicis longus. The distal belly and tendon of the extensor pollicis brevis become superficial (along with the abductor pollicis longus) in the distal posterolateral forearm and lie superficial to the radial group of muscles (the brachioradialis and extensors carpi radialis longus and brevis). The extensor pollicis brevis and abductor pollicis longus pass immediately anterior to the styloid process of the radius. The extensor pollicis brevis is involved with the superficial back arm line and deep front arm line myofascial meridians.

MISCELLANEOUS 1. The extensor pollicis brevis is one of the four muscles that make up the deep distal four group of the posterior forearm (the four muscles of this group are the abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis). 2. The distal tendon of the extensor pollicis brevis and the distal tendon of the abductor pollicis longus make up the lateral border of the anatomic snuffbox. These two tendons are very close together and can be difficult to distinguish from each other. The extensor pollicis brevis is the more posteromedial of the two. (Note: The anatomic snuffbox is bordered medially by the extensor pollicis longus.) 3. The extensor pollicis brevis and the abductor pollicis longus share a common synovial sheath. With excessive movements of the thumb, the friction between the tendons of the extensor pollicis brevis and/or abductor pollicis longus and the styloid process of the radius can cause a tenosynovitis (inflammation of the synovial sheath). This condition is known as de Quervain’s disease or de Quervain’s stenosing tenosynovitis.

366

Extensor Pollicis Longus (of Deep Distal Four Group) The name, extensor pollicis longus, tells us that this muscle extends the thumb and is long (longer than the extensor pollicis brevis). Derivation extensor: L. a muscle that extends a body part pollicis: L. thumb longus: L. longer Pronunciation eks-TEN-sor POL-i-sis LONG-us

ATTACHMENTS Posterior Ulna the middle 1/3 and the adjacent interosseus membrane to the Thumb via its dorsal digital expansion onto the posterior surface of the distal phalanx of the thumb

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extends the thumb at the CMC, MCP, and IP joints 2. Laterally rotates the thumb at the CMC joint

Reverse Mover Actions 1. Extends the carpal bone (trapezium) at the CMC joint; extends the first metacarpal at the MCP joint and extends the proximal phalanx at the IP joint 2. Medially rotates the carpal bone (trapezium) at the CMC joint

3. Extends the hand at the wrist joint

3. Extends the forearm at the wrist joint

4. Radially deviates the hand at the wrist joint

4. Radially deviates the forearm at the wrist joint

5. Supinates the forearm at the radioulnar joints

5. Supinates the ulna at the radioulnar joints and medially rotates the arm at the glenohumeral joint

6. Adducts the thumb at the CMC joint

6. Adducts the carpal bone (trapezium) at the CMC joint

CMC joint = carpometacarpal joint (of the thumb; saddle joint of the thumb); MCP joint = metacarpophalangeal joint; IP joint = interphalangeal joint

Standard Mover Action Notes • The extensor pollicis longus crosses the CMC joint of the thumb laterally (radially) to attach onto the distal phalanx of the thumb (with its fibers running vertically in the frontal plane). When the extensor pollicis longus contracts, it pulls the distal phalanx of the thumb laterally (radially) within the plane of the palm of the hand (frontal plane), away from the index finger. This action is called extension of the thumb. Therefore the extensor pollicis longus extends the thumb by extending the metacarpal of the thumb at the first CMC joint. (Note: Because of the rotational development of the thumb embryologically, the named actions of flexion and extension of the thumb occur within the frontal plane.) Additionally, the extensor pollicis longus crosses the MCP and IP joints of the thumb laterally (radially). Therefore it also extends the phalanges of the thumb at these joints. (action 1)

367

FIGURE 8-12

Posterior view of the extensor pollicis longus. The extensor pollicis brevis (EPB) has been ghosted in.

• The extensor pollicis longus crosses the first CMC joint posteriorly from medial in the forearm to attach more laterally onto the thumb (with its fibers running slightly horizontally in the transverse plane). When the extensor pollicis longus contracts, it pulls the thumb posterolaterally. This is lateral rotation of the thumb, because the anterior side of the thumb rotates laterally. Therefore the extensor pollicis longus laterally rotates the thumb at the first CMC joint. (action 2) • The extensor pollicis longus crosses the wrist joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it extends the hand at the wrist joint. (action 3) • The extensor pollicis longus crosses the wrist joint on the radial (lateral) side (with its fibers running vertically in the frontal plane); therefore it radially deviates (abducts) the hand at the wrist joint. (action 4) • The extensor pollicis longus crosses the ulna and radius in the posterior forearm with an ulnar-toradial orientation to its fibers (hence its fibers are running somewhat horizontally in the transverse plane). When the thumb and the hand are fixed to the radius of the forearm, and the extensor pollicis longus pulls at its distal attachment, the distal radius moves. If the forearm is in a position of pronation, the extensor pollicis longus’ line of pull causes the distal radius to be pulled in a posterolateral direction around the distal ulna (and the head of the radius to laterally rotate). This movement of the radius is called supination. Therefore the extensor pollicis longus

368

supinates the forearm at the radioulnar joints. (action 5) • The extensor pollicis longus can adduct the thumb at the CMC joint if the thumb is first in an abducted position. Adduction of the thumb at the CMC joint is a movement of the metacarpal of the thumb in the sagittal plane, perpendicular to, and toward the palm of the hand. (Note: Because of the rotational development of the thumb embryologically, the named actions of abduction and adduction of the thumb occur within the sagittal plane.) (action 6)

Reverse Mover Action Notes • The reverse action of movement of the metacarpal of the thumb at the first CMC joint is to move the carpal bone (trapezium) toward the metacarpal of the thumb at the CMC joint; this would occur if the distal end (the metacarpal) is fixed, perhaps because the thumb is gripping an immovable object. Movement of the trapezium would likely involve movement of the entire carpus (wrist) and forearm relative to the hand. (reverse actions 1, 2, 6) • Reverse actions at the wrist joint occur when the hand is fixed by holding onto an immovable object and the forearm moves relative to the fixed hand. (reverse actions 3, 4) • Supination of the forearm usually involves a mobile radius moving around a fixed ulna. The reverse action in which the ulna supinates around a fixed radius usually occurs if the hand is fixed by holding onto an immovable object. Because the elbow joint does not allow rotation, supination of the ulna causes the arm to move with it, causing medial rotation of the arm at the glenohumeral joint. (reverse action 5)

Motion 1. The extensor pollicis longus has one line of pull in an oblique plane, and therefore creates one motion, which is a combination of extension, lateral rotation, and adduction of the thumb at the CMC joint, extension of the thumb at the MCP and IP joints, extension and radial deviation of the hand at the wrist joint, and supination of the forearm at the RU joints.

Eccentric Antagonist Functions 1. Restrains/slows flexion of the CMC, MCP, and IP joints of the thumb 2. Restrains/slows medial rotation of the metacarpal and lateral rotation of the carpal bone (trapezium) at the CMC joint of the thumb 3. Restrains/slows wrist joint flexion and ulnar deviation 4. Restrains/slows pronation of the radioulnar joints 5. Restrains/slows abduction of the CMC joint of the thumb

Isometric Stabilization Functions 1. Stabilizes the CMC, MCP, and IP joints of the thumb 2. Stabilizes the wrist joint 3. Stabilizes the radioulnar joints

Additional Notes on Actions 1. Some sources state that the extensor pollicis longus is involved with thumb opposition; others say that it is involved instead with thumb reposition. Both may be true. The extensor pollicis longus extends and laterally rotates the thumb, which are component actions of thumb reposition. But the extensor pollicis longus also adducts the thumb, which is a component action of thumb opposition. Therefore, this muscle might be engaged in either opposition or reposition. 2. Whenever the extensor pollicis longus contracts quickly or powerfully to perform extension of the thumb at the CMC joint, it would also radially deviate the hand at the wrist joint. To prevent this, an ulnar deviator of the hand at the wrist joint (i.e., flexor carpi ulnaris or extensor carpi ulnaris) must contract to create an ulnar deviation force, stabilizing the hand so that it does not radially deviate. Palpate the ulnar side of the forearm when extending the thumb and this can be felt. 3. All three deep distal muscles of the posterior forearm that move the thumb (abductor pollicis longus, extensor pollicis brevis, and extensor pollicis longus) can do radial deviation (abduction) of the hand at the wrist joint.

369

I N N E RVAT I O N The Radial Nerve the posterior interosseus nerve, C7, C8

A R T E R I A L S U P P LY The Posterior Interosseus Artery (a branch of the Ulnar Artery) and the perforating branches of the Anterior Interosseus Artery (a branch of the Ulnar Artery)

PA L PAT I O N 1. With the client seated and the forearm in a position halfway between full pronation and full supination, place palpating hand on the posterolateral wrist. 2. Have the client actively extend the thumb at the carpometacarpal, metacarpophalangeal, and interphalangeal joints and feel for tensing of the distal tendon of the extensor pollicis longus. It is usually visible bordering the anatomic snuffbox on the ulnar (medial) side. 3. Continue palpating the extensor pollicis longus distally to the thumb and proximally to the attachment on the radial (lateral) surface of the ulna.

RELATIONSHIP TO OTHER STRUCTURES The extensor pollicis longus is one of four deep muscles found in the distal posterior forearm (the abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis). Most of the belly of the extensor pollicis longus is deep to the extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris. The extensor pollicis longus’ proximal attachment onto the posterior ulna is located between the abductor pollicis longus and the extensor indicis; it is distal to the abductor pollicis longus and proximal to the extensor indicis. The extensor pollicis longus is superficial to the proximal attachment of the extensor pollicis brevis. The bellies of the abductor pollicis longus and extensor pollicis brevis lie just lateral to the belly of the extensor pollicis longus. The distal belly and tendon of the extensor pollicis longus become superficial in the posterior wrist. They are superficial to the extensor carpi radialis longus and the extensor carpi radialis brevis. The distal tendon of the extensor pollicis longus turns around a bony fulcrum on the radius called the dorsal tubercle (also known as Lister’s tubercle) that alters its line of pull. The extensor pollicis longus is involved with the superficial back arm line myofascial meridian.

MISCELLANEOUS 1. The extensor pollicis longus is one of the four muscles that make up the deep distal four group of the posterior forearm (the four muscles of this group are the abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis). 2. The distal tendon of the extensor pollicis longus makes up the medial border of the anatomic snuffbox. (Note: The anatomic snuffbox is bordered laterally by the abductor pollicis longus and extensor pollicis brevis.) 3. The distal attachment of the extensor pollicis longus spreads out to become a fibrous aponeurotic expansion that covers the posterior, medial, and lateral sides of the proximal phalanx of the thumb. It then continues distally to attach onto the posterior side of the distal phalanx. This structure is called the dorsal digital expansion. 4. The dorsal digital expansion is also known as the extensor expansion and/or the dorsal hood. The name dorsal hood is given because it serves as a movable hood of tissue when the thumb flexes and extends. 5. The dorsal digital expansion of the thumb also serves as an attachment site for the abductor pollicis brevis and adductor pollicis (and the palmar interosseus muscle of the thumb, if present). Given that the dorsal digital expansion of the thumb crosses the interphalangeal joint posteriorly, these muscles can all extend the distal phalanx of the thumb at this joint.

370

371

Extensor Indicis (of Deep Distal Four Group) The name, extensor indicis, tells us that this muscle extends the index finger. Derivation extensor: L. a muscle that extends a body part indicis: L. index finger (finger two) Pronunciation eks-TEN-sor IN-di-sis

ATTACHMENTS Posterior Ulna the distal 1/3 and the interosseus membrane to the Index Finger (Finger Two) attaches into the ulnar side of the tendon of the extensor digitorum muscle (to attach onto the posterior surface of the middle and distal phalanges of the index finger via the dorsal digital expansion)

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extends the index finger at the MCP, PIP, and DIP joints 2. Extends the hand at the wrist joint 3. Adducts the index finger at the MCP joint 4. Supinates the forearm at the radioulnar joints

Reverse Mover Actions 1. Extends the second metacarpal at the MCP joint; extends the proximal phalanx at the PIP joint; extends the middle phalanx at the DIP joint 2. Extends the forearm at the wrist joint 3. Adducts the second metacarpal at the MCP joint 4. Supinates the ulna at the radioulnar joints and medially rotates the arm at the glenohumeral joint

MCP joint = metacarpophalangeal joint; PIP joint = proximal interphalangeal joint; DIP joint = distal interphalangeal joint

Standard Mover Action Notes • The extensor indicis crosses the second MCP joint (of the index finger) before it attaches into the distal tendon of the extensor digitorum muscle of the index finger. Because the extensor indicis crosses this joint posteriorly (with its fibers running vertically in the sagittal plane), it extends the index finger at the second MCP joint. Further, by attaching into the distal tendon of the extensor digitorum, the extensor indicis pulls on that tendon the same as if the belly of the extensor digitorum muscle itself had contracted and pulled on its own tendon. Therefore the extensor indicis has the same actions at the index finger as the extensor digitorum muscle has, namely, extension of the index finger at the PIP and DIP joints. (action 1)

372

FIGURE 8-13

Posterior view of the extensor indicis. The extensor pollicis longus (EPL) has been ghosted in.

• More specifically, it extends the proximal phalanx of the index finger at the MCP joint, extends the middle phalanx at the PIP joint, and extends the distal phalanx at the DIP joint. (action 1) • The extensor indicis crosses the wrist posteriorly (with its fibers running vertically in the sagittal plane); therefore it extends the hand at the wrist joint. (action 2) • The extensor indicis attaches from the ulna to the index finger, crossing the second MCP joint from medial to lateral (with its fibers running somewhat horizontally in the frontal plane). When the extensor indicis pulls on the index finger, it pulls the index finger medially toward the ulna (i.e., toward the middle finger). Therefore the extensor indicis can adduct the index finger at the second MCP joint. (action 3) • The extensor indicis crosses the ulna and radius in the posterior forearm with an ulnar-to-radial orientation to its fibers (hence its fibers are running somewhat horizontally in the transverse plane). When the index finger and the hand are fixed to the radius of the forearm, and the extensor indicis pulls at its distal attachment, the distal radius moves. If the forearm is in a position of pronation, the extensor indicis’ line of pull causes the distal radius to be pulled in a posterolateral direction around the distal ulna (and the head of the radius to laterally rotate). This movement of the radius is called supination. Therefore the extensor indicis supinates the forearm at the radioulnar joints. (action 4)

373

Reverse Mover Action Notes • The reverse actions move the more proximal bone at each joint. This would occur when the distal bone is fixed, usually when the index finger is gripping an immovable object. (reverse actions 1, 2, 3, 4) • Reverse actions at the wrist joint occur when the hand is fixed by holding onto an immovable object and the forearm moves relative to the fixed hand. (reverse action 2) • Supination of the forearm usually involves a mobile radius moving around a fixed ulna. The reverse action in which the ulna supinates around a fixed radius usually occurs if the hand is fixed by holding onto an immovable object. Because the elbow joint does not allow rotation, supination of the ulna causes the arm to move with it, causing medial rotation of the arm at the glenohumeral joint. (reverse action 4)

Motion 1. The extensor indicis has one line of pull in an oblique plane, and therefore creates one motion, which is a combination of extension of the index finger at the MCP, PIP, and DIP joints and extension of the hand at the wrist joint (as well as adduction of the index finger at the MCP joint and supination of the forearm at the RU joints).

Eccentric Antagonist Functions 1. Restrains/slows flexion of the index finger at the MCP, PIP, and DIP joints 2. Restrains/slows wrist joint flexion 3. Restrains/slows abduction of the index finger 4. Restrains/slows pronation of the radioulnar joints

Isometric Stabilization Functions 1. Stabilizes the MCP, PIP, and DIP joints of the index finger 2. Stabilizes the wrist joint 3. Stabilizes the radioulnar joints

Additional Note on Actions 1. The extensor indicis, by attaching into the distal tendon of the extensor digitorum, exerts its pull on the dorsal digital expansion of the index finger.

I N N E RVAT I O N The Radial Nerve the posterior interosseus nerve, C7, C8

A R T E R I A L S U P P LY The Posterior Interosseus Artery (a branch of the Ulnar Artery) and the perforating branches of the Anterior Interosseus Artery (a branch of the Ulnar Artery)

PA L PAT I O N 1. With the client seated and the forearm fully pronated at the radioulnar joints, place palpating fingers on the distal 1/3 of the ulna on the posterior side. 2. Have the client actively extend the index finger at the metacarpophalangeal and interphalangeal joints and feel for the contraction of the extensor indicis. 3. Continue palpating the extensor indicis distally and proximally as far as possible. Note: It may be difficult to distinguish the distal tendon of the extensor indicis from the distal tendon of the extensor digitorum that goes to the index finger. If the two can be felt, the extensor indicis will be the more medial (ulnar) of the two.

RELATIONSHIP TO OTHER STRUCTURES The extensor indicis is one of four deep muscles found in the distal posterior forearm (the abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis). Most of the

374

belly of the extensor indicis is deep to the extensor digitorum, the extensor digiti minimi, and the extensor carpi ulnaris. The extensor indicis attaches onto the posterior ulna just distal to the attachment of the extensor pollicis longus. The belly of the extensor indicis lies just medial to the belly of the extensor pollicis longus. The distal tendon of the extensor indicis becomes superficial in the posterior hand and lies just medial (ulnar) to the tendon of the extensor digitorum that attaches onto the index finger. The extensor indicis is involved with the superficial back arm line myofascial meridian.

MISCELLANEOUS 1. The extensor indicis is one of the four muscles that make up the deep distal four group of the posterior forearm (the four muscles of this group are the abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis). The extensor indicis is the only muscle of this group that moves the index finger instead of the thumb. 2. The extensor indicis is another extensor muscle (besides the extensor digitorum) of the index finger. This muscle helps us to point at things (or indicate, hence the name indicis). 3. Other than the index finger and the thumb, only the little finger has a second extensor muscle (extensor digiti minimi). 4. Both the extensor indicis to the index finger and extensor digiti minimi to the little finger attach into the ulnar side of the extensor digitorum tendon to which they attach.

375

REVIEW QUESTIONS 1. The anterior compartment of the forearm has _______ layers. List the muscles contained in each layer. ____________________________ 2. The posterior compartment of the forearm has _______ layers. List the muscles contained in each layer. ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ 3. What is the major functional difference between the flexor digitorum superficialis and the flexor digitorum profundus? ____________________________ ____________________________ ____________________________ 4. What structures travel through the carpal tunnel? ____________________________ ____________________________ ____________________________ 5. What is responsible for the partially flexed position of fingers two through five at the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints? ____________________________ ____________________________ 6. What effect has embryological development had on the thumb in regard to joint actions? ____________________________ ____________________________ ____________________________ ____________________________ 7. What function does medial rotation of the little finger at the carpometacarpal joint serve? ____________________________ ____________________________ 8. What is unique about the distal attachment on the fingers of the extensor digitorum? ____________________________ ____________________________ 9. What muscles define/make up the anatomic snuffbox? Be specific on their location relative to each other. ____________________________ ____________________________ ____________________________ ____________________________ 10. What two muscles share a common synovial sheath that travels past, and sometimes frictions with, the styloid process of the radius? What is the name given to this friction condition? ____________________________ ____________________________ ____________________________ For answers to these questions, visit http://evolve.elsevier.com/Muscolino/muscular

376

THINK IT THROUGH The distal tendon of the extensor pollicis longus turns around a bony fulcrum on the radius. What effect would this have on the muscle? Does it provide any functional significance? ____________________________ ____________________________ ____________________________ ____________________________ ____________________________

377

CHAPTER 9

378

Intrinsic Muscles of the Finger Joints CHAPTER OUTLINE Thenar eminence group Abductor pollicis brevis Flexor pollicis brevis Opponens pollicis Hypothenar eminence group Abductor digiti minimi manus Flexor digiti minimi manus Opponens digiti minimi Central compartment group Adductor pollicis Lumbricals manus Palmar interossei Dorsal interossei manus Superficial fascial muscle Palmaris brevis

OBJECTIVES After completing this chapter, the student should be able to perform the following for each of the muscles covered in the chapter: 1. Explain the general structure. 2. Explain the general function 3. State the attachments. 4. State the standard mover actions. 5. State the reverse mover actions. 6. Discuss the line(s) of pull the muscle has and the motion(s) created. 7. State the eccentric antagonist functions. 8. State the isometric stabilization functions. 9. State the nervous innervation.

10. State the arterial supply. 11. Describe the starting position for palpation. 12. Describe the steps for palpation. 13. Discuss the muscle’s relationship to other body structures. 14. Discuss additional information that may help with palpation, assessment, and clinical decision-making. CHAPTER OVERVIEW The muscles addressed in this chapter are the intrinsic muscles of the hand that move the fingers, including the thumb. Intrinsic muscles of the hand are wholly located within the hand;

379

in other words, they begin and end in the hand. Extrinsic muscles of the hand that also move the fingers are covered in Chapter 8 (extrinsic muscles of the hand attach proximally to the arm or forearm and then travel distally to enter and attach to the hand). Overview of STRUCTURE Structurally, intrinsic muscles of the hand that move the fingers can be divided into three groups: thenar eminence muscles, hypothenar eminence muscles, and central compartment muscles. There is one other muscle, the palmaris brevis, that does not belong to these groups (although it is occasionally placed into the hypothenar group because it overlies the hypothenar group). The thenar group is located on the lateral (radial) side of the proximal hand and creates the eminence there. The three thenar eminence group muscles are the abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis. All three thenar eminence muscles attach onto and move the thumb; pollicis means thumb. The hypothenar group is located on the medial (ulnar) side of the proximal hand and creates the eminence there. The three hypothenar eminence group muscles are the abductor digiti minimi manus, flexor digiti minimi manus, and opponens digiti minimi. All three hypothenar eminence muscles attach onto and move the little finger; digiti minimi means little finger (or little toe in the foot). Note the symmetry between the thenar and hypothenar groups. Each group contains three muscles, which include an abductor, a flexor, and an opponens. The central compartment group is located in the center of the hand between the thenar and hypothenar groups. The muscles of the central compartment are the adductor pollicis, lumbricals manus, palmar interossei, and dorsal interossei manus. The lumbricals manus, palmar interossei, and dorsal interossei manus all attach into the dorsal digital expansion of the hand.

Compartments of the Hand: Intrinsic hand musculature is usually divided into three compartments: thenar eminence group, hypothenar eminence group, and the central compartment. • The thenar eminence group is composed of three muscles: abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis. • The hypothenar eminence group is composed of three muscles: abductor digiti minimi manus, flexor digiti minimi manus, and opponens digiti minimi. • The central compartment is composed of four muscles/muscle groups: adductor pollicis, lumbricals manus, palmar interossei, and dorsal interossei manus. • Note: The palmaris brevis is sometimes considered to be a muscle of the hypothenar eminence group. Overview of FUNCTION The following general rules regarding actions can be stated for the functional groups of intrinsic finger muscles: Fingers two through five can move at three joints: the metacarpophalangeal (MCP), proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints (the little finger can also move at the carpometacarpal [CMC] joint). If a muscle crosses only the MCP joint, it can move the finger only at the MCP joint. If the muscle crosses the MCP and PIP joints, it can move the finger at both of these joints. If the muscle crosses the MCP, PIP, and DIP joints, it can move the finger at all three joints. The thumb (finger one) can move at three joints: the carpometacarpal (CMC), metacarpophalangeal (MCP), and interphalangeal (IP) joints. Similarly, a muscle can only move the thumb at a joint or joints that it crosses. If a muscle crosses the MCP, PIP, or DIP joints of fingers two through five on the anterior side, it can flex the finger at the joint(s) crossed; if a muscle crosses the MCP, PIP, or DIP joints of fingers two through five on the posterior side, it can extend the finger at the joint(s) crossed. If a muscle crosses the MCP joint of fingers two, four, or five on the side that faces the middle finger, it can adduct the finger at the MCP joint; if a muscle crosses the MCP joint of fingers two, three, or four on the side that faces away from the center of the middle finger, it can

380

abduct the finger at the MCP joint (the middle finger abducts in both directions, radial abduction and ulnar abduction). Regarding motion of the fingers, to be more specific, the proximal phalanx of the finger moves at the MCP joint, the middle phalanx moves at the PIP joint, and the distal phalanx moves at the DIP joint. Muscles that cross the CMC, MCP, and IP joints of the thumb on the medial side can flex the thumb at the joint(s) crossed; muscles that cross the CMC, MCP, and IP joints of the thumb on the lateral side can extend the thumb at the joint(s) crossed. Muscles that cross the CMC joint of the thumb on the anterior side can abduct the thumb at the CMC joint; muscles that cross the CMC joint of the thumb on the posterior side can adduct the thumb at the CMC joint. To be more specific, the metacarpal of the thumb moves at the CMC joint, the proximal phalanx moves at the MCP joint, and the distal phalanx moves at the IP joint. Note: Because of the rotational development of the thumb embryologically, the named actions of flexion and extension of the thumb occur within the frontal plane (not the sagittal plane); and abduction and adduction of the thumb occur within the sagittal plane (not the frontal plane). Every muscle that attaches into the dorsal digital expansion of the hand flexes at the MCP joint and extends at the IP joints. Reverse actions involve the proximal attachment moving toward the distal one. This would occur when the fingers are holding onto a fixed immovable object. Therefore reverse actions for all fingers involve the metacarpal moving at the MCP joint (relative to a fixed proximal phalanx). For fingers two through five, reverse actions involve the proximal phalanx moving at the PIP joint (relative to a fixed middle phalanx), and the middle phalanx moving at the DIP joint (relative to a fixed distal phalanx). For the thumb, reverse actions involve the proximal phalanx moving at the IP joint (relative to a fixed distal phalanx). B O X 9 - 1 N o t e R e g a r d i n g t h e Pa l m a r I n t e r o s s e i M u s c l e s There is a great deal of confusion regarding the naming of the intrinsic hand muscles of the thumb. Some sources state that there are four palmar interossei muscles, one of which goes to the thumb; other sources state that there are only three palmar interossei muscles, none of which attach to the thumb. Some sources state that the flexor pollicis brevis has only one part to it; others state that it has superficial and deep heads. Although all sources agree that the adductor pollicis has a transverse head and an oblique head, some state the deep head of the flexor pollicis brevis is actually part of the oblique head of the adductor pollicis; others state that the deep head of the flexor pollicis brevis is separate from the adductor pollicis. This confusion is caused by the great deal of variation that occurs in this region. From one body to another, the anatomy of the musculature varies, leading to confusion as to how to name the structures that are present. This book adheres to the following organization: there are three palmar interossei muscles, and the flexor pollicis brevis has two parts—a superficial head and a deep head. When another fasciculus (group of muscle fibers) is present in this region, it may be a true fourth palmar interosseus muscle (sometimes known as the palmar interosseus of Henle). It may also be another fasciculus of the deep head of the flexor pollicis brevis or another fasciculus of the oblique head of the adductor pollicis.

http://evolve.elsevier.com/Muscolino/muscular

381

Anterior (Palmar) View of the Musculature of the Right Hand—Superficial View with Palmar Aponeurosis

FIGURE 9-1 Anterior (palmar) views of the musculature of the right hand. A, Superficial view of the hand with the palmar aponeurosis. ADMM, Abductor digiti minimi manus; APB, abductor pollicis brevis; DIM, dorsal interosseus manus; FDMM, flexor digiti minimi manus; FPB, flexor pollicis brevis; OP, opponens pollicis.

382

Anterior (Palmar) View of the Musculature of the Right Hand—Superficial Muscular View

FIGURE 9-1 B, Superficial view of the musculature of the hand with the palmar aponeurosis removed. ADMM, Abductor digiti minimi manus; APB, abductor pollicis brevis; DIM, dorsal interosseus/interossei manus; FDMM, flexor digiti minimi manus; FPB, flexor pollicis brevis; ODM, opponens digiti minimi; OP, opponens pollicis; PI, palmar interossei.

383

Anterior (Palmar) View of the Musculature of the Right Hand—Intermediate Muscular View

FIGURE 9-1 C, Intermediate view with the more superficial thenar and hypothenar muscles cut. ADMM, Abductor digiti minimi manus; APB, abductor pollicis brevis; DIM, dorsal interosseus/interossei manus; FDMM, flexor digiti minimi manus; FPB, flexor pollicis brevis; ODM, opponens digiti minimi; OP, opponens pollicis; PI, palmar interossei.

384

Anterior (Palmar) View of the Musculature of the Right Hand—Deep Muscular View

FIGURE 9-1 D, Deep view with the more superficial thenar and hypothenar muscles, lumbricals manus, flexor digitorum muscles’ tendons, and all forearm muscles cut and/or removed. ADMM, Abductor digiti minimi manus; APB, abductor pollicis brevis; DIM, dorsal interosseus/interossei manus; FDMM, flexor digiti minimi manus; FPB, flexor pollicis brevis; ODM, opponens digiti minimi; OP, opponens pollicis; PI, palmar interossei.

385

Anterior (Palmar) View of the Musculature of the Right Hand—Deepest Muscular View

FIGURE 9-1 E, Deepest view of the palmar musculature. ADMM, Abductor digiti minimi manus; APB, abductor pollicis brevis; DIM, dorsal interosseus manus; FDMM, flexor digiti minimi manus; FPB, flexor pollicis brevis; ODM, opponens digiti minimi; OP, opponens pollicis; PI, palmar interosseus.

386

Posterior (Dorsal) View of the Musculature of the Right Hand

FIGURE 9-2

Posterior (dorsal) view of the right hand. DIM, Dorsal interosseus manus.

387

Transverse Plane Cross Section of the Right Wrist

FIGURE 9-3 A, Transverse plane cross section of the right wrist through the distal row of carpal bones. The four flexor digitorum superficialis tendons, four flexor digitorum profundus tendons, flexor pollicis longus tendon, and the median nerve are located deep to the transverse carpal ligament in the carpal tunnel. The view is proximal to distal.

388

Transverse Plane Cross Section of the Right Hand through the Metacarpal Bones

FIGURE 9-3 B, Cross-sectional view of the right hand through the metacarpal bones. DIM, Dorsal interosseus manus; FDP, flexor digitorum profundus; FDS, flexor digitorum superficialis; LM, lumbrical manus; PI, palmar interosseus. View is proximal to distal.

389

Dorsal Digital Expansion The dorsal digital expansion is an attachment site for the lumbricals manus, palmar interossei, dorsal interossei manus, and abductor digiti minimi manus muscles, which attach into it from the sides. The dorsal digital expansion is actually a fibrous aponeurotic expansion of the distal attachment of the extensor digitorum muscle on the fingers (index, middle, ring, and little fingers) that serves as a movable hood of tissue when the fingers flex and extend. The dorsal digital expansion begins on the dorsal, lateral, and medial sides of the proximal phalanx of each finger and then ultimately attaches onto the dorsal side of the middle and distal phalanges. Because the dorsal digital expansion eventually attaches onto the dorsal (posterior) side of the middle and distal phalanges, any muscle that attaches into the dorsal digital expansion can create extension of these phalanges at the interphalangeal joints. There is also a dorsal digital expansion of the thumb formed by the distal tendon of the extensor pollicis longus. The dorsal digital expansion is also known as the extensor expansion and/or the dorsal hood.

FIGURE 9-4

Views of the dorsal digital expansion of the index finger of the right hand. Dotted lines represent borders of underlying bones. A, Dorsal view. B, Lateral view.

390

Thenar Eminence Group ORGANIZATION OF THE THENAR MUSCLES The thenar eminence is an eminence of soft tissue located on the radial side of the palm of the hand. There are three muscles in the thenar eminence group: the abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis.

ATTACHMENTS All three thenar muscles attach proximally onto the flexor retinaculum and carpal bones. All three thenar muscles attach distally onto the thumb.

The abductor pollicis brevis and the flexor pollicis brevis attach onto the proximal phalanx of the thumb. The opponens pollicis attaches onto the metacarpal of the thumb.

FUNCTIONS All three thenar muscles move the thumb. In each case, the name of the muscle indicates its major joint action.

MISCELLANEOUS 1. The layering of the thenar muscles is approximately as follows: The abductor pollicis brevis is the most superficial of the three. The flexor pollicis brevis is intermediate. The opponens pollicis is the deepest of the three. 2. There are three muscles located in the hypothenar eminence that are analogous to the thenar muscles. The three hypothenar muscles are the abductor digiti minimi manus, flexor digiti minimi manus, and opponens digiti minimi. 3. The thenar muscles are located within the deep front arm line myofascial meridian.

I N N E RVAT I O N The three thenar muscles are innervated by the median nerve. (The ulnar nerve usually contributes to a small degree.)

A R T E R I A L S U P P LY The three thenar muscles receive their arterial supply from the radial artery.

391

FIGURE 9-5

Anterior views of the right thenar group muscles. A, Superficial view.

392

FIGURE 9-5

B, Deep view. The abductor pollicis brevis and flexor pollicis brevis have been cut. APB, Abductor pollicis brevis; FPB, flexor pollicis brevis; OP, opponens pollicis.

393

Abductor Pollicis Brevis The name, abductor pollicis brevis, tells us that this muscle abducts the thumb and is short (shorter than the abductor pollicis longus). Derivation abductor: L. a muscle that abducts a body part pollicis L. thumb brevis: L. shorter Pronunciation ab-DUK-tor POL-i-sis BRE-vis

ATTACHMENTS The Flexor Retinaculum and the Scaphoid and Trapezium the tubercle of the scaphoid and the tubercle of the trapezium to the Proximal Phalanx of the Thumb the radial (lateral) side of the base of the proximal phalanx and the dorsal digital expansion

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Abducts the thumb at the CMC joint 2. Flexes the thumb at the MCP joint 3. Extends the thumb at the CMC and IP joints

Reverse Mover Actions 1. Abducts the trapezium at the CMC joint 2. Flexes the metacarpal of the thumb at the MCP joint 3. Extends the trapezium at the CMC joint; extends the proximal phalanx of the thumb at the IP joint

CMC joint = carpometacarpal joint (of the thumb; saddle joint of the thumb); MCP joint = metacarpophalangeal joint; IP joint = interphalangeal joint

Standard Mover Action Notes • The abductor pollicis brevis crosses the first CMC joint of the thumb anteriorly to attach onto the proximal phalanx of the thumb (with its fibers running vertically in the sagittal plane). When the abductor pollicis brevis contracts, it pulls the metacarpal of the thumb within the sagittal plane in a direction that is perpendicular to and away from the plane of the palm of the hand. This action is called abduction of the thumb. Therefore the abductor pollicis brevis abducts the thumb by abducting the metacarpal of the thumb at the first CMC joint. (Note: Because of the rotational development of the thumb embryologically, the named actions of abduction and adduction of the thumb occur within the sagittal plane). Additionally, the abductor pollicis brevis also crosses the MCP joint of the thumb anteriorly, but this joint cannot abduct. (action 1)

394

FIGURE 9-6

Anterior view of the right abductor pollicis brevis.

• The abductor pollicis brevis crosses the MCP joint of the thumb medially (ulnar side) to attach onto the proximal phalanx of the thumb (with its fibers running vertically in the frontal plane). When the abductor pollicis brevis contracts, it pulls the proximal phalanx of the thumb in a medial (ulnar) direction within the plane of the palm of the hand (frontal plane), toward the index finger. This action is called flexion of the thumb. Therefore the abductor pollicis brevis flexes the thumb by flexing the proximal phalanx of the thumb at the MCP joint. (Note: Because of the rotational development of the thumb embryologically, the named actions of flexion and extension of the thumb occur within the frontal plane. (action 2) • The abductor pollicis brevis crosses the first CMC joint laterally (radially) to attach onto the proximal phalanx of the thumb (with its fibers running vertically in the frontal plane). When the abductor pollicis brevis contracts, it pulls the metacarpal of the thumb in a lateral (radial) direction within the plane of the palm of the hand (frontal plane), away from the index finger. This action is called extension of the thumb. Therefore the abductor pollicis brevis extends the thumb by extending the metacarpal of the thumb at the first CMC joint. Because CMC joint extension is coupled with lateral rotation, the abductor pollicis brevis can also laterally rotate the CMC joint. Additionally, because of its attachment into the dorsal digital expansion of the thumb, the abductor pollicis brevis also crosses the IP joint of the thumb laterally (radially). Therefore the abductor pollicis brevis extends the distal phalanx of the thumb at the IP joint of the thumb as well. (action 3)

Reverse Mover Action Notes • The reverse action of motion at the first CMC joint occurs when the carpal bone (trapezium)

395

moves toward the metacarpal of the thumb at the CMC joint. This occurs when the distal end (the metacarpal) is fixed, perhaps because the thumb is gripping an immovable object. Movement of the trapezium would likely involve movement of the entire carpus (wrist) and forearm relative to the hand. (reverse actions 1, 3) • The reverse action of the thumb at the MCP joint occurs when the metacarpal moves relative to the proximal phalanx of the thumb at the MCP joint. This occurs when the distal segment, the proximal phalanx, is fixed, such as when the thumb is gripping an immovable object. (reverse action 2) • The reverse action of IP joint extension involves the proximal phalanx moving instead of the distal phalanx. This occurs if the distal phalanx is fixed, usually because the thumb is gripping an immovable object. (reverse action 3)

Motion 1. The abductor pollicis brevis has one line of pull in an oblique plane and therefore creates one motion, which is a combination of abduction and extension of the thumb at the CMC joint (as well as flexion of the thumb at the MCP joint).

Eccentric Antagonist Functions 1. Restrains/slows adduction of the CMC joint of the thumb 2. Restrains/slows extension of the MCP joint of the thumb 3. Restrains/slows flexion of the CMC and IP joints of the thumb

Isometric Stabilization Functions 1. Stabilizes the CMC joint of the thumb 2. Stabilizes the MCP joint of the thumb 3. Stabilizes the IP joint of the thumb

Additional Notes on Actions 1. The abductor pollicis brevis could be stated as a muscle of thumb opposition because CMC joint opposition is composed of flexion, medial rotation, and abduction, and the abductor pollicis brevis does abduction of the thumb at the CMC joint. 2. Some sources state that the abductor pollicis brevis flexes the thumb at the CMC joint. Looking at the line of pull of this muscle relative to the anteroposterior axis of motion in the frontal plane for CMC joint flexion/extension, we see that the muscle lies nearly directly over the axis, therefore, it would likely be weak regarding extension or flexion at the CMC joint. However, it is possible or even likely that the more medial fibers would flex the CMC joint (and that the more lateral fibers would extend the CMC joint). 3. All three thenar muscles attach onto and move the thumb. (Note: All three hypothenar muscles attach onto and move the little finger.)

I N N E RVAT I O N The Median Nerve C8, T1

A R T E R I A L S U P P LY Branches of the Radial Artery (a terminal branch of the Brachial Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating fingers over the lateral (radial) aspect of the thenar eminence. 2. Ask the client to abduct the thumb at the first carpometacarpal joint against resistance and feel for the contraction of the abductor pollicis brevis. (Note: Distinguishing the ulnar [medial] border of the abductor pollicis brevis from the adjacent flexor pollicis brevis can be difficult.)

396

RELATIONSHIP TO OTHER STRUCTURES The abductor pollicis brevis is superficial in the thenar eminence. The abductor pollicis brevis is lateral to the flexor pollicis brevis. Where they overlap, the abductor pollicis brevis is superficial; the lateral portion of the flexor pollicis brevis is covered by the abductor pollicis brevis. The abductor pollicis brevis is also superficial to the opponens pollicis. The abductor pollicis brevis is located within the deep front arm line myofascial meridian.

MISCELLANEOUS 1. The three muscles of the thenar eminence are the abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis. (Note: There are three analogous hypothenar muscles. They are the abductor digiti minimi manus, flexor digiti minimi manus, and opponens digiti minimi.)

397

Flexor Pollicis Brevis The name, flexor pollicis brevis, tells us that this muscle flexes the thumb and is short (shorter than the flexor pollicis longus). Derivation flexor: L. a muscle that flexes a body part pollicis: L. thumb brevis: L. shorter Pronunciation POL-i-sis BRE-vis

ATTACHMENTS The Flexor Retinaculum and the Trapezium to the Proximal Phalanx of the Thumb

the radial (lateral) side of the base of the proximal phalanx

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes the thumb at the CMC and MCP joints 2. Abducts the thumb at the CMC joint

Reverse Mover Actions 1. Flexes the trapezium at the CMC joint; flexes the metacarpal of the thumb at the MCP joint 2. Abducts the trapezium at the CMC joint

CMC joint = carpometacarpal joint (of the thumb; saddle joint of the thumb); MCP joint = metacarpophalangeal joint

Standard Mover Action Notes • The flexor pollicis brevis crosses the CMC joint of the thumb medially (on the ulnar side) to attach onto the proximal phalanx of the thumb (with its fibers running vertically in the frontal plane). When the flexor pollicis brevis contracts, it pulls the metacarpal of the thumb in a medial (ulnar) direction within the plane of the palm of the hand (frontal plane), toward the index finger. This action is called flexion of the thumb. Therefore the flexor pollicis brevis flexes the thumb by flexing the metacarpal of the thumb at the first CMC joint. (Note: Because of the rotational development of the thumb embryologically, the named actions of flexion and extension of the thumb occur within the frontal plane.) Because CMC joint flexion is coupled with medial rotation, the flexor pollicis brevis can also medially rotate the CMC joint. Additionally, the flexor pollicis brevis crosses the MCP joint of the thumb medially. Therefore the flexor pollicis brevis flexes the thumb by flexing the proximal phalanx of the thumb at the MCP joint as well. (action 1)

398

FIGURE 9-7

Anterior view of the right flexor pollicis brevis.

• The flexor pollicis brevis crosses the CMC joint of the thumb anteriorly to attach onto the proximal phalanx of the thumb (with its fibers running vertically in the sagittal plane). When the flexor pollicis brevis contracts, it pulls the metacarpal of the thumb within the sagittal plane in a direction that is perpendicular to and away from the plane of the palm of the hand. This action is called abduction of the thumb. Therefore the flexor pollicis brevis abducts the thumb by abducting the metacarpal of the thumb at the first CMC joint. (Note: Because of the rotational development of the thumb embryologically, the named actions of abduction and adduction of the thumb occur within the sagittal plane.) Additionally, the flexor pollicis brevis crosses the MCP joint of the thumb anteriorly, but this joint cannot abduct. (action 2)

Reverse Mover Action Notes • The reverse action of motion at the first CMC joint occurs when the carpal bone (trapezium) moves toward the metacarpal of the thumb at the CMC joint. This occurs when the distal end (the metacarpal) is fixed, perhaps because the thumb is gripping an immovable object. Movement of the trapezium would likely involve movement of the entire carpus (wrist) and forearm relative to the hand. (reverse actions 1, 2) • The reverse action of motion at the MCP joint occurs when the metacarpal moves relative to the proximal phalanx of the thumb. This occurs when the distal segment, the proximal phalanx, is fixed, usually because the thumb is gripping an immovable object. (reverse action 1)

Motion 1. The flexor pollicis brevis has one line of pull in an oblique plane and therefore creates one

399

motion, which is a combination of flexion and abduction of the thumb at the CMC joint (as well as flexion of the thumb at the MCP joint).

Eccentric Antagonist Functions 1. Restrains/slows extension of the CMC and MCP joints of the thumb 2. Restrains/slows adduction of the CMC joint of the thumb

Isometric Stabilization Functions 1. Stabilizes the CMC and MCP joints of the thumb

Additional Notes on Actions 1. CMC joint flexion and medial rotation are coupled due to the shape of the articular surfaces, so any muscle that flexes the thumb at the CMC joint also medially rotates the thumb at the CMC joint. Therefore the flexor pollicis brevis also medially rotates the thumb at the CMC joint. 2. The flexor pollicis brevis could be stated as a muscle of thumb opposition because CMC joint opposition is composed of flexion, medial rotation, and abduction, and the flexor pollicis brevis does flexion and medial rotation of the thumb at the CMC joint. 3. Some sources state that the flexor pollicis brevis can adduct the thumb at the CMC joint. It would seem likely that the more medial fibers located next to the adductor pollicis muscle might have this line of pull and therefore this action, especially if the thumb is first abducted. 4. All three thenar muscles attach onto and move the thumb. (Note: All three hypothenar muscles attach onto and move the little finger.)

I N N E RVAT I O N The Median and Ulnar Nerves C8, T1 (superficial head: the median nerve; deep head: the ulnar nerve)

A R T E R I A L S U P P LY Branches of the Radial Artery (a terminal branch of the Brachial Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating fingers on the medial (ulnar) aspect of the thenar eminence. 2. Ask the client to flex the thumb at the first carpometacarpal joint and feel for the contraction of the medial portion of the flexor pollicis brevis. 3. Continue palpating the flexor pollicis brevis more laterally, deep to the abductor pollicis brevis. (Note: Discerning the lateral portion of the flexor pollicis brevis from the superficial abductor pollicis brevis can be difficult.)

RELATIONSHIP TO OTHER STRUCTURES The medial portion of the flexor pollicis brevis is superficial in the thenar eminence. The lateral portion of the flexor pollicis brevis is deep to the abductor pollicis brevis. The superficial head of the flexor pollicis brevis is superficial to the medial portion of the opponens pollicis. The deep head of the flexor pollicis brevis is deep to the medial portion of the opponens pollicis. Hence the medial portion of the opponens pollicis is sandwiched between the two heads of the flexor pollicis brevis. The distal tendon of the flexor pollicis longus is sandwiched between the two heads of the flexor pollicis brevis. The flexor pollicis brevis is located within the deep front arm line myofascial meridian.

MISCELLANEOUS 1. The three muscles of the thenar eminence are the abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis. (Note: There are three analogous hypothenar muscles. They are the abductor

400

digiti minimi manus, flexor digiti minimi manus, and opponens digiti minimi.) 2. The flexor pollicis brevis is usually considered to have a superficial and deep head. 3. Some sources state that the flexor pollicis brevis does not have a superficial and deep head but rather has only one part to it. What is called the deep head of the flexor pollicis brevis is considered by some sources to be part of the oblique head of the adductor pollicis and by other sources to be a palmar interosseus muscle of the thumb. 4. There is a sesamoid bone in the distal tendon of the flexor pollicis brevis. (Note: There is a second sesamoid bone of the thumb located in the distal tendon of the adductor pollicis.)

401

Opponens Pollicis The name, opponens pollicis, tells us that this muscle opposes the thumb. Derivation opponens: L. opposing pollicis: L. thumb Pronunciation op-PO-nens POL-i-sis

ATTACHMENTS The Flexor Retinaculum and the Trapezium the tubercle of the trapezium to the First Metacarpal (of the Thumb) the anterior surface and radial (lateral) border

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Opposes the thumb at the CMC joint 2. Flexes the thumb at the CMC joint

Reverse Mover Actions 1. Flexes, laterally rotates, and abducts the trapezium at the CMC joint 2. Flexes the trapezium at the CMC joint

3. Medially rotates the thumb at the CMC joint

3. Laterally rotates the trapezium at the CMC joint

4. Abducts the thumb at the CMC joint

4. Abducts the trapezium at the CMC joint

CMC joint = carpometacarpal joint (of the thumb; saddle joint of the thumb)

Standard Mover Action Notes • Opposition is not a specific cardinal plane action, but rather is the term given to a triplanar oblique plane motion that is a combination of three cardinal plane actions that occur at the CMC joint of the thumb, which are required to bring the pad of the thumb against the pad of another finger. Opposition involves flexion, medial rotation, and abduction of the metacarpal of the thumb. (actions 1, 2, 3, 4) • The opponens pollicis crosses the first CMC joint of the thumb medially (on the ulnar side) to attach onto the metacarpal of the thumb (with its fibers running vertically in the frontal plane). When the opponens pollicis contracts, it pulls the metacarpal of the thumb in a medial (ulnar) direction within the plane of the palm of the hand (frontal plane), toward the index finger. This action is called flexion of the thumb. Therefore the opponens pollicis flexes the thumb by flexing the metacarpal of the thumb at the first CMC joint. (Note: Because of the rotational development of the thumb embryologically, the named actions of flexion and extension of the thumb occur within the frontal plane.) The action of CMC joint flexion always couples with CMC joint medial rotation. (action 2)

402

FIGURE 9-8

Anterior view of the right opponens pollicis.

• The opponens pollicis crosses the first CMC joint on the anterior side from slightly medial on the flexor retinaculum to attach more laterally onto the metacarpal of the thumb (with its fibers running somewhat horizontally in the transverse plane). When the opponens pollicis contracts, it rotates the first metacarpal posteriorly toward the little finger (finger five), causing the medial surface of the thumb to face somewhat posteriorly. Therefore the opponens pollicis medially rotates the thumb by medially rotating the metacarpal of the thumb at the CMC joint. The action of CMC joint medial rotation always couples with CMC joint flexion. (action 3) • The opponens pollicis crosses the first CMC joint of the thumb anteriorly to attach onto the metacarpal of the thumb (with its fibers running vertically in the sagittal plane). When the opponens pollicis contracts, it pulls the metacarpal of the thumb within the sagittal plane in a direction that is perpendicular to and away from the plane of the palm of the hand. This action is called abduction of the thumb. Therefore the opponens pollicis abducts the thumb by abducting the metacarpal of the thumb at the first CMC joint. Note: Because of the rotational development of the thumb embryologically, the named actions of abduction and adduction of the thumb occur within the sagittal plane. (action 3)

Reverse Mover Action Notes • Given that opposition is an oblique plane motion that is a combination of three cardinal plane actions, the reverse action of opposition involves the reverse actions of all three of these cardinal plane components of opposition. (reverse actions 1, 2, 3, 4) • The reverse action of motion at the first CMC occurs when the carpal bone (trapezium) moves toward the metacarpal of the thumb at the CMC joint. This occurs when the distal end (the

403

metacarpal) is fixed, usually because the thumb is gripping an immovable object. Movement of the trapezium would likely involve movement of the entire carpus (wrist) and forearm relative to the hand. (reverse actions 1, 2, 3, 4)

Motion 1. The opponens pollicis has one line of pull in an oblique plane and therefore creates one motion, opposition, which is a combination of flexion, medial rotation, and abduction of the thumb at the CMC joint.

Eccentric Antagonist Functions 1. Restrains/slows reposition of the thumb at the CMC joint 2. Restrains/slows extension of the CMC joint of the thumb 3. Restrains/slows lateral rotation of the metacarpal and medial rotation of the trapezium at the CMC joint of the thumb 4. Restrains/slows adduction of the CMC joint of the thumb

Isometric Stabilization Function 1. Stabilizes the CMC joint of the thumb

Additional Notes on Actions 1. All three thenar muscles attach onto and move the thumb. (Note: All three hypothenar muscles attach onto and move the little finger.) 2. Some sources state that the opponens pollicis can also extend the thumb at the first metacarpophalangeal joint. If this were true, it would have to be the most lateral fibers that would create this action by pulling the thumb radially (laterally) away from the other fingers within the plane of the palm of the hand (the frontal plane).

I N N E RVAT I O N The Median and Ulnar Nerves C8, T1

A R T E R I A L S U P P LY Branches of the Radial Artery (a terminal branch of the Brachial Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating fingers over the lateral portion of the thenar eminence against the shaft of the metacarpal of the thumb (i.e., deep to the abductor pollicis brevis). 2. Have the client flex the thumb at the first carpometacarpal joint against resistance and feel for the contraction of the lateral portion of the opponens pollicis. 3. Continue palpating the opponens pollicis more medially, deep to the abductor and flexor pollicis brevis. (Note: Discerning the opponens pollicis from these two more superficial thenar eminence muscles can be difficult because they both can flex and/or abduct the metacarpal of the thumb at the first carpometacarpal joint.)

RELATIONSHIP TO OTHER STRUCTURES The opponens pollicis is the deepest of the three thenar muscles. The opponens pollicis is deep to the abductor pollicis brevis and the flexor pollicis brevis. Deep to the opponens pollicis is the distal attachment of the abductor pollicis longus. The opponens pollicis is located within the deep front arm line myofascial meridian.

MISCELLANEOUS 1. The three muscles of the thenar eminence are the abductor pollicis brevis, flexor pollicis brevis,

404

and opponens pollicis. (Note: There are three analogous hypothenar muscles. They are the abductor digiti minimi manus, flexor digiti minimi manus, and opponens digiti minimi.) 2. Both the opponens pollicis and the opponens digiti minimi attach onto their respective metacarpal bone (first and fifth) and not onto the phalanges, as do all the other thenar and hypothenar muscles. 3. The ulnar nerve component of the opponens pollicis is often absent. 4. Apes can oppose their thumb, but it is so short that it is not very functional for grasping objects.

405

Hypothenar Eminence Group The hypothenar eminence is an eminence of soft tissue located on the ulnar side of the palm of the hand. There are three muscles in the hypothenar eminence group: the abductor digiti minimi manus, flexor digiti minimi manus, and opponens digiti minimi.

ATTACHMENTS All three hypothenar muscles attach proximally onto the flexor retinaculum and/or the carpal bones. All three hypothenar muscles attach distally onto the little finger (finger five).

The abductor digiti minimi manus and flexor digiti minimi manus attach onto the proximal phalanx of the little finger. The opponens digiti minimi attaches onto the metacarpal of the little finger.

FUNCTIONS All three hypothenar muscles move the little finger. In each case, the name of the muscle indicates its major joint action.

MISCELLANEOUS The layering of the hypothenar muscles is approximately as follows: 1. The abductor digiti minimi manus is the most superficial of the three. 2. The flexor digiti minimi manus is intermediate. 3. The opponens digiti minimi is the deepest of the three. 4. There are three muscles located in the thenar eminence that are analogous to the hypothenar muscles. The three thenar muscles are the abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis. 5. The hypothenar muscles are located within the deep back arm line myofascial meridian.

I N N E RVAT I O N The three hypothenar muscles are innervated by the ulnar nerve.

A R T E R I A L S U P P LY The three hypothenar muscles receive their arterial supply from the ulnar artery.

406

FIGURE 9-9

Anterior views of the right hypothenar group muscles. A, Superficial view.

407

FIGURE 9-9 B, Deep view. The abductor digiti minimi manus and flexor digiti minimi manus have been cut. ADMM, Abductor digiti minimi manus; FDMM, flexor digiti minimi manus; ODM, opponens digiti minimi.

408

Abductor Digiti Minimi Manus The name, abductor digiti minimi manus, tells us that this muscle abducts the little finger. Derivation abductor: L. a muscle that abducts a body part digiti: L. refers to a digit (finger) minimi: L. least manus: L. refers to the hand Pronunciation ab-DUK-tor DIJ-i-tee MIN-i-mee MAN-us

ATTACHMENTS The Pisiform and the tendon of the flexor carpi ulnaris to the Proximal Phalanx of the Little Finger (Finger Five) the ulnar (medial) side of the base of the proximal phalanx and the dorsal digital expansion

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Abducts the little finger at the MCP joint 2. Abducts the little finger at the CMC joint 3. Flexes the little finger at the MCP and CMC joints 4. Extends the little finger at the PIP and DIP joints

Reverse Mover Actions 1. Abducts the fifth metacarpal at the MCP joint 2. Abducts the hamate at the CMC joint of the little finger 3. Flexes the fifth metacarpal at the MCP joint; distally glides the pisiform at the CMC joint. 4. Extends the proximal phalanx of the little finger at the PIP joint; extends the middle phalanx of the little finger at the DIP joint

MCP joint = metacarpophalangeal joint; CMC joint = carpometacarpal joint; PIP joint = proximal interphalangeal joint; DIP joint = distal interphalangeal joint

Standard Mover Action Notes • The abductor digiti minimi manus crosses the CMC and MCP joints of the little finger medially (on the ulnar side) from proximally at the wrist area to distally onto the proximal phalanx of the little finger (with its fibers running vertically in the frontal plane). When the abductor digiti minimi manus contracts, it pulls the fifth metacarpal and the proximal phalanx of the little finger medially (in an ulnar direction) into abduction. Therefore the abductor digiti minimi manus abducts the little finger by abducting the metacarpal at the CMC joint and the proximal phalanx at the MCP joint. (actions 1, 2)

409

FIGURE 9-10

Anterior view of the right abductor digiti minimi manus.

• Abduction of the little finger at the CMC joint is a motion of the metacarpal of the little finger in the frontal plane that is away from the thumb; this action is a component of reposition of the little finger (i.e., returning from opposition to the thumb). (action 2) • The abductor digiti minimi manus crosses the MCP joint of the little finger anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the little finger at the MCP joint. Flexion of the little finger at the MCP joint involves flexion of the proximal phalanx of the little finger at the MCP joint. (action 3) • The abductor digiti minimi manus attaches into the dorsal digital expansion, which crosses the PIP and DIP joints of the little finger on the posterior side (with the line of pull running vertically in the sagittal plane). Therefore the abductor digiti minimi manus extends the middle and distal phalanges of the little finger at the PIP and DIP joints of the little finger respectively. All muscles that attach into the dorsal digital expansion of the hand extend the interphalangeal (IP) joints. (action 4)

Reverse Mover Action Notes • The reverse action of motion at the fifth MCP joint is to move the metacarpal toward the proximal phalanx of the little finger. This occurs when the distal end (the proximal phalanx) is fixed, such as when the little finger is holding onto an immovable object. (reverse action 1) • The reverse action of motion at the fifth CMC joint is to move the hamate toward the metacarpal of the little finger. This occurs if the distal end (the metacarpal) is fixed, perhaps because the little finger is gripping an immovable object. Movement of the hamate would likely involve movement of the entire carpus (wrist) and forearm relative to the hand. (reverse action 2) • The reverse action of flexion of the little finger at the MCP joint occurs when the metacarpal flexes

410

relative to the proximal phalanx of the little finger. This occurs when the distal segment, the proximal phalanx, is fixed, such as when the little finger is gripping an immovable object. Similarly, at the CMC joint, with the distal attachment, the metacarpal, fixed, the proximal attachment, the pisiform, would be pulled into a non-axial glide in the distal direction. (reverse action 3) • The reverse action of PIP joint extension of the little finger occurs when the proximal phalanx moves instead of the middle phalanx at the PIP joint. The reverse action of DIP joint extension of the little finger occurs when the middle phalanx moves instead of the distal phalanx at the DIP joint. These reverse actions occur if the distal end is fixed, usually because the little finger is gripping an immovable object. (reverse action 4)

Motion 1. The abductor digiti minimi manus has one line of pull in an oblique plane and therefore creates one motion, which is a combination of abduction and flexion of the little finger at the MCP joint (as well as abduction and flexion at the CMC joint and extension at the PIP and DIP joints).

Eccentric Antagonist Functions 1. Restrains/slows adduction and extension of the MCP and CMC joints of the little finger 2. Restrains/slows flexion of the PIP and DIP joints of the little finger

Isometric Stabilization Functions 1. Stabilizes the MCP joint of the little finger 2. Stabilizes the CMC joint of the little finger 3. Stabilizes the PIP and DIP joints of the little finger

Additional Note on Actions 1. All three hypothenar muscles attach onto and move the little finger. (Note: All three thenar muscles attach onto and move the thumb.)

I N N E RVAT I O N The Ulnar Nerve C8, T1

A R T E R I A L S U P P LY Branches of the Ulnar Artery (A Terminal Branch of the Brachial Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating fingers on the medial aspect of the hypothenar eminence, directly distal to the pisiform. 2. Have the client actively abduct the little finger at the fifth metacarpophalangeal joint and feel for the contraction of the belly of the abductor digiti minimi manus. Resistance can be added. 3. Follow proximally and distally to its attachments.

RELATIONSHIP TO OTHER STRUCTURES The abductor digiti minimi manus is superficial in the medial part of the hypothenar eminence. The abductor digiti minimi manus is somewhat superficial to, and therefore somewhat overlies, the flexor digiti minimi manus. The abductor digiti minimi manus is located within the deep back arm line myofascial meridian.

MISCELLANEOUS 1. The abductor digiti minimi manus is also known as the abductor digiti minimi. However, this allows for confusion with the abductor digiti minimi pedis of the foot, which abducts the little toe of the foot.

411

2. The three muscles of the hypothenar eminence are the abductor digiti minimi manus, flexor digiti minimi manus, and opponens digiti minimi. (Note: There are three analogous thenar muscles. They are the abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis.) 3. The dorsal interossei manus muscles cross the metacarpophalangeal joints of the index, middle, and ring fingers (fingers two through four, respectively) on the side away from the middle finger; consequently, the dorsal interossei manus abduct the index, middle, and ring fingers. The abductor digiti minimi manus crosses the metacarpophalangeal joint of the little finger on the side away from the middle finger and abducts the little finger. Therefore the abductor digiti minimi manus can be regarded as an analogous muscle to the dorsal interossei manus with respect to structure and function. 4. Whenever the abductor digiti minimi manus contracts, the flexor carpi ulnaris also contracts to fix (stabilize) the proximal attachment, the pisiform, of the abductor digiti minimi manus. This can be easily palpated at the distal tendon of the flexor carpi ulnaris at the distal antero-ulnar wrist.

412

Flexor Digiti Minimi Manus The name, flexor digiti minimi manus, tells us that this muscle flexes the little finger. Derivation flexor: L. a muscle that flexes a body part digiti: L. refers to a digit (finger) minimi: L. least manus: L. refers to the hand Pronunciation FLEKS-or DIJ-i-tee MIN-i-mee MAN-us

ATTACHMENTS The Flexor Retinaculum and the Hamate the hook of the hamate to the Proximal Phalanx of the Little Finger (Finger Five) the antero-ulnar (anteromedial) side of the base of the proximal phalanx

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes the little finger at the MCP joint 2. Flexes the little finger at the CMC joint

Reverse Mover Actions 1. Flexes the fifth metacarpal at the MCP joint 2. Distally glides the hamate at the fifth CMC joint

MCP joint = metacarpophalangeal joint; CMC joint = carpometacarpal joint

Standard Mover Action Notes • The flexor digiti minimi manus crosses the MCP joint of the little finger anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the little finger at the MCP joint. Flexion of the little finger at the MCP joint involves flexion of the proximal phalanx of the little finger at the MCP joint. (action 1) • The flexor digiti minimi also crosses the CMC joint of the little finger anteriorly (with its fibers running vertically in the sagittal plane); therefore it also flexes the little finger at the CMC joint. Flexion of the little finger at the CMC joint involves flexion of the metacarpal of the little finger at the CMC joint. This joint action is a component motion of opposition of the little finger to meet the pad of the thumb. (action 2)

Reverse Mover Action Notes • The reverse action of flexion of the little finger at the MCP joint occurs when the metacarpal flexes relative to the proximal phalanx of the little finger. This occurs when the distal segment, the proximal phalanx, is fixed, such as when the little finger is gripping an immovable object. (reverse action 1)

413

FIGURE 9-11

Anterior view of the right flexor digiti minimi manus.

• The reverse action of flexion of the CMC joint of the little finger occurs when the hamate moves toward the metacarpal of the little finger at the CMC joint. This occurs if the distal end (the metacarpal) is fixed, perhaps because the little finger is gripping an immovable object. Movement of the hamate would likely involve movement of the entire carpus (wrist) and forearm relative to the hand.

Motion 1. The flexor digiti minimi manus has one line of pull in a cardinal plane and therefore creates one motion, which is a combination of flexion of the little finger at the MCP and CMC joints.

Eccentric Antagonist Functions 1. Restrains/slows extension of MCP joint of the little finger 2. Restrains/slows extension of CMC joint of the little finger

Isometric Stabilization Functions 1. Stabilizes the MCP joint of the little finger 2. Stabilizes the CMC joint of the little finger

Additional Notes on Actions 1. Flexion at the fifth CMC joint is coupled with slight lateral rotation (to create opposition of the little finger against the thumb pad). Therefore, given that the flexor digiti minimi flexes the fifth metacarpal at the CMC joint, it can also laterally rotate the fifth metacarpal at the CMC joint.

414

2. All three hypothenar muscles attach onto and move the little finger. (Note: All three thenar muscles attach onto and move the thumb.)

I N N E RVAT I O N The Ulnar Nerve C8, T1

A R T E R I A L S U P P LY Branches of the Ulnar Artery (a terminal branch of the Brachial Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating fingers toward the lateral edge of the hypothenar eminence, directly distal to the hook of the hamate. 2. Have the client actively flex the little finger at the fifth metacarpophalangeal joint and feel for the contraction of the lateral aspect of the belly of the flexor digiti minimi. Resistance can be added. 3. A part of the medial portion of the flexor digiti minimi manus, deep to the abductor digiti minimi manus, can be palpated as you continue palpating medially as long as the abductor digiti minimi manus is relaxed. (Be sure that the client is not abducting the little finger.)

RELATIONSHIP TO OTHER STRUCTURES The flexor digiti minimi manus lies in the hypothenar eminence, lateral and partially deep to the abductor digiti minimi manus. Partially deep to the flexor digiti minimi manus is the opponens digiti minimi. The flexor digiti minimi manus is located within the deep back arm line myofascial meridian.

MISCELLANEOUS 1. The flexor digiti minimi manus is also known as the flexor digiti minimi. However, this allows for confusion with the flexor digiti minimi pedis of the foot, which flexes the little toe. 2. The flexor digiti minimi manus is also known as the flexor digiti minimi brevis. However, the addition of the word brevis at the end of the name is not necessary and does not make sense in this case. Usually, the word brevis at the end of a muscle’s name is added to distinguish the muscle from a longer muscle that otherwise has the same name. In this case there is no flexor digiti minimi longus. 3. The three muscles of the hypothenar eminence are the abductor digiti minimi manus, flexor digiti minimi manus, and opponens digiti minimi. (Note: There are three analogous thenar muscles. They are the abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis.) 4. The flexor digiti minimi manus is the smallest of the three hypothenar muscles. 5. The flexor digiti minimi manus is often very small or entirely absent.

415

Opponens Digiti Minimi The name, opponens digiti minimi, tells us that this muscle opposes the little finger. Derivation opponens: L. opposing digiti: L. refers to a digit (finger) minimi: L. least Pronunciation op-PO-nens DIJ-i-tee MIN-i-mee

ATTACHMENTS The Flexor Retinaculum and the Hamater the hook of the hamate to the Fifth Metacarpal (of the Little Finger) the anterior surface and the medial (ulnar) border of the fifth metacarpal

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Opposes the little finger at the CMC joint 2. Flexes the little finger at the CMC joint

Reverse Mover Actions 1. Flexes, medially rotates, and adducts the hamate at the fifth CMC joint 2. Flexes the hamate at the CMC joint of the little finger

3. Laterally rotates the little finger at the CMC joint

3. Medially rotates the hamate at the CMC joint of the little finger

4. Adducts the little finger at the CMC joint

4. Adducts the hamate at the CMC joint of the little finger

CMC joint = carpometacarpal joint

Standard Mover Action Notes • Opposition of the little finger is not a specific cardinal plane action; rather, it is a triplanar oblique plane motion that is composed of flexion, lateral rotation, and adduction of the little finger at the CMC joint, all aimed to bring the pad of the little finger to meet the pad of the thumb. (actions 1, 2, 3, 4) • The opponens digiti minimi crosses the fifth CMC joint anteriorly to attach onto the metacarpal of the little finger (with its fibers running vertically in the sagittal plane). When the opponens digiti minimi contracts, it pulls the fifth metacarpal anteriorly into flexion. Therefore the opponens digiti minimi flexes the little finger by flexing the metacarpal of the little finger at the CMC joint. (action 2) • The opponens digiti minimi crosses the fifth CMC joint anteriorly from slightly more lateral on the flexor retinaculum to attach more medially onto the metacarpal of the little finger (with its fibers running somewhat horizontally in the transverse plane). When the opponens digiti minimi contracts, it rotates the fifth metacarpal anterolaterally toward the thumb, causing the anterior surface of the little finger to face somewhat laterally. Therefore the opponens digiti minimi laterally rotates the little finger by laterally rotating the metacarpal of the little finger at the CMC joint. (action 3)

416

FIGURE 9-12

Anterior view of the right opponens digiti minimi.

• The opponens digiti minimi crosses the fifth CMC joint anteriorly from laterally at the wrist area to medially onto the metacarpal of the little finger (with its fibers running slightly horizontally in the frontal plane). When the opponens digiti minimi contracts, it pulls the fifth metacarpal laterally into adduction. Therefore the opponens digiti minimi adducts the little finger by adducting the metacarpal of the little finger at the CMC joint. (action 4)

Reverse Mover Action Notes • Given that opposition is an oblique plane motion that is a combination of three cardinal plane actions, the reverse action of opposition involves the reverse actions of all three of these cardinal plane components of opposition. (reverse actions 1, 2, 3, 4) • The reverse action of motion at the fifth CMC occurs when the hamate moves toward the metacarpal of the little finger at the CMC joint. This occurs when the distal end (the metacarpal) is fixed, usually because the little finger is gripping an immovable object. Movement of the hamate would likely involve movement of the entire carpus (wrist) and forearm relative to the hand. (reverse actions 1, 2, 3, 4)

Motion 1. The opponens digiti minimi has one line of pull in an oblique plane and therefore creates one

417

motion, opposition, which is a combination of flexion, lateral rotation, and adduction of the little finger at the CMC joint.

Eccentric Antagonist Functions 1. Restrains/slows reposition of the little finger at the CMC joint 2. Restrains/slows extension and abduction of the CMC joint of the little finger 3. Restrains/slows medial rotation of the metacarpal and lateral rotation of the hamate of the CMC joint of the little finger

Isometric Stabilization Function 1. Stabilizes the CMC joint of the little finger

Additional Note on Actions 1. All three hypothenar muscles attach onto and move the little finger. (Note: All three thenar muscles attach onto and move the thumb.)

I N N E RVAT I O N The Ulnar Nerve C8, T1

A R T E R I A L S U P P LY Branches of the Ulnar Artery (a terminal branch of the Brachial Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating finger on the lateral aspect of the hypothenar eminence, directly distal to the hook of the hamate. 2. Have the client actively oppose the little finger at the fifth carpometacarpal joint and feel for the contraction of the belly of the opponens digiti minimi. 3. Continue palpating the opponens digiti minimi medially and try to follow it deep to the flexor digiti minimi manus and the abductor digiti minimi manus.

RELATIONSHIP TO OTHER STRUCTURES The medial portion of the opponens digiti minimi is deep to the abductor digiti minimi manus and the flexor digiti minimi manus. A small part of the lateral portion of the opponens digiti minimi is superficial in the most lateral aspect of the hypothenar eminence. The opponens digiti minimi is superficial to some of the more lateral tendons of the flexor digitorum superficialis and flexor digitorum profundus. The opponens digiti minimi is located within the deep back arm line myofascial meridian.

MISCELLANEOUS 1. The three muscles of the hypothenar eminence are the abductor digiti minimi manus, flexor digiti minimi manus, and opponens digiti minimi. (Note: There are three analogous thenar muscles. They are the abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis.) 2. Both the opponens digiti minimi and the opponens pollicis attach onto their respective metacarpal bone (fifth and first) and not onto the phalanges, as do all the other thenar and hypothenar muscles. 3. The flexor digiti minimi manus, which overlies the opponens digiti minimi, is often very small or entirely absent. When this occurs, the opponens digiti minimi will have relatively more superficial exposure. 4. The opponens digiti minimi is the largest of the three hypothenar muscles.

418

419

Central Compartment Group The central compartment is located between the thenar eminence and hypothenar eminence of the hand. There are four muscles/muscle groups in the central compartment group: the adductor pollicis, lumbricals manus, palmar interossei, and dorsal interossei manus.

ATTACHMENTS The lumbricals manus, palmar interossei, and dorsal interossei manus all attach distally into the dorsal digital expansion of the hand. The lumbricals manus all attach onto their respective finger on the radial (lateral) side. The palmar interossei attach onto fingers 2, 4, and 5 on the side that faces the middle finger. The dorsal interossei manus attach onto fingers 2, 3, and 4 on the side that is away from the center of the middle finger.

FIGURE 9-13 Anterior view of the right central compartment group muscles. DIM, Dorsal interosseus/interossei manus; PI, palmar interossei; FDP, flexor digitorum profundus. A, Superficial view.

420

FUNCTIONS The palmar interossei adduct fingers at the metacarpophalangeal joints. The dorsal interossei manus abduct fingers at the metacarpophalangeal joints. A mnemonic to remember the frontal plane actions of the interossei muscles of the hand is DAB PAD: Dorsals ABduct, Palmars ADduct. The lumbricals manus, palmar interossei, and dorsal interossei manus all flex fingers at the metacarpophalangeal joints and extend fingers at the interphalangeal joints.

I N N E RVAT I O N The four central compartment muscles are innervated by the ulnar nerve (two of the lumbricals manus are innervated by the median nerve).

A R T E R I A L S U P P LY The four central compartment muscles receive their arterial supply from branches of the radial and ulnar arteries (terminal branches of the brachial artery).

FIGURE 9-13

B, Deep view. The adductor pollicis and lumbricals manus have been cut. DIM, Dorsal

421

interosseus/interossei manus; PI, palmar interossei.

422

Adductor Pollicis The name, adductor pollicis, tells us that this muscle adducts the thumb. Derivation adductor: L. a muscle that adducts a body part pollicis: L. thumb Pronunciation ad-DUK-tor POL-i-sis

ATTACHMENTS Third Metacarpal to the Proximal Phalanx of the Thumb OBLIQUE HEAD: the anterior bases of the second and third metacarpals and the capitate to the OBLIQUE HEAD: the medial side of the base of the proximal phalanx and the dorsal digital expansion TRANSVERSE HEAD: the distal ⅔ of the anterior surface of the third metacarpal to the TRANSVERSE HEAD: the medial side of the base of the proximal phalanx

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Adducts the thumb at the CMC joint 2. Flexes the thumb at the CMC and MCP joints 3. Extends the thumb at the IP joint

Reverse Mover Actions 1. Adducts the trapezium at the CMC joint of the thumb 2. Flexes the trapezium at the CMC joint; flexes the metacarpal of the thumb at the MCP joint 3. Extends the proximal phalanx of the thumb at the IP joint

CMC joint = carpometacarpal joint (of the thumb; saddle joint of the thumb); MCP joint = metacarpophalangeal joint; IP joint = interphalangeal joint

Standard Mover Action Notes • The adductor pollicis crosses the CMC joint of the thumb posteriorly by attaching from posteromedially on the palm of the hand to anterolaterally onto the thumb (with its fibers running horizontally in the sagittal plane). When the thumb is first in a position of abduction and the adductor pollicis contracts, it pulls the thumb posteriorly, perpendicularly toward the plane of the palm of the hand. This action is called adduction of the thumb. Therefore the adductor pollicis adducts the thumb by adducting the metacarpal of the thumb at the CMC joint. (Note: Because of the rotational development of the thumb embryologically, the named actions of abduction and adduction of the thumb occur within the sagittal plane.) (action 1)

423

FIGURE 9-14

Anterior view of the right adductor pollicis.

• The adductor pollicis crosses the first CMC joint of the thumb from medially on the hand to more laterally onto the metacarpal of the thumb (with its fibers running in the frontal plane). When the adductor pollicis contracts, it pulls the thumb medially (in an ulnar direction) within the plane of the palm of the hand (frontal plane), toward its other attachment (the third metacarpal). This action is called flexion of the thumb. Therefore the adductor pollicis flexes the thumb by flexing the metacarpal of the thumb at the CMC joint. The adductor pollicis also crosses the first MCP joint of the thumb medially (with it fibers running in the frontal plane). Therefore the adductor pollicis also flexes the proximal phalanx of the thumb at the first MCP joint. (Note: Because of the rotational development of the thumb embryologically, the named actions of flexion and extension of the thumb occur within the frontal plane.) (action 2) • In addition to its major action of adduction of the thumb at the CMC joint, the adductor pollicis is extremely strong at flexing the thumb at the CMC joint. (actions 1, 2) • Because of its attachment into the dorsal digital expansion, which crosses the IP joint of the thumb on the lateral side (with its fibers running vertically in the frontal plane), the adductor pollicis can extend the thumb by extending the distal phalanx of the thumb at the IP joint. (action 3)

Reverse Mover Action Notes • The reverse action of motion at the first CMC joint occurs when the trapezium moves toward the

424

metacarpal of the thumb at the CMC joint. This occurs when the distal end (the metacarpal) is fixed, perhaps because the thumb is gripping an immovable object. Movement of the trapezium would likely involve movement of the entire carpus (wrist) and forearm relative to the hand. (reverse actions 1, 2) • The reverse action of the thumb at the MCP joint occurs when the metacarpal moves relative to the proximal phalanx of the thumb at the MCP joint. This occurs when the distal segment, the proximal phalanx, is fixed, such as when the thumb is gripping an immovable object. (reverse action 2) • The reverse action of IP joint extension involves the proximal phalanx moving instead of the distal phalanx. This occurs if the distal phalanx is fixed, usually because the thumb is gripping an immovable object. (reverse action 3)

Motions 1. In anatomic position, the adductor pollicis has one line of pull in the frontal (cardinal) plane and therefore creates one motion, which is flexion of the thumb at the CMC and MCP joints (and also extension of the thumb at the IP joint because of the pull of the dorsal digitorum expansion). 2. If the thumb is first in a position of abduction, the adductor pollicis has one line of pull in an oblique plane and therefore creates one motion, which is a combination of adduction and flexion of the thumb at the CMC joint (as well as flexion of the thumb at the MCP joint and extension at the IP joint).

Eccentric Antagonist Functions 1. Restrains/slows abduction of the CMC joint of the thumb 2. Restrains/slows extension of the CMC and MCP joints of the thumb 3. Restrains/slows flexion of the IP joint of the thumb

Isometric Stabilization Functions 1. Stabilizes the CMC, MCP, and IP joints of the thumb

Additional Notes on Actions 1. Opposition of the thumb is composed of flexion, medial rotation, and abduction of the thumb’s metacarpal at the CMC joint. Given that the adductor pollicis flexes the thumb at the CMC joint, it assists with opposition. Further, whenever the metacarpal of the thumb flexes, it also medially rotates; therefore the adductor pollicis can also be said to medially rotate the thumb at the CMC joint. 2. Opposition of the thumb results in the pad of the thumb meeting the pad of another finger. From anatomic position, this involves flexion, medial rotation, and abduction of the thumb at the CMC joint. However, if the thumb is first abducted, then moving it to meet another finger pad might involve adduction of the thumb (in the frontal plane toward the palm of the hand). In this way, the adductor pollicis might also be considered to assist opposition of the thumb. Technically however, opposition is defined from anatomic position, therefore thumb adduction is not defined as a component of thumb opposition. But practically, adduction of the thumb by the adductor pollicis might certainly be an important aspect of moving the thumb to meet another finger pad and potentially grip an object between the thumb and that finger.

I N N E RVAT I O N The Ulnar Nerve C8, T1

A R T E R I A L S U P P LY Branches of the Radial Artery (a terminal branch of the Brachial Artery)

PA L PAT I O N 1. With the client seated or supine and the thumb abducted at the carpometacarpal joint, place palpating fingers in the middle of the thumb web of the hand.

425

2. Have the client actively adduct the thumb at the first carpometacarpal joint against resistance and feel for the contraction of the adductor pollicis. 3. Continue palpating the adductor pollicis as far lateral and medial as possible toward its attachments.

RELATIONSHIP TO OTHER STRUCTURES Except for the part of the adductor pollicis that is superficial in the thumb web, the adductor pollicis is deeply situated in the hand. All the thenar muscles, the distal tendons of flexors digitorum superficialis and profundus (going to the second and third fingers), the distal tendon of the flexor pollicis longus, and the first and second lumbricals manus are superficial to the adductor pollicis. Although somewhat deep to the thenar muscles, the adductor pollicis also lies medial to the flexor pollicis brevis and the opponens pollicis. The distal attachment of the flexor carpi radialis and the shaft of the second metacarpal bone are deep to the adductor pollicis. From an anterior perspective, the first palmar interosseus and the first and second dorsal interossei manus are also deep to the adductor pollicis. The adductor pollicis is located within the deep front arm line myofascial meridian.

MISCELLANEOUS 1. The adductor pollicis has two heads: an oblique head and a transverse head. The oblique head runs more obliquely in the hand (i.e., its fiber direction is between vertical and horizontal in orientation). The transverse head runs transversely across the hand (i.e., its fiber direction is horizontal in orientation). (Note: The adductor hallucis of the foot also has two heads: an oblique head and a transverse head.) 2. There is a lot of variation and confusion regarding the region of the oblique head of the adductor pollicis. The oblique head often has a fasciculus (a group of muscle fibers) that joins with the flexor pollicis brevis and is called the deep head of the flexor pollicis brevis. 3. The oblique head of the adductor pollicis has a sesamoid bone located within it. (Note: There is a second sesamoid bone of the thumb located in the distal tendon of the flexor pollicis brevis.) 4. The majority of tissue of the thumb web of the hand is made up of the adductor pollicis and the first dorsal interosseus manus. 5. The attachment of the adductor pollicis into the dorsal digital expansion of the thumb is small and often absent. When it is absent, the adductor pollicis does not have the ability to extend the distal phalanx of the thumb at the interphalangeal joint of the thumb.

426

Lumbricals Manus There are four lumbrical manus muscles, named one, two, three, and four (from radial to ulnar). The name, lumbricals manus, tells us that these muscles are shaped like earthworms and are located in the hand. Derivation lumbricals: L. earthworms manus: L. refers to the hand Pronunciation LUM-bri-kuls MAN-us

ATTACHMENTS The Distal Tendons of the Flexor Digitorum Profundus One: the radial (lateral) side of the tendon of the index finger (finger two) Two: the radial side of the tendon of the middle finger (finger three) Three: the ulnar (medial) side of the tendon of the middle finger (finger three) and the radial side of the tendon of the ring finger (finger four) Four: the ulnar side of the tendon of the ring finger (finger four) and the radial side of the tendon of the little finger (finger five) to the Distal Tendons of the Extensor Digitorum (the Dorsal Digital Expansion) the radial side of the tendons merging into the dorsal digital expansion One: into the tendon of the index finger (finger two) Two: into the tendon of the middle finger (finger three) Three: into the tendon of the ring finger (finger four) Four: into the tendon of the little finger (finger five)

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extend fingers two through five at the PIP and DIP joints

Reverse Mover Actions 1. Extend the more proximal phalanges at the PIP and DIP joints

2. Flex fingers two through five at the MCP joints 3. Abduct/adduct fingers two through five at the MCP joints

2. Flex the metacarpals at the MCP joints 3. Abduct/adduct the metacarpals at the MCP joints

MCP joints = metacarpophalangeal joints; PIP joints = proximal interphalangeal joints; DIP joints = distal interphalangeal joints

Standard Mover Action Notes • The lumbricals manus, by attaching into the tendons of the extensor digitorum muscle (after the MCP joint but before the interphalangeal [IP] joints of the fingers), exert their pull on the distal attachments of the extensor digitorum, which are the distal phalanges of fingers two through five. The lumbricals manus, in effect, cross the PIP and DIP joints of fingers two through five posteriorly (with their pull exerted vertically in the sagittal plane) and therefore extend the middle phalanges at the PIP joints and extend the distal phalanges at the DIP joints of fingers two through five. (action 1)

427

FIGURE 9-15

Anterior view of the right lumbricals manus. The adductor pollicis has been ghosted in.

• The lumbricals manus cross the MCP joints of fingers two through five anteriorly (with their fibers running vertically in the sagittal plane); therefore they flex the proximal phalanges of fingers two through five at the MCP joints. (action 2) • The lumbricals manus cross the MCP joint of each finger on the radial side; therefore each lumbrical manus has the ability to either abduct or adduct the finger based on whether it pulls the finger toward or away from the reference line for abduction/adduction. The first lumbrical manus abducts the index finger, the second one radially abducts the middle finger, the third one adducts the ring finger, and the fourth one adducts the little finger. (action 3)

Reverse Mover Action Notes • Extending the more proximal phalanges at the interphalangeal joints refers to extending the proximal phalanges at the PIP joints and extending the middle phalanges at the DIP joints. (reverse action 1) • The reverse action of a finger at an MCP joint occurs when the metacarpal moves relative to the proximal phalanx of the finger at the MCP joint. This occurs when the distal segment, the proximal phalanx, is fixed, such as when the finger is gripping an immovable object. (reverse actions 2, 3)

428

Motion 1. Each lumbrical manus has one line of pull in an oblique plane and therefore creates one motion, which is a combination of extension of the finger at the PIP and DIP joints and flexion of the finger at the MCP joint, as well as abduction or adduction of the finger at the MCP joint.

Eccentric Antagonist Functions 1. Restrains/slows flexion of fingers two through five at the interphalangeal joints 2. Restrains/slows extension of fingers two through five at the MCP joints 3. Restrains/slows adduction/abduction of two through five fingers at the MCP joints

Isometric Stabilization Functions 1. Stabilizes the MCP and interphalangeal joints of fingers two through five

Additional Notes on Actions 1. The lumbricals pedis of the foot have similar actions in that they flex the toes at the metatarsophalangeal joints and extend the toes at the interphalangeal (IP) joints. 2. By flexing the MCP joint and simultaneously extending the proximal and distal IP joints, the lumbricals manus help to create a strong grip with the fingers opposed to the thumb. 3. In addition to directly contributing to extension of the fingers at the IP joints, the lumbricals manus and the interossei of the hand help create these actions in another manner. Whenever the extensor digitorum contracts, these intrinsic muscles of the hand create a flexion force at the MCP joint to keep the extensor digitorum from excessively extending the MCP joint and thereby losing its ability to create tension and extend the IP joints of the fingers. 4. All muscles that attach into the dorsal digital expansion of the hand flex the MCP joints and extend the IP joints.

I N N E RVAT I O N The Median and Ulnar Nerves C8, T1 (first and second lumbricals manus: the median nerve; third and fourth lumbricals manus: the ulnar nerve)

A R T E R I A L S U P P LY Branches of the Radial and Ulnar Arteries (terminal branches of the Brachial Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating fingers on the radial (lateral) side of the anterior shaft of the metacarpal of the little finger. 2. Have the client actively flex the little finger at the fifth metacarpophalangeal joint with the interphalangeal joints fully extended and feel for the contraction of the fourth lumbrical manus. 3. To palpate the third, second, and first lumbricals manus, follow the previously described procedure on the lateral sides of the ring, middle, and index fingers, respectively.

RELATIONSHIP TO OTHER STRUCTURES The lumbricals manus are actually not that deep in the palm of the hand. In the palm, they are deep only to the palmar fascia. As the lumbricals manus approach the phalanges, they dive deeper (more posteriorly) to attach onto the tendons of the extensor digitorum, which are on the posterior sides of the fingers. The bellies of the lumbricals manus are located between the distal tendons of the flexor digitorum profundus. Directly deep to the first and second lumbricals manus is the adductor pollicis. Directly deep to the third and fourth lumbricals manus are the metacarpals and the palmar interossei. The lumbricals manus are located within the superficial front arm line myofascial meridian.

MISCELLANEOUS 429

1. The lumbricals manus are actually four small separate muscles named from radial/lateral to ulnar/medial: one, two, three, and four. 2. The lumbricals manus are usually known as the lumbricals. However, this allows for confusion with the lumbricals pedis of the foot.

430

Palmar Interossei There are three palmar interossei, named one, two, and three (from radial to ulnar). The name, palmar interossei, tells us that these muscles are located between bones (metacarpals) on the palmar (anterior) side. Derivation palmar: L. refers to the palm interossei: L. between bones Pronunciation PAL-mar IN-ter-OSS-ee-I

ATTACHMENTS The Metacarpals of Fingers Two, Four, and Five The anterior side and on the “middle finger side” of the metacarpals: One: attaches to the metacarpal of the index finger (finger two) Two: attaches to the metacarpal of the ring finger (finger four) Three: attaches to the metacarpal of the little finger (finger five) to the Proximal Phalanges of Fingers Two, Four, and Five on the “Middle Finger Side” The base of the proximal phalanx and the dorsal digital expansion: One: attaches to the index finger (finger two) Two: attaches to the ring finger (finger four) Three: attaches to the little finger (finger five)

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Adduct fingers two, four, and five at the MCP joints 2. Flex fingers two, four, and five at the MCP joints

Reverse Mover Actions 1. Adduct the metacarpals of fingers two, four, and five at the MCP joints

3. Extend fingers two, four, and five at the PIP and DIP joints

2. Flex the metacarpals of fingers two, four, and five at the MCP joints 3. Extend the more proximal phalanges of fingers two, four, and five at the PIP and DIP joints

MCP joints = metacarpophalangeal joints; PIP joint = proximal interphalangeal joint; DIP joint = distal interphalangeal joint

Standard Mover Action Notes • The palmar interossei are always on the “middle finger side” of the metacarpals and phalanges (with their fibers running vertically in the frontal plane); therefore a palmar interosseus muscle pulls the finger to which it is attached toward the middle finger. This action is defined as adduction of the finger. (action 1)

431

FIGURE 9-16

Anterior view of the right palmar interossei. The adductor pollicis has been ghosted in.

• The first palmar interosseus muscle crosses the MCP joint of the index finger (finger two) on the medial side and therefore pulls the proximal phalanx of this finger medially, which is toward the middle finger (which is the axis for abduction/adduction of the fingers). Therefore the first palmar interosseus adducts the index finger at the MCP joint. The second and third palmar interossei cross the MCP joint of the ring and little fingers (fingers four and five) respectively on the lateral side and therefore pull these fingers laterally, toward the middle finger. Therefore the second and third palmar interossei adduct the ring finger and the little finger at the MCP joint. (action 1) • The palmar interossei cross the MCP joint on the palmar (anterior) side (with their fibers running vertically in the sagittal plane); therefore they flex the proximal phalanx of fingers two, four, and five at the MCP joint. (action 2) • Because of their attachment into the dorsal digital expansion of the extensor digitorum, the palmar interossei exert their pull through the dorsal digital expansion, which crosses the proximal and distal interphalangeal (IP) joints of the fingers on the posterior side (with the line of pull running vertically in the sagittal plane). Therefore the palmar interossei extend the middle phalanx at the proximal PIP joint and extend the distal phalanx at the DIP joint of fingers two, four, and five. (action 3)

432

Reverse Mover Action Notes • The reverse action of a finger at the MCP joint occurs when the metacarpal moves relative to the proximal phalanx of the finger. This occurs when the distal segment, the proximal phalanx, is fixed, such as when the finger is gripping an immovable object. (reverse actions 1, 2) • Extending the more proximal phalanges at the interphalangeal (IP) joints refers to extending the proximal phalanx at the PIP joint and extending the middle phalanx at the DIP joint. (reverse action 3)

Motion 1. Each palmar interosseus has one line of pull in an oblique plane and therefore creates one motion, which is a combination of adduction and flexion of the finger at the MCP joint, as well as extension of the finger at the PIP and DIP joints.

Eccentric Antagonist Functions 1. Restrains/slows abduction of fingers two, four, and five at the MCP joints 2. Restrains/slows extension of fingers two, four, and five at the MCP joints 3. Restrains/slows flexion of fingers two, four, and five at the PIP and DIP joints

Isometric Stabilization Functions 1. Stabilizes the MCP, PIP, and DIP joints of fingers two, four, and five

Additional Notes on Actions 1. A mnemonic for remembering the actions of the palmar interossei and the dorsal interossei manus muscles is DAB PAD. The Dorsals ABduct, and the Palmars ADduct. 2. Some sources state that the palmar interossei have the ability to create rotation at the MCP joints of the fingers to which they attach. Given their slight anterior to posterior orientation, this does seem possible, although likely very weak. The first palmar interosseus would laterally rotate the index finger; and the second and third palmar interossei would medially rotate the ring and little fingers respectively. 3. There are plantar interossei of the foot that have essentially identical actions (adduction of the toes at the metatarsophalangeal [MTP] joint, flexion of the toes at the MTP joint, and extension of the toes at the proximal and distal interphalangeal [IP] joints) to the palmar interossei of the hand. 4. In addition to directly contributing to extension of the fingers at the IP joints, the interossei of the hand and the lumbricals manus help create these actions in another manner. Whenever the extensor digitorum contracts, these intrinsic muscles of the hand create a flexion force at the MCP joint to keep the extensor digitorum from excessively extending the MCP joint and thereby losing its ability to create tension and extend the IP joints of the fingers. 5. All muscles that attach into the dorsal digital expansion of the hand flex the MCP joints and extend the IP joints.

I N N E RVAT I O N The Ulnar Nerve C8, T1; deep branch of the ulnar nerve

A R T E R I A L S U P P LY Branches of the Radial and Ulnar Arteries (terminal branches of the Brachial Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating fingers on the “middle finger side,” in this case, the medial (ulnar) side of the second metacarpal in the palm. 2. Have the client adduct the index finger by squeezing a pencil between the index and middle fingers and feel for the contraction of the first palmar interosseus against the second metacarpal. 3. To palpate the second and third palmar interossei, follow the previously described procedure on the middle finger (lateral/radial) side of the ring and little fingers, respectively.

433

RELATIONSHIP TO OTHER STRUCTURES The palmar interossei are located in a position that is palmar (anterior) on the metacarpals and slightly between the metacarpals. Each palmar interosseus muscle is located on the side of the metacarpal that faces the middle finger. (The middle finger has no palmar interosseus muscle attached to it.) From an anterior perspective, the palmar interossei are deep to all the other muscles of the anterior hand. From the anterior perspective, the metacarpal bones and the dorsal interossei manus are deep to the palmar interossei. The palmar interossei are involved with the superficial back arm line myofascial meridian.

MISCELLANEOUS 1. There are three palmar interossei muscles named from radial/lateral to ulnar/medial: one, two, and three. 2. There are three palmar interossei, one for each finger except the middle finger and the thumb. It makes sense that the middle finger would not have a palmar interosseus muscle. The palmar interossei adduct the fingers, and the middle finger, by definition, cannot adduct, because an imaginary line that runs through it when it is in anatomic position is the axis for abduction/adduction of the fingers (therefore, in either frontal plane direction the middle finger moves, it abducts). The thumb has its own adductor muscle (the adductor pollicis). 3. Many sources state that there is a fourth palmar interosseus muscle that attaches to the thumb. This would cause the naming of the palmar interossei muscles to change, because they are named from radial to ulnar (lateral to medial). Hence the palmar interosseus of the thumb would be one, the second palmar interosseus would attach to the index finger, the third palmar interosseus would attach to the ring finger, and the fourth palmar interosseus would attach to the little finger. This palmar interosseus muscle that attaches to the thumb is also known as the palmar interosseus of Henle. 4. Whether or not a true fourth palmar interosseus muscle exists, even some of the time, is controversial. Some sources name this extra muscle, or bundle of muscle fibers, as part of the oblique head of the adductor pollicis or as part of the deep head of the flexor pollicis brevis.

434

Dorsal Interossei Manus (DIM) There are four dorsal interossei manus muscles, named one, two, three, and four (from radial to ulnar). The name, dorsal interossei manus, tells us that these muscles are located between bones (metacarpals) on the dorsal (posterior) side and located in the hand. Derivation dorsal: L. back interossei: L. between bones manus: L. refers to the hand Pronunciation DOR-sul IN-ter-OSS-ee-i MAN-us

ATTACHMENTS The Metacarpals of Fingers One through Five Each one arises from the adjacent sides of two metacarpals: One: attaches onto the metacarpals of the thumb and index finger (fingers one and two) Two: attaches onto the metacarpals of the index and middle fingers (fingers two and three) Three: attaches onto the metacarpals of the middle and ring fingers (fingers three and four) Four: attaches onto the metacarpals of the ring and little fingers (fingers four and five) to the Proximal Phalanges of Fingers Two, Three, and Four on the Side That Faces Away from the Center of the Middle Finger The base of the proximal phalanx and the dorsal digital expansion: One: attaches to the lateral side of the index finger (finger two) Two: attaches to the lateral side of the middle finger (finger three) Three: attaches to the medial side of the middle finger (finger three) Four: attaches to the medial side of the ring finger (finger four)

435

FIGURE 9-17

Posterior view of the right dorsal interossei manus. The adductor pollicis, opponens pollicis, and abductor digiti minimi manus have been ghosted in.

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Abduct fingers two through four at the MCP joints 2. Flex fingers two through four at the MCP joints

Reverse Mover Actions 1. Abduct the metacarpals of fingers two through four at the MCP joints; flex and adduct the thumb at the CMC (saddle) joint 2. Flex the metacarpals of fingers two through four at the MCP joints

3. Extend fingers two through four at the PIP and DIP joints

3. Extend the more proximal phalanges of fingers two through four at the PIP and DIP joints

MCP joints = metacarpophalangeal joints; CMC joints = carpometacarpal joints; PIP joints = proximal interphalangeal joints; DIP joints = distal interphalangeal joints

Standard Mover Action Notes • The dorsal interossei manus (DIM) are always on the side of the metacarpals and phalanges (with their fibers running vertically in the frontal plane) that faces away from the axis of

436

abduction/adduction, which is an imaginary line drawn through the center of the middle finger when the middle finger is in anatomic position. Therefore they pull the fingers away from this axis, abducting the fingers. (action 1) • The first and second DIM cross the MCP joints of the index and middle fingers laterally. They pull the proximal phalanx of these fingers laterally, away from the axis of abduction/adduction. Therefore the first DIM abducts the index finger, and the second DIM “radially abducts” the middle finger at the MCP joints respectively. The third and fourth DIM cross the MCP joints of the middle and ring fingers medially. They pull the proximal phalanx of these fingers medially, away from the axis of abduction/adduction. Therefore the third DIM “ulnar abducts” the middle finger, and the fourth DIM abducts the ring finger at the MCP joints respectively. (action 1) • The DIM cross the MCP joints anteriorly (with their fibers running vertically in the sagittal plane); therefore they flex the proximal phalanges of the index, middle, and ring fingers at the MCP joints. (action 2) • The DIM attach into the dorsal digital expansion, which crosses the PIP and DIP joints of the fingers on the posterior side (with the line of pull running vertically in the sagittal plane). Therefore the DIM extend the middle phalanx at the PIP joint and extend the distal phalanx at the DIP joint of the index, middle, and ring fingers. (action 3)

Reverse Mover Action Notes • The reverse action of a finger at the MCP joint occurs when the metacarpal moves relative to the proximal phalanx of the finger. This occurs when the distal segment, the proximal phalanx, is fixed, such as when the finger is gripping an immovable object. (reverse actions 1, 2) • When the index finger is fixed (stabilized), the head of the first dorsal interosseus manus that attaches to the thumb pulls its thumb attachment medially and posteriorly toward the index finger, causing flexion and adduction of the thumb at the thumb’s CMC (saddle) joint. (reverse action 1) • Extending the more proximal phalanges at the PIP and DIP joints refers to extending the proximal phalanx at the PIP joint and extending the middle phalanx at the DIP joint. (reverse action 3)

Motion 1. Each dorsal interosseus manus has one line of pull in an oblique plane and therefore creates one motion, which is a combination of abduction and flexion of the finger at the MCP joint, as well as extension of the finger at the PIP and DIP joints.

Eccentric Antagonist Functions 1. Restrains/slows adduction of fingers two through four at the MCP joints 2. Restrains/slows extension of fingers two through four at the MCP joints 3. Restrains/slows flexion of fingers two through four at the PIP and DIP joints

Isometric Stabilization Functions 1. Stabilizes the MCP and IP joints of fingers two through four 2. Stabilizes the CMC joint of the thumb

Additional Notes on Actions 1. A mnemonic for remembering the actions of the dorsal interossei manus (DIM) and the palmar interossei muscles is DAB PAD. The Dorsals ABduct, and the Palmars Adduct. 2. The reverse actions of the first dorsal interosseus manus muscle of flexing and adducting the thumb are important toward assisting opposition of the thumb to grip an object between the thumb and another finger. 3. Given that the first dorsal interosseus manus has an anterior to posterior orientation, especially if the thumb is in a position of abduction (away from the palm of the hand in the sagittal plane), then with the thumb fixed the first dorsal interosseus manus can medially rotate the metacarpal of the index finger at the MCP joint. 4. In addition to directly contributing to extension of the fingers at the interphalangeal (IP) joints, the interossei of the hand and the lumbricals manus help create these actions in another manner. Whenever the extensor digitorum contracts, these intrinsic muscles of the hand create a flexion

437

force at the MCP joint to keep the extensor digitorum from excessively extending the MCP joint and thereby losing its ability to create tension and extend the IP joints of the fingers. 5. Regarding reverse actions, the DIM can also adduct metacarpals of fingers four and five at the CMC joints. Similar to how the first DIM can move the metacarpal of the thumb, the fourth DIM can move the metacarpal of the little finger into adduction by pulling it toward the midline of the hand (if the distal ring finger attachment is fixed). The third DIM can move the metacarpal of the ring finger into adduction (if the distal middle finger attachment is fixed). Theoretically, the second DIM can adduct the metacarpal of the index finger in a similar manner; however, the CMC joint of the index finger is fairly locked and does not freely allow this motion. 6. There are four dorsal interossei pedis of the foot that have essentially identical actions (abduction of the toes at the metatarsophalangeal [MTP] joint, flexion of the toes at the MTP joint, and extension of the toes at the proximal and distal IP joints) to the DIM of the hand.

I N N E RVAT I O N The Ulnar Nerve C8, T1; deep branch of the ulnar nerve

A R T E R I A L S U P P LY Branches of the Radial and Ulnar Arteries (terminal branches of the Brachial Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating fingers against the dorsal radial side of the second metacarpal. 2. Have the client abduct the index finger against resistance and feel for the contraction of the first dorsal interosseus manus. 3. To palpate the other three dorsal interossei manus, palpate between the metacarpals from the dorsal side while resisting the client from abducting the finger to which the dorsal interosseus manus is attached.

RELATIONSHIP TO OTHER STRUCTURES The dorsal interossei manus are located between the metacarpals on the dorsal (posterior) side of the hand. Each dorsal interosseus manus muscle attaches on the side of the proximal phalanx that faces away from the center of the middle finger. (The middle finger has two dorsal interossei manus muscles, one on each side.) From the anterior perspective, the dorsal interossei manus are deep to the palmar interossei. The first dorsal interosseus manus muscle is mostly deep to the adductor pollicis. From the posterior perspective, the dorsal interossei manus are superficial and located between the extensor digitorum tendons and between the metacarpal bones. The first dorsal interosseus manus muscle is superficial in the thumb web. The dorsal interossei manus are involved with the superficial back arm line myofascial meridian.

MISCELLANEOUS 1. There are four dorsal interossei manus muscles named from radial/lateral to ulnar/medial: one, two, three, and four. 2. There are four dorsal interossei manus muscles: one to abduct the index finger, one to abduct the ring finger, and two to abduct the middle finger (the thumb and little finger have their own abductor muscles). The dorsal interosseus manus muscle that attaches onto the radial side of the middle finger “radially abducts” the middle finger at the metacarpophalangeal joint; the dorsal interosseus manus muscle that attaches onto the ulnar side of the middle finger “ulnar abducts” the middle finger at the metacarpophalangeal joint. 3. The first dorsal interosseus manus muscle (the largest) is sometimes known as the abductor indicis. 4. The dorsal interossei manus are bipennate in shape. 5. Given that the abductor digiti minimi manus and the abductor pollicis brevis are intrinsic hand

438

muscles that abduct the little finger and the thumb, they can be considered to be analogous to the dorsal interossei manus, which abduct the other three fingers (index, middle, and ring). 6. The majority of tissue of the thumb web of the hand is made up of the first dorsal interosseus manus muscle and the adductor pollicis.

439

Palmaris Brevis The name, palmaris brevis, tells us that this muscle attaches into the palm of the hand and is short (shorter than the palmaris longus). Derivation palmaris: L. refers to the palm brevis: L. shorter Pronunciation pall-MA-ris BRE-vis

ATTACHMENTS The Flexor Retinaculum and the Palmar Aponeurosis to the Dermis of the Ulnar (Medial) Border of the Hand

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Wrinkles the skin of the palm

Reverse Mover Actions 1. Wrinkles the skin of the palm

Standard Mover Action Note • The palmaris brevis attaches from lateral to medial in the hand (with its fibers running horizontally). When the palmaris brevis contracts, it pulls its medial attachment, the dermis of the ulnar (medial) side of the hand, laterally toward the center of the palm of the hand; this causes the skin of the ulnar side of the hand to wrinkle. This wrinkling of the skin is thought to accentuate or increase the size of the hypothenar eminence. By so doing, it is believed to slightly contribute to the strength and security of the palmar grip. (action 1)

Reverse Mover Action Note • The reverse action of the palmaris brevis would be if the more central fascia of the hand is moved toward the skin and fascia of the ulnar border of the hand. This still results in wrinkling of the skin of the palm of the hand; in other words, the same action as the standard mover action. (reverse action 1)

Motion 1. The palmaris brevis has one line of pull and therefore creates one motion, which is to wrinkle the skin of the palm toward the center of the muscle.

Eccentric Antagonist Function 1. Restrains/slows stretching of the skin of the palm

440

FIGURE 9-18

Anterior view of the right palmaris brevis.

Eccentric Antagonist Function Note • Restraining/slowing stretching of the skin of the palm restrains the skin from being stretched or lengthened out. This is not a very relevant or important function.

Isometric Stabilization Function 1. Little or no joint stabilization function. Perhaps the palmaris brevis adds negligible or slight stabilization to the medial carpal and metacarpal bones.

Isometric Stabilization Function Note • The palmaris brevis is a very thin superficial fascial muscle and does not attach into any bones. Therefore it does not have any significant joint stabilization function.

I N N E RVAT I O N The Ulnar Nerve C8, T1

441

A R T E R I A L S U P P LY The Ulnar Artery (a terminal branch of the Brachial Artery) and the superficial palmar branch of the Radial Artery

PA L PAT I O N 1. The palmaris brevis is located in the dermis proximally on the ulnar side of the palm, superficial to the hypothenar muscle group. However, it is too thin to palpate and distinguish from adjacent tissue.

RELATIONSHIP TO OTHER STRUCTURES The palmaris brevis is superficial in the medial (ulnar) side of the hand. The hypothenar muscles are all deep to the palmaris brevis. The palmaris brevis is located within the deep back arm line myofascial meridian.

MISCELLANEOUS 1. The palmaris brevis is a very thin, quadrilateral-shaped muscle. 2. The palmaris brevis overlies the hypothenar eminence. Like all the muscles of the hypothenar eminence, it is innervated by the ulnar nerve. 3. Some sources consider the palmaris brevis to be part of the hypothenar group of muscles.

442

REVIEW QUESTIONS 1. From a structural viewpoint, the intrinsic muscles of the hand that move the fingers can be divided into how many groups? Name them. ____________________________ ____________________________ ____________________________ 2. What is true of every muscle that attaches into the dorsal digital expansion of the hand? ____________________________ ____________________________ 3. Running between the two heads of the flexor pollicis brevis are the_______ ____________________________ 4. The two sesamoid bones of the thumb are located in what muscles? ____________________________ ____________________________ 5. Describe the motion of opposition of the thumb. ____________________________ ____________________________ ____________________________ 6. The flexor carpi ulnaris contracts to stabilize the proximal attachment of what intrinsic hand muscle? ____________________________ 7. What is the mnemonic recommended for distinguishing the frontal plane motions of the interossei muscles of the hand? ____________________________ ____________________________ 8. If the thumb is in a position of abduction, what motion is created by the adductor pollicis? ____________________________ ____________________________ 9. Describe the location of the distal attachment onto the fingers of the lumbricals manus, the palmar interossei, and the dorsal interossei manus muscles. ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ 10. Squeezing a pencil between the index and middle fingers is a way to palpate what two muscles? ____________________________ ____________________________ For answers to these questions, visit http://evolve.elsevier.com/Muscolino/muscular

443

THINK IT THROUGH There are three palmar interossei muscles, but four dorsal interossei manus muscles. Why is this the case? ____________________________ ____________________________ ____________________________ ____________________________ ____________________________

444

PA R T 3

The Skeletal Muscles of the Axial Body OUTLINE Chapter 10: Muscles of the Spinal Joints Chapter 11: Muscles of the Rib Cage Joints Chapter 12: Muscles of the Temporomandibular Joints Chapter 13: Muscles of Facial Expression

445

CHAPTER 10

446

Muscles of the Spinal Joints CHAPTER OUTLINE Full spine: Erector spinae group Iliocostalis Longissimus Spinalis Transversospinalis group Semispinalis Multifidus Rotatores Interspinales Intertransversarii Neck and head: Sternocleidomastoid Scalene group Anterior scalene Middle scalene Posterior scalene Prevertebral group Longus colli Longus capitis Rectus capitis anterior Rectus capitis lateralis Splenius capitis Splenius cervicis Suboccipital group Rectus capitis posterior major Rectus capitis posterior minor Obliquus capitis inferior Obliquus capitis superior Low back: Quadratus lumborum Anterior abdominal wall muscles Rectus abdominis External abdominal oblique Internal abdominal oblique Transversus abdominis Psoas minor

447

OBJECTIVES After completing this chapter, the student should be able to perform the following for each of the muscles covered in the chapter: 1. Explain the general structure. 2. Explain the general function 3. State the attachments. 4. State the standard mover actions. 5. State the reverse mover actions. 6. Discuss the line(s) of pull the muscle has and the motion(s) created. 7. State the eccentric antagonist functions. 8. State the isometric stabilization functions. 9. State the nervous innervation.

10. State the arterial supply. 11. Describe the starting position for palpation. 12. Describe the steps for palpation. 13. Discuss the muscle’s relationship to other body structures. 14. Discuss additional information that may help with palpation, assessment, and clinical decision-making. CHAPTER OVERVIEW The muscles addressed in this chapter are the muscles whose principal function is usually considered to be movement of the trunk, neck, and/or head at the spinal joints. Other muscles in the body can also move the spinal joints, but they are placed in different chapters because their primary function is usually considered to be at another joint. These muscles are located in Chapters 4, 5, 11, 12, 13, and 14. Overview of STRUCTURE Structurally, muscles of the spinal joints may be categorized based on three factors: the region of the spine, their location, and their depth. Regionally, they may be divided into three groups: those that run the full length of the spine, those that are primarily located only in the neck, and those that are primarily located only in the low back. Regarding location, they can be described as being anterior or posterior. Regarding their depth, they can be divided based on whether they are superficial or deep. Beyond these categories, certain spinal muscle groups exist. There are two muscle groups that run the full length of the spine, from the pelvis to the head. These are the erector spinae and transversospinalis groups; collectively, they are often referred to as the paraspinal muscles. In the neck, there are the scalene, prevertebral, and suboccipital groups (the hyoid group is addressed in Chapter 12. The scalene and prevertebral groups are located anteriorly and the suboccipital group is located posteriorly. In the abdominal region, there is the group of anterior abdominal wall muscles. Generally, the larger, more superficial muscles of the spine are important for creating motion, and the deeper, smaller ones function to stabilize the spine. Overview of FUNCTION The following general rules regarding actions can be stated for the functional groups of muscles of the spinal joints: If a muscle crosses the spinal joints anteriorly with a vertical direction to its fibers, it can flex the trunk, neck, and/or head at the spinal joints by moving the superior attachment down toward the inferior attachment in front. If a muscle crosses the spinal joints posteriorly with a vertical direction to its fibers, it can extend the trunk, neck, and/or head at the spinal joints by moving the superior attachment down toward the inferior attachment in back.

448

If a muscle crosses the spinal joints laterally, it can laterally flex to that side (ipsilaterally laterally flex) the trunk, neck, and/or head at the spinal joints by moving the superior attachment down toward the inferior attachment on that side of the body. Right and left rotators of the spine have a horizontal component to their fiber direction and wrap around the body part that they move. Describing a muscle from inferior to superior, ipsilateral (same-side) rotators located posteriorly on the body run from medial to lateral and those located anteriorly on the body run from lateral to medial. Describing a muscle from inferior to superior, contralateral (opposite-side) rotators located posteriorly on the body run from lateral to medial and those located anteriorly on the body run from medial to lateral. Reverse actions of these muscles involve the lower spine being moved relative to the upper spine at the spinal joints. These reverse actions usually occur when the client is lying down so the lower attachment is free to move. If the muscle attaches onto the pelvis, the reverse action involves movement of the pelvis at the lumbosacral spinal joint as well. The reverse action of flexion of the upper spine relative to the lower spine is flexion of the lower spine relative to the upper spine, and posterior tilt of the pelvis if the muscle attaches to it. The reverse action of extension of the upper spine relative to the lower spine is extension of the lower spine relative to the upper spine, and anterior tilt of the pelvis if the muscle attaches to it. The reverse action of lateral flexion of the upper spine relative to the lower spine is lateral flexion of the lower spine relative to the upper spine, and elevation of the same side of the pelvis (and therefore depression of the opposite side of the pelvis) if the muscle attaches to it. The reverse action of ipsilateral rotation of the upper spine relative to the lower spine is contralateral rotation of the lower spine relative to the upper spine, and contralateral rotation of the pelvis if the muscle attaches to it. The reverse action of contralateral rotation of the upper spine relative to the lower spine is ipsilateral rotation of the lower spine relative to the upper spine, and ipsilateral rotation of the pelvis if the muscle attaches to it.

http://evolve.elsevier.com/Muscolino/muscular

449

Posterior Views of the Muscles of the Trunk— Superficial and Intermediate Views

FIGURE 10-1

Posterior views of the muscles of the trunk. A, Superficial view on the left and an intermediate view on the right.

450

Posterior Views of the Muscles of the Trunk—Deep Views

FIGURE 10-1

B, Two deep views, the right side deeper than the left. The external abdominal oblique has been ghosted in.

451

Anterior Views of the Muscles of the Trunk— Superficial and Intermediate Views

FIGURE 10-2 Anterior views of the muscles of the trunk. A, Superficial view on the right and an intermediate view on the left. The muscles of the neck and thigh have been ghosted in.

452

Anterior Views of the Muscles of the Trunk—Deep Views

FIGURE 10-2

B, Deep views with the posterior abdominal wall seen on the left. The muscles of the neck, arm, and thigh have been ghosted in.

453

Right Lateral View of the Muscles of the Trunk

FIGURE 10-3

Right lateral view of the muscles of the trunk. The latissimus dorsi and deltoid have been ghosted in.

454

Transverse Plane Cross Sections of the Trunk

FIGURE 10-4

Transverse plane cross sections of the trunk. A, Thoracic cross section. B, Lumbar cross section.

455

FIGURE 10-4 C, Cross section of anterior abdominal wall above the arcuate line. The aponeuroses of the three anterolateral abdominal wall muscles pass anterior and posterior to the rectus abdominis, ensheathing it. D, Cross section of anterior abdominal wall below the arcuate line. The aponeuroses of all three anterolateral abdominal wall muscles pass anterior to the rectus abdominis. EAO, External abdominal oblique; IAO, internal abdominal oblique; RA, rectus abdominis; TA, transversus abdominis.

456

Posterior Views of the Neck and Upper Back Region— Superficial Views

FIGURE 10-5

Posterior views of the neck and upper back region. A, Superficial views. The trapezius, sternocleidomastoid, and deltoid have been removed on the right side.

457

Posterior Views of the Neck and Upper Back Region— Intermediate Views

FIGURE 10-5 B, Intermediate views. The serratus posterior superior, splenius capitis and cervicis, levator scapulae, supraspinatus, infraspinatus, teres minor and major, and triceps brachii have been removed on the right side.

458

Posterior Views of the Neck and Upper Back Region— Deep Views

FIGURE 10-5 C, Deep views. The iliocostalis, longissimus, and spinalis of the erector spinae group and the semispinalis of the transversospinalis group have been removed on the right side.

459

Anterior Views of the Neck and Upper Chest Region— Superficial Views

FIGURE 10-6

Anterior views of the neck and upper chest region. A, Superficial views. The platysma has been removed on the left side.

460

Anterior Views of the Neck and Upper Chest Region— Intermediate and Deep Views

FIGURE 10-6 B, Intermediate view with the head extended. The sternocleidomastoid (SCM) has been cut on the right side; the SCM and omohyoid have been removed and the sternohyoid has been cut on the left side. C, Deep view. The anterior scalene and longus capitis, as well as the brachial plexus of nerves and subclavian artery and vein, have been cut and/or removed on the left side. The clavicles and blood vessels have been ghosted in.

461

Right Lateral View of the Muscles of the Neck Region

FIGURE 10-7

Right lateral view of the muscles of the neck region.

462

Cross-Sectional View of the Neck

FIGURE 10-8

Cross section of the neck at the C5 vertebral level.

463

FULL SPINE  

464

Erector Spinae Group The name, erector spinae, tells us that this muscle makes the spine erect. (Given that the spine usually bends forward into flexion, to make it erect would be to perform extension of the spine.) Derivation erector: L. to erect spinae: L. thorn (refers to the spine) Pronunciation ee-REK-tor SPEE-nee

ATTACHMENTS Pelvis to the Spine, Rib Cage, and Head

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extends the trunk, neck, and head at the spinal joints 2. Laterally flexes the trunk, neck, and head at the spinal joints 3. Ipsilaterally rotates the trunk, neck, and head at the spinal joints

Reverse Mover Actions 1. Anteriorly tilts the pelvis at the LS joint and extends the lower spine relative to the upper spine 2. Elevates the same-side pelvis at the LS joint and laterally flexes the lower spine relative to the upper spine 3. Contralaterally rotates the pelvis at the LS joint and contralaterally rotates the lower spine relative to the upper spine

LS joint = lumbosacral joint

Standard Mover Action Notes • The erector spinae group crosses the spinal joints posteriorly from the pelvis all the way to the head (with its fibers running vertically in the sagittal plane). Therefore the erector spinae group extends the trunk and the neck at the spinal joints and extends the head at the atlanto-occipital joint (AOJ). (action 1) • The erector spinae group crosses the spinal joints laterally from the pelvis all the way to the head (with its fibers running vertically in the frontal plane). Therefore the erector spinae group laterally flexes the trunk and the neck at the spinal joints and laterally flexes the head at the AOJ. (action 2) • The arrangement of the erector spinae group is generally such that its inferior attachment is medial and its superior attachment is more lateral (with its fibers running somewhat horizontally in the transverse plane). When the inferior attachment is fixed and the erector spinae group contracts, it pulls this superolateral attachment posteromedially toward the midline, causing the anterior surface of the trunk and/or the neck and/or the head to face the same side of the body on which the erector spinae group is attached. Therefore the erector spinae group ipsilaterally rotates the trunk and the neck at the spinal joints and ipsilaterally rotates the head at the AOJ. (action 3)

465

FIGURE 10-9

Posterior view of the right erector spinae group.

Reverse Mover Action Notes • When we think of motions of the spine, we usually think of the upper spine moving relative to the fixed lower spine. However, the reverse action of moving the lower spine relative to the upper spine is also possible; these reverse actions usually occur when the client is lying down so that the lower attachment is mobile. Furthermore, if the pelvis is moved, because the LS joint does not allow a large degree of motion, the lumbar spine will move with the pelvis, causing the lumbar spine to move under (relative to) the thoracic spine. (reverse actions 1, 2, 3) • With the superior attachments fixed, the erector spinae group, by pulling superiorly on the posterior pelvis, anteriorly tilts the pelvis at the LS joint. (reverse action 1) • When the erector spinae contracts and the superior attachments are fixed, it pulls superiorly on the lateral pelvis (because the fibers are running vertically), elevating the pelvis on that side at the LS joint. Elevation of one side of the pelvis causes the other side to depress. Therefore the erector spinae group ipsilaterally elevates and contralaterally depresses the pelvis. (reverse action 2) • When the superior attachments of the erector spinae group are fixed and the erector spinae group contracts, it pulls on the inferior pelvic attachment. (Because the fibers of the erector spinae group have a slight horizontal orientation in the transverse plane, the pelvis will rotate in the transverse plane.) The posterior pelvis is pulled posterolaterally toward the side of the body on which the

466

erector spinae group is attached, causing the anterior pelvis to face the opposite side of the body from the side of the body on which the erector spinae group is attached. Therefore the erector spinae group contralaterally rotates the pelvis at the LS joint. (reverse action 3) • The reverse action of ipsilaterally rotating the upper spine (relative to the fixed lower spine and pelvis) is to contralaterally rotate the pelvis and lower spine (relative to the fixed upper spine). In other words, if the right-sided erector spinae group does right rotation of the upper spine, then its reverse action would be to do left rotation of the pelvis and lower spine. (reverse action 3)

Motion 1. The erector spinae group effectively has one line of pull in an oblique plane and therefore creates one motion, which is a combination of extension, lateral flexion, and ipsilateral rotation of the spine.

Eccentric Antagonist Functions 1. Restrains/slows flexion, opposite-side lateral flexion, and contralateral rotation of the trunk, neck, and head 2. Restrains/slows posterior tilt and ipsilateral depression of the pelvis 3. Restrains/slows ipsilateral rotation of the pelvis and lower spine

Eccentric Antagonist Function Note • The eccentric function of restraining/slowing flexion of the trunk is extremely important. The erector spinae eccentrically contracts to control our descent toward the floor every time we bend over into flexion.

Isometric Stabilization Functions 1. Stabilizes the spinal joints 2. Stabilizes the ribs at the sternocostal and costospinal joints 3. Stabilizes the sacroiliac joint

Isometric Stabilization Function Notes • The erector spinae group can help stabilize the sacroiliac joint because the iliocostalis and longissimus attach inferiorly to the iliac crest and sacrum.

Additional Notes on Actions 1. Only the longissimus muscle of the erector spinae group attaches onto the head and can move the head at the AOJ (the capitis portion of the spinalis usually fuses with and is considered to be part of the semispinalis capitis of the transversospinalis group). 2. Only the iliocostalis and longissimus muscles of the erector spinae group attach onto the pelvis and can move the pelvis at the LS joint. 3. The erector spinae attaches onto the rib cage and therefore can potentially move the ribs at the sternocostal and costospinal joints. Elevating the ribs would primarily assist inspiration; depressing the ribs would primarily assist expiration. The iliocostalis lumborum and thoracis lumborum would be the most active in regard to rib joint motion.

I N N E RVAT I O N Spinal Nerves dorsal rami of cervical, thoracic, and lumbar spinal nerves

A R T E R I A L S U P P LY The dorsal branches of the Posterior Intercostal and Lumbar Arteries (all branches of the Aorta) and the Thoracodorsal Artery (a branch of the Subclavian Artery)

PA L PAT I O N 1. With the client prone, place palpating hands lateral to the spinous processes of the vertebral column in the lumbar region and feel for the vertical orientation of the fibers of the erector spinae.

467

2. Continue palpating the erector spinae inferiorly and superiorly toward its attachments. 3. To engage the erector spinae group, ask the client to actively extend the upper part of the body (trunk, neck, and head) off the table and feel for the contraction of the erector spinae group, particularly in the lumbar and lower thoracic regions.

RELATIONSHIP TO OTHER STRUCTURES Although much of the erector spinae group lies on either side of the spinous processes of the spine in the laminar groove (over the laminae, between the spinous processes and the transverse processes), especially in the lower back, keep in mind that this group also attaches to the ribs and attaches quite far laterally. The erector spinae group is deep in the back and neck. In the lumbar region, the erector spinae group is deep to the latissimus dorsi and the serratus posterior inferior. In the thoracic region the erector spinae group is deep to the trapezius, latissimus dorsi, rhomboids major and minor, serratus posterior superior, splenius capitis, and splenius cervicis. In the cervical region, the erector spinae group is deep to the trapezius, splenius capitis, splenius cervicis, and sternocleidomastoid. In the trunk, the transversospinalis muscle group, the quadratus lumborum, and the rib cage are deep to the erector spinae group. In the neck, the suboccipital muscle group is deep to the erector spinae group. The erector spinae group is located within the superficial back line and spiral line myofascial meridians.

MISCELLANEOUS 1. The erector spinae group can be divided into three subgroups. These three subgroups are (from lateral to medial) the iliocostalis, the longissimus, and the spinalis. 2. Generally, the following statements can be made regarding the erector spinae subgroups:

• The iliocostalis attaches from the ilium to the ribs. • The longissimus is the longest of the three subgroups. • The spinalis attaches from spinous processes to spinous processes. 3. Of the three subgroups of the erector spinae, only the iliocostalis and longissimus attach onto the pelvis, and only the longissimus attaches onto the head. (Occasionally, there is spinalis capitis musculature that attaches to the head.) 4. Each of the three subgroups of the erector spinae can be further subdivided into three subgroups. They are the iliocostalis lumborum, thoracis, and cervicis; the longissimus thoracis, cervicis, and capitis; and the spinalis thoracis, cervicis, and capitis. (Note: The spinalis capitis often blends with and is therefore considered to be a part of the semispinalis capitis of the transversospinalis group.) 5. The erector spinae group is also known as the sacrospinalis group. 6. The term paraspinal musculature is also used to describe the erector spinae and the transversospinalis groups together. 7. In the lumbosacral region, the erector spinae musculature attaches into the thoracolumbar fascia of the low back. 8. There is very little erector spinae musculature in the neck; and what is present is fairly lateral in location (longissimus capitis). The large mass of paraspinal musculature present in the neck is the semispinalis of the transversospinalis group.

468

Iliocostalis (of Erector Spinae Group) The name, iliocostalis, tells us that this muscle attaches from the ilium to the ribs. Derivation ilio: L. refers to the ilium costalis: L. refers to the ribs Pronunciation IL-ee-o-kos-TA-lis

ATTACHMENTS ENTIRE ILIOCOSTALIS: Sacrum, Iliac Crest, and Ribs Three through Twelve to the ENTIRE ILIOCOSTALIS: Ribs One through Twelve and Transverse Processes of C4-C7 ILIOCOSTALIS LUMBORUM: Medial Iliac Crest and the Medial and Lateral Sacral Crests to the ILIOCOSTALIS LUMBORUM: Angles of Ribs Seven through Twelve ILIOCOSTALIS THORACIS: Angles of Ribs Seven through Twelve to the ILIOCOSTALIS THORACIS: Angles of Ribs One through Six and the Transverse Process of C7 ILIOCOSTALIS CERVICIS: Angles of Ribs Three through Six to the ILIOCOSTALIS CERVICIS: Transverse Processes of C4-C6

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions

Reverse Mover Actions

1. Extends the trunk and neck at the spinal joints 2. Laterally flexes the trunk and neck at the spinal joints 3. Ipsilaterally rotates the trunk and neck at the spinal joints

1. Anteriorly tilts the pelvis at the LS joint and extends the lower spine relative to the upper spine 2. Elevates the same-side pelvis at the LS joint and laterally flexes the lower spine relative to the upper spine 3. Contralaterally rotates the pelvis at the LS joint and contralaterally rotates the lower spine relative to the upper spine

LS joint = lumbosacral joint

Standard Mover Action Notes • The iliocostalis crosses the spinal joints posteriorly from the pelvis all the way to the lower neck (with its fibers running vertically in the sagittal plane); therefore it extends the trunk and the neck at the spinal joints. (action 1)

469

FIGURE 10-10

Posterior view of the iliocostalis bilaterally. The other two erector spinae muscles have been ghosted in on the left side.

• The iliocostalis crosses the spinal joints laterally from the pelvis all the way to the lower neck (with its fibers running vertically in the frontal plane); therefore it laterally flexes the trunk and the neck at the spinal joints. (action 2) • The arrangement of the iliocostalis is generally such that its inferior attachment is medial and its superior attachment is more lateral (with its fibers running somewhat horizontally in the transverse plane). When the inferior attachment is fixed and the iliocostalis contracts, it pulls this superolateral attachment posteromedially toward the midline, causing the anterior surface of the trunk and/or the neck to face the same side of the body on which the iliocostalis is attached. Therefore the iliocostalis ipsilaterally rotates the trunk and the neck at the spinal joints. (action 3)

Reverse Mover Action Notes • When we think of motions of the spine, we usually think of the upper spine moving relative to the fixed lower spine. However, the reverse action of moving the lower spine relative to the upper spine is also possible (this usually occurs when the client is lying down so the lower attachment is mobile). Further, if the pelvis is moved, because the LS joint does not allow a large degree of motion, the lumbar spine will move with the pelvis, causing the lumbar spine to move under (relative to) the thoracic spine. (reverse actions 1, 2, 3)

470

• When the iliocostalis contracts and the superior attachments are fixed, it pulls superiorly on the posterior pelvis, anteriorly tilting the pelvis at the LS joint (in the sagittal plane). (reverse action 1) • When the iliocostalis contracts and the superior attachments are fixed, it pulls superiorly on the lateral pelvis, elevating the pelvis on that side (in the frontal plane) at the LS joint. Elevation of one side of the pelvis causes the other side to depress. Therefore the iliocostalis ipsilaterally elevates and contralaterally depresses the pelvis. (reverse action 2) • When the iliocostalis contracts and the superior attachments are fixed, it pulls the posterior pelvis posterolaterally toward the side of the body to which the iliocostalis is attached (note that there is a horizontal component in the transverse plane to the direction of the fibers), causing the anterior pelvis to face the opposite side of the body from the side of the body to which the iliocostalis is attached. Therefore the iliocostalis contralaterally rotates the pelvis at the LS joint. (reverse action 3) • The reverse action of ipsilaterally rotating the upper spine (relative to the fixed lower spine and pelvis) is to contralaterally rotate the pelvis and lower spine (relative to the fixed upper spine). In other words, if the right-sided iliocostalis does right rotation of the upper spine, its reverse action would be to do left rotation of the pelvis and lower spine. (reverse action 3)

Motion 1. The iliocostalis effectively has one line of pull in an oblique plane and therefore creates one motion, which is a combination of extension, lateral flexion, and ipsilateral rotation of the spine.

Eccentric Antagonist Functions 1. Restrains/slows flexion, opposite-side lateral flexion, and contralateral rotation of the trunk and neck 2. Restrains/slows posterior tilt and same-side depression of the pelvis 3. Restrains/slows ipsilateral rotation of the pelvis and lower spine

Eccentric Antagonist Function Note • The eccentric function of restraining/slowing flexion of the trunk is extremely important. The iliocostalis eccentrically contracts to control our descent toward the floor every time we bend over into flexion.

Isometric Stabilization Functions 1. Stabilizes the spinal joints 2. Stabilizes the ribs at the sternocostal and costospinal joints 3. Stabilizes the sacroiliac joint

Isometric Stabilization Function Note • Because the iliocostalis attaches inferiorly to the iliac crest and sacrum, it can help stabilize the sacroiliac joint.

Additional Notes on Actions 1. Only the iliocostalis and longissimus muscles of the erector spinae group attach onto the pelvis and can move the pelvis at the LS joint. 2. The iliocostalis attaches onto the rib cage and therefore can potentially move the ribs at the sternocostal and costospinal joints. Elevating the ribs would primarily assist inspiration; depressing the ribs would primarily assist expiration. Theoretically, given that the other iliocostalis attachments are both inferior and superior, the iliocostalis should be able to depress and/or elevate ribs. However, because the pelvic attachment of the iliocostalis lumborum is likely the most stable attachment, depression of the ribs is probably the strongest action of the iliocostalis upon the rib cage.

I N N E RVAT I O N Spinal Nerves dorsal rami of the lower cervical and the thoracic and upper lumbar spinal nerves

471

A R T E R I A L S U P P LY The dorsal branches of the Posterior Intercostal and Lumbar Arteries (all branches of the Aorta) and the Thoracodorsal Artery (a branch of the Subclavian Artery)

PA L PAT I O N 1. With the client prone, locate the erector spinae group in the lumbar and thoracic regions (see the Palpation section for this muscle group on page 300). 2. Once located, the iliocostalis will be the most lateral fibers of the erector spinae group. 3. Palpate the iliocostalis from the pelvis to the rib attachments.

RELATIONSHIP TO OTHER STRUCTURES The iliocostalis, as part of the erector spinae group, is fairly deep in the posterior trunk. The iliocostalis is deep to the latissimus dorsi, serratus posterior inferior, trapezius, rhomboids major and minor, serratus posterior superior, splenius capitis, and splenius cervicis (as well as the longissimus and semispinalis capitis in the neck). Deep to the iliocostalis are the multifidus, the quadratus lumborum, the rib cage, and the external and internal intercostal muscles. The iliocostalis is the most lateral of the erector spinae muscles. It often runs far enough laterally to be deep to the scapula. The iliocostalis is located within the superficial back line and spiral line myofascial meridians.

MISCELLANEOUS 1. The iliocostalis is also known as the iliocostocervicalis. 2. The iliocostalis can be subdivided into the iliocostalis lumborum, the iliocostalis thoracis, and the iliocostalis cervicis. 3. Of the three subgroups of the erector spinae group, the iliocostalis has the most lateral attachment (onto the ribs). Keep this in mind when doing manual therapy on the erector spinae group. The iliocostalis often attaches lateral enough to be deep to the scapula!

472

Longissimus (of Erector Spinae Group) The name, longissimus, tells us that this muscle is long. It is the longest of the erector spinae subgroups. Derivation longissimus: L. very long Pronunciation lon-JIS-i-mus

ATTACHMENTS ENTIRE LONGISSIMUS: Sacrum, Iliac Crest, Transverse Processes and Spinous Processes of L1-L5 and T1-T5, and the Articular Processes of C5-C7 to the ENTIRE LONGISSIMUS: Ribs Four through Twelve, Transverse Processes of T1-T12 and C2C6, and the Mastoid Process of the Temporal Bone LONGISSIMUS THORACIS: Medial Iliac Crest, Posterior Sacrum, and the Transverse Processes and Spinous Processes of L1-L5 to the LONGISSIMUS THORACIS: Transverse Processes of all the Thoracic Vertebrae and the Lower Nine Ribs (between the tubercles and the angles) LONGISSIMUS CERVICIS: Transverse Processes of the Upper Five Thoracic Vertebrae to the LONGISSIMUS CERVICIS: Transverse Processes of C2-C6 (posterior tubercles) LONGISSIMUS CAPITIS: Transverse Processes of the Upper Five Thoracic Vertebrae and the Articular Processes of the Lower Three Cervical Vertebrae to the LONGISSIMUS CAPITIS: Mastoid Process of the Temporal Bone

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extends the trunk, neck, and head at the spinal joints 2. Laterally flexes the trunk, neck, and head at the spinal joints 3. Ipsilaterally rotates the trunk, neck, and head at the spinal joints

Reverse Mover Actions 1. Anteriorly tilts the pelvis at the LS joint and extends the lower spine relative to the upper spine 2. Elevates the same-side pelvis at the LS joint and laterally flexes the lower spine relative to the upper spine 3. Contralaterally rotates the pelvis at the LS joint and contralaterally rotates the lower spine relative to the upper spine

LS joint = lumbosacral joint

473

FIGURE 10-11

Posterior view of the longissimus bilaterally. The other two erector spinae muscles have been ghosted in on the left side.

Standard Mover Action Notes • The longissimus crosses the spinal joints posteriorly from the pelvis all the way to the head (with its fibers running vertically in the sagittal plane). Therefore the longissimus extends the trunk and the neck at the spinal joints and extends the head at the atlanto-occipital joint (AOJ). (action 1) • The longissimus crosses the spinal joints laterally from the pelvis all the way to the head (with its fibers running vertically in the frontal plane). Therefore the longissimus laterally flexes the trunk and the neck at the spinal joints and laterally flexes the head at the AOJ. (action 2) • The arrangement of the longissimus is generally such that its inferior attachment is medial and its superior attachment is more lateral (with its fibers running somewhat horizontally in the transverse plane). When the inferior attachment is fixed and the longissimus contracts, it pulls this superolateral attachment posteromedially toward the midline, causing the anterior surface of the trunk and/or the neck and/or the head to face the same side of the body on which the longissimus is attached. Therefore the longissimus ipsilaterally rotates the trunk and the neck at the spinal joints and ipsilaterally rotates the head at the AOJ. (reverse action 3)

Reverse Mover Action Notes

474

• When we think of motions of the spine, we usually think of the upper spine moving relative to the fixed lower spine. However, the reverse action of moving the lower spine relative to the upper spine is also possible (this usually occurs when the client is lying down so the lower attachment is mobile). Further, if the pelvis is moved, because the LS joint does not allow a large degree of motion, the lumbar spine will move with the pelvis, causing the lumbar spine to move under (relative to) the thoracic spine. (reverse actions 1, 2, 3) • When the longissimus contracts and the superior attachments are fixed, it pulls superiorly on the posterior pelvis, anteriorly tilting the pelvis at the LS joint. (reverse action 1) • When the longissimus contracts and the superior attachments are fixed, it pulls superiorly on the lateral pelvis (because the fibers are running vertically), elevating the pelvis on that side at the LS joint. Elevation of one side of the pelvis causes the other side to depress. Therefore the longissimus ipsilaterally elevates and contralaterally depresses the pelvis. (reverse action 2) • When the longissimus contracts and the superior attachments are fixed, it pulls the posterior pelvis posterolaterally toward the side of the body on which the longissimus is attached (note that there is a horizontal component to the direction of fibers), causing the anterior pelvis to face the opposite side of the body from the side of the body on which the longissimus is attached. Therefore the longissimus contralaterally rotates the pelvis at the LS joint. (reverse action 3) • The reverse action of ipsilaterally rotating the upper spine (relative to the fixed lower spine and pelvis) is to contralaterally rotate the pelvis and lower spine (relative to the fixed upper spine). In other words, if the right-sided longissimus does right rotation of the upper spine, its reverse action would be to do left rotation of the pelvis and lower spine. (reverse action 3)

Motion 1. The longissimus effectively has one line of pull in an oblique plane and therefore creates one motion, which is a combination of extension, lateral flexion, and ipsilateral rotation of the spine.

Eccentric Antagonist Functions 1. Restrains/slows flexion, opposite-side lateral flexion, and contralateral rotation of the trunk, neck, and head 2. Restrains/slows posterior tilt and same-side depression of the pelvis 3. Restrains/slows ipsilateral rotation of the pelvis and lower spine

Eccentric Antagonist Function Note • The eccentric function of restraining/slowing flexion of the trunk is extremely important. The longissimus eccentrically contracts to control our descent toward the floor every time we bend over into flexion.

Isometric Stabilization Functions 1. Stabilizes the spinal joints 2. Stabilizes the ribs at the sternocostal and costospinal joints 3. Stabilizes the sacroiliac joint

Isometric Stabilization Function Note • Because longissimus attaches inferiorly to the iliac crest and sacrum, it can help stabilize the sacroiliac joint.

Additional Notes on Actions 1. Only the longissimus muscle of the erector spinae group attaches onto the head and can move the head at the AOJ (the capitis portion of the spinalis usually fuses with and is considered to be part of the semispinalis capitis of the transversospinalis group). 2. Only the iliocostalis and longissimus muscles of the erector spinae group attach onto the pelvis and can move the pelvis at the LS joint. 3. The longissimus lumborum attaches onto the rib cage and therefore can potentially move the ribs at the sternocostal and costospinal joints. Assuming that the lumbopelvic attachment is fixed, contraction of the longissimus lumborum would create depression of the rib cage (specifically ribs 1-9). Depression of the rib cage assists in expiration when breathing.

475

I N N E RVAT I O N Spinal Nerves dorsal rami of the lower cervical and the thoracic and lumbar spinal nerves

A R T E R I A L S U P P LY The dorsal branches of the Posterior Intercostal and Lumbar Arteries (all branches of the Aorta)

PA L PAT I O N 1. With the client prone, locate the erector spinae group in the lumbar and thoracic regions (see the Palpation section for this muscle group on page 300). 2. Once located, palpate the longissimus between the spinalis (medially) and the iliocostalis (laterally). The longissimus will be palpable as a mass of musculature running vertically. 3. Note that the longissimus gradually courses further lateral as it ascends the trunk.

RELATIONSHIP TO OTHER STRUCTURES The longissimus is located between the iliocostalis (which is directly lateral to it) and the spinalis (which is directly medial to it). The longissimus is deep to the latissimus dorsi, serratus posterior inferior, trapezius, rhomboids major and minor, serratus posterior superior, splenius capitis, and splenius cervicis. From the posterior perspective, the longissimus attachment onto the mastoid process of the temporal bone is deep to the mastoid process attachment of the sternocleidomastoid and the splenius capitis. Deep to the longissimus are the multifidus, rotatores, levatores costarum, intertransversarii, quadratus lumborum, the rib cage, and the external and internal intercostal muscles. The longissimus cervicis’ inferior attachment is in the thoracic region, medial to the longissimus thoracis. Most of the longissimus cervicis is deep to the longissimus capitis. The longissimus capitis lies between the longissimus cervicis (which is directly lateral to it) and the splenius capitis (which is directly medial to it). The longissimus is located within the superficial back line and spiral line myofascial meridians.

MISCELLANEOUS 1. The longissimus can be subdivided into the longissimus thoracis, the longissimus cervicis, and the longissimus capitis. 2. The longissimus is the longest and the largest of the three subgroups of the erector spinae group. 3. Of the three subgroups of the erector spinae group, the longissimus has the most superior attachment (onto the mastoid process of the temporal bone) and is the only erector spinae musculature that has an appreciable presence in the cervical region. 4. In the lumbar region, the longissimus blends with the iliocostalis. In the thoracic region, the longissimus blends with the spinalis. 5. The longissimus thoracis also attaches into the thoracolumbar fascia.

476

Spinalis (of Erector Spinae Group) The name, spinalis, tells us that this muscle attaches from spinous processes to spinous processes. Derivation spinalis: L. refers to spinous processes Pronunciation spy-NA-lis

ATTACHMENTS ENTIRE SPINALIS: Spinous Processes of T11-L2; and the Spinous Process of C7 and the Nuchal Ligament to the ENTIRE SPINALIS: Spinous Processes of T4-T8; and the Spinous Process of C2 SPINALIS THORACIS: Spinous Processes of T11-L2 to the SPINALIS THORACIS: Spinous Processes of T4-T8 SPINALIS CERVICIS: Inferior Nuchal Ligament and the Spinous Process of C7 to the SPINALIS CERVICIS: Spinous Process of C2 SPINALIS CAPITIS: Usually Considered to Be the Medial Part of the Semispinalis Capitis

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extends the trunk and neck at the spinal joints

Reverse Mover Actions 1. Extends the lower spine relative to the upper spine

2. Laterally flexes the trunk and neck at the spinal joints

2. Laterally flexes the lower spine relative to the upper spine

Standard Mover Action Notes • The spinalis crosses the spinal joints posteriorly (with its fibers running vertically in the sagittal plane). Therefore the spinalis extends the trunk and the neck at the spinal joints. (action 1) • The spinalis crosses the spinal joints laterally (with its fibers running vertically in the frontal plane). Therefore the spinalis laterally flexes the trunk and the neck at the spinal joints. (action 2) • Extension is the strongest action of the spinalis. Its lateral flexion ability is weak. (actions 1, 2)

Reverse Mover Action Notes • When we think of motions of the spine, we usually think of the upper spine moving relative to the fixed lower spine. However, the reverse action of moving the lower spine relative to the fixed upper spine is also possible. These reverse actions usually occur when the client is lying down so that the inferior attachment is mobile. (reverse actions 1, 2)

477

FIGURE 10-12

Posterior view of the spinalis bilaterally. The other two erector spinae muscles have been ghosted in on the left side.

Motion • The spinalis effectively has one line of pull in an oblique plane and therefore creates one motion, which is a combination of extension and lateral flexion of the spine.

Eccentric Antagonist Functions 1. Restrains/slows flexion and opposite-side lateral flexion of the trunk and neck

Eccentric Antagonist Function Note • The eccentric function of restraining/slowing flexion of the trunk is extremely important. The spinalis eccentrically contracts to control our descent toward the floor every time we bend over into flexion.

Isometric Stabilization Function 1. Stabilizes the spinal joints

478

Additional Notes on Actions 1. Some sources state that the spinalis can perform ipsilateral rotation of the spine, as can the other two groups of the erector spinae group. Given the direction of fibers (there is virtually no horizontal component because the attachments are from spinous processes to spinous processes), this action is either unlikely or extremely weak. 2. Some sources consider the spinalis to have a capitis portion that attaches to the head and therefore can move the head at the atlanto-occipital joint (AOJ). Other sources state that the capitis portion fuses with and is considered to be part of the semispinalis capitis (of the transversospinalis group). If the spinalis is not considered to attach to the head, the longissimus is the only erector spinae muscle that can move the head at the AOJ.

I N N E RVAT I O N Spinal Nerves dorsal rami of the lower cervical and the thoracic spinal nerves

A R T E R I A L S U P P LY The dorsal branches of the Posterior Intercostal and Lumbar Arteries (all branches of the Aorta)

PA L PAT I O N 1. The spinalis is a small and deep muscle that blends with the longissimus and semispinalis. It is best palpated along with the longissimus (see the Palpation section for this muscle on page 307). 2. If palpable, the spinalis will be the most medial fibers of the erector spinae. It can be very challenging to distinguish from the adjacent erector spinae and transversospinalis musculature.

RELATIONSHIP TO OTHER STRUCTURES The spinalis fibers are the most medial of all the fibers of the erector spinae group. The spinalis is deep to the latissimus dorsi, serratus posterior inferior, trapezius, rhomboids major and minor, serratus posterior superior, splenius capitis, and splenius cervicis. Deep to the spinalis are the multifidus, the rotatores, and the vertebrae. The spinalis is located within the superficial back line and spiral line myofascial meridians.

MISCELLANEOUS 1. The spinalis can be subdivided into the spinalis thoracis, the spinalis cervicis, and the spinalis capitis. 2. Of the three subgroups of the erector spinae group, the spinalis is the smallest and located the most medial. 3. The spinalis is significant in the thoracic region only. 4. The spinalis thoracis usually blends intimately with the longissimus. 5. The spinalis capitis is also known as the biventer cervicis, because a band of tendon cuts across it transversely, effectively dividing it into two bellies (biventer means two bellies). 6. Usually the spinalis capitis blends with the medial part of the semispinalis capitis (of the transversospinalis group) and is therefore usually considered to be a part of the semispinalis capitis. When the spinalis capitis is present as a distinct muscle, it is very small, and located medial to the semispinalis capitis. 7. The spinalis cervicis is often absent. 8. When present, the attachment levels of the spinalis cervicis are variable. Its inferior attachment often reaches to T1-T2, and its superior attachment often reaches to C3-C4.

479

Transversospinalis Group The name, transversospinalis, tells us that this muscle group attaches from transverse processes (inferiorly) to spinous processes (superiorly). Derivation transverso: L. refers to transverse processes spinalis: L. refers to spinous processes Pronunciation trans-VER-so-spy-NA-lis

ATTACHMENTS Pelvis to the Spine and the Head

Generally running from transverse process below to spinous process above

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extends the trunk, neck, and head at the spinal joints

Reverse Mover Actions

2. Laterally flexes the trunk, neck, and head at the spinal joints

1. Anteriorly tilts the pelvis at the LS joint and extends the lower spine relative to the upper spine 2. Elevates the same-side pelvis at the LS joint and laterally flexes the lower spine relative to the upper spine

3. Contralaterally rotates the trunk and neck at the spinal joints

3. Ipsilaterally rotates the pelvis at the LS joint and ipsilaterally rotates the lower spine relative to the upper spine

LS joint = lumbosacral joint

Standard Mover Action Notes • The transversospinalis group crosses the spinal joints posteriorly from the pelvis all the way to the head (with its fibers running vertically in the sagittal plane). Therefore the transversospinalis group extends the trunk and the neck at the spinal joints and extends the head at the atlantooccipital joint (AOJ). (action 1) • Of the three muscles of the transversospinalis group, the semispinalis is best suited to create extension because its fibers are the most vertical in orientation (in the sagittal plane). The semispinalis capitis of the semispinalis muscle is the largest muscle in the posterior neck and likely the most powerful extensor of the neck and head. (action 1) • The transversospinalis group crosses the spinal joints laterally from the pelvis all the way to the head (with its fibers running vertically in the frontal plane). Therefore the transversospinalis group laterally flexes the trunk and the neck at the spinal joints and laterally flexes the head at the AOJ. (action 2)

480

FIGURE 10-13

Posterior view of the transversospinalis group. The semispinalis and multifidus are seen on the right; the rotatores are seen on the left.

• The arrangement of the transversospinalis group is generally from a transverse process inferolaterally to a spinous process superomedially (with its fibers running somewhat horizontally in the transverse plane). The inferior attachment is usually more fixed (because the inferior attachment on the trunk and/or pelvis is connected to the thighs, legs, and feet, which are grounded); therefore the superior attachment usually moves. When the transversospinalis group contracts, it pulls the superior attachment on the spinous processes posterolaterally toward the more inferolateral transverse processes, causing the anterior surface of the body part that is moved to face the opposite side of the body. Therefore the transversospinalis group contralaterally rotates the trunk and the neck at the spinal joints. (The transversospinalis group also crosses the AOJ to attach onto the head. However, the direction of fibers of the transversospinalis is nearly directly vertical at this point. Therefore the transversospinalis has little or no ability to rotate the head at the AOJ.) (action 3) • Only the semispinalis muscle of the transversospinalis group attaches onto the head and can move the head at the AOJ. (actions 1, 2) • The direction of the fibers of the three subgroups of the transversospinalis varies. The semispinalis subgroup is the most vertical, the rotatores subgroup is the most horizontal, and the multifidus subgroup is between the other two in orientation. Given these directions of fibers, it

481

would make sense that the semispinalis is best suited for the extension/lateral flexion component of their spinal actions and the rotatores would be best suited for the contralateral rotation component of their spinal actions. (Hence the name rotatores; because they are horizontal in the transverse plane, they do rotation.) (actions 1, 2, 3)

Reverse Mover Action Notes • When we think of motions of the spine, we usually think of the upper spine moving relative to the fixed lower spine. However, if the upper attachment of the transversospinalis musculature is fixed, the reverse action of moving the lower spine relative to the upper spine can occur. Further, if the pelvis is moved, because the LS joint does not allow a large degree of motion, the lumbar spine will move with the pelvis, causing the lumbar spine to move under (relative to) the thoracic spine. (reverse actions 1, 2, 3) • When the transversospinalis musculature contracts and the superior attachments are fixed, it pulls superiorly on the posterior pelvis, anteriorly tilting the pelvis at the LS joint. (reverse action 1) • When the transversospinalis musculature contracts and the superior attachments are fixed, it pulls superiorly on the lateral pelvis, elevating the pelvis on that side (in the frontal plane) at the LS joint. Elevation of one side of the pelvis causes the other side to depress. Therefore the transversospinalis group ipsilaterally elevates and contralaterally depresses the pelvis. (reverse action 2) • When the transversospinalis musculature contracts and the superior attachments are fixed, it pulls on the inferior pelvic attachment. Because the fibers of the transversospinalis group have a slight horizontal orientation in the transverse plane, the pelvis will rotate. When the transversospinalis group contracts, it pulls the posterior pelvis posteromedially toward the spine, causing the anterior pelvis to face the same side of the body on which the transversospinalis group is attached. Therefore the transversospinalis group ipsilaterally rotates the pelvis at the LS joint. (reverse action 3) • The reverse action of contralaterally rotating the upper spine (relative to the fixed lower spine and pelvis) is to ipsilaterally rotate the pelvis and lower spine (relative to the fixed upper spine). In other words, if the right-sided transversospinalis group does left rotation of the upper spine, its reverse action would be to do right rotation of the pelvis and lower spine. (reverse action 3) • Only the multifidus of the transversospinalis group attaches onto the pelvis and can move the pelvis at the LS joint. (reverse actions 1, 2, 3)

Motion 1. The transversospinalis group effectively has one line of pull in an oblique plane and therefore creates one motion, which is a combination of extension, lateral flexion, and contralateral rotation of the spine.

Eccentric Antagonist Functions 1. Restrains/slows flexion and opposite-side lateral flexion of the trunk, neck, and head 2. Restrains/slows ipsilateral rotation of the trunk and neck 3. Restrains/slows posterior tilt and same-side depression of the pelvis 4. Restrains/slows contralateral rotation of the pelvis and lower spine

Isometric Stabilization Functions 1. Stabilizes the spinal joints 2. Stabilizes the sacroiliac joint

Isometric Stabilization Function Notes • The multifidus is credited, along with the transversus abdominis (and pelvic floor musculature), as being one of the most important muscles of core stabilization. • Because the multifidus attaches inferiorly to the iliac crest and sacrum, the transversospinalis group can help stabilize the sacroiliac joint. The multifidus is also the largest muscle of the low back.

482

Additional Note on Actions 1. As a general rule, transversospinalis musculature attaches posteriorly on the spine, just lateral to the midline, from transverse processes inferiorly to spinous processes superiorly. Therefore the group as a whole does extension, lateral flexion, and contralateral rotation of the spine at the spinal joints (standard open-chain kinematics). However, because of the nearly perfectly vertical line of pull of the semispinalis capitis, the transversospinalis can extend and laterally flex the head, but cannot contralaterally rotate it.

I N N E RVAT I O N Spinal Nerves dorsal rami of cervical, thoracic, and lumbar spinal nerves

A R T E R I A L S U P P LY The Occipital Artery (a branch of the External Carotid Artery) and the dorsal branches of the Posterior Intercostal and Lumbar Arteries (all branches of the Aorta) and the Deep Cervical Artery (a branch of the Thyrocervical Trunk)

PA L PAT I O N 1. With the client prone, place palpating fingers over the laminar groove of the thoracic spine. 2. Have the client slightly extend the neck and trunk and rotate to the opposite side and feel for the contraction of the transversospinalis musculature. Palpate the transversospinalis throughout the thoracic and lumbar regions. 3. To palpate the transversospinalis of the neck, have the client supine and palpate deep to the upper trapezius between the spinous processes and the facets.

RELATIONSHIP TO OTHER STRUCTURES The transversospinalis group is very deep in the back and lies in the laminar groove (over the laminae, between the spinous processes and the transverse processes) of the spine. In the trunk, the transversospinalis group is directly deep to the erector spinae group. In the neck the transversospinalis group is deep to the trapezius, the splenius capitis, and the sternocleidomastoid. In the trunk, the vertebrae are directly deep to the transversospinalis group. In the neck, the suboccipitals are directly deep to the transversospinalis group. The transversospinalis group is located within the superficial back line myofascial meridian.

MISCELLANEOUS 1. The name, transversospinalis, tells us that this muscle group attaches from a transverse process (transverso) to a spinous process (spinalis). The transverse process attachment is the inferior attachment; the spinous process attachment is the superior attachment. 2. The inferior attachment of the transversospinalis group is not always precisely onto the transverse processes. Sometimes the inferior attachment is onto the mammillary or articular processes of the vertebrae. 3. The transversospinalis muscle group can be divided into three subgroups. These three subgroups are (from superficial to deep) the semispinalis, the multifidus, and the rotatores. 4. The following statements can be made regarding the transversospinalis subgroups:

• The rotatores attach superiorly to the vertebrae one to two levels above the inferior attachment. • The multifidus attaches superiorly to vertebrae three to four levels above the inferior attachment. • The semispinalis attaches superiorly to vertebrae five or more levels above the inferior attachment. • Note: Not all textbooks follow these criteria for naming the subgroups of the transversospinalis. However, this is probably the simplest and clearest designation. 5. Of the three subgroups of the transversospinalis, only the multifidus attaches onto the pelvis, and only the semispinalis attaches onto the head. 6. The term paraspinal musculature is also used to describe the erector spinae and the transversospinalis groups together. 7. The semispinalis is best developed and quite massive in the cervical region.

483

8. The multifidus is best developed and quite massive in the lumbar region.

484

Semispinalis (of Transversospinalis Group) The name, semispinalis, tells us that this muscle is associated with spinous processes. Derivation semi: L. half spinalis: L. refers to spinous processes Pronunciation SEM-ee-spy-NA-lis

ATTACHMENTS ENTIRE SEMISPINALIS: Transverse Processes of C7-T10 and the Articular Processes of C4-C6 to the ENTIRE SEMISPINALIS: Spinous Processes of C2-T4 and the Occipital Bone (Five-Six Segmental Levels Superior to the Inferior Attachment) SEMISPINALIS THORACIS: Transverse Processes of T6-T10 to the SEMISPINALIS THORACIS: Spinous Processes of C6-T4 SEMISPINALIS CERVICIS: Transverse Processes of T1-T5 to the SEMISPINALIS CERVICIS: Spinous Processes of C2-C5 SEMISPINALIS CAPITIS: Transverse Processes of C7-T6 and the Articular Processes of C4-C6 to the SEMISPINALIS CAPITIS: Occipital Bone between the Superior and Inferior Nuchal Lines

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extends the trunk, neck, and head at the spinal joints

Reverse Mover Actions 1. Extends the lower spine relative to the upper spine

2. Laterally flexes the trunk, neck, and head at the spinal joints

2. Laterally flexes the lower spine relative to the upper spine

3. Contralaterally rotates the trunk and neck at the spinal joints

3. Ipsilaterally rotates the lower spine relative to the upper spine

Standard Mover Action Notes • The semispinalis crosses the spinal joints posteriorly from the thoracic region all the way to the head (with its fibers running vertically in the sagittal plane). Therefore the semispinalis extends the trunk and the neck at the spinal joints and extends the head at the atlanto-occipital joint (AOJ). (action 1) • Of the three muscles of the transversospinalis group, the semispinalis is best suited to create extension because its fibers are the most vertical in orientation (in the sagittal plane). The semispinalis capitis is the largest muscle in the posterior neck and likely the most powerful extensor of the neck and head. (action 1)

485

FIGURE 10-14

Posterior view of the semispinalis. The semispinalis thoracic and cervicis are seen on the right; the semispinalis capitis is seen on the left.

• The semispinalis crosses the spinal joints laterally from the thoracic region all the way to the head (with its fibers running vertically in the frontal plane). Therefore the semispinalis laterally flexes the trunk and the neck at the spinal joints and laterally flexes the head at the AOJ. (action 2) • The arrangement of the semispinalis is generally from a transverse process inferolaterally to a spinous process superomedially (with its fibers running somewhat horizontally in the transverse plane). The inferior attachment is usually more fixed (because the inferior attachment on the trunk is connected to the pelvis, thighs, legs, and feet, which are grounded); therefore the superior attachment usually moves. When the semispinalis contracts, it pulls the superior attachment on the spinous processes posterolaterally toward the more inferolateral transverse processes, causing the anterior surface of the body part that is moved to face the opposite side of the body. Therefore the semispinalis contralaterally rotates the trunk and the neck at the spinal joints. (action 3) • The semispinalis only attaches as low as T10. Therefore it only moves the thoracic spine of the trunk (not the lumbar spine). (actions 1, 2, 3) • Only the semispinalis muscle of the transversospinalis group attaches onto the head and can move the head at the AOJ. (actions 1, 2) • The semispinalis cannot contralaterally rotate the head at the AOJ because its fibers are perfectly

486

vertical when they cross the AOJ. (action 3)

Reverse Mover Action Notes • When we think of motions of the spine, we usually think of the upper spine moving relative to the fixed lower spine. However, the reverse action of moving the lower spine relative to the fixed upper spine is also possible. These reverse actions often occur when the client is lying down so that the inferior attachment is mobile. (reverse actions 1, 2, 3) • The reverse action of contralaterally rotating the upper spine (relative to the fixed lower spine) is to ipsilaterally rotate the lower spine (relative to the fixed upper spine). In other words, if the right-sided semispinalis does left rotation of the upper spine, its reverse action would be to do right rotation of the lower spine. (reverse action 3)

Motion 1. The semispinalis effectively has one line of pull in an oblique plane and therefore creates one motion, which is a combination of extension, lateral flexion, and contralateral rotation of the spine.

Eccentric Antagonist Functions 1. Restrains/slows flexion and opposite-side lateral flexion of the trunk, neck, and head 2. Restrains/slows ipsilateral rotation of the trunk and neck 3. Restrains/slows contralateral rotation of the lower spine relative to the upper spine

Isometric Stabilization Functions 1. Stabilizes the spinal joints 2. Stabilizes the head at the AOJ

Additional Note on Actions 1. The line of pull of the semispinalis capitis is nearly perfectly vertical so it cannot contribute to rotation of the head (and upper neck).

I N N E RVAT I O N Spinal Nerves dorsal rami of cervical and thoracic spinal nerves

A R T E R I A L S U P P LY The Occipital Artery (a branch of the External Carotid Artery) and the dorsal branches of the Posterior Intercostal Arteries (branches of the Aorta) and the Deep Cervical Artery (a branch of the Costocervical Trunk)

PA L PAT I O N 1. With the client supine with the hand in the small of the back (to help relax the trapezius), place palpating fingers in the posteromedial neck, immediately lateral to the spinous processes, and feel for the semispinalis capitis deep to the trapezius. 2. Continue palpating the semispinalis superiorly toward the occipital attachment between the superior and inferior nuchal lines.

RELATIONSHIP TO OTHER STRUCTURES The semispinalis thoracis is directly deep to the erector spinae group. The semispinalis cervicis is deep to the spinalis cervicis and the semispinalis capitis. In the neck, the semispinalis capitis is deep to the upper trapezius, splenius capitis, splenius cervicis, and sternocleidomastoid, and superficial to the suboccipital muscles. The occipital attachment of the semispinalis capitis is sandwiched between the trapezius and sternocleidomastoid more superficially, and the suboccipitals deeper. The semispinalis is located within the superficial back line myofascial meridian.

487

MISCELLANEOUS 1. A semispinalis muscle attaches to a transverse process inferiorly and runs superiorly to attach onto the spinous process of a vertebra, five or more levels above the inferior attachment. Most commonly, a semispinalis muscle attaches six levels superior to the inferior attachment. 2. The semispinalis can be subdivided into the semispinalis thoracis, the semispinalis cervicis, and the semispinalis capitis. 3. The semispinalis capitis is the largest of the three subdivisions of the semispinalis and is the largest muscle of the posterior neck. 4. The spinalis capitis (of the erector spinae group) usually blends with the medial part of the semispinalis capitis. Therefore the spinalis capitis is usually considered to be a part of the semispinalis capitis. (Occasionally, the spinalis capitis is a distinct muscle.) 5. When the spinalis capitis of the erector spinae group does blend with the medial portion of the semispinalis capitis, this muscle may be known as the biventer cervicis, because a band of tendon often cuts across it transversely, effectively dividing it into two bellies (biventer means two bellies), and because it is in the neck (cervicis means neck). 6. The inferior attachments of the semispinalis capitis are variable and often attach to the transverse process of T7 and/or to the spinous processes of C7-T1. 7. The inferior attachments of the semispinalis cervicis are variable and often attach to the transverse process of T6. 8. The greater occipital nerve, which innervates the posterior half of the scalp, pierces through the semispinalis capitis (and the upper trapezius). When the semispinalis capitis is tight, the greater occipital nerve can be compressed, causing a tension headache that is felt in the posterior head. (This condition is also known as greater occipital neuralgia.) 9. Manual therapists/physicians often blame the upper trapezius and/or erector spinae musculature for tightness in the client’s/patient’s posterior neck, when often it is due to tight semispinalis musculature.

488

Multifidus (of Transversospinalis Group) The name, multifidus, tells us that this muscle is made up of many separate muscles that split to go to separate attachments. Derivation multi: L. many fidus: L. to split Pronunciation mul-TIF-id-us

ATTACHMENTS Posterior Sacrum, Posterior Superior Iliac Spine (PSIS), Posterior Sacroiliac Ligament, and L5-C4 Vertebrae LUMBAR REGION: All Mamillary Processes (not transverse processes) THORACIC REGION: All Transverse Processes CERVICAL REGION: The Articular Processes of C4-C7 (not transverse processes) to the Spinous processes of Vertebrae Three-Four Segmental Levels Superior to the Inferior Attachment

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extends the trunk and neck at the spinal joints

Reverse Mover Actions

2. Laterally flexes the trunk and neck at the spinal joints

1. Anteriorly tilts the pelvis at the LS joint and extends the lower spine relative to the upper spine 2. Elevates the same-side pelvis at the LS joint and laterally flexes the lower spine relative to the upper spine

3. Contralaterally rotates the trunk and neck at the spinal joints

3. Ipsilaterally rotates the pelvis at the LS joint and ipsilaterally rotates the lower spine relative to the upper spine

LS joint = lumbosacral joint

Standard Mover Action Notes • The multifidus crosses the spinal joints posteriorly from the pelvis all the way to the cervical spine (with its fibers running vertically in the sagittal plane). Therefore the multifidus extends the trunk and the neck at the spinal joints. (action 1) • The multifidus crosses the spinal joints laterally from the pelvis all the way to the cervical spine (with its fibers running vertically in the frontal plane). Therefore the multifidus laterally flexes the trunk and the neck at the spinal joints. (action 2) • The arrangement of the multifidus is generally from a transverse process (or mamillary process or articular process) inferolaterally to a spinous process superomedially (with its fibers running somewhat horizontally in the transverse plane). The inferior attachment is usually more fixed (because the inferior attachment on the trunk and/or pelvis is connected to the thighs, legs, and feet, which are grounded); therefore the superior attachment usually moves. When the multifidus contracts, it pulls the superior attachment on the spinous processes posterolaterally toward the more inferolateral transverse processes, causing the anterior surface of the body part that is moved to face the opposite side of the body. Therefore the multifidus contralaterally rotates the trunk and the neck at the spinal joints. (action 3)

489

FIGURE 10-15

Posterior view of the right multifidus. The rotatores have been ghosted in on the left.

Reverse Mover Action Notes • When we think of motions of the spine, we usually think of the upper spine moving relative to the fixed lower spine. However, if the upper attachments of the multifidus are fixed, the reverse action of moving the lower spine relative to the upper spine can occur. Further, if the pelvis is moved, because the LS joint does not allow a large degree of motion, the lumbar spine will move with the pelvis, causing the lumbar spine to move under (relative to) the thoracic spine. (reverse actions 1, 2, 3) • When the multifidus contracts and the superior attachments are fixed, it pulls superiorly on the posterior pelvis (in the sagittal plane), anteriorly tilting the pelvis at the LS joint. (reverse action 1) • When the multifidus contracts and the superior attachments are fixed, it pulls superiorly on the pelvis (in the frontal plane), elevating the pelvis on that side at the LS joint. Elevation of one side of the pelvis causes the other side to depress. Therefore the multifidus ipsilaterally elevates and contralaterally depresses the pelvis. (reverse action 2) • When the superior attachments of the multifidus are fixed and it contracts, it pulls on the inferior pelvic attachment. (Because the fibers of the multifidus have a slight horizontal orientation in the transverse plane, the pelvis will rotate.) When the multifidus contracts, it pulls the posterior pelvis posteromedially toward the spine, causing the anterior pelvis to face the same side of the

490

body to which the multifidus group is attached. Therefore the multifidus ipsilaterally rotates the pelvis at the LS joint. (reverse action 3) • The reverse action of contralaterally rotating the upper spine (relative to the fixed lower spine and pelvis) is to ipsilaterally rotate the pelvis and lower spine (relative to the fixed upper spine). In other words, if the right-sided multifidus does left rotation of the upper spine, its reverse action would be to do right rotation of the pelvis and lower spine. (reverse action 3)

Motion 1. The multifidus effectively has one line of pull in an oblique plane and therefore creates one motion, which is a combination of extension, lateral flexion, and contralateral rotation of the spine.

Eccentric Antagonist Functions 1. Restrains/slows flexion, opposite-side lateral flexion, and ipsilateral rotation of the trunk and neck 2. Restrains/slows posterior tilt and same-side depression of the pelvis 3. Restrains/slows ipsilateral rotation of the pelvis and lower spine

Isometric Stabilization Functions 1. Stabilizes the spinal joints 2. Stabilizes the sacroiliac joint

Isometric Stabilization Function Notes • The multifidus is credited, along with the transversus abdominis (and pelvic floor musculature), as being one of the most important muscles of core stabilization. • Because the multifidus attaches inferiorly to the iliac crest and sacrum, it can help stabilize the sacroiliac joint.

Additional Note on Actions 1. Of the transversospinalis group, only the multifidus attaches onto the pelvis and can move the pelvis at the LS joint.

I N N E RVAT I O N Spinal Nerves dorsal rami of cervical, thoracic, and lumbar spinal nerves

A R T E R I A L S U P P LY The dorsal branches of the Posterior Intercostal and Lumbar Arteries (all branches of the Aorta)

PA L PAT I O N 1. With the client prone, place palpating fingers just lateral to the midline of the upper sacrum. 2. Have the client extend (and perhaps slightly contralaterally rotate) the trunk, neck, and head off the table and feel for the contraction of the multifidus. 3. Continue palpating the multifidus into the lumbar and thoracic regions.

RELATIONSHIP TO OTHER STRUCTURES In the lumbar region, the multifidus group is directly deep to the erector spinae musculature. In the thoracic and cervical region, the multifidus group is directly deep to the semispinalis. The rotatores and vertebrae are directly deep to the multifidus group. The multifidus is located within the superficial back line myofascial meridian.

MISCELLANEOUS 1. The attachments for the multifidus group are from a transverse process (or mamillary process or articular process) inferiorly to a spinous process superiorly.

491

2. By the usual definition, the multifidus group attaches to a spinous process three to four levels superior to its inferior attachment. 3. The multifidus group is bulkiest in the lumbosacral region and is the largest muscle in the low back. 4. Some sources describe the multifidus group as having layers that span from one to four vertebrae superior to the inferior attachment. More specifically, they describe three layers. The most superficial layer goes from a transverse process inferiorly, to spinous processes three to four levels superiorly. The next layer goes from the same transverse process to spinous processes two to three levels superiorly. Some sources state that the deepest layer goes from the same transverse process to the spinous process of the very next vertebra superiorly. (More conventional naming of the transversospinalis group would name some of these fibers as rotatores.) 5. Very little erector spinae musculature overlies the multifidus in the lumbar region. However, in this region, the tendinous fibers of the erector spinae are very thick and difficult to palpate through.

492

Rotatores (of Transversospinalis Group) The name, rotatores, tells us that these muscles perform rotation. Derivation rotatores: L. to turn, a muscle revolving a body part on its axis Pronunciation ro-ta-TO-reez

ATTACHMENTS Transverse Process (inferiorly) to the Lamina (superiorly)

One-Two Segmental Levels Superior to the Inferior Attachment

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Contralaterally rotate the trunk and neck at the spinal joints

Reverse Mover Actions 1. Ipsilaterally rotate the lower spine relative to the upper spine

2. Extend the trunk and neck at the spinal joints

2. Extend the lower spine relative to the upper spine

3. Laterally flex the trunk and neck at the spinal joints

3. Laterally flex the lower spine relative to the upper spine

Standard Mover Action Notes • The arrangement of the rotatores group is generally from a transverse process inferolaterally to a lamina superomedially (with its fibers running nearly horizontally in the transverse plane). The inferior attachment is usually more fixed (because the inferior attachment on the trunk is connected to the pelvis, thighs, legs, and feet, which are grounded); therefore the superior attachment usually moves. When the rotatores group contracts, it pulls the superior attachment on the lamina posterolaterally toward the more inferolateral transverse processes, causing the anterior surface of the body part that is moved to face the opposite side of the body. Therefore the rotatores group contralaterally rotates the trunk and the neck at the spinal joints. (action 1) • Of the three muscles of the transversospinalis group, the rotatores are best suited to create rotation because their fibers are the most horizontal in orientation (in the transverse plane), hence the name rotatores. (action 1) • The rotatores group crosses the spinal joints posteriorly from a transverse process inferiorly, to a lamina superiorly (with their fibers running somewhat vertically in the sagittal plane). Therefore the rotatores extend the trunk and the neck at the spinal joints. (action 2)

493

FIGURE 10-16

Posterior view of the right rotatores. The multifidus has been ghosted in on the left.

• The rotatores cross the spinal joints laterally (with their fibers running slightly vertically in the frontal plane). Therefore the multifidus laterally flexes the trunk and neck at the spinal joints. (action 3) • Because the fiber direction of the rotatores is nearly horizontal and only slightly vertically, the rotatores are very weak at extension and lateral flexion. (actions 2, 3)

Reverse Mover Action Notes • When we think of motions of the spine, we usually think of the upper spine moving relative to the fixed lower spine. However, if the upper attachments of the rotatores are fixed, the reverse action of moving the lower spine relative to the upper spine can occur. (reverse actions 1, 2, 3) • The reverse action of contralaterally rotating the upper spine (relative to the fixed lower spine) is to ipsilaterally rotate the lower spine (relative to the fixed upper spine). In other words, if the right-sided rotatores do left rotation of the upper spine, their reverse action would be to do right rotation of the lower spine. (reverse action 1)

Motion 1. The rotatores effectively have one line of pull in an oblique plane and therefore create one motion, which is a combination of contralateral rotation, extension, and lateral flexion of the spine.

494

Eccentric Antagonist Functions 1. Restrains/slows ipsilateral rotation, flexion, and opposite-side lateral flexion of the trunk and neck 2. Restrains/slows contralateral rotation of the lower spine relative to the upper spine

Isometric Stabilization Function 1. Stabilizes the spinal joints

Isometric Stabilization Function Note • Being very deep and small muscles, the rotatores are probably more important for stabilization than for movement of the spine.

I N N E RVAT I O N Spinal Nerves dorsal rami of cervical, thoracic, and lumbar spinal nerves

A R T E R I A L S U P P LY The dorsal branches of the Posterior Intercostal and Lumbar Arteries (all branches of the Aorta)

PA L PAT I O N 1. With the client prone, place your palpating fingers in the client’s laminar groove of the thoracic region. 2. Have the client slightly extend and rotate the trunk to the opposite side and feel for the contraction of the rotatores. 3. Note: The rotatores are very small and extremely deep muscles that are virtually impossible to palpate and discern from adjacent musculature.

RELATIONSHIP TO OTHER STRUCTURES The rotatores are extremely deep in the laminar groove. They are directly deep to the multifidus. Deep to the rotatores are the vertebrae. The rotatores are located within the superficial back line myofascial meridian.

MISCELLANEOUS 1. The name rotatores tells us that this musculature performs rotation (of the spine). Given that rotation is a transverse/horizontal plane motion, it makes sense that the rotatores are the most horizontal in orientation of the transversospinalis musculature. 2. By the usual definition, the rotatores group attaches to a lamina one to two levels superior to its inferior attachment. 3. The rotatores are usually divided into a brevis component that attaches to the vertebra immediately superior and a longus component that skips one vertebra to attach to the vertebra two levels above the inferior attachment. 4. The rotatores can also be subdivided into three subgroups: the rotatores lumborum, rotatores thoracis, and rotatores cervicis. 5. Only the rotatores thoracis subgroup is well developed. The rotatores lumborum and rotatores cervicis are only represented by irregular muscle bundles that are similar in arrangement to the rotatores thoracis. 6. Some sources believe that the main role of the rotatores is proprioceptive by providing precise monitoring of spinal joint positions.

495

Interspinales The name, interspinales, tells us that these muscles are located between spinous processes of the vertebrae. Derivation inter: L. between spinales: L. refers to spinous processes Pronunciation IN-ter-spy-NA-leez

ATTACHMENTS From a Spinous Process to the Spinous Process directly superior CERVICAL REGION: There are six pairs of interspinales located between T1-C2 THORACIC REGION: There are two pairs of interspinales located between T2-T1 and T12-T11 LUMBAR REGION: There are four pairs of interspinales located between L5-L1

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extend the neck and trunk at the spinal joints

Reverse Mover Actions 1. Extend the lower spine relative to the upper spine

Standard Mover Action Notes • Each interspinalis muscle attaches from a spinous process of a vertebra inferiorly to the spinous process of the vertebra directly superior. Therefore the interspinales cross the vertebral joints posteriorly (with their fibers running vertically in the sagittal plane). Assuming the inferior vertebral attachment is fixed, when an interspinalis muscle contracts, it pulls the superior vertebra posteriorly and inferiorly toward the inferior vertebra, which creates extension of the superior vertebra of the neck and/or trunk at the spinal joint between them. (action 1) • The interspinales only extend the cervical and lumbar spinal joints. (action 1)

Reverse Mover Action Notes • When we think of motions of the spine, we usually think of the upper spine moving relative to the fixed lower spine. However, if the upper attachment of the interspinales is fixed, the reverse action of moving the lower spine relative to the upper spine can occur. This usually occurs when the client is lying down so that the lower attachment is mobile. (reverse action 1)

496

FIGURE 10-17

Posterior view of the right and left interspinales.

Motion 1. The interspinales have one line of pull in the sagittal plane and therefore their motion is their cardinal plane joint action, extension of the spine.

Eccentric Antagonist Functions 1. Restrains/slows flexion of the neck and trunk at the spinal joints

Isometric Stabilization Function 1. Stabilizes the cervical and lumbar spinal joints

Isometric Stabilization Function Note • Some sources believe that the interspinales do not have sufficient strength or leverage to actually create movement of the spine, but they may be important as fixator (stabilizer) muscles of the spine.

Additional Notes on Actions

497

1. Some sources believe that the main role of the interspinales is proprioceptive by providing precise monitoring of spinal joint positions. 2. If the vertebrae are rotated away from anatomic position, the interspinales’ line of pull could rotate them back toward anatomic position. In this regard, the interspinales can act as movers to rotate the spine toward anatomic position, and act as antagonists to restrain/slow rotation of the spine away from anatomic position. For this reason, they may be known as de-rotators.

I N N E RVAT I O N Spinal Nerves dorsal rami

A R T E R I A L S U P P LY The dorsal branches of the Posterior Intercostal Arteries (branches of the Aorta)

PA L PAT I O N 1. With the client seated, place a palpating finger between two adjacent vertebral spinous processes in the lumbar region. 2. Have the client slightly flex the trunk and feel for the interspinales. 3. Then have the client extend the trunk back to its starting position and feel for the contraction of the interspinales. 4. The same approach can be tried in the cervical region. However, because of the thickness of the nuchal ligament, palpation of the cervical interspinales can be difficult.

RELATIONSHIP TO OTHER STRUCTURES The interspinales are paired muscles that are located on either side of the interspinous ligaments, between the apices of spinous processes of adjacent vertebrae. The interspinales are located deep to the supraspinous ligament (the nuchal ligament in the cervical region). The interspinales are located within the superficial back line myofascial meridian.

MISCELLANEOUS 1. The interspinales are paired muscles on either side of the interspinous ligaments. 2. The interspinales are not located throughout the entire spine. They are primarily found in the cervical region (six pairs between C2 and T1) and the lumbar region (four pairs between L1 and L5). In the thoracic region, there are usually only two pairs found at T2-T1 and T12-T11. 3. The interspinales vary in location and are occasionally also found at T3-T2, L1-T12, and S1-L5.

498

Intertransversarii The name, intertransversarii, tells us that these muscles are located between transverse processes of the vertebrae. Derivation inter: L. between transversarii: L. refers to transverse processes Pronunciation IN-ter-trans-ver-SA-ri-eye

ATTACHMENTS From a Transverse Process to the Transverse process directly superior CERVICAL REGION: There are seven pairs of intertransversarii muscles (anterior and posterior sets) located between C1 and T1 on each side of the body. THORACIC REGION: There are three intertransversarii muscles between T10 and L1 on each side of the body. LUMBAR REGION: There are four pairs of intertransversarii muscles (medial and lateral sets) located between L1 and L5 on each side of the body.

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Laterally flex the neck and trunk at the spinal joints

Reverse Mover Actions 1. Laterally flex the lower spine relative to the upper spine

Standard Mover Action Notes • Each intertransversarii muscle attaches from a transverse process of one vertebra and runs superiorly to attach onto the transverse process of the vertebra directly superior. Therefore it crosses the spinal joint laterally (with its fibers running vertically in the frontal plane). Assuming the inferior vertebral attachment is fixed, when an intertransversarii muscle contracts, it pulls the superior vertebra inferiorly and laterally toward the inferior vertebra, which creates lateral flexion of the superior vertebra of the neck and/or trunk at the spinal joint between them. (action 1) • The intertransversarii only laterally flex the cervical and lumbar spinal joints. (action 1)

Reverse Mover Action Notes • When we think of motions of the spine, we usually think of the upper spine moving relative to the fixed lower spine. However, if the upper attachment of the intertransversarii is fixed, the reverse action of moving the lower spine relative to the upper spine can occur. This usually occurs when the client is lying down so that the lower attachment is mobile. (reverse action 1)

499

FIGURE 10-18

Posterior view of the right intertransversarii. The levatores costarum have been ghosted in on the left.

Motion 1. The intertransversarii have one line of pull in the frontal plane and therefore their motion is their cardinal plane joint action, lateral flexion of the spine.

Eccentric Antagonist Functions 1. Restrain/slow opposite-side lateral flexion of the neck and trunk at the spinal joints

Isometric Stabilization Functions 1. Stabilize the cervical and lumbar spinal joints

Isometric Stabilization Function Note • The intertransversarii are considered to be primarily important not as movers of the spine, but as fixator (i.e., stabilizer) postural muscles.

Additional Notes on Actions

500

1. Some sources believe that the main role of the intertransversarii is proprioceptive by providing precise monitoring of spinal joint positions. 2. If the vertebrae are rotated away from anatomic position, the intertransversarii’s line of pull could rotate them back toward anatomic position. In this regard, the intertransversarii can act as movers to rotate the spine toward anatomic position, and act as antagonists to restrain/slow rotation of the spine away from anatomic position. For this reason, they may be known as de-rotators.

I N N E RVAT I O N Spinal Nerves dorsal and ventral rami

A R T E R I A L S U P P LY The dorsal branches of the Posterior Intercostal Arteries (branches of the Aorta)

PA L PAT I O N 1. The intertransversarii muscles are small and very deep. Palpating and distinguishing them from adjacent musculature is extremely difficult if not impossible.

RELATIONSHIP TO OTHER STRUCTURES The thoracic and lumbar intertransversarii are located between transverse processes and are very deep. The latissimus dorsi, erector spinae, and serratus posterior inferior are all superficial to the thoracic and lumbar intertransversarii. The cervical intertransversarii are located between the transverse processes and are very deep. The trapezius, splenius capitis, splenius cervicis, and semispinalis capitis are all superficial to the cervical intertransversarii. The intertransversarii are located within the superficial back line myofascial meridian.

MISCELLANEOUS 1. The anterior cervical intertransversarii attach onto the anterior tubercles of the transverse processes of the cervical spine, and the posterior cervical intertransversarii attach onto the posterior tubercles of the transverse processes of the cervical spine. The lumbar medial intertransversarii attach to accessory and mammillary processes of the lumbar vertebrae, and the lumbar lateral intertransversarii attach to transverse processes of the lumbar vertebrae. 2. The intertransversarii between C1 (atlas) and C2 (axis) are often absent. 3. Essentially, the intertransversarii do not exist in the thoracic region. The levatores costarum and the intercostals are considered to be homologous with the two sets of intertransversarii in the thoracic region. 4. Ventral and dorsal rami of spinal nerves run between and pierce through the intertransversarii, especially in the cervical region.

501

NECK AND HEAD  

502

Sternocleidomastoid (SCM) The name, sternocleidomastoid, tells us that this muscle attaches to the sternum, the clavicle, and the mastoid process of the temporal bone. Derivation sterno: Gr. refers to the sternum cleido: Gr. refers to the clavicle mastoid: Gr. refers to the mastoid process Pronunciation STER-no-KLI-do-MAS-toyd

ATTACHMENTS STERNAL HEAD: Manubrium of the Sternum the anterior superior surface Clavicular Head: Medial Clavicle the medial ⅓ to the Mastoid Process of the Temporal Bone and the lateral ½ of the superior nuchal line of the occipital bone

FUNCTIONS Concentric (Shortening) Mover Actions

Standard Mover Action Notes • The sternocleidomastoid (SCM) crosses the joints of the lower neck anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the lower neck at the cervical spinal joints. (action 1) • Because the SCM courses posteriorly as it ascends from the sternum/clavicle to the head, it crosses the joints of the upper neck posteriorly. Therefore it extends the upper neck at the cervical spinal joints and extends the head at the atlanto-occipital joint (AOJ). (action 2) • The SCM is the only muscle that can flex one region of the neck and extend another region (every other muscle either flexes or extends the neck). Exactly where the dividing line is located is determined by the degree of curvature of the client’s neck. (actions 1, 2)

503

FIGURE 10-19

Lateral view of the right sternocleidomastoid. The trapezius has been ghosted in.

• The SCM crosses the spinal joints laterally (with its fibers running vertically in the frontal plane); therefore it laterally flexes the neck at the cervical spinal joints and laterally flexes the head at the AOJ. (action 3) • The clavicular head is more active than the sternal head with lateral flexion of the neck and head. (action 3) • The SCM wraps around the neck from the sternum/clavicle anteriorly to the cranium more posteriorly (with its fibers running somewhat horizontally in the transverse plane). When the SCM contracts, it pulls on the cranium, causing the anterior surface of the neck and/or the head to face the opposite side of the body from the side to which it is attached. Therefore the SCM contralaterally rotates the neck at the cervical spinal joints and the head at the AOJ. (action 4) • The sternal head is more active than the clavicular head with contralateral rotation of the neck and head. (action 4)

Reverse Mover Action Notes • If the cranial attachment of the SCM is fixed, the sternal/clavicular attachment must move. Because the SCM has its fibers running vertically from the sternum/clavicle, the sternum and the clavicle would be elevated toward the cranial attachment. Elevating the sternum and clavicle can assist in lifting the rib cage during inspiration (breathing in). Therefore the SCM is an accessory muscle of respiration. (reverse action 1) • With the cranial attachment of the SCM fixed, the sternal/clavicular attachment will be pulled in the transverse plane such that the anterior surface of the trunk will come to face the same side of the body to which the SCM is attached. Therefore the SCM can ipsilaterally rotate the trunk at the

504

spinal joints (the reverse action of contralateral rotation of the upper spine relative to the fixed lower spine is ipsilateral rotation of the lower spine relative to the fixed upper spine). This reverse action requires the cranial attachment to be sufficiently fixed so that the weight of the trunk is moved relative to it. (reverse action 2)

Motion 1. The SCM has one line of pull in an oblique plane and therefore creates one motion, which is a combination of flexion of the lower neck, extension of the head and upper neck, and lateral flexion and contralateral rotation of the head and neck.

Eccentric Antagonist Functions 1. Restrains/slows extension of the lower neck at the spinal joints 2. Restrains/slows flexion of the upper neck and head at the spinal joints 3. Restrains/slows opposite-side lateral flexion and ipsilateral rotation of the neck and head at the spinal joints 4. Restrains/slows depression of the sternum and clavicle 5. Restrains/slows ipsilateral rotation of the trunk

Isometric Stabilization Functions 1. Stabilizes the cervical spinal joints and the sternoclavicular joint

Isometric Stabilization Function Note • The SCM stabilizes the entire neck, including the head at the AOJ. By attaching to the sternum and clavicle, it also helps to stabilize the sternoclavicular joint.

Additional Notes on Actions 1. The SCM can strongly contribute to protraction (anterior translation) of the head. Protraction of the head is effectively flexion of the lower cervical spine and extension of the head and upper cervical spine, the exact sagittal plane actions of the SCM. 2. Some sources state that the action of the SCM at the upper neck can change from extension to flexion if the position of the head changes sufficiently, thus changing the line of pull of the SCM relative to the cervical spinal joints. 3. The dividing line between where the SCM flexes the lower neck versus extends the upper neck depends upon the posture of the person’s cervical spine. The greater the lower cervical spine hypolordosis and forward head carriage, the lower will be the dividing line between flexion and extension because the line of pull of the SCM passes posteriorly to more of the cervical spinal joints. 4. The SCM may also be able to weakly upwardly rotate the clavicle at the sternoclavicular joint.

I N N E RVAT I O N Spinal Accessory Nerve (CN XI) and C2, C3

A R T E R I A L S U P P LY The Occipital and Posterior Auricular Arteries (branches of the External Carotid Artery) and the Superior Thyroid Artery (a branch of the External Carotid Artery)

PA L PAT I O N 1. Have the client supine with the neck and head rotated contralaterally. 2. Then have the client lift the head and neck up into the air toward the ceiling and the SCM will visibly contract. 3. Palpate the SCM from attachment to attachment.

RELATIONSHIP TO OTHER STRUCTURES Except for the platysma (which is superficial to all anterior neck muscles), the SCM is superficial

505

throughout its entire course. The following muscles are deep to the SCM (listed from inferior to superior): infrahyoids, scalenes, levator scapulae, digastric, and splenius capitis. The attachment of the SCM onto the mastoid process of the temporal bone and the superior nuchal line of the occipital bone is superficial to the splenius capitis and lateral to the trapezius. The SCM is located within the superficial front line and lateral line myofascial meridians.

MISCELLANEOUS 1. The SCM’s major superior attachment is the mastoid process attachment of the temporal bone. However, it also has a thin aponeurotic attachment to the occipital bone. 2. The carotid sinus of the common carotid artery lies directly deep and medial to the SCM, midway up the neck. Given the neurologic reflex that occurs to lower blood pressure when the carotid sinus is pressed, manual therapy to this region must be done judiciously, especially with weak and/or elderly clients. 3. The SCM and the scalenes are often injured as a result of car accidents. This trauma is usually called whiplash, wherein the head and neck are forcefully thrown anteriorly and posteriorly (like a whip being lashed). When the head and the neck are thrown posteriorly, the anterior cervical musculature may be torn; or the muscle spindle reflex may occur, causing the anterior cervical musculature to spasm. When the head and the neck are thrown anteriorly, the same trauma may occur to the posterior musculature. 4. The SCM is an excellent landmark for palpating other muscles of the neck. Locate the posterior (lateral) border of the SCM and the anterior border of the upper trapezius, and then palpate in the tall narrow triangular space that is located between them; this triangular area is called the posterior triangle of the neck. Locating the medial border of the SCM can be used as a landmark for palpating the longus colli and longus capitis (of the prevertebral group). 5. When the SCM is the dominant neck flexor, it contributes to forward (protracted) head posture (which is caused by flexion of the lower neck and extension of the head and upper neck). This places the center of gravity of the head anterior to the trunk, thereby requiring constant isometric contraction of the cervicocranial extensor musculature (e.g., upper trapezius, semispinalis capitis) to keep the head from falling into flexion due to the force of gravity. 6. To avoid overly contracting the SCM and the resultant forward posture that it causes, it is important to counsel clients when getting up from a supine posture to not lead with their chin, in other words to gently tuck the chin before attempting to get up.

506

Scalene Group The scalenes are a group of muscles that are found in the anterolateral neck. There are three scalene muscles: the anterior scalene, middle scalene, and posterior scalene.

ATTACHMENTS As a group, the scalenes attach from superiorly on the transverse processes of the cervical spine to inferiorly on the first and second ribs. The names of the scalenes refer to their relative location with respect to each other: the anterior scalene is the most anterior of the three; the posterior scalene is the most posterior of the three; and the middle scalene is in the middle, sandwiched between the other two.

FUNCTIONS As a group, the scalenes flex and laterally flex the neck at the spinal joints and/or elevate the first and second ribs at the sternocostal and costospinal joints. The scalenes are considered to be the prime movers of lateral flexion of the neck at the spinal joints. By elevating the first and second ribs, the scalenes can help elevate and expand the rib cage, which expands the thoracic cavity, thereby creating more space for the lungs to expand for inspiration. Therefore the scalenes are accessory muscles of respiration. There is controversy regarding the role of the scalenes with respect to rotation of the neck. Some sources state that the scalenes perform contralateral rotation; other sources state that they perform ipsilateral rotation. Other sources state that the scalenes perform rotation without specifying whether it is contralateral or ipsilateral rotation. Still others are silent on this issue. Given the direction of fibers and the consequent line of pull, it seems likely that of all the scalenes, the anterior scalene is best suited for rotation and that it would perform contralateral rotation of the neck at the cervical spinal joints.

MISCELLANEOUS 1. The scalenes are superficial in the posterior triangle of the neck (bounded by the posterior/lateral border of the SCM, the anterior border of the upper trapezius, and the clavicle). 2. Of the scalenes, the middle scalene is the longest and the largest, and the posterior scalene is the shortest and the smallest. 3. When palpating the scalenes, care must be taken because the brachial plexus of nerves and the subclavian artery exit between the anterior and middle scalenes. 4. There is a fourth scalene muscle called the scalenus minimus that is sometimes present, unilaterally or bilaterally. When present, it is usually found posterior to the anterior scalene, attaching from the transverse process (anterior tubercle) of C7 to the first rib (inner border) and the pleural membrane of the lung. 5. The scalenes are located within the deep front line myofascial meridian.

I N N E RVAT I O N The scalenes are innervated by cervical spinal nerves (ventral rami).

A R T E R I A L S U P P LY Arterial supply to the scalenes is provided by either the ascending cervical artery or the transverse cervical artery.

CLINICAL APPLICATIONS The scalenes and the sternocleidomastoid are often injured as a result of car accidents. This trauma is usually called whiplash, wherein the head and neck are forcefully thrown anteriorly and posteriorly (like a whip being lashed). When the head and the neck are thrown posteriorly, the anterior cervical musculature may be torn; or the muscle spindle reflex may occur, causing the

507

anterior cervical musculature to spasm. When the head and the neck are thrown anteriorly, the same trauma may occur to the posterior musculature. If the head and neck are thrown laterally, the same trauma may occur to the opposite side lateral flexion musculature. The brachial plexus of nerves and the subclavian artery run between the anterior and middle scalenes. If these muscles are tight, entrapment of these nerves and/or the artery can occur. When this happens, it is called anterior scalene syndrome, one of the four types of thoracic outlet syndrome. This condition can cause sensory symptoms (e.g., tingling, pain, numbness) and/or motor symptoms (e.g., weakness and/or partial paralysis) in the upper extremity. Tight scalenes can also contribute to another type of thoracic outlet syndrome called costoclavicular syndrome. Costoclavicular syndrome is an entrapment of the brachial plexus of nerves and/or the subclavian artery and vein between the clavicle and the first rib. If the scalenes are tight, they can contribute to this condition by pulling the first rib up against the clavicle, compressing these neurovascular structures.

FIGURE 10-20

Anterior view of the scalenes. All three scalenes are seen on the right; the posterior scalene and ghosted-in middle scalene are seen on the left.

508

Anterior Scalene (of Scalene Group) The name, anterior scalene, tells us that this muscle has a steplike or ladderlike shape and is located anteriorly (anterior to the middle and posterior scalenes). Derivation anterior: L. before, in front of scalene: L. uneven, ladder Pronunciation an-TEE-ri-or SKAY-leen

ATTACHMENTS Transverse Processes of the Cervical Spine the anterior tubercles of C3-C6 to the First Rib the scalene tubercle on the inner border

FUNCTIONS Concentric (Shortening) Mover Actions

Standard Mover Action Notes • The anterior scalene crosses the cervical spinal joints anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the neck at the cervical spinal joints. (action 1) • The anterior scalene crosses the cervical spinal joints laterally (with its fibers running vertically in the frontal plane); therefore it laterally flexes the neck at the cervical spinal joints. (action 2) • The attachment of the anterior scalene onto the first rib is more anterior than the transverse process attachments (therefore the fibers are running slightly horizontally in the transverse plane). When the anterior scalene contracts, it pulls the transverse processes anteromedially toward the first rib, causing the anterior surface of the vertebrae to face the opposite side of the body from the side to which the anterior scalene is attached. Therefore the anterior scalene contralaterally rotates the neck at the cervical spinal joints. (action 3) • There is controversy regarding the role of the scalene group with respect to rotation of the neck. Some sources state that the scalenes perform contralateral rotation; other sources state that they perform ipsilateral rotation. Other sources state rotation without specifying whether it is contralateral or ipsilateral rotation, and still others are silent on this issue. Given the direction of fibers and the consequent line of pull, it seems likely that of all the scalenes, the anterior scalene is best suited for rotation and that it would perform contralateral rotation of the neck at the cervical spinal joints. (action 3)

509

FIGURE 10-21

Anterior view of the anterior scalene bilaterally. The other two scalenes have been ghosted in on the left side.

Reverse Mover Action Notes • When the cervical attachment of the anterior scalene is fixed, the first rib must move. Given that the fiber direction of the anterior scalene is vertical from the first rib up to the cervical vertebrae, the anterior scalene elevates the first rib at the sternocostal and the costospinal joints. (reverse action 1) • By elevating the first rib, the anterior scalene can help elevate and expand the rib cage, which expands the thoracic cavity, thereby creating more space for the lungs to expand for inspiration. Therefore the anterior scalene is an accessory muscle of respiration. Knowing that it contracts with inspiration is important when engaging it to palpate it. (reverse action 1)

Motion 1. The anterior scalene has one line of pull in an oblique plane and therefore creates one motion, which is a combination of flexion, lateral flexion, and contralateral rotation of the neck at the spinal joints.

Eccentric Antagonist Functions 1. Restrains/slows extension, opposite-side lateral flexion, and ipsilateral rotation of the neck at the spinal joints 2. Restrains/slows depression of the first rib at the sternocostal and costospinal joints

Isometric Stabilization Functions 1. Stabilizes the cervical spinal joints 2. Stabilizes the first rib

I N N E RVAT I O N Cervical Spinal Nerves ventral rami; C4-C6

A R T E R I A L S U P P LY The Ascending Cervical Artery (a branch of the Inferior Thyroid Artery)

510

PA L PAT I O N 1. With the client seated or supine, place palpating fingers just superior to the clavicle and just lateral to the lateral border of the clavicular head of the sternocleidomastoid. 2. Have the client take in short, quick breaths through the nose and feel for the contraction of the anterior scalene. The middle scalene will also contract; it is located directly lateral to the anterior scalene. 3. Note: Because of the proximity of the brachial plexus and subclavian artery, palpation in this area must be done carefully.

RELATIONSHIP TO OTHER STRUCTURES The anterior scalene is superficial in the posterior triangle of the neck (bounded by the SCM, upper trapezius, and clavicle). The inferior portion of the anterior scalene is superficial, except where the clavicle and the omohyoid (and the platysma, which is superficial to all anterior neck muscles) cross in front of it. The superior portion of the anterior scalene is deep to the sternocleidomastoid. Directly posterolateral to the anterior scalene is the middle scalene. Deep to the anterior scalene are the brachial plexus of nerves, the subclavian artery, and the pleural membrane of the lung. If one looks at the relationship between the anterior scalene and the longus capitis, as well as the superior part of the longus colli, it can be seen that, except for the interruption of the attachment to the transverse processes of the cervical spine, there is a continuous line of pull from the first rib (the most inferior attachment of the anterior scalene) to the atlas (C1) and the head (the most superior attachments of the longus colli and longus capitis). The anterior scalene is located within the deep front line myofascial meridian.

MISCELLANEOUS 1. The anterior scalene is part of the scalene group, which comprises the anterior, middle, and posterior scalenes. 2. The brachial plexus of nerves and the subclavian artery run between the anterior and middle scalenes. If these muscles are tight, entrapment of these nerves and/or the artery can occur. When this happens, it is called anterior scalene syndrome, one of the four types of thoracic outlet syndrome. This condition can cause sensory symptoms (e.g., tingling, pain, numbness) and/or motor symptoms (e.g., weakness and/or partial paralysis) in the upper extremity. 3. The anterior scalene can also contribute to another type of thoracic outlet syndrome called costoclavicular syndrome. Costoclavicular syndrome is an entrapment of the brachial plexus of nerves and/or the subclavian artery and vein between the clavicle and the first rib (the costoclavicular space). If the anterior scalene is tight, it can contribute to this condition by pulling the first rib up against the clavicle, compressing these neurovascular structures. 4. Very close to the superior attachment of the anterior scalene is the common carotid artery. Given the neurologic reflex that occurs to lower blood pressure when the carotid sinus of the common carotid artery is pressed, massage to this region must be done judiciously, especially with weak and/or elderly clients. 5. The scalenes, and the sternocleidomastoid, are often injured as a result of car accidents. This trauma is usually called whiplash, wherein the head and neck are forcefully thrown anteriorly and posteriorly (like a whip being lashed). When the head and neck are thrown posteriorly, the anterior cervical musculature may be torn; or the muscle spindle reflex may occur, causing the anterior cervical musculature to spasm. When the head and neck are thrown anteriorly, the same trauma may occur to the posterior musculature. If the head and neck are thrown laterally, the same trauma may occur to the opposite-side lateral flexion musculature.

511

Middle Scalene (of Scalene Group) The name, middle scalene, tells us that this muscle has a steplike or ladderlike shape and is located in the middle of the scalene group (between the anterior and posterior scalenes). Derivation middle: L. middle (between) scalene: L. uneven, ladder Pronunciation MI-dil SKAY-leen

ATTACHMENTS Transverse Processes of the Cervical Spine the posterior tubercles of C2-C7 to the First Rib the superior surface

FUNCTIONS Concentric (Shortening) Mover Actions

Standard Mover Action Notes • The middle scalene crosses the cervical spinal joints anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the neck at the cervical spinal joints. (action 1) • The middle scalene crosses the cervical spinal joints laterally (with its fibers running vertically in the frontal plane); therefore it laterally flexes the neck at the cervical spinal joints. (action 2)

Reverse Mover Action Notes • When the cervical attachment of the middle scalene is fixed, the first rib must move. Given that the fiber direction of the middle scalene is vertical from the first rib up to the cervical vertebrae, the middle scalene elevates the first rib at the sternocostal and costospinal joints. (reverse action 1) • By elevating the first rib, the middle scalene can help elevate and expand the rib cage, which expands the thoracic cavity, thereby creating more space for the lungs to expand for inspiration. Therefore the middle scalene is an accessory muscle of respiration. Knowing that it contracts with inspiration is important when engaging it to palpate it. (reverse action 1)

512

FIGURE 10-22

Anterior view of the middle scalene bilaterally. The other two scalenes have been ghosted in on the left side.

Motion 1. The middle scalene has one line of pull in an oblique plane and therefore creates one motion, which is a combination of flexion and lateral flexion of the neck at the spinal joints.

Eccentric Antagonist Functions 1. Restrains/slows extension and opposite-side lateral flexion of the neck at the spinal joints 2. Restrains/slows depression of the first rib at the sternocostal and costospinal joints

Isometric Stabilization Functions 1. Stabilizes the cervical spinal joints 2. Stabilizes the first rib

Additional Note on Actions 1. The attachment of the middle scalene onto the first rib is more anterior than the transverse process attachments; therefore, like the anterior scalene, the middle scalene likely has the ability to contralaterally rotate the neck at the spinal joints.

I N N E RVAT I O N Cervical Spinal Nerves ventral rami; C3-C8

A R T E R I A L S U P P LY The Transverse Cervical Artery (a branch of the Thyrocervical Trunk)

PA L PAT I O N 1. With the client seated or supine, place palpating fingers just superior to the clavicle, in the middle of the posterior triangle of the neck (between the sternocleidomastoid and upper trapezius). 2. Have the client take in short, quick breaths through the nose and feel for the contraction of the middle scalene. The anterior and posterior scalenes will also contract. The anterior scalene is located medial to the middle scalene and the posterior scalene is located lateral to the middle

513

scalene. 3. Note: Because of the proximity of the brachial plexus and subclavian artery, palpation in this area must be done carefully.

RELATIONSHIP TO OTHER STRUCTURES The middle scalene is superficial in the posterior triangle of the neck (bounded by the SCM, upper trapezius, and clavicle). Like the anterior scalene, the inferior portion of the middle scalene is superficial, except where the clavicle and the omohyoid (and the platysma, which is superficial to all anterior neck muscles) cross in front of it. The superior portion of the middle scalene, like the anterior scalene, is deep to the sternocleidomastoid. Directly anteromedial to the middle scalene is the anterior scalene. Posterolateral to the middle scalene are the posterior scalene and the levator scapulae. The middle scalene is located within the deep front line myofascial meridian.

MISCELLANEOUS 1. The middle scalene is part of the scalene group, which comprises the anterior, middle, and posterior scalenes. 2. The middle scalene is the largest and the longest of the scalenes. 3. The nerve to the rhomboids (the dorsal scapula nerve) and some of the spinal nerve segments to the nerve to the serratus anterior (long thoracic nerve) pierce the middle scalene. 4. The brachial plexus of nerves and the subclavian artery run between the anterior and middle scalenes. If these muscles are tight, entrapment of these nerves and/or the artery can occur. When this happens, it is called anterior scalene syndrome, one of the four types of thoracic outlet syndrome. This condition can cause sensory symptoms (e.g., tingling, pain, numbness) and/or motor symptoms (e.g., weakness and/or partial paralysis) in the upper extremity. 5. The middle scalene can also contribute to another type of thoracic outlet syndrome called costoclavicular syndrome. Costoclavicular syndrome is an entrapment of the brachial plexus of nerves and/or the subclavian artery and vein between the clavicle and the first rib (the costoclavicular space). If the middle scalene is tight, it can contribute to this condition by pulling the first rib up against the clavicle, compressing these neurovascular structures. 6. The scalenes, and the sternocleidomastoid, are often injured as a result of car accidents. This trauma is usually called whiplash, wherein the head and neck are forcefully thrown anteriorly and posteriorly (like a whip being lashed). When the head and neck are thrown posteriorly, the anterior cervical musculature may be torn; or the muscle spindle reflex may occur, causing the anterior cervical musculature to spasm. When the head and neck are thrown anteriorly, the same trauma may occur to the posterior musculature. If the head and neck are thrown laterally, the same trauma may occur to the opposite-side lateral flexion musculature.

514

Posterior Scalene (of Scalene Group) The name, posterior scalene, tells us that this muscle has a steplike or ladderlike shape and is located posteriorly (posterior to the middle and anterior scalenes). Derivation posterior: L. behind, toward the back scalene: L. uneven, ladder Pronunciation pos-TEE-ri-or SKAY-leen

ATTACHMENTS Transverse Processes of the Cervical Spine the posterior tubercles of C5-C7 to the Second Rib the external surface

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Laterally flexes the neck at the spinal joints

Reverse Mover Actions 1. Elevates the second rib at the sternocostal and costospinal joints

Standard Mover Action Notes • The posterior scalene crosses the cervical spinal joints laterally (with its fibers running vertically in the frontal plane); therefore it laterally flexes the neck at the cervical spinal joints. Given that the posterior scalene only crosses the lower three cervical vertebrae, its action of lateral flexion would occur only at the lower neck. (action 1)

Reverse Mover Action Notes • When the cervical attachment of the posterior scalene is fixed, the second rib must move. Given that the fiber direction of the posterior scalene is vertical from the second rib up to the cervical vertebrae, the posterior scalene elevates the second rib at the sternocostal and costospinal joints. (reverse action 1) • By elevating the second rib, the posterior scalene can help elevate and expand the rib cage, which expands the thoracic cavity, thereby creating more space for the lungs to expand for inspiration. Therefore the posterior scalene is an accessory muscle of respiration. Knowing that it contracts with inspiration is important when engaging it to palpate it. (reverse action 1)

Motion 1. The posterior scalene has one line of pull in the frontal plane and therefore its motion is its cardinal plane joint action, lateral flexion of the neck.

515

FIGURE 10-23

Anterior view of the posterior scalene bilaterally. The other two scalenes have been ghosted in on the left side.

Eccentric Antagonist Functions 1. Restrains/slows opposite-side lateral flexion of the neck at the spinal joints and depression of the second rib at the sternocostal and costospinal joints

Isometric Stabilization Functions 1. Stabilizes the lower cervical spinal joints 2. Stabilizes the second rib

I N N E RVAT I O N Cervical Spinal Nerves ventral rami; C6-C8

A R T E R I A L S U P P LY The Transverse Cervical Artery (a branch of the Thyrocervical Trunk)

PA L PAT I O N 1. With the client seated, place palpating fingers just superior to the clavicle and just medial to the clavicular attachment of the upper trapezius. 2. Have the client take in short, quick breaths through the nose and feel for the contraction of the posterior scalene. The anterior and middle scalenes will also contract. They are located medial to the posterior scalene.

RELATIONSHIP TO OTHER STRUCTURES The posterior scalene is superficial in the posterior triangle of the neck (bounded by the SCM, upper trapezius, and clavicle). In this space, the posterior scalene is directly anterior to the upper trapezius and the levator scapulae and directly posterior to the middle scalene. The posterior scalene is the most posterior of the three scalenes. Consequently, it is situated almost directly lateral in the inferior neck and is the most superficial from the lateral perspective. To attach onto the second rib, the posterior scalene passes over (on the external side of) the first rib. The posterior scalene is located within the deep front line myofascial meridian.

516

MISCELLANEOUS 1. The posterior scalene is part of the scalene group, which comprises the anterior, middle, and posterior scalenes. 2. The posterior scalene is the smallest and the shortest of the three scalenes. 3. The scalenes, and the sternocleidomastoid, are often injured as a result of car accidents. This trauma is usually called whiplash, wherein the head and neck are forcefully thrown first in one direction and then in the opposite direction (like a whip being lashed). If the head and neck are thrown laterally, the opposite-side lateral flexion musculature may be torn; or the muscle spindle reflex may occur, causing the lateral flexion cervical musculature to spasm. 4. The posterior scalene is the most challenging scalene muscle to palpate and discern.

517

Prevertebral Group The prevertebral group comprises four muscles that are situated deep in the anterior neck. They are called the prevertebrals because they are just in front of (before, i.e., the prefix pre-) the vertebral column from the anterior perspective. The four muscles of the prevertebral group are the longus colli and longus capitis of the anterior neck and head, and the two smaller rectus capitis anterior and rectus capitis lateralis, running from the atlas to the occiput. The prevertebrals are clinically important because they function primarily to stabilize the neck and head. These muscles are commonly injured during a whiplash trauma when the neck and head are forcefully thrown back into extension. When injured or overused (for example, when doing a lot of sit-ups/crunches/curl-ups), the longus muscles often create the sensation of a sore throat, especially when swallowing. Whereas the two rectus muscles are difficult if not impossible to palpate and work, the two longus muscles can be fairly easily accessed.

FIGURE 10-24 Anterior views of the prevertebral group. The prevertebral group is composed of the longus colli, longus capitis, rectus capitis anterior, and rectus capitis lateralis. A, The longus colli, rectus capitis anterior, and rectus capitis lateralis are shown on the right side. The longus capitis is seen on the left side.

518

FIGURE 10-24 B, The longus colli is seen on the right and the longus capitis is seen on the left. The rectus capitis anterior and rectus capitis lateralis have been ghosted in bilaterally. C, The rectus capitis anterior and rectus capitis lateralis are seen bilaterally. The longus colli has been ghosted in on the right and the longus capitis has been ghosted in on the left.

519

Longus Colli (of Prevertebral Group) The name, longus colli, tells us that this muscle is long and found in the neck. Derivation longus: L. long colli: L. refers to the neck Pronunciation LONG-us KOL-eye

ATTACHMENTS Entire Muscle: Transverse Processes and Anterior Bodies of C3-T3 Vertebrae to the Entire Muscle: Transverse Processes and Anterior Bodies of C2-C6 and the Anterior Arch of C1 SUPERIOR OBLIQUE PART:

the transverse processes of C3-C5 to the

the anterior arch of C1 INFERIOR OBLIQUE PART: the anterior bodies of T1-T3 to the

the transverse processes of C5-C6 VERTICAL PART: the anterior bodies of C5-T3 to the

the anterior bodies of C2-C4 FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes the neck at the spinal joints 2. Laterally flexes the neck at the spinal joints 3. Contralaterally rotates the neck at the spinal joints

Reverse Mover Actions 1. Flexes the lower neck and upper back relative to the upper neck 2. Laterally flexes the lower neck and upper back relative to the upper neck 3. Ipsilaterally rotates the lower neck and upper back relative to the upper neck

Standard Mover Action Notes • The longus colli crosses the joints of the neck anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the neck at the cervical spinal joints. All parts of the longus colli perform this action. (action 1) • The longus colli is considered to be a strong flexor of the neck at the cervical spinal joints. (action 1) • The longus colli crosses the joints of the neck laterally (with its fibers running vertically in the frontal plane); therefore it laterally flexes the neck at the cervical spinal joints. Particularly the superior and inferior oblique parts of the longus colli perform this action. (action 2)

520

FIGURE 10-25

Anterior view of the right longus colli. The longus capitis has been ghosted in on the left.

• The fibers of the inferior oblique part of the longus colli run from medial on the anterior bodies of the inferior vertebrae, to lateral onto the transverse processes of the superior vertebrae. (Therefore the fibers are running slightly horizontally in the transverse plane.) If the inferior attachment is fixed and the longus colli contracts, it pulls on the superior attachment, causing the anterior surface of the vertebrae to face the opposite side of the body from the side of the body to which the longus colli is attached. Therefore the longus colli contralaterally rotates the neck at the cervical spinal joints. The inferior oblique part of the longus colli performs this action. (action 3)

Reverse Mover Action Notes • The reverse actions of the longus colli occur when the upper attachment is fixed and the vertebrae of the lower neck and upper back move relative to the upper neck. This usually occurs when the client is lying down so that the lower attachment is mobile. (reverse actions 1, 2, 3) • The reverse action of contralaterally rotating the upper neck (relative to the fixed lower attachment) is to ipsilaterally rotate the lower spine (relative to the fixed upper attachment). In other words, if the right-sided longus colli does left rotation of the upper neck, its reverse action would be right rotation of the lower neck and upper back (relative to the upper neck). This reverse action usually occurs when the client is lying down so that the lower attachment is mobile. (reverse action 3)

Motion 1. The longus colli has one line of pull in an oblique plane and therefore creates one motion, which is a combination of flexion, lateral flexion, and contralateral rotation of the neck at the spinal joints.

Eccentric Antagonist Functions 1. Restrains/slows extension and opposite-side lateral flexion of the neck at the spinal joints 2. Restrains/slows ipsilateral rotation of the neck at the spinal joints 3. Restrains/slows contralateral rotation of the lower neck and upper back at the spinal joints

521

(relative to the upper attachment)

Isometric Stabilization Functions 1. Stabilizes the cervical and upper thoracic spinal joints

Isometric Stabilization Function Note • The longus colli and other prevertebral muscles are important for fixing (stabilizing) the neck and head while talking, swallowing, coughing, and sneezing. They also fix/stabilize the neck during rapid arm movements.

Additional Note on Actions 1. A number of sources state the longus colli does ipsilateral rotation of the neck at the spinal joints. Looking at the line of pull of this muscle, it would seem that the superior oblique fibers would have a weak line of pull for ipsilateral rotation, but the inferior oblique fibers would create contralateral rotation. Regardless of which cervical spine rotation this muscle does, its leverage force for rotation is weak so rotation is not a major function of the longus colli.

I N N E RVAT I O N Cervical Spinal Nerves ventral rami; C2-C6

A R T E R I A L S U P P LY The Inferior Thyroid Artery (a branch of the Thyrocervical Trunk) and the Vertebral Artery (a branch of the Subclavian Artery) and the Ascending Pharyngeal Artery (a branch of the External Carotid Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating fingers just medial to the medial border of the sternocleidomastoid. 2. Press gently but firmly into the client’s anterior neck in a posterior and slightly medial direction, feeling for the bodies and transverse processes of the cervical spine. 3. Have the client flex the head and neck against gentle resistance and feel for the contraction of the longuscolli. Discerning the longus colli from the longus capitis is difficult. 4. Note: Be careful with palpation in this region because the common carotid artery, larynx, and trachea are located nearby.

RELATIONSHIP TO OTHER STRUCTURES The longus colli is deep in the anterior neck (along with the longus capitis). The longus colli is deep to the hyoid bone, the suprahyoid and infrahyoid muscles, the larynx, trachea, and the esophagus. The longus colli lies against the cervical and upper thoracic vertebral bodies. The longus colli is generally inferior to the longus capitis. Where they overlap, the longus colli is deep to the longus capitis. If one looks at the relationship between the longus colli (and the longus capitis) to the anterior scalene, it can be seen that, except for the interruption of the attachment to the transverse processes of the cervical spine, there is a continuous line of pull from the first rib (the most inferior attachment of the anterior scalene) to the atlas (C1) and the head (the most superior attachments of the longus colli and longus capitis). The inferior part of the longus colli (the inferior part of the inferior oblique part) lies deep to the sternum. The longus colli is located within the deep front line myofascial meridian.

MISCELLANEOUS 1. The longus colli and the longus capitis, along with the rectus capitis anterior and the rectus

522

capitis lateralis, are often grouped together and called the prevertebral muscles. (From an anterior perspective, they are just before [i.e., pre-] the vertebral column.) 2. The longus colli has three parts: the superior oblique part, the inferior oblique part, and the vertical part. 3. There is a general pattern of attachments for the longus colli. The attachments of the vertical part are from anterior bodies to anterior bodies. The attachments of the inferior oblique part are from anterior bodies to transverse processes. The attachments of the superior oblique part are from transverse processes to the anterior arch of the atlas (C1). All transverse process attachments of the longus muscles are to the anterior tubercles of the transverse processes. 4. The longus colli and longus capitis are often injured in a whiplash accident, wherein the head and neck are forcefully thrown anteriorly and posteriorly (like a whip being lashed). 5. The longus colli and longus capitis are also often aggravated when doing a lot of situps/crunches/curl-ups. 6. Talking, swallowing, coughing, and sneezing can exacerbate deep anterior neck pain in people who have a tight or injured longus colli. 7. Clients with a tight longus colli and/or longus capitis often describe feeling as though they have a sore throat, especially when swallowing.

523

Longus Capitis (of Prevertebral Group) The name, longus capitis, tells us that this muscle is long and attaches to the head. Derivation longus: L. long capitis: L. refers to the head Pronunciation LONG-us KAP-i-tis

ATTACHMENTS Transverse Processes of the Cervical Spine the anterior tubercles of C3-C5 to the Occiput the inferior surface of the basilar part of the occiput (just anterior to the foramen magnum)

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes the neck and head at the spinal joints 2. Laterally flexes the neck and head at the spinal joints

Reverse Mover Actions 1. Flexes the lower neck relative to the head 2. Laterally flexes the lower neck relative to the head

Standard Mover Action Notes • The longus capitis crosses the atlanto-occipital joint (AOJ) and the joints of the upper neck anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the head at the AOJ and the upper neck at the cervical spinal joints. (action 1) • The longus capitis crosses the AOJ and the joints of the upper neck laterally (with its fibers running vertically in the frontal plane); therefore it laterally flexes the head at the AOJ and the upper neck at the cervical spinal joints. (action 2)

Reverse Mover Action Note • The usual action of the longus capitis is to move the upper neck and head relative to the fixed lower attachment. The reverse action of the longus capitis occurs when the upper attachment is fixed and the vertebrae of the lower neck move relative to the upper neck and head. This usually occurs when the client is lying down so that the inferior attachment is mobile. (reverse actions 1, 2)

Motion 1. The longus capitis has one line of pull in an oblique plane and therefore creates one motion, which is a combination of flexion and lateral flexion of the neck at the spinal joints.

524

FIGURE 10-26

Anterior view of the right longus capitis. The longus colli has been ghosted in on the left.

Eccentric Antagonist Functions 1. Restrains/slows extension and opposite-side lateral flexion of the neck and head at the spinal joints

Isometric Stabilization Function 1. Stabilizes the upper cervical spinal joints, including the head at the AOJ

Isometric Stabilization Function Note • The longus capitis and other prevertebral muscles are important for fixing (stabilizing) the neck and head while talking, swallowing, coughing, and sneezing. They also fix the neck during rapid arm movements.

Additional Note on Actions 1. Some sources state that the longus capitis is capable of rotating the head and the neck at the spinal joints, however there is disagreement regarding whether it creates ipsilateral or contralateral rotation. Given the fiber direction of the longus capitis, it would seem likely that the line of pull would cause ipsilateral rotation of the head and neck. Regardless of the direction, rotation would not be a strong action of the longus capitis.

I N N E RVAT I O N Cervical Spinal Nerves ventral rami; C1-C3

525

A R T E R I A L S U P P LY The Inferior Thyroid Artery (a branch of the Thyrocervical Trunk) and the Vertebral Artery (a branch of the Subclavian Artery) and the Ascending Pharyngeal Artery (a branch of the External Carotid Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating fingers just medial to the medial border of the sternocleidomastoid. 2. Press gently but firmly into the client’s anterior neck in a posterior and slightly medial direction, feeling for the bodies and transverse processes of the cervical spine. 3. Have the client flex the head and neck against gentle resistance and feel for the contraction of the longus capitis. Discerning the longus capitis from the longus colli is difficult. 4. Note: Be careful with palpation in this region because the common carotid artery and larynx are located nearby.

RELATIONSHIP TO OTHER STRUCTURES The longus capitis is deep in the anterior neck (along with the longus colli). The longus capitis is deep to the hyoid bone, the suprahyoid muscles, the trachea, and the esophagus. The longus capitis is generally superior to the longus colli. Where they overlap, the longus colli is deep to the longus capitis. The rectus capitis anterior is also deep to the longus capitis. If one looks at the relationship between the longus capitis (and the superior part of the longus colli) and the anterior scalene, it can be seen that, except for the interruption of the attachment to the transverse processes of the cervical spine, there is a continuous line of pull from the first rib (the most inferior attachment of the anterior scalene) to the atlas (C1) and the head (the most superior attachments of the longus colli and longus capitis). The longus capitis is located within the deep front line myofascial meridian.

MISCELLANEOUS 1. The longus capitis and the longus colli, along with the rectus capitis anterior and the rectus capitis lateralis, are often grouped together and called the prevertebral muscles. (From an anterior perspective, they are just before [i.e., pre-] the vertebral column.) 2. The vertebral attachments of the longus capitis are variable; the longus capitis often attaches to C6. 3. The longus capitis and longus colli are often injured in a whiplash accident, wherein the head and neck are forcefully thrown anteriorly and posteriorly (like a whip being lashed). 4. The longus capitis and longus colli are also often aggravated when doing a lot of situps/crunches/curl-ups. 5. Talking, swallowing, coughing, and sneezing can exacerbate deep anterior neck pain in people who have a tight or injured longus capitis. 6. Clients with a tight longus capitis and/or longus colli often describe feeling as though they have a sore throat, especially when swallowing.

526

Rectus Capitis Anterior (of Prevertebral Group) The name, rectus capitis anterior, tells us that the fibers of this muscle run straight and attach to the head anteriorly. Derivation rectus: L. straight capitis: L. refers to the head anterior: L. before, in front of Pronunciation REK-tus KAP-i-tis an-TEE-ri-or

ATTACHMENTS The Atlas (C1) the anterior surface of the base of the transverse process to the Occiput the inferior surface of the basilar part of the occiput (just anterior to the foramen magnum)

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes the head at the AOJ

Reverse Mover Actions 1. Flexes the atlas relative to the head at the AOJ

AOJ = atlanto-occipital joint

Standard Mover Action Notes • The rectus capitis anterior crosses the AOJ between the atlas (C1) and the occiput anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the head on the atlas at the AOJ. (action 1)

Reverse Mover Action Notes • The usual action of the rectus capitis anterior is to flex the head relative to the atlas. The reverse action would be if the head is fixed and the atlas flexes toward the head at the AOJ. This usually only happens if the client is lying supine so the lower attachment is mobile (e.g., if the client is lying supine and brings the feet up and over and behind the head). (reverse action 1)

Motion 1. The rectus capitis anterior has one line of pull in the sagittal plane and therefore its motion is its cardinal plane joint action, flexion of the head at the AOJ.

Eccentric Antagonist Function 1. Restrains/slows extension of the AOJ

527

FIGURE 10-27

Anterior view of the rectus capitis anterior bilaterally. The rectus capitis lateralis has been ghosted in on the left.

Isometric Stabilization Function 1. Stabilizes the head at the AOJ

Isometric Stabilization Function Note • The rectus capitis anterior and other prevertebral muscles are important for fixing (stabilizing) the neck and head while talking, swallowing, coughing, and sneezing.

Additional Notes on Actions 1. Some sources state that the rectus capitis anterior can rotate the head at the AOJ; however, there is disagreement on whether it creates ipsilateral or contralateral rotation. Looking at its line of pull, it would most likely create ipsilateral rotation. Either way, its rotation force would be weak. 2. Some sources state that the rectus capitis anterior can laterally flex the head at the AOJ. The line of pull does indicate that this muscle could create lateral flexion, but its force would be weak.

I N N E RVAT I O N Cervical Spinal Nerves ventral rami; C1-C2

A R T E R I A L S U P P LY The Vertebral Artery (a branch of the Subclavian Artery)

PA L PAT I O N 1. The rectus capitis anterior is located very deep and high in the anterior neck between the atlas (C1) and the occiput and is usually not palpable.

RELATIONSHIP TO OTHER STRUCTURES The rectus capitis anterior is very deep in the anterior neck. Directly superficial to the rectus capitis anterior is the longus capitis. The attachment of the rectus capitis anterior on the atlas (C1) is directly medial to the attachment of

528

the rectus capitis lateralis on the atlas. From the atlas attachments, the rectus capitis anterior runs superiorly and medially to attach onto the occiput, whereas the rectus capitis lateralis runs superiorly and slightly laterally to attach onto the occiput. The rectus capitis anterior is located within the deep front line myofascial meridian.

MISCELLANEOUS 1. The rectus capitis anterior and the rectus capitis lateralis, along with the longus colli and the longus capitis, are often grouped together and called the prevertebral muscles. (From an anterior perspective, they are just before [i.e., pre-] the vertebral column.) 2. In addition to the rectus capitis anterior, there is also a rectus capitis lateralis, a rectus capitis posterior major, and a rectus capitis posterior minor. These four muscles attach onto the occiput (hence, capitis). 3. The rectus capitis anterior is often injured in a whiplash accident. 4. Because the rectus capitis anterior contracts to stabilize the head when talking, swallowing, coughing, and sneezing, these activities can exacerbate deep anterior neck pain in people who have a tight or injured rectus capitis anterior.

529

Rectus Capitis Lateralis (of Prevertebral Group) The name, rectus capitis lateralis, tells us that the fibers of this muscle run straight and attach to the head laterally. Derivation rectus: L. straight capitis: L. refers to the head lateralis: L. refers to the side Pronunciation REK-tus KAP-i-tis la-ter-A-lis

ATTACHMENTS The Atlas (C1) the superior surface of the transverse process to the Occiput the inferior surface of the jugular process of the occiput

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Laterally flexes the head at the AOJ

Reverse Mover Actions 1. Laterally flexes the atlas relative to the head at the AOJ

AOJ = atlanto-occipital joint

Standard Mover Action Notes • The rectus capitis lateralis crosses the AOJ between the atlas (C1) and the occiput laterally (with its fibers running vertically in the frontal plane); therefore it laterally flexes the head on the atlas at the AOJ. (action 1)

Reverse Mover Action Notes • The usual action of the rectus capitis lateralis is to laterally flex the head relative to the atlas. The reverse action would be if the head is fixed and the atlas laterally flexes toward the head at the AOJ. This usually only happens if the client is lying down so that the lower attachment is mobile. (reverse action 1)

Motion 1. The rectus capitis lateralis has one line of pull in the frontal plane and therefore its motion is its cardinal plane joint action, lateral flexion of the head at the AOJ.

Eccentric Antagonist Function 1. Restrains/slows opposite-side lateral flexion at the AOJ

Isometric Stabilization Function 1. Stabilizes the head at the AOJ

530

FIGURE 10-28

Anterior view of the rectus capitis lateralis bilaterally. The rectus capitis anterior has been ghosted in on the left.

Additional Notes on Actions 1. Some sources state that the rectus capitis lateralis can flex the head at the AOJ. Given that its line of pull is anterior to the axis for motion in the sagittal plane (in other words, this muscle crosses the vertebrae anteriorly), the rectus capitis lateralis would have the ability to flex the head at the AOJ. However, the leverage force would be small and this would be a weak action of this muscle. 2. The rectus capitis lateralis runs directly vertically. Therefore it has no moment arm for rotation when the body is in anatomic position. However, if the head were first rotated, the rectus capitis lateralis would have the ability to rotate the head back to anatomic position. In this manner, the rectus capitis lateralis is a de-rotator. 3. The rectus capitis lateralis and other prevertebral muscles are important for fixing (stabilizing) the neck and head when talking, swallowing, coughing, and sneezing.

I N N E RVAT I O N Cervical Spinal Nerves ventral rami; C1-C2

A R T E R I A L S U P P LY The Vertebral Artery (a branch of the Subclavian Artery) and the Occipital Artery (a branch of the External Carotid Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating fingers just superior to the transverse process of the atlas (the transverse process of the atlas is posterior to the ramus of the mandible, anterior to the mastoid process of the temporal bone, and inferior to the ear). 2. Palpate superiorly to the transverse processes of the atlas and a bit deeper and feel for the rectus capitis lateralis. Discerning its muscle belly from the adjacent musculature is difficult. 3. Note: The styloid process of the temporal bone is very close to this region. Care must be taken to not use too much pressure because the styloid process is a delicate structure.

531

RELATIONSHIP TO OTHER STRUCTURES The rectus capitis lateralis is deep in the anterolateral neck. The attachment of the rectus capitis lateralis on the atlas is directly lateral to the attachment of the rectus capitis anterior on the atlas. From the atlas attachments, the rectus capitis lateralis runs superiorly and slightly laterally to attach onto the occiput, whereas the rectus capitis anterior runs superiorly and medially to attach onto the occiput. From a lateral perspective, the styloid process of the temporal bone is superficial to the rectus capitis lateralis. The rectus capitis lateralis may be involved with the deep front line and lateral line myofascial meridians.

MISCELLANEOUS 1. The rectus capitis lateralis and the rectus capitis anterior, along with the longus colli and the longus capitis, are often grouped together and called the prevertebral muscles. (From an anterior perspective, they are just before [i.e., pre-] the vertebral column.) 2. In addition to the rectus capitis lateralis, there is also a rectus capitis anterior, a rectus capitis posterior major, and a rectus capitis posterior minor. These four muscles attach onto the occiput (hence, capitis). 3. The rectus capitis lateralis is often injured in a whiplash accident. 4. Because the rectus capitis lateralis contracts to stabilize the head when talking, swallowing, coughing, and sneezing, these activities can exacerbate deep anterior neck pain in people who have a tight or injured rectus capitis lateralis. 5. The rectus capitis lateralis muscles are considered to be homologous to the posterior intertransversarii muscles of the spine.

532

Splenius Capitis The name, splenius capitis, tells us that this muscle is shaped like a bandage (a narrow rectangle) and attaches onto the head. Derivation splenius: Gr. bandage capitis: L. refers to the head Pronunciation SPLEE-nee-us KAP-i-tis

ATTACHMENTS Nuchal Ligament from C3-C6 and the Spinous Processes of C7-T4 to the Mastoid Process of the Temporal Bone and the Occipital Bone

the lateral ⅓ of the superior nuchal line of the occiput

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extends the head and neck at the spinal joints

Reverse Mover Actions 1. Extends the upper thoracic and lower cervical spine relative to the head and upper cervical spine

2. Laterally flexes the head and neck at the spinal joints

2. Laterally flexes the upper thoracic and lower cervical spine relative to the head and upper cervical spine

3. Ipsilaterally rotates the head and neck at the spinal joints

3. Contralaterally rotates the upper thoracic and lower cervical spine relative to the head and upper cervical spine

Standard Mover Action Notes • The splenius capitis crosses the atlanto-occipital joint (AOJ) and the joints of the cervical spine posteriorly (with its fibers running vertically in the sagittal plane). Therefore the splenius capitis extends the head at the AOJ and the neck at the cervical spinal joints. (action 1) • The splenius capitis crosses the AOJ and the joints of the cervical spine laterally (with its fibers running vertically in the frontal plane). Therefore the splenius capitis laterally flexes the head at the AOJ and the neck at the cervical spinal joints. (action 2) • The splenius capitis attaches from the nuchal ligament/spinous processes attachment and then wraps around the neck anteriorly to attach onto the cranium (with its fibers running somewhat horizontally in the transverse plane). When the splenius capitis contracts, it pulls the cranial attachment posteromedially, causing the anterior surface of the head and/or the neck to face the same side of the body to which the splenius capitis is attached. Therefore the splenius capitis ipsilaterally rotates the head at the AOJ and the neck at the cervical spinal joints. (action 3)

533

FIGURE 10-29

Posterior view of the right splenius capitis. The trapezius has been ghosted in.

Reverse Mover Action Notes • When we think of motions of the spine, we usually think of the upper spine moving relative to the fixed lower spine. However, the reverse action of moving the lower spine relative to the fixed upper spine is also possible. This usually occurs when the client is lying down so that the inferior attachment is mobile. (reverse actions 1, 2, 3) • The reverse action of ipsilateral rotation of the head and upper spine relative to the fixed lower spine is to contralaterally rotate the lower spine relative to the fixed head and upper spine. In other words, if the right-sided splenius capitis does right rotation of the head and neck, its reverse action would be to do left rotation of the upper thoracic and lower cervical spine. (reverse action 3)

Motion 1. The splenius capitis has one line of pull in an oblique plane and therefore creates one motion, which is a combination of extension, lateral flexion, and ipsilateral rotation of the head and neck at the spinal joints.

Eccentric Antagonist Functions 1. Restrains/slows flexion, opposite-side lateral flexion, and contralateral rotation of the head and neck 2. Restrains/slows flexion, opposite-side lateral flexion, and ipsilateral rotation of the lower spinal attachment relative to the head

Isometric Stabilization Functions 1. Stabilizes the head, neck, and upper thoracic vertebrae

534

I N N E RVAT I O N Cervical Spinal Nerves dorsal rami of the middle cervical spinal nerves

A R T E R I A L S U P P LY The Occipital Artery (a branch of the External Carotid Artery)

PA L PAT I O N 1. With the client seated, place your palpating hand in the superior aspect of the posterior triangle of the neck (the area between the sternocleidomastoid and the upper trapezius). 2. Ask the client to actively rotate the head and the neck and feel for the contraction of the same-side splenius capitis. Resistance can be added. 3. Try to continue palpating the splenius capitis toward its superior attachment deep to the sternocleidomastoid, and its inferior attachment deep to the upper trapezius.

RELATIONSHIP TO OTHER STRUCTURES Most of the splenius capitis is deep to the trapezius inferiorly and the sternocleidomastoid superiorly. The most inferior part of the splenius capitis is deep to the rhomboid minor and the serratus posterior superior. The attachment of the splenius capitis onto the mastoid process is deep (anterior) to the sternocleidomastoid but superficial (posterior) to the longissimus capitis. There is a small part of the splenius capitis that is superficial in the posterior triangle of the neck between the trapezius and the sternocleidomastoid. The inferior portion of the splenius cervicis lies directly inferior to the splenius capitis. Where the splenius capitis and the splenius cervicis overlap, the splenius cervicis is deep to the splenius capitis. The erector spinae group lies deep to the splenius capitis. The splenius capitis is located within the lateral line and spiral line myofascial meridians.

MISCELLANEOUS 1. The left and right splenius capitis muscles bilaterally form a V shape. Because of their V shape, the left and right splenius capitis muscles are sometimes known as the golf tee muscles. 2. The inferior attachment of the splenius capitis is variable and often attaches only as far inferior as the spinous process of T3. 3. The mastoid attachment of the splenius capitis is sandwiched between the attachment of the sternocleidomastoid (which is posterior to it) and the attachment of the longissimus capitis (which is anterior to it). 4. The splenius capitis and splenius cervicis often blend together. By definition, any fibers that attach superiorly onto the head are defined as splenius capitis and any fibers that attach superiorly onto the cervical spine are defined as splenius cervicis.

535

Splenius Cervicis The name, splenius cervicis, tells us that this muscle is shaped like a bandage (a narrow rectangle) and attaches onto the cervical spine (the neck). Derivation splenius: Gr. bandage cervicis: L. refers to the cervical spine Pronunciation SPLEE-nee-us SER-vi-sis

ATTACHMENTS Spinous Processes of T3-T6 to the Transverse Processes of C1-C3

the posterior tubercles of the transverse processes

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extends the neck at the spinal joints

Reverse Mover Actions 1. Extends the upper thoracic spine relative to the upper cervical spine

2. Laterally flexes the neck at the spinal joints

2. Laterally flexes the upper thoracic spine relative to the upper cervical spine

3. Ipsilaterally rotates the neck at the spinal joints

3. Contralaterally rotates the upper thoracic spine relative to the upper cervical spine

Standard Mover Action Notes • The splenius cervicis crosses the joints of the cervical spine posteriorly (with its fibers running vertically in the sagittal plane). Therefore the splenius cervicis extends the neck at the cervical spinal joints. (action 1) • The splenius cervicis crosses the joints of the cervical spine laterally (with its fibers running vertically in the frontal plane). Therefore the splenius cervicis laterally flexes the neck at the cervical spinal joints. (action 2) • The splenius cervicis attaches from the spinous processes of the upper thoracic region and then wraps around the neck anteriorly to attach onto the upper cervical transverse processes (with its fibers running somewhat horizontally in the transverse plane). When the splenius cervicis contracts, it pulls the neck posteromedially, causing the anterior surface of the neck to face the same side of the body to which the splenius cervicis is attached. Therefore the splenius cervicis ipsilaterally rotates the neck at the cervical spinal joints. (action 3)

Reverse Mover Action Notes • When we think of motions of the spine, we usually think of the upper spine moving relative to the fixed lower spine. However, the reverse action of moving the lower spine relative to the fixed upper spine is also possible. This usually occurs when the client is lying down so that the inferior attachment is mobile. (reverse actions 1, 2, 3)

536

FIGURE 10-30

Posterior view of the right splenius cervicis. The splenius capitis has been ghosted in.

• The reverse action of ipsilateral rotation of the upper spine relative to the fixed lower spine is to contralaterally rotate the lower spine relative to the fixed upper spine. In other words, if the rightsided splenius cervicis does right rotation of the neck, its reverse action would be to do left rotation of the upper thoracic spine. (reverse action 3)

Motion 1. The splenius cervicis has one line of pull in an oblique plane and therefore creates one motion, which is a combination of extension, lateral flexion, and ipsilateral rotation of the neck at the spinal joints.

Eccentric Antagonist Functions 1. Restrains/slows flexion, opposite-side lateral flexion, and contralateral rotation of the neck 2. Restrains/slows flexion, opposite-side lateral flexion, and ipsilateral rotation of the lower spinal attachment relative to the upper cervical spine

Isometric Stabilization Functions 1. Stabilizes the cervical and upper thoracic vertebrae

Additional Note on Actions 1. The splenius capitis and splenius cervicis have the same actions, except that the splenius capitis moves the head and neck, whereas the splenius cervicis only moves the neck (because the splenius capitis crosses the atlanto-occipital joint to attach to and move the head; the splenius cervicis does not).

I N N E RVAT I O N Cervical Spinal Nerves

537

dorsal rami of the lower cervical spinal nerves

A R T E R I A L S U P P LY The Occipital Artery (a branch of the External Carotid Artery) and the dorsal branches of the Upper Posterior Intercostal Arteries

PA L PAT I O N 1. With the client seated, place palpating hand over the splenius cervicis between the splenius capitis and levator scapulae. 2. Ask the client to actively rotate the neck and feel for the contraction of the same-side splenius cervicis. Gentle resistance can be given. 3. Palpate as much of the splenius cervicis as possible. 4. Note: It is challenging to palpate and discern this muscle from adjacent musculature.

RELATIONSHIP TO OTHER STRUCTURES The splenius cervicis is deep to the trapezius, the rhomboids, and the serratus posterior superior. Toward its superior attachment, the splenius cervicis is also deep to the splenius capitis. From the posterior perspective, the cervical transverse process attachment of the splenius cervicis is superficial (posterior) to the cervical transverse process attachments of the levator scapulae and the scalenes. The inferior portion of the splenius cervicis lies directly inferior to the splenius capitis. The erector spinae musculature lies deep to the splenius cervicis. The splenius cervicis is located within the spiral line myofascial meridian.

MISCELLANEOUS 1. The left and right splenius cervicis muscles bilaterally form a V shape. 2. The superior attachment of the splenius cervicis is variable and often attaches only onto the transverse processes of C1-C2.

538

Suboccipital Group The suboccipitals are a group of four short muscles located deep in the posterior suboccipital region. There are four suboccipital muscles: the rectus capitis posterior major, rectus capitis posterior minor, obliquus capitis inferior, and obliquus capitis superior.

ATTACHMENTS The names of the suboccipital muscles generally refer to their fiber direction: Rectus means straight. The rectus capitis posterior major and minor attach from the spinous process of C2 and the posterior tubercle of C1, respectively, and run approximately straight up to the inferior nuchal line of the occiput. Obliquus means slanted. The obliquus capitis inferior and superior run in a slanted fashion. The obliquus capitis inferior slants from the spinous process of C2 to the transverse process of C1, and the obliquus capitis superior slants slightly from the transverse process of C1 to the occiput (between the inferior and superior nuchal lines). The suboccipitals are found deep to the upper trapezius, sternocleidomastoid, splenius capitis, and semispinalis capitis (of the transversospinalis group).

FUNCTIONS The major actions of the suboccipital group are extension and anterior translation (protraction) of the head on the neck at the atlanto-occipital joint. The obliquus capitis inferior ipsilaterally rotates the atlas (C1) on the axis (C2) at the atlantoaxial joint. The suboccipital muscles are generally thought to be more important as postural stabilization muscles, providing fine control of head posture, than as movers. Some sources believe that the main role of the suboccipital group is proprioceptive by providing precise monitoring of the position of the head and upper cervical vertebrae.

MISCELLANEOUS 1. The suboccipital muscles are not the only muscles located in the suboccipital region. When tight muscles are palpated in this region, they are not always the suboccipital muscles; they can also be the superior attachments of the trapezius, splenius capitis, splenius cervicis, semispinalis capitis, or perhaps even the longissimus capitis or the sternocleidomastoid. 2. When the suboccipital musculature is chronically tight, tension headaches often occur. 3. The suboccipital muscles are located within the superficial back line myofascial meridian.

I N N E RVAT I O N The four suboccipital muscles are innervated by the suboccipital nerve (dorsal ramus of C1).

A R T E R I A L S U P P LY The four suboccipital muscles receive the majority of their arterial supply from the occipital artery.

539

Views of the Suboccipital Group

FIGURE 10-31 Views of the suboccipital group. A, Posterior view. B, Right lateral view. Note the anterior to posterior horizontal direction of the rectus capitis posterior minor (RCPMin) and the obliquus capitis superior (OCS). This fiber direction is ideal for anterior translation of the head at the atlanto-occipital joint.

540

Rectus Capitis Posterior Major (of Suboccipital Group) The name, rectus capitis posterior major, tells us that the fibers of this muscle run straight (straighter than the two obliquus capitis suboccipital muscles). It also tells us that this muscle attaches to the head posteriorly and is large (larger than the rectus capitis posterior minor). Derivation rectus: L. straight capitis: L. refers to the head posterior: L. behind, toward the back major: L. larger Pronunciation REK-tus KAP-i-tis pos-TEE-ri-or MAY-jor

ATTACHMENTS The Spinous Process of the Axis (C2) to the Occiput

the lateral ½ of the inferior nuchal line

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extends the head at the AOJ 2. Laterally flexes the head at the AOJ 3. Ipsilaterally rotates the head at the AOJ

Reverse Mover Actions 1. Extends the upper cervical spine relative to the head 2. Laterally flexes the upper cervical spine relative to the head 3. Contralaterally rotates the upper cervical spine relative to the head

AOJ = atlanto-occipital joint

Standard Mover Action Notes • The rectus capitis posterior major crosses the AOJ posteriorly (with its fibers running vertically in the sagittal plane); therefore it extends the head on the atlas (C1) at the AOJ. (action 1) • The rectus capitis posterior major crosses the AOJ from near the midline on the axis (C2) to more laterally on the occiput (with its fibers running vertically in the frontal plane). Therefore the rectus capitis posterior major laterally flexes the head on the atlas at the AOJ. (action 2) • The rectus capitis posterior major crosses the AOJ with its fibers wrapping around the suboccipital region from posteriorly on the axis, to more anteriorly on the occiput (with its fibers running somewhat horizontally in the transverse plane). When the rectus capitis posterior major contracts, it pulls on the occiput, causing the anterior surface of the head to face the same side of the body to which the rectus capitis posterior major is attached. Therefore the rectus capitis posterior major ipsilaterally rotates the head on the atlas at the AOJ. (action 3)

541

FIGURE 10-32 Views of the rectus capitis posterior major. A, Posterior view bilaterally. The other three suboccipital muscles have been ghosted in on the left. B, Right lateral view. The other three suboccipital muscles have been ghosted in. RCPMin, Rectus capitis posterior minor; OCS, obliquus capitis superior; OCI, obliquus capitis inferior.

Reverse Mover Action Notes • If the head is fixed, the rectus capitis posterior major can move the atlas and axis relative to the head. This is only likely to occur when the client is lying down so that the inferior attachments are mobile. (reverse actions 1, 2, 3) • The reverse action of ipsilateral rotation of the head relative to the spine is to contralaterally rotate the spine relative to the head. (reverse action 3)

Motion 1. The rectus capitis posterior major has one line of pull in an oblique plane and therefore creates one motion, which is a combination of extension, lateral flexion, and ipsilateral rotation of the head at the AOJ.

Eccentric Antagonist Functions 1. Restrains/slows flexion, opposite-side lateral flexion, and contralateral rotation of the head

542

Isometric Stabilization Functions 1. Stabilizes the head and atlas at the AOJ 2. Stabilizes the atlantoaxial joint

Isometric Stabilization Function Note • The suboccipital muscles are generally thought to be more important as postural stabilization muscles, providing fine control of head posture, than as movers.

Additional Notes on Actions 1. The rectus capitis posterior major crosses the joint between the atlas and the axis (the atlantoaxial joint) in the same manner that it crosses the joint between the head and the atlas (the AOJ). Therefore the rectus capitis posterior major can perform the same actions at the atlantoaxial joint that it performs at the AOJ, except that the atlantoaxial joint does not permit lateral flexion. Therefore the rectus capitis posterior major extends and ipsilaterally rotates the atlas (C1) on the axis (C2) at the atlantoaxial joint. 2. Some sources believe that the main role of the suboccipital group is proprioceptive by providing precise monitoring of the position of the head and upper cervical vertebrae.

I N N E RVAT I O N The Suboccipital Nerve dorsal ramus of C1

A R T E R I A L S U P P LY The Occipital Artery (a branch of the External Carotid Artery) and the Deep Cervical Artery (a branch of the Costocervical Trunk) and the muscular branches of the Vertebral Artery (a branch of the Subclavian Artery)

PA L PAT I O N 1. With the client supine and as relaxed as possible, place palpating fingers slightly superior and lateral to the spinous process of the axis (C2), which is the most prominent spinous process in the upper cervical region. 2. Feel for the fibers of the rectus capitis posterior major running superolaterally from the spinous process of the axis toward the occiput.

RELATIONSHIP TO OTHER STRUCTURES The rectus capitis posterior major, as with all the suboccipital muscles, is very deep in the suboccipital region. It is deep to the trapezius and the semispinalis capitis. Deep to the rectus capitis posterior major are the occiput, the atlas (C1), and the axis (C2). The rectus capitis posterior major lies directly lateral to the rectus capitis posterior minor. The occipital attachment of the rectus capitis posterior major is deep to the occipital attachment of the obliquus capitis superior. The rectus capitis posterior major borders the suboccipital triangle of the neck. The suboccipital triangle is located between the rectus capitis posterior major, the obliquus capitis inferior, and the obliquus capitis superior. The suboccipital nerve and the vertebral artery are located in the suboccipital triangle. The rectus capitis posterior major is located within the superficial back line myofascial meridian.

MISCELLANEOUS 1. The rectus capitis posterior major is one of four muscles that are called the suboccipital muscles. They are the rectus capitis posterior major, rectus capitis posterior minor, obliquus capitis inferior, and obliquus capitis superior. 2. In addition to the four suboccipital muscles, there is a rectus capitis anterior and a rectus capitis lateralis.

543

3. The rectus capitis posterior major and the rectus capitis posterior minor both attach to the inferior nuchal line of the occiput.

544

Rectus Capitis Posterior Minor (of Suboccipital Group) The name, rectus capitis posterior minor, tells us that the fibers of this muscle run straight (straighter than the two obliquus capitis suboccipital muscles). It also tells us that this muscle attaches to the head posteriorly and is small (smaller than the rectus capitis posterior major). Derivation rectus: L. straight capitis: L. refers to the head posterior: L. behind, toward the back minor: L. smaller Pronunciation REK-tus KAP-i-tis pos-TEE-ri-or MY-nor

ATTACHMENTS The Posterior Tubercle of the Atlas (C1) to the Occiput

the medial ½ of the inferior nuchal line

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Protracts the head at the AOJ 2. Extends the head at the AOJ 3. Laterally flexes the head at the AOJ

Reverse Mover Actions 1. Retracts the atlas relative to the head (at the AOJ) 2. Extends the atlas relative to the head (at the AOJ) 3. Laterally flexes the atlas relative to the head (at the AOJ)

AOJ = atlanto-occipital joint

Standard Mover Action Notes • The rectus capitis posterior minor runs primarily horizontally from the atlas anteriorly to the occiput posteriorly (this is best appreciated when the muscle is viewed laterally). When it contracts, it pulls the occiput anteriorly toward the atlas; therefore it protracts (anteriorly translates) the head at the AOJ. (action 1) • The rectus capitis posterior minor crosses the AOJ posteriorly (with its fibers running slightly vertically in the sagittal plane); therefore it extends the head on the atlas (C1) at the AOJ. This action is relatively weak because the muscle’s fibers primarily run horizontally. (action 2) • The rectus capitis posterior minor crosses the AOJ from near the midline on the atlas (C1) to more laterally on the occiput (with its fibers running slightly vertically in the frontal plane). Therefore it laterally flexes the head on the atlas at the AOJ. This action is relatively weak because the muscle’s fibers primarily run horizontally. (action 3)

545

FIGURE 10-33 Views of the rectus capitis posterior minor (RCPMin). A, Posterior view bilaterally. The other three suboccipital muscles have been ghosted in on the left. B, Right lateral view. The obliquus capitis superior (OCS) has been ghosted in. OCI, Obliquus capitis inferior; RCPMaj, rectus capitis posterior major.

Reverse Mover Action Notes • If the head is fixed, the rectus capitis posterior minor can move the atlas relative to the head at the AOJ. This is only likely to occur when the client is lying down so the inferior attachment is mobile. (reverse actions 1, 2, 3)

Motion 1. The rectus capitis posterior minor has one line of pull in an oblique plane and therefore creates one motion, which is a combination of protraction, extension, and lateral flexion of the head at the AOJ.

Eccentric Antagonist Functions 1. Restrains/slows retraction, flexion, and opposite-side lateral flexion of the head

Isometric Stabilization Function

546

1. Stabilizes the head and atlas at the AOJ

Isometric Stabilization Function Notes • The suboccipital muscles are generally thought to be more important as postural stabilization muscles, providing fine control of head posture, than as movers.

Additional Notes on Actions 1. Some sources state that the rectus capitis posterior minor can ipsilaterally rotate the head at the AOJ. Comparing its line of pull with the line of pull of the rectus capitis posterior major, it does seem clear that it has the ability to create ipsilateral rotation. However, the AOJ permits very little rotation; therefore the ability of the rectus capitis posterior minor to create rotation at the AOJ is considered negligible by many sources. 2. The rectus capitis posterior minor has an attachment directly into the dura mater of the brain and spinal cord at the foramen magnum. The purpose of the dura mater attachment seems to be to protect the dura mater from folding on itself and/or getting pinched when the head protracts on the atlas at the AOJ. 3. Some sources believe that the main role of the suboccipital group is proprioceptive by providing precise monitoring of the position of the head and upper cervical vertebrae.

I N N E RVAT I O N The Suboccipital Nerve dorsal ramus of C1

A R T E R I A L S U P P LY The Occipital Artery (a branch of the External Carotid Artery) and muscular branches of the Vertebral Artery (a branch of the Subclavian Artery) and the Deep Cervical Artery (a branch of the Costocervical Trunk)

PA L PAT I O N 1. With the client supine and as relaxed as possible, place palpating fingers just inferior to the occiput and very slightly lateral of midline, and feel for the fibers of the rectus capitis posterior minor running superiorly from the posterior tubercle of the atlas (C1) toward the occiput.

RELATIONSHIP TO OTHER STRUCTURES The rectus capitis posterior minor, as with all the suboccipital muscles, is very deep in the suboccipital region. It is deep to the trapezius and the semispinalis capitis. Deep to the rectus capitis posterior minor are the occiput and the atlas (C1). The rectus capitis posterior minor lies directly medial to the rectus capitis posterior major. The rectus capitis posterior minor is located within the superficial back line myofascial meridian.

MISCELLANEOUS 1. The rectus capitis posterior minor is one of four muscles that are called the suboccipital muscles. They are the rectus capitis posterior major, rectus capitis posterior minor, obliquus capitis inferior, and obliquus capitis superior. 2. In addition to the four suboccipital muscles, there is a rectus capitis anterior and a rectus capitis lateralis. 3. The rectus capitis posterior major and the rectus capitis posterior minor both attach to the inferior nuchal line of the occiput. 4. In addition to the inferior nuchal line attachment, the rectus capitis posterior minor also attaches more inferiorly onto the occiput between the inferior nuchal line and the foramen magnum. A connective tissue attachment of the rectus capitis posterior minor has been discovered that attaches directly into the dura mater. Although tightness of any of the posterior cervical musculature in the suboccipital region may cause tension headaches, given this dura mater attachment, tightness of the rectus capitis posterior minor may more easily precipitate a tension headache than the other

547

muscles in the region. 5. Given its action of protraction of the head at the atlanto-occipital joint, a tight rectus capitis posterior minor can contribute to a posture of forward head carriage, in other words, the head being held anteriorly (protracted).

548

Obliquus Capitis Inferior (of Suboccipital Group) The name, obliquus capitis inferior, tells us that the fibers of this muscle run obliquely (in comparison to the two rectus capitis posterior suboccipital muscles). It also tells us that this muscle attaches near the head (this is the only one of the four suboccipital muscles that does not attach directly onto the head) and is located inferiorly (inferior to the obliquus capitis superior). Derivation obliquus: L. oblique capitis: L. refers to the head inferior: L. below Pronunciation ob-LEE-kwus KAP-i-tis in-FEE-ri-or

ATTACHMENTS The Spinous Process of the Axis (C2) to the Transverse Process of the Atlas (C1)

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Ipsilaterally rotates the atlas at the AAJ

Reverse Mover Actions 1. Contralaterally rotates the axis relative to the atlas (at the AAJ)

AAJ = atlantoaxial joint

Standard Mover Action Notes • The obliquus capitis inferior attaches from the spinous process of the axis (C2) to the transverse process of the atlas (C1), with its fibers running horizontally in the transverse plane. When the obliquus capitis inferior contracts, it pulls the transverse process of the atlas toward the spinous process of the axis, causing the anterior surface of the atlas to face the same side of the body to which the obliquus capitis inferior is attached. Therefore the obliquus capitis inferior ipsilaterally rotates the atlas on the axis at the AAJ. (Note: If the head is fixed to the atlas, the head will “go along for the ride” and the head and the atlas together will rotate on the axis.) (action 1) • Rotation of the atlas relative to the axis at the AAJ is an extremely important motion. Nearly half of the rotation of the craniocervical region occurs at the AAJ. (action 1)

Reverse Mover Action Notes • If the head and atlas are fixed, the obliquus capitis inferior can move the axis (C2) relative to the atlas (C1). This is only likely to occur when the client is lying down so that the inferior attachment is mobile. (reverse action 1)

549

FIGURE 10-34 Views of the obliquus capitis inferior (OCI). A, Posterior view bilaterally. The other three suboccipital muscles have been ghosted in on the left. B, Right lateral view. The other three suboccipital muscles have been ghosted in. OCS, obliquus capitis superior; RCPMaj, rectus capitis posterior major; RCPMin, rectus capitis posterior minor.

• The reverse action of ipsilateral rotation of the atlas at the AAJ is contralateral rotation of the axis at the AAJ. (reverse action 1)

Motion 1. The obliquus capitis inferior has one line of pull in the transverse plane and therefore its motion is its cardinal plane joint action, ipsilateral rotation of the atlas at the AAJ.

Eccentric Antagonist Functions 1. Restrains/slows contralateral rotation of the atlas 2. Restrains/slows ipsilateral rotation of the axis

Isometric Stabilization Function 1. Stabilizes the atlas and axis at the AAJ

Isometric Stabilization Function Note

550

• The suboccipital muscles are generally thought to be more important as postural stabilization muscles of the head/upper cervical region than as movers. However, of the four suboccipitals, the obliquus capitis inferior is the most important as a mover, because its location affords it excellent leverage to rotate the atlas.

Additional Notes on Actions 1. The obliquus capitis inferior is the only suboccipital muscle that does not cross the atlantooccipital joint to attach to the head. Therefore it is the only suboccipital muscle that cannot move the head at the atlanto-occipital joint. It moves the atlas (C1) at the AAJ. However, as stated in the first note for standard action #1, if the head is fixed to the atlas, the head will “go along for the ride” with the atlas, and the head and the atlas together will rotate on the axis. 2. Some sources state that the obliquus capitis inferior can laterally flex the atlas at the AAJ. Given its line of pull, this action should be possible. However, given that there is not much lateral flexion motion possible at the AAJ, this motion would be somewhat negligible. 3. Some sources state that the obliquus capitis inferior can extend the atlas at the AAJ. However, given that this muscle’s line of pull is primarily horizontal, this action would be weak at best. 4. Some sources believe that the main role of the suboccipital group is proprioceptive by providing precise monitoring of the position of the head and upper cervical vertebrae.

I N N E RVAT I O N The Suboccipital Nerve dorsal ramus of C1

A R T E R I A L S U P P LY The Deep Cervical Artery (a branch of the Costocervical Trunk) and the descending branch of the Occipital Artery (a branch of the External Carotid Artery) and the muscular branches of the Vertebral Artery (a branch of the Subclavian Artery)

PA L PAT I O N 1. With the client supine and as relaxed as possible, place palpating fingers on the spinous process of the axis (C2), which is the most prominent spinous process in the upper cervical region, and feel for the fibers of the obliquus capitis inferior running laterally and slightly superiorly from the spinous process of the axis toward the transverse process of the atlas (C1). 2. Have the client gently ipsilaterally rotate the head and neck and feel for the contraction of the muscle. Resistance may be added.

RELATIONSHIP TO OTHER STRUCTURES The obliquus capitis inferior, as with all of the suboccipital muscles, is very deep in the suboccipital region. It is deep to the trapezius, splenius capitis, semispinalis capitis, and the sternocleidomastoid. Deep to the obliquus capitis inferior are the atlas (C1) and the axis (C2). The obliquus capitis inferior borders the suboccipital triangle of the neck. The suboccipital triangle is located between the rectus capitis posterior major, the obliquus capitis inferior, and the obliquus capitis superior. The suboccipital nerve and the vertebral artery are located in the suboccipital triangle. The greater occipital nerve exits from deeper in the neck directly inferior to the obliquus capitis inferior. The obliquus capitis inferior is located within the superficial back line myofascial meridian.

MISCELLANEOUS 1. The obliquus capitis inferior is one of four muscles that are called the suboccipital muscles. They are the rectus capitis posterior major, rectus capitis posterior minor, obliquus capitis inferior, and obliquus capitis superior. 2. In addition to the four suboccipital muscles, there is a rectus capitis anterior and a rectus capitis

551

lateralis. 3. The obliquus capitis inferior and the obliquus capitis superior both attach to the transverse process of the atlas. Four other muscles also attach to the transverse process of the atlas: the levator scapulae, splenius cervicis, rectus capitis anterior, and rectus capitis lateralis. 4. The name obliquus capitis inferior is a misnomer in that this muscle does not attach to the head; therefore the word capitis should not be in the name.

552

Obliquus Capitis Superior (of Suboccipital Group) The name, obliquus capitis superior, tells us that the fibers of this muscle run obliquely (in comparison to the two rectus capitis posterior suboccipital muscles). It also tells us that this muscle attaches onto the head and is located superiorly (superior to the obliquus capitis inferior). Derivation obliquus: L. oblique capitis: L. refers to the head superior: L. above Pronunciation ob-LEE-kwus KAP-i-tis sue-PEE-ri-or

ATTACHMENTS The Transverse Process of the Atlas (C1) to the Occiput

between the superior and inferior nuchal lines

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Protracts the head at the AOJ 2. Laterally flexes the head at the AOJ

Reverse Mover Actions 1. Retracts the atlas relative to the head (at the AOJ) 2. Laterally flexes the atlas relative to the head (at the AOJ)

3. Extends the head at the AOJ

3. Extends the atlas relative to the head (at the AOJ)

4. Contralaterally rotates the head at the AOJ

4. Ipsilaterally rotates the atlas relative to the head (at the AOJ)

AOJ = atlanto-occipital joint

Standard Mover Action Notes • The obliquus capitis superior runs primarily horizontally from the atlas anteriorly to the occiput posteriorly (this is best appreciated when the muscle is viewed laterally). When it contracts, it pulls the occiput anteriorly toward the atlas; therefore it protracts (anteriorly translates) the head on the atlas (C1) at the AOJ. (action 1) • The obliquus capitis superior crosses the AOJ laterally (with its fibers running slightly vertically in the frontal plane); therefore it laterally flexes the head on the atlas at the AOJ. (action 2) • The obliquus capitis superior crosses the AOJ posteriorly (with its fibers running slightly vertically in the sagittal plane); therefore it extends the head on the atlas at the AOJ. (action 3) • When the obliquus capitis superior contracts and moves the occiput, it pulls the occipital attachment slightly laterally in the transverse plane toward the attachment on the atlas. This causes the head to face the opposite side of the body from which the obliquus capitis superior is attached. Therefore the obliquus capitis superior contralaterally rotates the head on the atlas at the AOJ. (action 4)

553

FIGURE 10-35 Views of the obliquus capitis superior (OCS). A, Posterior view bilaterally. The other three suboccipital muscles have been ghosted in on the left. B, Right lateral view. The other three suboccipital muscles have been ghosted in. OCI, Obliquus capitis inferior; RCPMaj, rectus capitis posterior major; RCPMin, rectus capitis posterior minor.

Reverse Mover Action Notes • If the head is fixed, the obliquus capitis superior can move the atlas relative to the head. This is only likely to occur when the client is lying down so that the inferior attachment is mobile. (reverse actions 1, 2, 3, 4) • The reverse action of contralateral rotation of the head at the AOJ is ipsilateral rotation of the atlas at the AOJ. (reverse action 4)

Motion 1. The obliquus capitis superior has one line of pull in an oblique plane and therefore creates one motion, which is a combination of protraction, lateral flexion, extension, and contralateral rotation of the head at the AOJ.

Eccentric Antagonist Functions 1. Restrains/slows retraction, opposite-side lateral flexion, flexion, and ipsilateral rotation of the

554

head

Isometric Stabilization Function 1. Stabilizes the head and atlas at the AOJ

Isometric Stabilization Function Note • The suboccipital muscles are generally thought to be more important as postural stabilization muscles, providing fine control of head posture, than as movers.

Additional Notes on Actions 1. Some sources state that the obliquus capitis superior can ipsilaterally rotate the head at the AOJ. However, given the line of pull of this muscle, when it pulls the occipital attachment toward the atlas on the same side of the head, it would cause the anterior surface of the head to orient toward the opposite side of the body, not the same side of the body. Therefore this muscle would cause contralateral rotation, not ipsilateral rotation. 2. Some sources believe that the main role of the suboccipital group is proprioceptive by providing precise monitoring of the position of the head and upper cervical vertebrae.

I N N E RVAT I O N The Suboccipital Nerve dorsal ramus of C1

A R T E R I A L S U P P LY The Occipital Artery (a branch of the External Carotid Artery) and the Deep Cervical Artery (a branch of the Costocervical Trunk) and the muscular branches of the Vertebral Artery (a branch of the Subclavian Artery)

PA L PAT I O N 1. With the client supine and as relaxed as possible, place palpating fingers just inferior to the occiput, between the transverse process of the atlas (C1) and the occiput, and feel for the fibers of the obliquus capitis superior running superiorly and medially from the transverse process of the atlas toward the occiput. 2. This muscle is challenging to palpate and discern from adjacent musculature.

RELATIONSHIP TO OTHER STRUCTURES The obliquus capitis superior, as with all of the suboccipital muscles, is very deep in the suboccipital region. It is deep to the trapezius, the splenius capitis, the semispinalis capitis, and the sternocleidomastoid. Deep to the obliquus capitis superior are the occiput and the atlas (C1). The occipital attachment of the obliquus capitis superior is superficial to the occipital attachment of the rectus capitis posterior major. The occipital attachment of the obliquus capitis superior is slightly lateral (and partially deep) to the occipital attachment of the semispinalis capitis. The obliquus capitis superior borders the suboccipital triangle of the neck. The suboccipital triangle is located between the rectus capitis posterior major, the obliquus capitis inferior, and the obliquus capitis superior. The suboccipital nerve and the vertebral artery are located in the suboccipital triangle. The obliquus capitis superior is located within the superficial back line and the lateral line myofascial meridians.

MISCELLANEOUS 1. The obliquus capitis superior is one of four muscles that are called the suboccipital muscles. They are the rectus capitis posterior major, rectus capitis posterior minor, obliquus capitis inferior, and

555

obliquus capitis superior. 2. In addition to the four suboccipital muscles, there is a rectus capitis anterior and a rectus capitis lateralis. 3. The obliquus capitis superior and the obliquus capitis inferior both attach to the transverse process of the atlas (C1). Four other muscles also attach to the transverse process of the atlas: the levator scapulae, splenius cervicis, rectus capitis anterior, and rectus capitis lateralis. 4. Given its action of protraction of the head at the atlanto-occipital joint, a tight obliquus capitis superior can contribute to a posture of forward head posture, in other words, the head being held anteriorly (protracted).

556

LOW BACK  

557

Quadratus Lumborum (QL) The name, quadratus lumborum, tells us that this muscle is shaped somewhat like a square and is located in the lumbar (i.e., lower back) region. Derivation quadratus: L. squared lumborum: L. loin (low back) Pronunciation kwod-RAY-tus lum-BOR-um

ATTACHMENTS Twelfth Rib and the Transverse Processes of L1-L4 the medial ½ of the inferior border of the twelfth rib to the Posterior Iliac Crest the posteromedial iliac crest and the iliolumbar ligament

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions

Reverse Mover Actions

1. Elevates the same-side pelvis at the LS joint and laterally flexes the lower lumbar spine relative to the upper lumbar spine (at the spinal joints) 2. Anteriorly tilts the pelvis at the LS joint and extends the lower lumbar spine relative to the upper lumbar spine (at the spinal joints)

1. Laterally flexes the trunk at the spinal joints twelfth rib at the costospinal joints

2. Depresses the

3. Extends the trunk at the spinal joints

LS joint = lumbosacral joint

Standard Mover Action Notes • With the superior attachments fixed, the quadratus lumborum elevates the same-side (ipsilateral) pelvis at the LS joint (in the frontal plane) by pulling up on the lateral pelvis. Elevation of one side of the pelvis causes the other side to depress. Therefore the quadratus lumborum performs ipsilateral elevation and contralateral depression of the pelvis. (action 1) • With the superior attachments fixed, the quadratus lumborum anteriorly tilts the pelvis (in the sagittal plane) at the LS joint by pulling up on the posterior pelvis. (action 2) • When the pelvis moves, because the LS joint does not allow a large degree of motion, the lower lumbar spine will move with the pelvis, causing the lower lumbar spine to laterally flex and extend under (relative to) the upper lumbar spine. (actions 1, 2)

558

FIGURE 10-36

Posterior view of the quadratus lumborum (QL). The erector spinae group has been ghosted in on the left side.

Reverse Mover Action Notes • The quadratus lumborum crosses the spinal joints laterally (with its fibers running vertically in the frontal plane); therefore when it contracts and the inferior pelvic attachment is fixed, it laterally flexes the trunk at the spinal joints. (reverse action 1) • When the pelvic attachment is fixed and the quadratus lumborum contracts, it pulls the twelfth rib inferiorly toward the pelvis. Therefore the quadratus lumborum depresses the twelfth rib at the costospinal joints. (reverse action 2) • The reverse action of the quadratus lumborum is when the upper attachment moves instead of the lower (pelvic) attachment. The quadratus lumborum has two upper attachments, the lumbar spine and the twelfth rib. Therefore it has two frontal plane reverse actions to ipsilateral (sameside) elevation of the pelvis: lateral flexion of the spine and depression of the twelfth rib. (reverse actions 1, 2) • The quadratus lumborum crosses the spinal joints posteriorly (with its fibers running vertically in the sagittal plane); therefore when it contracts and the inferior pelvis attachment is fixed, it extends the trunk at the spinal joints. (reverse action 3)

559

Motions 1. The quadratus lumborum has one line of pull upon the pelvis in an oblique plane and therefore creates one motion, which is a combination of elevation and anterior tilt of the pelvis at the LS joint (as well as lateral flexion and extension of the lower lumbar spine relative to the upper lumbar spine). 2. Regarding its reverse action pull on the trunk, the quadratus lumborum has one line of pull in an oblique plane and therefore creates one motion, which is a combination of lateral flexion and extension of the lumbar spine and depression of the twelfth rib.

Eccentric Antagonist Functions 1. Restrains/slows same-side depression and posterior tilt of the pelvis 2. Restrains/slows flexion and opposite-side lateral flexion of the trunk 3. Restrains/slows elevation of the twelfth rib

Isometric Stabilization Functions 1. Stabilizes the pelvis, lumbar spinal joints, and the twelfth rib

Isometric Stabilization Function Note • Stabilization of the twelfth rib is an important function of the quadratus lumborum. The quadratus lumborum’s force of depression of the twelfth rib stabilizes the twelfth rib from elevating when the diaphragm contracts and pulls superiorly on it. By stabilizing the rib cage attachment of the diaphragm, the contraction of the diaphragm acts to drop its dome, thereby increasing the superior to inferior volume of the thoracic cavity for inspiration (this occurs during abdominal [belly] breathing).

Additional Notes on Actions 1. Some sources state that the quadratus lumborum can rotate the lumbar spine. Looking at the line of pull of the muscle compared to the vertical axis for transverse plane rotation, it appears that the line of pull is fairly directly over the axis, so the muscle would have little strength to rotate the lumbar spine. However, if the spine were first rotated, the quadratus lumborum would be able to pull it back toward anatomic position; therefore the quadratus lumborum is a de-rotator. Ipsilaterally rotating a contralaterally rotated spine would appear to be the stronger action. 2. According to some sources, the primary function of the lateral fibers of the quadratus lumborum is to act as a mover of the trunk and/or the pelvis, whereas the primary function of the medial fibers is to posturally stabilize the trunk.

I N N E RVAT I O N Lumbar Plexus T12, L1, L2, L3

A R T E R I A L S U P P LY Branches of the Subcostal and Lumbar Arteries (all branches of the Aorta) and the Iliolumbar Artery (a branch of the Internal Iliac Artery)

PA L PAT I O N 1. With the client prone, place palpating hand superior to the iliac crest and just lateral to the erector spinae musculature. 2. Have the client elevate the pelvis on the side you are palpating and press in medially, deep to the erector spinae, feeling for the contraction of the quadratus lumborum. (Note: Elevation of the pelvis in this position involves moving the pelvis along the plane of the table, toward the head.) 3. Continue palpating the quadratus lumborum deep to the erector spinae; palpate medially toward the lumbar transverse processes, superomedially toward the twelfth rib, and inferomedially toward the iliac crest.

560

RELATIONSHIP TO OTHER STRUCTURES The quadratus lumborum is very deep and forms part of the posterior abdominal body wall. The majority of the quadratus lumborum is deep to the erector spinae. A small portion of the lateral part of the quadratus lumborum is deep to the muscles of the abdominal wall (external abdominal oblique, internal abdominal oblique, and transversus abdominis). Deep (anterior) to the quadratus lumborum are the abdominal viscera. Slightly anterior and medial to the quadratus lumborum is the psoas major. The quadratus lumborum is involved with the lateral line and located within the deep front line myofascial meridians.

MISCELLANEOUS 1. A common variation of the quadratus lumborum is to also have an attachment onto the transverse process of L5. 2. When working on the quadratus lumborum, you can position the client either prone, supine, or side lying. However, because much of it is deep (to the massive erector spinae musculature), it must be accessed with palpatory pressure from lateral to medial (i.e., come in from the side). 3. Keep in mind that the quadratus lumborum is not the only muscle in the lateral lumbar region and should not be blamed for all pain in that area. The erector spinae group is also present in the lateral lumbar region, is functionally active, and also is likely to develop tension and pain. 4. The quadratus lumborum can elevate the pelvis. Often the term hiking up the hip is used to describe this action. However, this term can be misleading and ambiguous. Generally, when the term hip is used (unless the context is otherwise made very clear), it is assumed that movement of the femur at the hip joint is meant, not movement of the pelvis at the lumbosacral joint. 5. Presence of the quadratus lumborum muscles helps to cushion and protect the kidneys.

561

Anterior Abdominal Wall Muscles The anterior abdominal wall consists of four muscles that attach from the trunk to the pelvis. These muscles are the rectus abdominis, external abdominal oblique, internal abdominal oblique, and transversus abdominis.

ATTACHMENTS The rectus abdominis is located anteromedially. The external and internal abdominal obliques and the transversus abdominis are located anterolaterally (and laterally and posterolaterally).

The external abdominal oblique is the most superficial of the three anterolateral abdominal wall muscles. The internal abdominal oblique is in the middle. The transversus abdominis is the deepest of the three anterolateral abdominal wall muscles. These three anterolateral abdominal muscles attach far posterior into the low back. The rectus abdominis is enclosed within the rectus sheath (a sheath of muscular fascia). The midline aponeuroses of the external abdominal oblique, internal abdominal oblique, and the transversus abdominis muscles come together to form the rectus sheath (also known as the abdominal aponeurosis), which encloses (ensheathes) the rectus abdominis. The rectus sheath covers the entire anterior surface of the rectus abdominis. However, posteriorly it only covers the upper ⅔ of the muscle, from the superior attachment of the muscle to the arcuate line, located approximately halfway between the umbilicus and the pubic bone. (See crosssectional Figures 10-4C and 10-4D on page 291.) The inguinal ligament is actually part of the inferior fascial attachment of the external abdominal oblique.

FUNCTIONS All four muscles of the anterior abdominal wall can compress the abdominal contents, which plays an important role in expiration and expulsion of abdominal contents (e.g., vomiting, expulsion of feces from the intestines, and expulsion of urine from the bladder). All of the muscles of the anterior abdominal wall, except for the transversus abdominis, can flex and laterally flex the trunk at the spinal joints and posteriorly tilt and elevate the same-side pelvis at the lumbosacral joint. The transversus abdominis cannot move the skeleton. Its action is compression of the abdominal contents. The external abdominal oblique of one side of the body is synergistic with the internal abdominal oblique on the opposite side of the body, with respect to rotation of the trunk at the spinal joints. Note the similarity of the direction of fibers of these muscles. It is very interesting to compare exactly how the four abdominal oblique muscles are synergistic and/or antagonistic to each other. For example, the right internal abdominal oblique and right external abdominal oblique are synergistic with regard to flexion in the sagittal plane, synergistic with regard to right lateral flexion in the frontal plane, and antagonistic with regard to rotations in the transverse plane. Hence two muscles may be both synergistic and antagonistic to each other. This exemplifies the idea that whenever we look to determine whether two muscles are synergistic or antagonistic to each other, we need to do so relative to a specific joint action within one plane.

MISCELLANEOUS 1. Two other muscles, the pyramidalis (see Figure 10-2, B) and the cremaster ( website.evolve), are also located in the anterior abdominal wall. 2. The anterior abdominal wall muscles are located within the superficial front line, the lateral line, and the spiral line myofascial meridians.

562

I N N E RVAT I O N The anterior abdominal wall muscles are innervated by intercostal nerves.

A R T E R I A L S U P P LY The rectus abdominis receives the majority of its arterial supply from the superior and inferior epigastric arteries. The three lateral anterior abdominal wall muscles receive the majority of their arterial supply from the posterior intercostal and subcostal arteries.

563

Anterior Abdominal Wall Muscles—Superficial View

FIGURE 10-37

Anterior views of the four muscles of the anterior abdominal wall. A, Superficial views.

564

Anterior Abdominal Wall Muscles—Deep View

FIGURE 10-37

B, Deep view. The psoas major and minor, iliacus, diaphragm, and quadratus lumborum have been ghosted in on the left.

565

Rectus Abdominis (of Anterior Abdominal Wall) The name, rectus abdominis, tells us that this muscle runs straight up the abdomen. Derivation rectus: L. straight abdominis: L. refers to the abdomen Pronunciation REK-tus ab-DOM-i-nis

ATTACHMENTS Pubis the crest and symphysis of the pubis to the Xiphoid Process and the Cartilage of Ribs Five through Seven

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes the trunk at the spinal joints 2. Laterally flexes the trunk at the spinal joints 3. Compresses the abdominopelvic cavity 4. Depresses the rib cage

Reverse Mover Actions 1. Posteriorly tilts the pelvis at the LS joint and flexes the lower trunk relative to the upper trunk (at the spinal joints) 2. Elevates the same-side pelvis at the LS joint and laterally flexes the lower trunk relative to the upper trunk (at the spinal joints) 3. Compresses the abdominopelvic cavity 4. Posteriorly tilts and elevates the same-side pelvis (as indicated above)

LS joint = lumbosacral joint

Standard Mover Action Notes • The rectus abdominis crosses the spinal joints anteriorly (with its fibers running vertically in the sagittal plane) and attaches onto the pelvis. When the pelvis is fixed and the rectus abdominis contracts, it pulls the trunk toward the pelvis anteriorly. Therefore the rectus abdominis flexes the trunk at the spinal joints. (action 1) • The rectus abdominis crosses the spinal joints slightly on the lateral side (with its fibers running vertically in the frontal plane). When the pelvis is fixed and the rectus abdominis contracts, it pulls the trunk toward the pelvis laterally. Therefore the rectus abdominis laterally flexes the trunk at the spinal joints. Because the rectus abdominis is very close to the midline, it has poor leverage for this action. (action 2) • The rectus abdominis attaches from the trunk to the pelvis in the anterior abdominal wall (with its fibers running vertically). When both the trunk and the pelvis are fixed and the rectus abdominis contracts, it tautens in toward the abdomen and exerts a compressive force on the abdominal contents. Compressing the abdominopelvic cavity also causes compression of the thoracic cavity because the abdominal contents push up against the diaphragm. Compression of the body cavities is important when expelling matter from the body, such as when breathing out, coughing, sneezing, vomiting, urinating, defecating, or giving birth. Helping to breathe out means that the rectus abdominis is an accessory muscle of respiration. (action 3)

566

FIGURE 10-38

Anterior view of the rectus abdominis bilaterally. The external abdominal oblique has been ghosted in on the left.

• If the pelvic attachment of the rectus abdominis is fixed and the muscle contracts, it will pull the rib cage attachment inferiorly. Normally, this would flex the entire trunk at the spinal joints. However, if extensor muscles of the trunk fix (stabilize) the trunk and prevent it from flexing, the lower rib cage will depress. This action is important when breathing out. Therefore the rectus abdominis can act directly on the rib cage as an accessory muscle of respiration. (action 4)

Reverse Mover Action Notes • When we think of motions of the spine, we usually think of the upper spine moving relative to the fixed lower spine. However, the reverse action of moving the lower spine relative to the upper spine is also possible. Further, if the pelvis is moved, because the LS joint does not allow a large degree of motion, the lumbar spine will move with the pelvis, causing the lower region of the spine to move relative to the upper region of the spine. These reverse actions often happen when the client is lying down so that the inferior attachment is mobile (e.g., turning in bed). (reverse actions 1, 2, 4) • The rectus abdominis crosses the spinal joints anteriorly (with its fibers running vertically in the sagittal plane) and attaches onto the pelvis. When the trunk is fixed and the rectus abdominis contracts, it pulls the pelvis toward the trunk anteriorly. This motion is called posterior tilt of the

567

pelvis and occurs at the LS joint. (reverse actions 1, 4) • If the upper attachment of the rectus abdominis stays fixed and the lower attachment moves, the pelvis will elevate on that side and depress on the opposite side at the LS joint. Therefore the rectus abdominis performs ipsilateral elevation and contralateral depression of the pelvis. Because the inferior attachment of the rectus abdominis is so close to the midline, it has very poor leverage for ipsilateral elevation of the pelvis. (reverse actions 2, 4) • The action of compression of the abdominal contents occurs when both ends of the rectus abdominis are fixed and the muscle belly tautens in toward the abdomen. Given that this effect is caused by an equal pull on both attachments, the reverse action is the same as the standard mover action. (reverse action 3)

Motions 1. The rectus abdominis has one line of pull upon the trunk in an oblique plane and therefore creates one motion, which is a combination of flexion and lateral flexion of the trunk at the spinal joints (as well as compression of the abdominopelvic cavity and depression of the rib cage). 2. The rectus abdominis has one line of pull upon the pelvis in an oblique plane and therefore creates one motion, which is a combination of posterior tilt and ipsilateral elevation (as well as compression of the abdominopelvic cavity).

Eccentric Antagonist Functions 1. Restrains/slows extension and opposite-side lateral flexion of the trunk 2. Restrains/slows anterior tilt and same-side depression of the pelvis 3. Restrains/slows expansion of the abdominopelvic cavity 4. Restrains/slows elevation of the rib cage

Eccentric Antagonist Function Note • The eccentric function of restraining/slowing extension of the trunk is important when returning to the floor during a curl-up exercise.

Isometric Stabilization Functions 1. Stabilizes the lumbar spinal joints 2. Stabilizes the pelvis 3. Stabilizes the rib cage

Isometric Stabilization Function Note • Stabilization of the lumbar spinal joints and the pelvis is stabilization of the core of the body (also known as the Powerhouse). Although the transversus abdominis is best known for this function, the other abdominal muscles can assist.

Additional Notes on Actions 1. Performing curl-ups (crunches, sit-ups) is an effective way to engage and strengthen the rectus abdominis. If neck discomfort occurs, reverse curl-ups can be done in which the pelvis is anteriorly tilted toward the trunk and lifted from the floor (and the lower trunk flexes up toward the upper trunk) instead of flexing the (upper) trunk toward the pelvis. 2. It is often asserted that moving the superior attachment of the rectus abdominis (such as flexing the trunk when doing a curl-up) only engages the upper compartments, and moving the inferior attachment (such as posteriorly tilting the pelvis when doing a reverse curl-up) only engages the lower compartments. However, it is not possible for the upper or lower compartments to generate tension if the entire muscle does not engage. For example, if the upper compartments were to be relaxed and the lower compartments were to engage to move the pelvis, the lower compartments would end up exerting their pull on the fibers of the upper compartments, stretching them longer, instead of exerting their pull to move the pelvis. Similarly, if the lower compartments were relaxed and the upper compartments engaged, their tension force would be dissipated pulling on (and lengthening) the relaxed lower compartment fibers. Therefore regardless of which attachment moves, all compartments of the rectus abdominis must engage and contract.

568

I N N E RVAT I O N Intercostal Nerves ventral rami of T5-T12

A R T E R I A L S U P P LY The Superior Epigastric Artery (a branch of the Internal Thoracic Artery) and the Inferior Epigastric Artery (a branch of the External Iliac Artery) and the terminal branches of the Subcostal and Posterior Intercostal Arteries (all branches of the Aorta)

PA L PAT I O N 1. With the client supine with a pillow placed under the knees, place palpating hands between the xiphoid process of the sternum and the adjacent ribs superiorly, and the pubis inferiorly. 2. Have the client alternate between mild flexion of the trunk (a small curl-up) and relaxation so that you can feel for the contraction of the rectus abdominis. 3. Palpate the rectus abdominis superiorly toward its rib cage attachment and inferiorly toward its pelvic attachment.

RELATIONSHIP TO OTHER STRUCTURES The rectus abdominis is superficial in the anteromedial abdomen. It is encased in the rectus sheath (also known as the abdominal aponeurosis), which is made up of the aponeuroses of the external and internal abdominal obliques and the transversus abdominis. Deep to the rectus abdominis is the peritoneum of the abdominal cavity. Lateral to the rectus abdominis are the other three muscles of the anterior abdominal wall, the external and internal abdominal obliques and the transversus abdominis. Medial to the rectus abdominis is the linea alba. The rectus abdominis is located within the superficial front line myofascial meridian.

MISCELLANEOUS 1. Three fibrous bands known as tendinous inscriptions transect the rectus abdominis muscle and divide it into four sections or boxes. For this reason, the rectus abdominis muscles in a welldeveloped individual are often known as the eight-pack (8-pack) muscle. (Actually, it is more often incorrectly labeled the six-pack [6-pack] muscle, because six of the eight compartments are more visible.) 2. Each rectus abdominis is encased in the rectus sheath, which is made up of the aponeuroses of the other three anterior abdominal wall muscles (the external and internal abdominal obliques and the transversus abdominis). The two rectus sheaths (left and right) meet in the midline of the abdomen and form the linea alba. 3. The four muscles of the anterior abdominal wall are the rectus abdominis, external abdominal oblique, internal abdominal oblique, and transversus abdominis. All of these muscles compress against the abdominal contents and help create a flat abdomen. 4. When old-fashioned straight-legged sit-ups are done, the movement that occurs is not flexion of the trunk at the spinal joints but rather anterior tilt of the pelvis at the hip joints (with the trunk moving up into the air because it is fixed to the pelvis). In this circumstance, the movers are not the abdominal wall muscles but rather the flexors of the hip joints (because anterior tilt of the pelvis at the hip joint is the reverse action of flexion of the thigh at the hip joint). The abdominal wall muscles do contract, but not as movers; they contract as fixators (i.e., stabilizers) of the pelvis, locking it to the trunk. 5. The lateral border of the rectus abdominis is a good landmark for palpation of the psoas major deep in the abdominopelvic cavity. Find the lateral border of the rectus abdominis and then drop immediately lateral to it to place your contact. Aim your pressure posteromedial toward the psoas major. 6. The width of the rectus abdominis is quite variable. It is often much wider than seen in Figure 1038.

569

570

External Abdominal Oblique (of Anterior Abdominal Wall) The name, external abdominal oblique, tells us that this muscle is located externally in the abdomen (superficial to the internal abdominal oblique) and its fibers are oriented obliquely. Derivation external: L. outside abdominal: L. refers to the abdomen oblique: L. slanting, diagonal Pronunciation EKS-turn-al ab-DOM-in-al o-BLEEK

ATTACHMENTS Anterior Iliac Crest, Pubic Bone, and the Abdominal Aponeurosis the pubic crest and tubercle to the Lower Eight Ribs (Ribs Five through Twelve) the inferior border of the ribs

FIGURE 10-39

Views of the right external abdominal oblique. A, Anterior view. B, Right lateral view.

FUNCTIONS 571

Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes the trunk at the spinal joints 2. Laterally flexes the trunk at the spinal joints 3. Contralaterally rotates the trunk at the spinal joints 4. Compresses the abdominopelvic cavity 5. Depresses the rib cage

Reverse Mover Actions 1. Posteriorly tilts the pelvis at the LS joint and flexes the lower trunk relative to the upper trunk (at the spinal joints) 2. Elevates the same-side pelvis at the LS joint and laterally flexes the lower trunk relative to the upper trunk (at the spinal joints) 3. Ipsilaterally rotates the pelvis at the LS joint and ipsilaterally rotates the lower trunk relative to the upper trunk (at the spinal joints) 4. Compresses the abdominopelvic cavity 5. Posteriorly tilts, elevates the same side, and ipsilaterally rotates the pelvis (as indicated above)

LS joint = lumbosacral joint

Standard Mover Action Notes • The external abdominal oblique crosses the spinal joints anteriorly (with its fibers running vertically in the sagittal plane) and attaches onto the pelvis. When the pelvis is fixed and the external abdominal oblique contracts, it pulls the trunk toward the pelvis anteriorly. Therefore the external abdominal oblique flexes the trunk at the spinal joints. (action 1) • The external abdominal oblique crosses the spinal joints laterally (with its fibers running vertically in the frontal plane). When the pelvis is fixed and the external abdominal oblique contracts, it pulls the trunk toward the pelvis laterally. Therefore the external abdominal oblique laterally flexes the trunk at the spinal joints. (action 2) • The external abdominal oblique wraps around the trunk (with its fibers running somewhat horizontally in the transverse plane). When the pelvis is fixed and the external abdominal oblique contracts, it pulls on the trunk, causing the anterior surface of the trunk to face the opposite side of the body from the side of the body to which it is attached. Therefore the external abdominal oblique contralaterally rotates the trunk at the spinal joints. (action 3) • The external and internal abdominal obliques are the prime movers of rotation of the trunk at the spinal joints. (action 3) • The external abdominal oblique attaches from the trunk to the pelvis in the abdominal wall (with its fibers running somewhat vertically). When both the trunk and the pelvis are fixed and the external abdominal oblique contracts, it exerts a compressive force on the abdomen. Compressing the abdominopelvic cavity also causes compression of the thoracic cavity because the abdominal contents push up against the diaphragm. Compression of the body cavities is important when expelling matter from the body, such as when breathing out, coughing, sneezing, vomiting, urinating, defecating, or giving birth. Helping to breathe out means that the external abdominal oblique is an accessory muscle of respiration. (action 4) • If the pelvic attachment of the external abdominal oblique is fixed and it contracts, it will pull the rib cage attachment inferiorly. Normally, this would flex and/or laterally flex the entire trunk at the spinal joints. However, if extensor and opposite-side lateral flexor muscles of the trunk fix (stabilize) the trunk and prevent it from moving, the lower eight ribs will depress. This action is important when breathing out. Therefore the external abdominal oblique can act directly on the rib cage as an accessory muscle of respiration. (action 5)

Reverse Mover Action Notes • When we think of motions of the spine, we usually think of the upper spine moving relative to the fixed lower spine. However, the reverse action of moving the lower spine relative to the upper spine is also possible. Further, if the pelvis is moved, because the LS joint does not allow a large degree of motion, the lumbar spine will move with the pelvis, causing the lower region of the spine to move relative to the upper region of the spine. These reverse actions often happen when the client is lying down so that the inferior attachment is mobile (e.g., turning in bed). (reverse actions 1, 2, 3, 5) • The external abdominal oblique crosses the spinal joints anteriorly (with its fibers running vertically in the sagittal plane) and attaches onto the pelvis. When the trunk is fixed and the external abdominal oblique contracts, it pulls the pelvis toward the trunk anteriorly. This motion is called posterior tilt of the pelvis and occurs at the LS joint. (reverse actions 1, 5) • When the superior attachments of the external abdominal oblique are fixed and it contracts, it pulls the lateral pelvis superiorly toward the rib cage. Therefore the external abdominal oblique elevates the pelvis on that side at the LS joint. Elevation of one side of the pelvis causes the other

572

side to depress. Therefore the external abdominal oblique performs ipsilateral elevation and contralateral depression of the pelvis. (reverse actions 2, 5) • When the superior attachments of the external abdominal oblique are fixed and it contracts, it pulls on the inferior attachment, the pelvis, causing the anterior surface of the pelvis to face the same side of the body to which the external abdominal oblique is attached (because the fibers of the external abdominal oblique have a horizontal orientation in the transverse plane). Therefore the external abdominal oblique ipsilaterally rotates the pelvis at the LS joint. (reverse action 3) • The reverse action of contralaterally rotating the upper spine (relative to the fixed lower spine and pelvis) is to ipsilaterally rotate the pelvis and lower spine (relative to the fixed upper spine). In other words, if the right-sided external abdominal oblique does left rotation of the upper spine, its reverse action would be to do right rotation of the pelvis at the LS joint and to do right rotation of the lower spine relative to the upper spine. (reverse actions 3, 5) • The action of compression of the abdominal contents occurs when both ends of the external abdominal oblique are fixed and the muscle belly tautens in toward the abdomen. Given that this effect is caused by an equal pull on both attachments, the reverse action is the same as the standard mover action. (reverse action 4)

Motions 1. The external abdominal oblique has one line of pull upon the trunk in an oblique plane and therefore creates one motion, which is a combination of flexion, lateral flexion, and contralateral rotation of the trunk at the spinal joints (as well as compression of the abdominopelvic cavity and depression of the rib cage). 2. The external abdominal oblique has one line of pull upon the pelvis in an oblique plane and therefore creates one motion, which is a combination of posterior tilt, ipsilateral elevation, and ipsilateral rotation (as well as compression of the abdominopelvic cavity).

Eccentric Antagonist Functions 1. Restrains/slows extension and opposite-side lateral flexion of the trunk 2. Restrains/slows anterior tilt and same-side depression of the pelvis 3. Restrains/slows ipsilateral rotation of the upper trunk and contralateral rotation of the pelvis and lower trunk 4. Restrains/slows expansion of the abdominopelvic cavity 5. Restrains/slows elevation of the rib cage

Eccentric Antagonist Function Note • The eccentric function of restraining/slowing extension of the trunk is important when returning to the floor during a curl-up exercise.

Isometric Stabilization Functions 1. Stabilizes the lumbar spinal joints 2. Stabilizes the pelvis 3. Stabilizes the rib cage

Isometric Stabilization Function Note • Stabilization of the lumbar spinal joints and the pelvis is stabilization of the core of the body (also known as the Powerhouse). Although the transversus abdominis is best known for this function, the other abdominal muscles can assist.

Additional Notes on Actions 1. With regard to flexion, all four abdominal obliques are synergistic to each other. 2. With regard to lateral flexion of the trunk at the spinal joints, the external and internal abdominal obliques on the same side are synergistic to each other. 3. The external abdominal oblique is a contralateral rotator of the trunk at the spinal joints, and the internal abdominal oblique is an ipsilateral rotator of the trunk at the spinal joints; hence with regard to trunk rotation (i.e., transverse plane actions), they are considered to be antagonistic to each other. However, the external abdominal oblique on one side of the body is synergistic with the

573

internal abdominal oblique on the opposite side of the body during trunk rotation. Similarly, the external abdominal oblique is an ipsilateral rotator of the pelvis at the LS joint, and the internal abdominal oblique is a contralateral rotator of the pelvis at the LS joint; hence with regard to pelvic rotation (i.e., transverse plane actions), they are considered to be antagonistic to each other. However, the external abdominal oblique on one side of the body is synergistic with the internal abdominal oblique on the opposite side of the body during pelvic rotation. Note the similarity of the direction of their fibers. 4. Performing curl-ups (crunches, sit-ups) is an effective way to engage and strengthen the external abdominal obliques, especially if rotation is added to the flexion (some repetitions rotated to the right and some repetitions rotated to the left). If neck discomfort occurs, reverse curl-ups can be done in which the pelvis is anteriorly tilted toward the trunk and lifted from the floor (and the lower trunk flexes up toward the upper trunk) instead of flexing the (upper) trunk toward the pelvis. The pelvis can also be rotated as it is lifted to better engage the external abdominal obliques.

I N N E RVAT I O N Intercostal Nerves ventral rami of T7-T12

A R T E R I A L S U P P LY The Subcostal and Posterior Intercostal Arteries (all branches of the Aorta) and the Deep Circumflex Iliac Artery (a branch of the External Iliac Artery) and the Inferior Epigastric Artery (a branch of the External Iliac Artery)

PA L PAT I O N 1. With the client supine with a pillow placed under the knees, place palpating hands on the anterolateral abdomen between the iliac crest and the lower ribs. 2. Ask the client to rotate the trunk at the spinal joints to the opposite side (along with slight flexion of the trunk) and feel for the contraction of the external abdominal oblique. 3. Continue palpating the external abdominal oblique superolaterally toward the rib attachments and inferomedially toward the iliac crest and the abdominal aponeurosis.

RELATIONSHIP TO OTHER STRUCTURES The external abdominal oblique is located lateral to the rectus abdominis. The external abdominal oblique is the most superficial of the three layers of the anterolateral abdominal wall. Directly deep to the external abdominal oblique is the internal abdominal oblique, and deep to that is the transversus abdominis. The external abdominal oblique interdigitates with the serratus anterior (at ribs five through nine) along the anterolateral body wall. The external abdominal oblique’s fibers also meet fibers of the latissimus dorsi (at approximately a perpendicular angle at ribs ten through twelve) along the posterolateral body wall. Keep in mind that the external abdominal oblique is located not only in the anterior abdominal wall but also in the lateral abdominal wall; it reaches all the way to the posterior abdominal wall, where it interdigitates with the latissimus dorsi at ribs ten through twelve. The external abdominal oblique is located within the lateral line and spiral line and involved with the superficial front line myofascial meridians.

MISCELLANEOUS 1. If you were to put your hand into a coat pocket, your fingers would be pointing along the direction of the fibers of the external abdominal oblique on that side. For this reason, the external abdominal obliques are sometimes called the pocket muscles. 2. The aponeurosis of the external abdominal oblique, between the anterior superior iliac spine and the pubic tubercle, forms the inguinal ligament. 3. The abdominal aponeurosis is actually the midline aponeurosis of the three anterolateral abdominal wall muscles (external and internal abdominal obliques and the transversus abdominis).

574

The abdominal aponeurosis is also known as the rectus sheath because it envelops/ensheathes the rectus abdominis.

575

Internal Abdominal Oblique (of Anterior Abdominal Wall) The name, internal abdominal oblique, tells us that this muscle is located internally in the abdomen (deep to the external abdominal oblique) and its fibers are oriented obliquely. Derivation internal: L. inside abdominal: L. refers to the abdomen oblique: L. slanting, diagonal Pronunciation in-TURN-al ab-DOM-in-al o-BLEEK

ATTACHMENTS Inguinal Ligament, Iliac Crest, and the Thoracolumbar Fascia the lateral ⅔ of the inguinal ligament to the Lower Three Ribs (Ten through Twelve) and the Abdominal Aponeurosis

FIGURE 10-40

Views of the right internal abdominal oblique. A, Anterior view. B, Right lateral view.

FUNCTIONS

576

Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes the trunk at the spinal joints 2. Laterally flexes the trunk at the spinal joints 3. Ipsilaterally rotates the trunk at the spinal joints 4. Compresses the abdominopelvic cavity 5. Depresses the rib cage

Reverse Mover Actions 1. Posteriorly tilts the pelvis at the LS joint and flexes the lower trunk relative to the upper trunk (at the spinal joints) 2. Elevates the same-side pelvis at the LS joint and laterally flexes the lower trunk relative to the upper trunk (at the spinal joints) 3. Contralaterally rotates the pelvis at the LS joint and contralaterally rotates the lower trunk relative to the upper trunk (at the spinal joints) 4. Compresses the abdominopelvic cavity 5. Posteriorly tilts, elevates the same-side, and contralaterally rotates the pelvis (as indicated above)

LS joint = lumbosacral joint

Standard Mover Action Notes • The internal abdominal oblique crosses the spinal joints anteriorly (with its fibers running vertically in the sagittal plane) and attaches onto the pelvis. When the pelvis is fixed and the internal abdominal oblique contracts, it pulls the trunk toward the pelvis anteriorly. Therefore the internal abdominal oblique flexes the trunk at the spinal joints. (action 1) • The internal abdominal oblique crosses the spinal joints laterally (with its fibers running vertically in the frontal plane). When the pelvis is fixed and the internal abdominal oblique contracts, it pulls the trunk toward the pelvis laterally. Therefore the internal abdominal oblique laterally flexes the trunk at the spinal joints. (action 2) • The internal abdominal oblique wraps around the trunk (with its fibers running somewhat horizontally in the transverse plane). When the pelvis is fixed and the internal abdominal oblique contracts, it pulls on the trunk, causing the anterior surface of the trunk to face the same side of the body to which it is attached. Therefore the internal abdominal oblique ipsilaterally rotates the trunk at the spinal joints. (action 3) • The external and internal abdominal obliques are the prime movers of rotation of the trunk at the spinal joints. (action 3) • The internal abdominal oblique attaches from the trunk to the pelvis in the anterior abdominal wall (with its fibers running somewhat vertically). When both the trunk and the pelvis are fixed and the internal abdominal oblique contracts, it exerts a compressive force on the abdomen. Compressing the abdominopelvic cavity also causes compression of the thoracic cavity because the abdominal contents push up against the diaphragm. Compression of the body cavities is important when expelling matter from the body, such as when breathing out, coughing, sneezing, vomiting, urinating, defecating, or giving birth. Helping to breathe out means that the internal abdominal oblique is an accessory muscle of respiration. (action 4) • If the pelvic attachment of the internal abdominal oblique is fixed and it contracts, it will pull the rib cage attachment inferiorly. Normally, this would flex and/or laterally flex the entire trunk at the spinal joints. However, if extensor and opposite-side lateral flexor muscles of the trunk fix (stabilize) the trunk and prevent it from moving, the lower ribs will depress. This action is important when breathing out. Therefore the internal abdominal oblique can act directly on the rib cage as an accessory muscle of respiration. (action 5)

Reverse Mover Action Notes • When we think of motions of the spine, we usually think of the upper spine moving relative to the fixed lower spine. However, the reverse action of moving the lower spine relative to the upper spine is also possible. Further, if the pelvis is moved, because the LS joint does not allow a large degree of motion, the lumbar spine will move with the pelvis, causing the lower region of the spine to move relative to the upper region of the spine. These reverse actions often happen when the client is lying down so that the inferior attachment is mobile (e.g., turning in bed). (reverse actions 1, 2, 3, 5) • The internal abdominal oblique crosses the spinal joints anteriorly (with its fibers running vertically in the sagittal plane) and attaches onto the pelvis. When the trunk is fixed and the internal abdominal oblique contracts, it pulls the pelvis toward the trunk anteriorly. This motion is called posterior tilt of the pelvis and occurs at the LS joint. (reverse actions 1, 5) • When the superior attachments of the internal abdominal oblique are fixed and it contracts, it pulls the lateral pelvis superiorly toward the rib cage. Therefore the internal abdominal oblique elevates the pelvis on that side at the LS joint. Elevation of one side of the pelvis causes the other

577

side to depress. Therefore the internal abdominal oblique performs ipsilateral elevation and contralateral depression of the pelvis. (reverse actions 2, 5) • When the superior attachments of the internal abdominal oblique are fixed and it contracts, it pulls on the inferior attachment, the pelvis, causing the anterior surface of the pelvis to face the opposite side of the body from the side of the body on which the internal abdominal oblique is attached (because the fibers of the internal abdominal oblique have a horizontal orientation in the transverse plane). Therefore the internal abdominal oblique contralaterally rotates the pelvis at the LS joint. (reverse action 3) • The reverse action of ipsilaterally rotating the upper spine (relative to the fixed lower spine and pelvis) is to contralaterally rotate the pelvis and lower spine (relative to the fixed upper spine). In other words, if the right-sided internal abdominal oblique does right rotation of the upper spine, its reverse action would be to do left rotation of the pelvis at the LS joint and to do left rotation of the lower spine relative to the upper spine. (reverse actions 3, 5) • The action of compression of the abdominal contents occurs when both ends of the internal abdominal oblique are fixed and the muscle belly tautens in toward the abdomen. Given that this effect is caused by an equal pull on both attachments, the reverse action is the same as the standard mover action. (reverse action 4)

Motions 1. The internal abdominal oblique has one line of pull upon the trunk in an oblique plane and therefore creates one motion, which is a combination of flexion, lateral flexion, and ipsilateral rotation of the trunk at the spinal joints (as well as compression of the abdominopelvic cavity and depression of the rib cage). 2. The internal abdominal oblique has one line of pull upon the pelvis in an oblique plane and therefore creates one motion, which is a combination of posterior tilt, ipsilateral elevation, and contralateral rotation (as well as compression of the abdominopelvic cavity).

Eccentric Antagonist Functions 1. Restrains/slows extension and opposite-side lateral flexion of the trunk 2. Restrains/slows anterior tilt and same-side depression of the pelvis 3. Restrains/slows contralateral rotation of the trunk and ipsilateral rotation of the pelvis and lower trunk 4. Restrains/slows expansion of the abdominopelvic cavity 5. Restrains/slows elevation of the rib cage

Eccentric Antagonist Function Note • The eccentric function of restraining/slowing extension of the trunk is important when returning to the floor during a curl-up exercise.

Isometric Stabilization Functions 1. Stabilizes the spinal joints 2. Stabilizes the pelvis 3. Stabilizes the rib cage

Isometric Stabilization Function Notes • Stabilization of the lumbar spinal joints and the pelvis is stabilization of the core of the body (also known as the Powerhouse). Although the transversus abdominis is best known for this function, the other abdominal muscles can assist.

Additional Notes on Actions 1. With regard to flexion, all four abdominal obliques are synergistic to each other. 2. With regard to lateral flexion of the trunk at the spinal joints, the external and internal abdominal obliques on the same side are synergistic to each other. 3. The internal abdominal oblique is an ipsilateral rotator of the trunk at the spinal joints, and the external abdominal oblique is a contralateral rotator of the trunk at the spinal joints; hence with regard to trunk rotation (i.e., transverse plane actions), they are considered to be antagonistic to

578

each other. However, the internal abdominal oblique on one side of the body is synergistic with the external abdominal oblique on the opposite side of the body during trunk rotation. Similarly, the internal abdominal oblique is a contralateral rotator of the pelvis at the LS joint, and the external abdominal oblique is an ipsilateral rotator of the pelvis at the LS joint; hence with regard to pelvic rotation (i.e., transverse plane actions), they are considered to be antagonistic to each other. However, the internal abdominal oblique on one side of the body is synergistic with the external abdominal oblique on the opposite side of the body during pelvic rotation. Note the similarity of the direction of their fibers. 4. Performing curl-ups (crunches, sit-ups) is an effective way to engage and strengthen the internal abdominal obliques, especially if rotation is added to the flexion (some repetitions rotated to the right and some repetitions rotated to the left). If neck discomfort occurs, reverse curl-ups can be done in which the pelvis is anteriorly tilted toward the trunk and lifted from the floor (and the lower trunk flexes up toward the upper trunk) instead of flexing the (upper) trunk toward the pelvis. The pelvis can also be rotated as it is lifted to better engage the internal abdominal obliques.

I N N E RVAT I O N Intercostal Nerves ventral rami of T7-L1

A R T E R I A L S U P P LY The Subcostal and Posterior Intercostal Arteries (all branches of the Aorta) and the Deep Circumflex Iliac Artery (a branch of the External Iliac Artery) and the Inferior Epigastric Artery (a branch of the External Iliac Artery)

PA L PAT I O N 1. With the client supine with a pillow placed under the knees, place palpating hands on the anterolateral abdomen between the iliac crest and the lower ribs. 2. Ask the client to actively rotate the trunk at the spinal joints to the same side (along with slight flexion of the trunk) and feel for the contraction of the internal abdominal oblique. 3. Continue palpating the internal abdominal oblique superiorly and inferiorly toward its attachments. 4. Note: Discerning the contraction of the internal abdominal oblique from the contraction of the external abdominal oblique can be challenging if the client has not developed these muscles.

RELATIONSHIP TO OTHER STRUCTURES The internal abdominal oblique is located lateral to the rectus abdominis. The internal abdominal oblique is the middle muscle of the three anterolateral abdominal wall muscles. It is deep to the external abdominal oblique and superficial to the transversus abdominis. Keep in mind that the internal abdominal oblique is located not only in the anterior abdominal wall but also in the lateral abdominal wall and posterior abdominal wall. It attaches posteriorly into the thoracolumbar fascia (just lateral to the erector spinae), and via the thoracolumbar fascia, attaches into the transverse processes of the lumbar spine. The internal abdominal oblique is located within the lateral line and spiral line and involved with the superficial front line myofascial meridians.

MISCELLANEOUS 1. If you were to put your hand into a coat pocket, your fingers would be pointing along the direction of the fibers of the external abdominal oblique on that side. The fibers of the internal abdominal oblique are 90 degrees opposite (i.e., perpendicular) to those of the external abdominal oblique. 2. The midline aponeuroses of the external abdominal oblique, the internal abdominal oblique, and the transversus abdominis form the rectus sheath that envelops/ensheathes the rectus abdominis. Part of the internal abdominal oblique’s midline aponeurosis actually splits and wraps around the

579

rectus abdominis both superficially and deep. (This occurs superior to the arcuate line, which is located approximately halfway between the umbilicus and the pubic bone. See cross-sectional Figures 10-4C and 10-4D on page 291.)

580

Transversus Abdominis (of Anterior Abdominal Wall) The name, transversus abdominis, tells us that this muscle runs transversely across the abdomen. Derivation transversus: L. running transversely abdominis: L. refers to the abdomen Pronunciation trans-VER-sus ab-DOM-i-nis

ATTACHMENTS Inguinal Ligament, Iliac Crest, Thoracolumbar Fascia, and the Lower Costal Cartilages the lateral ⅔ of the inguinal ligament; the costal cartilages of ribs seven through twelve to the Abdominal Aponeurosis linea alba

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions

Reverse Mover Actions 1. Compresses abdominopelvic cavity 1. Compresses abdominopelvic cavity

Standard Mover Action Notes • The transversus abdominis attaches from the thoracolumbar fascia posteriorly, to the linea alba anteriorly, and from the lower ribs superiorly, to the iliac crest and inguinal ligament inferiorly (with its fibers running horizontally). The transversus abdominis does not cause skeletal movement. Instead, the two transversus abdominis muscles bilaterally act like a sphincter muscle, pulling in and compressing the abdominopelvic cavity. Compressing the abdominopelvic cavity also causes compression of the thoracic cavity because the abdominal contents push up against the diaphragm. Compression of the body cavities is important when expelling matter from the body, such as when breathing out, coughing, sneezing, vomiting, urinating, defecating, or giving birth. Helping to breathe out means that the transversus abdominis is an accessory muscle of respiration. (action 1)

581

FIGURE 10-41

Views of the right transversus abdominis. A, Anterior view. B, Right lateral view.

Reverse Mover Action Notes • The action of compression of the abdominal contents occurs when both ends of the transversus abdominis are fixed and the muscle belly tautens in toward the abdomen. Given that this effect is caused by an equal pull on both attachments, the reverse action is the same as the standard action. (reverse action 1)

Motion 1. The transversus abdominis has one line of pull around the body (in the transverse plane), and therefore its motion is compression of the abdominopelvic cavity.

Eccentric Antagonist Function 1. Restrains/slows expansion of the abdominopelvic cavity

Isometric Stabilization Functions 1. Stabilizes the lumbar spinal joints 2. Stabilizes the pelvis 3. Stabilizes the lower ribs

Isometric Stabilization Function Notes • The transversus abdominis, along with the multifidus, is credited as being one of the most important muscles for core stabilization of the body. The core of the body (also known as the Powerhouse) is bounded by the anterior, posterior, and lateral abdominal walls, and the diaphragm above and the pelvic floor below. • The transversus abdominis can also tighten and stabilize the linea alba. This can help increase the efficiency of the actions of the external and internal abdominal obliques because they attach via the abdominal aponeurosis into the linea alba.

Additional Note on Actions

582

1. Because the fibers of the transversus abdominis run horizontally in the transverse plane, it would seem that this muscle is ideally suited to create rotation of the trunk at the spinal joints; however, this action seems to be negligible at best. For rotation to occur, its anterior attachment (abdominal aponeurosis) would have to stay fixed, so that it could pull on its spinal attachment (theoretically causing the spinous processes to rotate to that side, which rotates the anterior surfaces of the vertebral bodies to the opposite side, creating contralateral rotation of the trunk). However, fixing the anterior attachment (abdominal aponeurosis) cannot be done by the contralateral transversus abdominis because it would then also pull on the same vertebrae from the opposite side, fighting the ability of the other transversus abdominis to rotate the vertebrae. (Note: The same problem would occur if the contralateral external abdominal oblique were to contract to stabilize the abdominal aponeurosis. Therefore, for rotation to occur, the abdominal aponeurosis would have to be stabilized by the contralateral internal abdominal oblique.)

I N N E RVAT I O N Intercostal Nerves ventral rami of T7-L1

A R T E R I A L S U P P LY The Subcostal and Posterior Intercostal Arteries (all branches of the Aorta) and the Deep Circumflex Iliac Artery (a branch of the External Iliac Artery) and the Inferior Epigastric Artery (a branch of the External Iliac Artery)

PA L PAT I O N 1. With the client supine with a pillow placed under the knees, place palpating hands on the anterolateral abdomen between the iliac crest and the lower ribs. 2. Have the client forcefully exhale and feel for the contraction of the transversus abdominis. 3. The external and internal abdominal obliques will likely engage with this action as well. Discerning the contraction of the transversus abdominis from these other muscles is extremely challenging.

RELATIONSHIP TO OTHER STRUCTURES The transversus abdominis is lateral to the rectus abdominis. The transversus abdominis is the deepest of the three anterolateral abdominal wall muscles. It is directly deep to the internal abdominal oblique. Deep to the transversus abdominis is the peritoneum of the abdominal cavity. Keep in mind that the transversus abdominis is located not only in the anterior abdominal wall but also in the lateral abdominal wall and the posterior abdominal wall. It attaches posteriorly into the thoracolumbar fascia (just lateral to the erector spinae), and via the thoracolumbar fascia, attaches into the transverse processes of the lumbar spine. The transversus abdominis is involved with the superficial front line, lateral line, and spiral line myofascial meridians.

MISCELLANEOUS 1. The transversus abdominis contributes (along with the external and internal abdominal obliques) to the rectus sheath, which encloses/ensheathes the rectus abdominis. 2. The upper fibers of the transversus abdominis are contiguous and blend with the diaphragm and the transversus thoracis (another muscle that runs transversely in the trunk). 3. The transversus abdominis is sometimes called the corset muscle because it wraps around the abdomen like a corset and, like a corset, it functions to hold in the abdomen.

583

584

Psoas Minor The name, psoas minor, tells us that this muscle is located in the loin (low back) area and is small (smaller than the psoas major). Derivation psoas: Gr. loin (low back) minor: L. smaller Pronunciation SO-as MY-nor

ATTACHMENTS Anterolateral Bodies of T12 and L1 and the disc between T12 and L1 to the Pubis the pectineal line of the pubis and the iliopectineal eminence (of the ilium and the pubis)

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions

Reverse Mover Actions 1. Posteriorly tilts the pelvis at the LS joint and flexes the lower trunk relative to the upper trunk (at the spinal joints) 1. Flexes the trunk at the spinal joints 2. Laterally flexes the trunk at the spinal joints 2. Elevates the same-side pelvis at the LS joint and laterally flexes the lower trunk relative to the upper trunk (at the spinal joints)

LS joint = lumbosacral joint

Standard Mover Action Notes • The psoas minor crosses the vertebral column anteriorly (with its fibers running vertically in the sagittal plane) and attaches onto the pelvis. When the pelvis is fixed and the psoas minor contracts, the trunk flexes at the spinal joints toward the pelvis. (action 1) • The psoas minor crosses the spinal joints slightly on the lateral side (with its fibers running vertically in the frontal plane). When the pelvis is fixed and the psoas minor contracts, it pulls the trunk toward the pelvis laterally. Therefore the psoas minor laterally flexes the trunk at the spinal joints. However, because the psoas minor is very close to the midline, it has poor leverage for this action. (action 2)

Reverse Mover Action Notes • When we think of motions of the spine, we usually think of the upper spine moving relative to the fixed lower spine. However, the reverse action of moving the lower spine relative to the upper spine is also possible (this usually occurs when the client is lying down so that the inferior attachment is mobile). Further, if the pelvis is moved, because the LS joint does not allow a large degree of motion, the lumbar spine will move with the pelvis, causing the lower spine to move relative to the upper spine. (reverse actions 1, 2)

585

FIGURE 10-42

Anterior view of the psoas minor bilaterally. The psoas major has been ghosted in on the left.

• The psoas minor crosses the vertebral column anteriorly (with its fibers running vertically in the sagittal plane) and attaches onto the pelvis. When the trunk is fixed and the psoas minor contracts, it pulls the pelvis anteriorly and superiorly toward the spine. This motion is called posterior tilt of the pelvis and occurs at the LS joint. (reverse action 1) • If the upper attachment of the psoas minor stays fixed and the lower attachment moves, the pelvis will elevate on that side and depress on the opposite side. Therefore the psoas minor ipsilaterally elevates and contralaterally depresses the pelvis at the LS joint. (reverse action 2) • Because the inferior attachment of the psoas minor is so close to the midline, it has very poor leverage for ipsilateral elevation of the pelvis. (reverse action 2)

Motions 1. The psoas minor has one line of pull upon the trunk in an oblique plane and therefore creates one motion, which is a combination of flexion and lateral flexion of the trunk at the spinal joints. 2. The psoas minor has one line of pull upon the pelvis in an oblique plane and therefore creates one motion, which is a combination of posterior tilt and ipsilateral elevation.

Eccentric Antagonist Functions

586

1. Restrains/slows extension and opposite-side lateral flexion of the trunk 2. Restrains/slows anterior tilt and same-side depression of the pelvis

Isometric Stabilization Functions 1. Stabilizes the lumbar spinal joints 2. Stabilizes the pelvis

Additional Note on Actions 1. The psoas minor is fairly weak and usually not considered to be a very important muscle.

I N N E RVAT I O N L1 Spinal Nerve a branch from L1

A R T E R I A L S U P P LY Lumbar Arteries (branches of the Descending Aorta) and the Arteria Lumbalis Ima of the Median Sacral Artery (a branch of the Aorta), the lumbar branch of the Iliolumbar Artery (a branch of the Internal Iliac Artery), and the Common Iliac Artery (a branch of the Aorta)

PA L PAT I O N 1. With the client supine, place your palpating fingers on the anterior abdomen, halfway between the umbilicus and anterior superior iliac spine (ASIS), just lateral to the rectus abdominis. 2. First locate the psoas major (see the Palpation section for this muscle in Chapter 14. 3. Now palpate for the psoas minor lying on the psoas major. Do not engage the psoas minor because it will cause the more superficial abdominal wall muscles to contract and block your palpation. 4. If the psoas minor is tight, it may be possible to feel and distinguish it from the psoas major.

RELATIONSHIP TO OTHER STRUCTURES The psoas minor is deep in the abdomen and lies directly anterior to the psoas major. Anterior (superficial) to the psoas minor are the abdominal viscera. The psoas minor is located within the deep front line myofascial meridian.

MISCELLANEOUS 1. The psoas minor is absent in about 40% of the population. 2. The iliopectineal eminence (of the ilium and pubis) is also known as the iliopubic eminence. 3. A condition called psoas minor syndrome has been reported wherein the psoas minor in teenagers has not kept up with the osseous growth of the trunk and pelvis and consequently is pulled taut and becomes painful.

587

REVIEW QUESTIONS 1. What generalization can be made about the muscles of the spine when looked at from a depth perspective? ____________________________ ____________________________ ____________________________ 2. Which of the erector spinae muscles runs far enough laterally to be deep to the scapula? ____________________________ 3. Which of the paraspinal muscles comprises the largest mass of musculature in the neck? ____________________________ 4. It has been suggested that the main role of the rotatores is not movement, but_______. 5. The _______ and the _______ run between the anterior and middle scalenes. Tightness of these muscles can contribute to which thoracic outlet syndromes? 6. The prevertebral group is made up of what four muscles? As a group, what is their primary function? ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ 7. A portion of the _______ is superficial in the posterior triangle of the neck, between the trapezius and the sternocleidomastoid. 8. What are the borders of the suboccipital triangle and what is contained within these borders? ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ 9. Explain the importance of the stabilization of the twelfth rib to breathing by the quadratus lumborum. ____________________________ ____________________________ ____________________________ ____________________________ 10. The inguinal ligament is part of the inferior fascial attachment of what muscle? ____________________________ For answers to these questions, visit http://evolve.elsevier.com/Muscolino/muscular

588

THINK IT THROUGH Discuss the synergist/antagonist relationship between the abdominal oblique muscles. How does this relationship relate to a client’s history, assessment, and treatment? ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________

589

C H A P T E R 11

590

Muscles of the Rib Cage Joints CHAPTER OUTLINE External intercostals Internal intercostals Transversus thoracis Diaphragm Serratus posterior superior Serratus posterior inferior Levatores costarum Subcostales

OBJECTIVES After completing this chapter, the student should be able to perform the following for each of the muscles covered in the chapter: 1. Explain the general structure. 2. Explain the general function. 3. State the attachments. 4. State the standard mover actions. 5. State the reverse mover actions. 6. Discuss the line(s) of pull the muscle has and the motion(s) created. 7. State the eccentric antagonist functions. 8. State the isometric stabilization functions. 9. State the innervation.

10. State the arterial supply. 11. Describe the starting position for palpation. 12. Describe the steps for palpation. 13. Discuss the muscle’s relationship to other body structures. 14. Discuss additional information that may help with palpation, assessment, and clinical decision-making. CHAPTER OVERVIEW The muscles addressed in this chapter are the muscles whose principal function is usually considered to be movement of the rib cage (at the sternocostal and costospinal joints). Other muscles in the body can also move the ribs, but they are placed in different chapters because their primary function is usually considered to be at another joint. These muscles are covered in Chapters 4, 5, and 10. Overview of STRUCTURE Structurally, muscles that move the rib cage attach to the rib cage. The other attachment of these muscles is usually considered to be either superior or inferior to the rib attachment for elevation or depression motions, respectively. These muscles may be located anteriorly,

591

posteriorly, and/or laterally. Overview of FUNCTION The following general rules regarding actions can be stated for the functional groups of muscles of the rib cage: If a muscle attaches to the rib cage and its other attachment is superior to the rib cage attachment, it can elevate the ribs to which it is attached at the sternocostal and costospinal joints. If a muscle attaches to the rib cage and its other attachment is inferior to the rib cage attachment, it can depress the ribs to which it is attached at the sternocostal and costospinal joints. As a rule, muscles that elevate ribs contract with inspiration, and muscles that depress ribs contract with expiration. One notable exception to this rule is when muscles depress the lower ribs and contract to stabilize the lower rib cage attachment of the diaphragm so that when the diaphragm contracts, it can better depress its dome (central tendon) toward the rib cage attachment for abdominal (belly) breathing.

http://evolve.elsevier.com/Muscolino/muscular

592

Posterior Views of the Muscles of the Trunk— Superficial and Intermediate Views

FIGURE 11-1

Posterior views of the muscles of the trunk. A, Superficial view on the left and an intermediate view on the right.

593

Posterior Views of the Muscles of the Trunk—Deep Views

FIGURE 11-1 B, Two deep views; the right side is deeper than the left. The external abdominal oblique has been ghosted in on the left side. The intercostals have been ghosted in on the right side between ribs eight and twelve to show the subcostales.

594

Anterior Views of the Muscles of the Trunk— Superficial and Intermediate Views

FIGURE 11-2 Anterior views of the muscles of the trunk. A, Superficial view on the right and an intermediate view on the left. The muscles of the neck and thigh have been ghosted in.

595

Anterior Views of the Muscles of the Trunk—Deep Views

FIGURE 11-2

B, Deep views with the posterior abdominal wall seen on the left. The muscles of the neck, arm, and thigh have been ghosted in.

596

Right Lateral View of the Muscles of the Trunk— Superficial View

FIGURE 11-3

Right lateral view of the muscles of the trunk. A, Superficial view. The latissimus dorsi and deltoid have been ghosted in.

597

Right Lateral View of the Muscles of the Trunk—Deep View

FIGURE 11-3

B, Deep view.

598

External Intercostals The name, external intercostals, tells us that these muscles are located between ribs and are external (superficial to the internal intercostals). Derivation external: L. outside inter: L. between costals: L. refers to the ribs Pronunciation EKS-turn-al in-ter-KOS-tals

ATTACHMENTS In the Intercostal Spaces of Ribs One through Twelve Each external intercostal attaches from the inferior border of one rib to the superior border of the rib directly inferior.

FIGURE 11-4

Views of the right external intercostals. A, Anterior view. B, Posterior view.

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Elevate ribs two through twelve at the sternocostal and costospinal joints 2. Contralaterally rotate the trunk at the spinal joints

Reverse Mover Actions 1. Depress ribs one through eleven at the sternocostal and costospinal joints 2. Ipsilaterally rotate the lower trunk relative to the upper trunk (at the spinal joints)

599

3. Flex the trunk at the spinal joints

3. Flex the lower trunk relative to the upper trunk (at the spinal joints)

4. Extend the trunk at the spinal joints

4. Extend the lower trunk relative to the upper trunk (at the spinal joints)

5. Laterally flex the trunk at the spinal joints

5. Laterally flex the lower trunk relative to the upper trunk (at the spinal joints)

Standard Mover Action Notes • The external intercostals are located in the intercostal spaces and attach from the inferior margin of the more superior rib to the superior margin of the more inferior rib. When the superior rib is fixed and an external intercostal muscle contracts, it pulls superiorly on the inferior rib, thus elevating it. Therefore the external intercostals elevate ribs two through twelve at the sternocostal and costospinal joints. Elevation of the ribs is necessary for inspiration; therefore the external intercostals are respiratory muscles. (action 1) • The external intercostals have the same fiber direction as the external abdominal oblique on the same side of the body; therefore they have the same actions of the trunk, namely, contralateral rotation, flexion, and lateral flexion. (actions 2, 3, 5) • The anterior external intercostal fibers can do flexion. The posterior fibers can do extension. All fibers, but especially the most lateral ones, can do lateral flexion. (actions 3, 4, 5)

Reverse Mover Action Notes • The external intercostals are located in the intercostal spaces and attach from the inferior margin of the more superior rib to the superior margin of the more inferior rib. If the lower rib is fixed and an external intercostal muscle contracts, it pulls inferiorly on the superior rib, thus depressing it. Therefore the external intercostals depress ribs one through eleven at the sternocostal and costospinal joints. Depression of the ribs is necessary for expiration; therefore the external intercostals are respiratory muscles. (reverse action 1) • The standard mover action occurs when the upper trunk moves toward the lower trunk. The reverse mover action occurs if the superior attachments are fixed and the inferior attachments move so that the lower trunk moves toward the upper trunk. This usually occurs when the client is lying down so that the lower trunk is mobile. It should be noted that the reverse action of flexion is flexion, the reverse action of extension is extension, and the reverse action of lateral flexion is lateral flexion. The only difference is that the lower trunk moves toward the upper trunk instead of vice versa. However, the reverse action of contralateral rotation of the upper trunk is ipsilateral rotation of the lower trunk. (reverse actions 2, 3, 4, 5)

Motions Because the external intercostals have more than one line of pull, they can create more than one motion. 1. When contracting in mass, the anterior fibers have one line of pull in an oblique plane and therefore create one motion, which is a combination of contralateral rotation, flexion, and lateral flexion of the trunk at the spinal joints (as well as elevating the ribs at the sternocostal and costospinal joints). 2. When contracting in mass, the posterior fibers have one line of pull in an oblique plane and therefore create one motion, which is a combination of contralateral rotation, extension, and lateral flexion of the trunk at the spinal joints (as well as elevating the ribs at the sternocostal and costospinal joints).

Eccentric Antagonist Functions 1. Restrain/slow depression of ribs two through twelve and elevation of ribs one through eleven 2. Restrain/slow ipsilateral rotation of the upper trunk and contralateral rotation of the lower trunk 3. Restrain/slow flexion, extension, and opposite-side lateral flexion of the trunk

Isometric Stabilization Functions 1. Stabilize the ribs 2. Stabilize the spinal joints

Isometric Stabilization Function Note

600

• The external intercostals (and internal intercostals) are also involved in fixation (i.e., stabilization) of the rib cage during other movements of the body.

Additional Note on Actions 1. Given the location of the external intercostals, it is clear that they are involved in respiration. However, there is controversy regarding whether they elevate or depress the ribs during respiration. Generally, it is stated that they act during inspiration by elevating ribs; however, this is not known for certain. Given that the external intercostals are located in eleven intercostal spaces, and that these eleven intercostal spaces are located in the anterior, lateral, and posterior trunk, it is likely that different parts of this muscle group are active in different parts of the respiratory cycle. Some sources state that the upper and more lateral external intercostals are especially active with inspiration.

I N N E RVAT I O N Intercostal Nerves

A R T E R I A L S U P P LY Anterior Intercostal Arteries (branches of the Internal Thoracic Artery) and the Posterior Intercostal Arteries (branches of the Aorta) and the branches of the Costocervical Trunk (a branch of the Subclavian Artery) and the Superior Thoracic Artery (a branch of the Axillary Artery)

PA L PAT I O N 1. With the client supine, locate the hard surfaces of two adjacent ribs and place palpating fingers into the intercostal space between them. 2. Feel for the external intercostal muscle. Distinguishing between the external and internal intercostals is extremely difficult. 3. Palpate the external intercostals in other regions of the rib cage wherever possible.

RELATIONSHIP TO OTHER STRUCTURES The external intercostals are located in the intercostal spaces between ribs one through twelve. Therefore they are deep to all muscles that overlie the rib cage. Note that the external intercostals are not located between the costal cartilages of the ribs. The external intercostals are directly superficial to the internal intercostals. The external intercostals are located within the lateral line myofascial meridian.

MISCELLANEOUS 1. The fibers of the external intercostals are oriented in the same direction as the fibers of the sameside external abdominal oblique. For this reason, the external intercostals between the ribs appear to be extensions of the external abdominal oblique. 2. The external intercostals are thicker than the internal intercostals. 3. Regardless of the controversy over the exact actions of the external intercostals, it is clear that they are involved in respiration. Therefore the external intercostals (and the internal intercostals) should be addressed in any client who has a respiratory condition. Further, athletes may also greatly benefit from having these muscles worked on because of the great demand for respiration during exercise. 4. The intercostal muscles are the meat that is eaten when one eats ribs or spare ribs.

601

Internal Intercostals The name, internal intercostals, tells us that these muscles are located between ribs and are internal (deep to the external intercostals). Derivation internal: L. inside inter: L. between costals: L. refers to the ribs Pronunciation IN-turn-al in-ter-KOS-tals

ATTACHMENTS In the Intercostal Spaces of Ribs One through Twelve Each internal intercostal attaches from the superior border of one rib and its costal cartilage to the inferior border of the rib and its costal cartilage that is directly superior.

FIGURE 11-5

Views of the right internal intercostals. A, Anterior view. B, Posterior view.

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions

Reverse Mover Actions

602

1. Depress ribs one through eleven at the sternocostal and costospinal joints

1. Elevate ribs two through twelve at the sternocostal and costospinal joints

2. Ipsilaterally rotate the trunk at the spinal joints 3. Flex the trunk at the spinal joints

2. Contralaterally rotate the lower trunk relative to the upper trunk (at the spinal joints)

4. Extend the trunk at the spinal joints

4. Extend the lower trunk relative to the upper trunk (at the spinal joints)

5. Laterally flex the trunk at the spinal joints

5. Laterally flex the lower trunk relative to the upper trunk (at the spinal joints)

3. Flex the lower trunk relative to the upper trunk (at the spinal joints)

Standard Mover Action Notes • The internal intercostals are located in the intercostal spaces and attach from the inferior margin of the more superior rib to the superior margin of the more inferior rib. If the lower rib is fixed and an internal intercostal muscle contracts, it pulls inferiorly on the superior rib, thus depressing it. Therefore the internal intercostals depress ribs one through eleven at the sternocostal and costospinal joints. Depression of the ribs is necessary for expiration; therefore the internal intercostals are respiratory muscles. (action 1) • The internal intercostals have the same fiber direction as the internal abdominal oblique on the same side of the body; therefore they have the same actions of the trunk at the spinal joints, namely, ipsilateral rotation, flexion, and lateral flexion. (actions 2, 3, 5) • The anterior internal intercostal fibers can do flexion. The posterior fibers can do extension. All fibers, but especially the most lateral ones, can do lateral flexion. (actions 3, 4, 5)

Reverse Mover Action Notes • The internal intercostals are located in the intercostal spaces and attach from the inferior margin of the more superior rib to the superior margin of the more inferior rib. When the superior rib is fixed and an internal intercostal muscle contracts, it pulls superiorly on the inferior rib, thus elevating it. Therefore the internal intercostals elevate ribs two through twelve at the sternocostal and costospinal joints. Elevation of the ribs is necessary for inspiration; therefore the internal intercostals are respiratory muscles. (reverse action 1) • The standard mover action occurs when the upper trunk moves toward the lower trunk. The reverse mover action occurs if the superior attachments are fixed and the inferior attachments move so that the lower trunk moves toward the upper trunk. This usually occurs when the client is lying down so that the lower trunk is mobile. It should be noted that the reverse action of flexion is flexion, the reverse action of extension is extension, and the reverse action of lateral flexion is lateral flexion. The only difference is that the lower trunk moves toward the upper trunk instead of vice versa. However, the reverse action of ipsilateral rotation of the upper trunk is contralateral rotation of the lower trunk. (reverse actions 2, 3, 4, 5)

Motions Because the internal intercostals have more than one line of pull, they can create more than one motion. 1. When contracting in mass, the anterior fibers have one line of pull in an oblique plane and therefore create one motion, which is a combination of ipsilateral rotation, flexion, and lateral flexion of the trunk at the spinal joints (as well as depressing the ribs at the sternocostal and costospinal joints). 2. When contracting in mass, the posterior fibers have one line of pull in an oblique plane and therefore create one motion, which is a combination of ipsilateral rotation, extension, and lateral flexion of the trunk at the spinal joints (as well as depressing the ribs at the sternocostal and costospinal joints).

Eccentric Antagonist Functions 1. Restrain/slow elevation of ribs one through eleven and depression of ribs two through twelve 2. Restrain/slow contralateral rotation of the upper trunk and ipsilateral rotation of the lower trunk 3. Restrain/slow flexion, extension, and opposite-side lateral flexion of the trunk

Isometric Stabilization Functions 1. Stabilize the ribs 2. Stabilize the spinal joints

603

Isometric Stabilization Function Note • The internal intercostals (and external intercostals) are also involved in fixation (i.e., stabilization) of the rib cage during other movements of the body.

Additional Note on Actions 1. Given the location of the internal intercostals, it is clear that they are involved in respiration. However, there is controversy regarding whether they elevate or depress the ribs during respiration. Generally, it is stated that they act during expiration by depressing ribs; however, this is not known for certain. Given that the internal intercostals are located in eleven intercostal spaces, and that these eleven intercostal spaces are located in the anterior, lateral, and posterior trunk, it is likely that different parts of this muscle group are active in different parts of the respiratory cycle. Some sources state that the fibers located between the costal cartilages (interchondral fibers) are especially active with inspiration and that the fibers located between the bones of the ribs themselves (interosseus fibers) are especially active with expiration.

I N N E RVAT I O N Intercostal Nerves

A R T E R I A L S U P P LY Anterior Intercostal Arteries (branches of the Internal Thoracic Artery) and the Posterior Intercostal Arteries (branches of the Aorta) and the branches of the Costocervical Trunk (a branch of the Subclavian Artery) and the Superior Thoracic Artery (a branch of the Axillary Artery)

PA L PAT I O N 1. The internal intercostals are deep to the external intercostals, except between the costal cartilages, where there are no external intercostals. The internal intercostals may be palpated superficially in the intercostal spaces between costal cartilages, or they may be palpated deep to the external intercostals. Discerning between the external and internal intercostals is extremely difficult.

RELATIONSHIP TO OTHER STRUCTURES The internal intercostals are located in the intercostal spaces between ribs one through twelve. Therefore they are deep to all muscles that overlie the rib cage. They are directly deep to the external intercostals, except in the intercostal spaces between the costal cartilages where no external intercostal muscles are located. The internal intercostals are superficial to the innermost intercostals, the subcostales, and the pleural membrane of the lung. The internal intercostals are located within the lateral line myofascial meridian.

MISCELLANEOUS 1. Anteriorly, the internal intercostals are located in the spaces between the costal cartilages. (The external intercostals are not.) 2. Posteriorly, the muscle fibers of the internal intercostals only reach as far as the angle of the ribs. However, the internal intercostals attach into the internal intercostal membrane, which reaches farther medially to attach into the spine. 3. The fibers of the internal intercostals are oriented in the same direction as the fibers of the sameside internal abdominal oblique. For this reason, the internal intercostals between the ribs appear to be extensions of the internal abdominal oblique of the abdomen. 4. The internal intercostals are generally thinner than the external intercostals. The thickest region of the internal intercostals is between the costal cartilages. 5. Regardless of the controversy over the exact actions of the internal intercostals, it is clear that they are involved in respiration. Therefore the internal intercostals (and the external intercostals) should be addressed in any client who has a respiratory condition. Further, athletes may also greatly benefit from having these muscles worked on because of the great demand for respiration during

604

exercise. 6. There is another layer of muscles called the innermost intercostals or intercostals intimi, which is located directly deep to the internal intercostals and has an identical direction of fibers to the internal intercostals. This third layer of intercostal musculature, which had been considered to be the deeper layer of the internal intercostals, is now considered by many sources to be a distinct muscle layer. 7. The intercostal muscles are the meat that is eaten when one eats ribs or spare ribs.

605

Transversus Thoracis The name, transversus thoracis, tells us that this muscle runs transversely across the thoracic region. Derivation transversus: L. running transversely thoracis: Gr. refers to the thorax (chest) Pronunciation trans-VER-sus thor-AS-is

ATTACHMENTS Internal Surfaces of the Sternum, the Xiphoid Process, and the Adjacent Costal Cartilages the inferior ⅔ of the sternum, and the costal cartilages of ribs four through seven to the Internal Surfaces of Costal Cartilages Two through Six

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Depresses ribs two through six at the sternocostal and costospinal joints

Reverse Mover Actions 1. Elevates the sternum

Standard Mover Action Notes • The transversus thoracis has its fibers running somewhat vertically, attaching from the sternum and the xiphoid process inferiorly, to the costal cartilages of ribs two through six superiorly. When the transversus thoracis contracts, it pulls the second through sixth costal cartilages inferiorly toward the sternum and xiphoid process. Therefore the transversus thoracis depresses costal cartilages two through six and thereby depresses ribs two through six at the sternocostal and costospinal joints. This action is necessary for expiration. (action 1) • The primary role of the transversus thoracis is as a respiratory muscle. By depressing the costal cartilages, and therefore ribs two through six, the volume of the rib cage decreases for expiration.

Reverse Mover Action Notes • The reverse action is moving the sternum toward the ribs and may occur in conjunction with lifting the trunk such as when extending and straightening the thoracic spine. Elevation of the sternum may also be involved in inspiration when breathing. (reverse action 1)

Motion 1. The transversus thoracis has one line of pull. Its motion is its joint action, depression of the ribs.

606

FIGURE 11-6

Anterior view of the right transversus thoracis.

Eccentric Antagonist Functions 1. Restrains/slows elevation of ribs two through six 2. Restrains/slows depression of the sternum

Isometric Stabilization Functions 1. Stabilizes the rib cage and sternum

Additional Note on Actions 1. Muscles that depress (or elevate) the ribs are usually oriented vertically. The lower fibers of the transversus thoracis are oriented nearly perfectly horizontally, yet they can depress the ribs to which they attach because they cross inferior to the axis of motion for these ribs at the sternocostal joint.

I N N E RVAT I O N Intercostal Nerves

A R T E R I A L S U P P LY The Anterior Intercostal Arteries (branches of the Internal Thoracic Artery)

PA L PAT I O N

607

The transversus thoracis is deep to the rib cage itself and essentially not discernable when palpated. A small portion of it may be palpable just lateral to the xiphoid process of the sternum, or some pressure may translate through to it if applied with your palpating fingers in the medial intercostal spaces between ribs two through six, just lateral to the sternum.

RELATIONSHIP TO OTHER STRUCTURES The transversus thoracis is deep to the rib cage and all the musculature that overlies the anterior thoracic region, as well as the intercostal muscles. The transversus thoracis is superficial to the pleural membrane of the lungs. The transversus thoracis is located within the deep front line myofascial meridian.

MISCELLANEOUS 1. The superior fibers of the transversus thoracis run primarily vertically, but the inferior fibers run horizontally (i.e., transversely). 2. The transversus thoracis is also known as the sternocostalis or as the triangularis sternae. 3. The transversus thoracis is internal (i.e., it is located within the thoracic cavity). 4. The inferior fibers of the transversus thoracis are contiguous with the superior fibers of the transversus abdominis, another deep trunk muscle that runs transversely. 5. The attachments of the transversus thoracis vary.

608

Diaphragm The name, diaphragm, tells us that this muscle is a partition. Derivation diaphragm: Gr. partition Pronunciation DI-a-fram

ATTACHMENTS ENTIRE MUSCLE: Internal Surfaces of the Rib Cage and Sternum, and the Spine COSTAL PART: Internal Surfaces of the Lower Six Ribs (Ribs Seven through Twelve) and their Costal Cartilages STERNAL PART: Internal Surface of the Xiphoid Process of the Sternum LUMBAR PART: L1-L3 The lumbar attachments consist of two aponeuroses, called the medial and lateral arcuate ligaments, and two tendons, called the right and left crura. to the Central Tendon (Dome) of the Diaphragm

609

FIGURE 11-7

Views of the diaphragm. A, Anterior view. B, Inferior view. The psoas major, quadratus lumborum, and transversus abdominis are shown on the right side.

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Increases the volume of (expands) the thoracic cavity via abdominal breathing

Reverse Mover Actions 1. Increases the volume of (expands) the thoracic cavity via thoracic breathing

Standard Mover Action Notes • If the bony peripheral attachments are fixed and the diaphragm contracts, the pull is on the central tendon, which causes it (i.e., the top of the dome) to drop down against the abdominal viscera. This increases the superior-inferior dimension of the thoracic cavity to allow the lungs to inflate and expand for inspiration. (action 1) • The diaphragm is the prime mover of inspiration. (action 1) • The diaphragm is unusual in that one of its attachments is located 360 degrees around the lower

610

rib cage, and the other attachment is the center of the muscle itself, its dome, a region of fibrous tissue known as the central tendon (in reality a broad flat aponeurosis). Similar to any skeletal muscle, either attachment can be fixed with the other attachment mobile. Typically, the rib cage attachment is more fixed; therefore the central dome tends to move first. When this occurs, the central dome drops down, thereby increasing the superior to inferior height of the thoracic cavity, allowing for the lungs to fill with air. When this occurs, because the dome compresses into the abdominopelvic cavity, its contents are pushed out anteriorly and the belly is seen to rise. This is known as belly breathing or abdominal breathing. (action 1)

Reverse Mover Action Notes • As the diaphragm continues to contract, the pressure caused by the resistance of the abdominal viscera prohibits the central dome from dropping any farther and the dome now becomes less able to move (i.e., more fixed). The pull exerted by the contraction of the fibers of the diaphragm now pull peripherally on the rib cage, elevating the lower ribs outward laterally and causing the anterior rib cage and sternum to push anteriorly. This further increases the volume of the thoracic cavity to allow the lungs to inflate and expand for inspiration. (reverse action 1) • The reverse action of the diaphragm (reverse to abdominal breathing) could be considered to occur when the central dome can drop no farther because there is too much resistance from the compressed abdominal contents. At this point, the rib cage is now more mobile and is pulled upward toward the central dome. This causes the ribs to lift outward, thereby increasing the medial to lateral dimension and anterior to posterior dimension of the thoracic cavity, allowing the lungs to fill further with air for inspiration. When this occurs, the rib cage is seen to expand. This is known as chest breathing or thoracic breathing. Both aspects of diaphragm contraction (abdominal and thoracic breathing) occur when breathing in deeply. (reverse action 1) • Keep in mind that the diaphragm only elevates the lower half (six ribs) of the rib cage. Other accessory muscles of respiration such as the scalenes and intercostals contract to elevate the upper half of the rib cage. (reverse action 1)

Motions 1. The diaphragm’s line of pull upon its central dome creates one motion, which is to pull it down. 2. Regarding its reverse action pull on the rib cage, the diaphragm’s line of pull creates one motion, which is to elevate the lower ribs.

Eccentric Antagonist Function 1. Restrains/slows compression of the thoracic cavity

Isometric Stabilization Function 1. Stabilizes the trunk, including the joints of the lower rib cage and the thoracic and lumbar spinal joints

Isometric Stabilization Function Note • When the lungs inflate with air, the thoracic cavity becomes more rigid. Further, because when it contracts, the diaphragm drops down against the abdominopelvic cavity, the abdominopelvic cavity is also compressed, becoming more rigid. The result is that core (Powerhouse) stability is increased, including the thoracic and lumbar spinal joints. Increasing the stability of the core increases the efficiency with which muscles that attach from the core to the extremities can move the extremities because their proximal attachment is held so stable. This is the reason why people intuitively take in and hold a deep breath when performing a joint action that requires great strength.

Additional Notes on Actions 1. The diaphragm is the primary muscle of respiration but is by no means the only one. The exact pattern of a client’s breathing is usually determined by the precise coordination of the diaphragm with the many accessory muscles of respiration. Among respiratory muscles, the diaphragm is the only one that must contract for quiet relaxed breathing. Many other (accessory) muscles of inspiration can also contract when more forceful inspiration is needed. No muscle contraction is

611

necessary for quiet relaxed expiration; when the diaphragm relaxes, its elastic recoil is sufficient to press up against the lungs and expel air. When forceful expiration is needed, many accessory muscles of expiration can be engaged. 2. The diaphragm is essentially shaped like a dome. This dome is somewhat asymmetric, with the anterior aspect of it being higher than the posterior aspect. Its attachments peripherally onto the posterior rib cage and the lumbar vertebrae are its lowest points. The attachments peripherally onto the anterior rib cage and the xiphoid process of the sternum are somewhat higher. From these peripheral attachments, the fibers essentially run vertically and toward the center of the body to converge together into the central tendon (dome) of the diaphragm. Thus the diaphragm attaches into itself centrally at the central tendon. When the diaphragm contracts, the volume of the thoracic cavity can increase in two ways. If the peripheral rib cage attachment is fixed and the central tendon drops toward the rib cage, the superior to inferior diameter of the thoracic cavity increases. This aspect of the diaphragm’s contraction is usually called abdominal breathing or belly breathing because the abdominal contents are pushed outward and the belly is seen to rise. If the central tendon is fixed and the rib cage attachment lifts outward and upward toward the central tendon, the side-to-side and front-to-back diameter of the thoracic cavity increases. This aspect of the diaphragm’s contraction is usually called thoracic breathing or chest breathing because the rib cage is seen to expand. Either way, when the thoracic cavity increases in volume, the lungs can inflate and expand for inspiration. Usually, the central tendon is the more mobile attachment and moves first until the resistance of the abdominal viscera stops it, and then the rib cage attachment moves. Which attachment moves first and to what degree will vary from person to person and be based on the relative resistance to motion of the central tendon and rib cage. If the client is overweight or wearing very tight clothing, there is greater resistance to belly breathing. If the client has tight chest muscles or degenerative joint disease (osteoarthritis) of the joints of the rib cage, there is more resistance to chest breathing. 3. Movement of the rib cage attachments laterally outward and upward is usually described as bucket handle motion because like a bucket handle that is fixed in two places and lifts in the center, the ribs are fixed at the sternum and spine and lift in the center (laterally) between these two attachments. The movement of the sternum that occurs is often described as a pump handle motion because it lifts out and up anteriorly, similar to how a pump handle moves.

I N N E RVAT I O N The Phrenic Nerve C3-C5

A R T E R I A L S U P P LY Branches of the Aorta and the Internal Thoracic Artery (a branch of the Subclavian Artery) the Superior and Inferior Phrenic Arteries (both branches of the Aorta) and the Musculophrenic and Pericardiacophrenic Arteries (both branches of the Internal Thoracic Artery)

PA L PAT I O N 1. With the client supine with a pillow placed under the knees, place palpating fingers on the inferior margin of the anterior rib cage. 2. Have the client take in a deep breath and then slowly exhale. 3. As the client exhales, curl your fingertips under (inferior and then deep to) the rib cage and feel for the diaphragm, palpating gently, yet firmly, as deep as possible against the internal surface of the ribs.

RELATIONSHIP TO OTHER STRUCTURES The diaphragm separates the thoracic cavity from the abdominal cavity. The heart and lungs sit (superiorly) on the diaphragm. The liver and stomach are located (inferiorly) under the diaphragm. The medial and lateral arcuate ligaments of the diaphragm actually attach across the psoas major and the quadratus lumborum muscles, respectively. The diaphragm is located within the deep front line myofascial meridian.

612

MISCELLANEOUS 1. The diaphragm is a partition between the thoracic cavity and the abdominal (i.e., abdominopelvic) cavity. The term diaphragm means partition. 2. The medial arcuate ligament of the diaphragm surrounds the psoas major and runs from the body of L2 to the transverse process of L1. The lateral arcuate ligament of the diaphragm surrounds the quadratus lumborum and runs from the transverse process of L1 to the twelfth rib. 3. The central tendon of the diaphragm is a thin but strong aponeurosis located near the center of the muscle (at its dome). It is flattened somewhat at its center because the heart sits on it there. Each side of the dome is sometimes referred to as a cupola. 4. The dome of the diaphragm is higher on the right than the left because the liver pushes up on the right side. With maximal expiration, the dome is located at approximately the level of the fourth costal cartilage on the right (approximately the level of the right nipple) and the fifth costal cartilage on the left. With maximal inspiration, the dome drops as much as 4 inches (10 cm). The diaphragm is higher when a person lies down; and if lying on the side, the side of the diaphragm against the bed is higher than the other side. 5. The two crura (singular: crus) of the diaphragm are not symmetric. The right crus is broader and attaches farther inferiorly than the left crus. 6. The costal fibers of the diaphragm interdigitate with the transversus abdominis. 7. There are a number of openings in the diaphragm to allow passage of structures between the thoracic and abdominal cavities. The largest openings are for the esophagus, the aorta, and the inferior vena cava. 8. The diaphragm is unusual in that it is under both conscious control and unconscious control. More specifically, contraction of the diaphragm is under constant unconscious regulation by the brainstem. However, we routinely override this brainstem control whenever we choose to sing, talk, sigh, hold our breath, or otherwise consciously change our breathing pattern. 9. The innervation to the diaphragm is provided by the phrenic nerve, composed of spinal nerves C3, C4, and C5. (C3, 4, 5 keeps the diaphragm alive!) 10. It is often stated that the diaphragm is the only unilateral skeletal muscle in the body. In one sense, this is true. However, in another sense, it is not true because the diaphragm forms from right and left sides, each innervated by a separate phrenic nerve. 11. A hiatal hernia is when part of the stomach herniates (ruptures) through the diaphragm into the thoracic cavity.

613

Serratus Posterior Superior The name, serratus posterior superior, tells us that this muscle has a serrated appearance and is posterior and superior in location (posterior to the serratus anterior and superior to the serratus posterior inferior). Derivation serratus: L. a notching posterior: L. behind, toward the back superior: L. above Pronunciation ser-A-tus pos-TEE-ri-or sue-PEE-ri-or

ATTACHMENTS Spinous Processes of C7-T3 and the lower nuchal ligament to Ribs Two through Five the superior borders and the external surfaces

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Elevates ribs two through five at the sternocostal and costospinal joints

Reverse Mover Actions 1. Contralaterally rotates C7-T3 at the spinal joints

Standard Mover Action Notes • The serratus posterior superior attaches from ribs two through five inferiorly, to the vertebral column superiorly (with its fibers running somewhat vertically). When the serratus posterior superior contracts, it pulls the ribs superiorly toward the vertebral attachment. Therefore the serratus posterior superior elevates ribs two through five at the sternocostal and costospinal joints. (action 1) • Elevation of ribs is important for respiration. By elevating upper ribs, the thoracic cavity expands, which creates more space for the lungs to fill with air. Therefore the serratus posterior superior is a muscle of inspiration. (action 1)

Reverse Mover Action Notes • If the rib cage attachment of the serratus posterior superior is fixed, the vertebral attachment could be pulled toward the ribs. This would result in the spinous processes of C7-T3 being pulled toward the rib attachments, which would result in the anterior surface of the vertebrae rotating to the opposite side. Therefore the serratus posterior superior can contralaterally rotate the trunk (specifically C7-T3) at the spinal joints. Given how thin this muscle is, this action would be very weak. (reverse action 1)

614

FIGURE 11-8

Posterior view of the right serratus posterior superior. The splenius capitis has been ghosted in.

Motion 1. The serratus posterior superior’s line of pull creates one motion, which is to elevate ribs two through five.

Eccentric Antagonist Functions 1. Restrains/slows depression of ribs two through five 2. Restrains/slows ipsilateral rotation of C7-T3

Isometric Stabilization Functions 1. Stabilizes the upper ribs 2. Stabilizes C7 and upper thoracic spinal joints

Additional Note on Actions 1. The serratus posterior superior may have an additional function; that is to act as a retinaculum that runs perpendicular to and holds down the paraspinal (erector spinae and transversospinalis)

615

musculature. Holding down the paraspinal musculature prevents bowstringing (lifting away from the body wall), thereby acting to strengthen the effectiveness of the paraspinal contraction.

I N N E RVAT I O N Intercostal Nerves intercostal nerves two through five

A R T E R I A L S U P P LY The dorsal branches of the Posterior Intercostal Arteries (branches of the Aorta)

PA L PAT I O N 1. With the client prone, place palpating hand in the region of the upper rhomboids. 2. Have the client take in a moderately deep breath and feel for the contraction of the serratus posterior superior. 3. Note: It is very challenging to discern the serratus posterior superior from the overlying rhomboids.

RELATIONSHIP TO OTHER STRUCTURES The serratus posterior superior is directly deep to the rhomboids. The serratus posterior superior is directly superficial to the erector spinae musculature and the lower portions of the splenius capitis and the splenius cervicis. The serratus posterior superior is involved with the spiral line myofascial meridian.

MISCELLANEOUS 1. The serrated appearance of the serratus posterior superior comes from attaching onto separate ribs, which creates the notched look of a serrated knife. 2. The serratus posterior superior is a thin, quadrilateral-shaped muscle. 3. The serratus posterior superior is variable with regard to its attachments. Its most common variation is that its spinal attachment is only C7-T2 instead of C7-T3.

616

Serratus Posterior Inferior The name, serratus posterior inferior, tells us that this muscle has a serrated appearance and is posterior and inferior in location (posterior to the serratus anterior and inferior to the serratus posterior superior). Derivation serratus: L. a notching posterior: L. behind, toward the back inferior: L. below Pronunciation ser-A-tus pos-TEE-ri-or in-FEE-ri-or

ATTACHMENTS Spinous Processes of T11-L2 to Ribs Nine through Twelve

the inferior borders and the external surfaces

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Depresses ribs nine through twelve at the sternocostal and costospinal joints

Reverse Mover Actions 1. Contralaterally rotates T11-L2 at the spinal joints

Standard Mover Action Notes • The serratus posterior inferior attaches from ribs nine through twelve superiorly, to the vertebral column inferiorly (with its fibers running somewhat vertically). When the serratus posterior inferior contracts, it pulls the ribs inferiorly toward the vertebral attachment. Therefore the serratus posterior inferior depresses ribs nine through twelve at the sternocostal and costospinal joints. (action 1) • The action of depressing ribs nine through twelve is considered to be important for respiration. Theoretically, the fact that the serratus posterior inferior depresses ribs nine through twelve would seem to indicate that this muscle is a muscle of expiration. However, its main function regarding the lower ribs is not to be a mover and actually move the lower ribs into depression, but rather to fix (stabilize) the lower ribs in place so that they do not elevate when the diaphragm contracts and exerts an upward pull on them. In this manner, if the lower rib cage attachments of the diaphragm are fixed, the dome of the diaphragm drops down more efficiently, thus increasing the superior to inferior size of the thoracic cavity for the lungs to expand and fill with air. Therefore the serratus posterior inferior is a muscle of inspiration (primarily as a fixator [i.e., stabilizer]). It must be noted that there is some controversy regarding the role of the serratus posterior inferior with regard to respiration. Some sources state that it is not involved with respiration at all. Other sources list it as a muscle of expiration rather than inspiration. However, looking at its biomechanical role of fixing the lower ribs against the pull of the diaphragm clearly places the serratus posterior inferior as a muscle of inspiration. (action 1)

617

FIGURE 11-9

Posterior view of the serratus posterior inferior bilaterally. The latissimus dorsi has been ghosted in on the left side.

Reverse Mover Action Notes • If the rib cage attachment of the serratus posterior inferior is fixed, the vertebral attachment could be pulled toward the ribs. This would result in the spinous processes of T11-L2 being pulled toward the rib attachments, which would result in the anterior surface of the vertebrae rotating to the opposite side. Therefore the serratus posterior inferior can contralaterally rotate the trunk (specifically T12-L2) at the spinal joints. Given how thin this muscle is, this action would be very weak. (reverse action 1)

Motion 1. The serratus posterior inferior’s line of pull creates one motion, which is to depress ribs nine through twelve.

Eccentric Antagonist Functions 1. Restrains/slows elevation of ribs nine through twelve 2. Restrains/slows ipsilateral rotation of T12-L2

618

Isometric Stabilization Functions 1. Stabilizes the lower ribs 2. Stabilizes thoracolumbar spinal joints

Isometric Stabilization Function Note • Stabilization of the lower ribs is an important function of the serratus posterior inferior. Its force of depression of the lower ribs stabilizes them from elevating when the diaphragm contracts and pulls superiorly on them. By stabilizing the rib cage attachment of the diaphragm, the contraction of the diaphragm acts to drop its dome, thereby increasing the superior to inferior volume of the thoracic cavity for inspiration (this occurs during abdominal [belly] breathing). (See second Standard Mover Action Note above.)

Additional Notes on Actions 1. Theoretically, if the upper two slips of the serratus posterior inferior pull on ribs nine and ten, and if these ribs are fixed to vertebrae T9 and T10, the serratus posterior inferior could ipsilaterally rotate T9 and T10 at the spinal joints (via their rib attachments). 2. The serratus posterior inferior may have a weak ability to extend the trunk at the spinal joints. 3. The serratus posterior inferior may have an additional function; that is to act as a retinaculum that runs perpendicular to and holds down the paraspinal (erector spinae and transversospinalis) musculature. Holding down the paraspinal musculature prevents bowstringing (lifting away from the body wall), thereby acting to strengthen the effectiveness of the paraspinal contraction.

I N N E RVAT I O N Subcostal Nerve and Intercostal Nerves intercostal nerves nine through eleven

A R T E R I A L S U P P LY The dorsal branches of the Posterior Intercostal Arteries (branches of the Aorta)

PA L PAT I O N 1. With the client prone, place palpating hand in the upper lumbar region. 2. Have the client take in a moderately deep breath and feel for the contraction of the serratus posterior inferior. 3. Note: It is very challenging to discern the serratus posterior inferior from the overlying latissimus dorsi.

RELATIONSHIP TO OTHER STRUCTURES The serratus posterior inferior is directly deep to the latissimus dorsi. Directly deep to the serratus posterior inferior is the erector spinae group. The serratus posterior inferior may be involved with the superficial front arm line and superficial back line myofascial meridians.

MISCELLANEOUS 1. The serrated appearance of the serratus posterior inferior comes from attaching onto separate ribs, which creates the notched look of a serrated knife. 2. The serratus posterior inferior is a thin, quadrilateral-shaped muscle. 3. The serratus posterior inferior is variable with regard to its spinal and costal (rib) attachments.

619

Levatores Costarum The name, levatores costarum, tells us that these muscles elevate the ribs. Derivation levator: L. lifter costarum: L. refers to the ribs Pronunciation le-va-TO-rez (singular: le-VAY-tor) kos-TAR-um

ATTACHMENTS Transverse Processes of C7-T11 the tips of the transverse processes to Ribs One through Twelve (inferiorly) the external surfaces of the ribs, between the tubercle and the angle

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Elevate the ribs at the sternocostal and costospinal joints

Reverse Mover Actions 1. Laterally flex, extend, and contralaterally rotate the trunk at the spinal joints

Standard Mover Action Notes • The levatores costarum attach from superiorly on a vertebral transverse process to inferiorly onto a rib (with their fibers running vertically). When the vertebral attachment is fixed and the levatores costarum contract, they pull the costal attachments (i.e., the ribs) superiorly toward the vertebral attachment. Therefore the levatores costarum elevate the ribs at the sternocostal and costospinal joints. (action 1) • As elevators of the ribs, the levatores costarum can help increase the volume of the thoracic cavity and therefore increase the volume of the lungs. Hence they are muscles of inspiration (accessory muscles of respiration). (action 1)

Reverse Mover Action Notes • When the rib attachment of the levatores costarum is fixed and the levatores costarum contract, they pull the vertebral attachment toward the rib attachment. Because the levatores costarum cross the spinal joints posteriorly (with their fibers running somewhat vertically in the sagittal plane), they extend the trunk at the spinal joints. Because the levatores costarum cross the spinal joints laterally (with their fibers running somewhat vertically in the frontal plane), they laterally flex the trunk at the spinal joints. Because the levatores costarum run somewhat horizontally (in the transverse plane), they pull the vertebral attachment posterolaterally toward the rib attachment. This causes the anterior surface of the trunk to face the opposite side of the body from the side on which the levatores costarum are attached. Therefore the levatores costarum contralaterally rotate the trunk at the spinal joints. (reverse action 1)

620

FIGURE 11-10

Posterior view of the right levatores costarum.

• The levatores costarum’s reverse action of lateral flexion, extension, and contralateral rotation of the trunk can only occur in the thoracic spine. These actions would not be very strong. (reverse action 1)

Motion 1. The levatores costarum’s line of pull creates one motion, which is to elevate the ribs.

Eccentric Antagonist Functions 1. Restrains/slows depression of the ribs 2. Restrains/slows opposite-side lateral flexion, flexion, and ipsilateral rotation of the thoracic vertebrae

Isometric Stabilization Functions 1. Stabilizes the sternocostal and costospinal joints 2. Stabilizes the thoracic spinal joints

Isometric Stabilization Function Note • Some sources state that the primary function of the levatores costarum is to stabilize the spinal

621

joints and ribs.

Additional Note on Actions 1. The levatores costarum, although small, have excellent leverage to move the ribs. A small upward movement of a rib close to the vertebral attachment results in a large motion laterally.

I N N E RVAT I O N Spinal Nerves dorsal rami

A R T E R I A L S U P P LY The dorsal branches of the Posterior Intercostal Arteries (branches of the Aorta)

PA L PAT I O N 1. With the client prone, place palpating fingers on the erector spinae musculature over the angles of the ribs. Have the client slowly and deeply breathe in and out. Try to feel for the contraction of the levatores costarum. 2. The levatores costarum are small and very deep muscles. Palpating and discerning them from the adjacent musculature is extremely difficult if not impossible.

RELATIONSHIP TO OTHER STRUCTURES The levatores costarum are deep to the trapezius, latissimus dorsi, serratus posterior superior, serratus posterior inferior, and the erector spinae muscles. Deep to the levatores costarum are the intercostal muscles. The levatores costarum are located within the superficial back line myofascial meridian.

MISCELLANEOUS 1. The levatores costarum attach from a transverse process of a vertebra and orient inferiorly and laterally to attach onto the rib directly inferior to the vertebral attachment. However, the levatores costarum that attach to vertebrae T8-T10 have a second slip of tissue that also attaches to the second rib below that vertebral attachment (i.e., ribs ten through twelve). When this occurs, the two parts of the levatores costarum are called the levatores costarum breves and the levatores costarum longi. 2. The levatores costarum are considered to be homologous to the intertransversarii of the cervical and lumbar regions.

622

Subcostales The name, subcostales, tells us that these muscles are “under” (i.e., deep to) the ribs. Derivation sub: L. under costales: L. refers to the ribs Pronunciation sub-kos-TAL-eez

ATTACHMENTS Ribs Ten through Twelve the internal surface of the ribs, near the angle to Ribs Eight through Ten the internal surfaces of the ribs, near the angle

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions Reverse Mover Actions 1. Depress ribs eight through ten at the sternocostal and costospinal joints 1. Elevate ribs ten through twelve at the sternocostal and costospinal joints

Standard Mover Action Note • The subcostales attach from the internal surface of a rib and run superiorly (with their fibers running vertically), skipping one rib to attach onto the internal surface of a more superior rib. When the subcostales contract, they pull the more superior rib inferiorly toward the more inferior rib. Therefore the subcostales depress ribs eight through ten at the sternocostal and costospinal joints. This action assists forceful expiration by decreasing the size of the thoracic cavity; hence the subcostales are respiratory muscles. (action 1)

Reverse Mover Action Note • If the upper ribs’ (eight through ten) attachments of the subcostales are fixed, the subcostales would elevate the lower ribs (ten through twelve) instead of depressing the upper ribs. Elevating ribs is usually considered important for inspiration because lifting ribs increases the volume of the thoracic cavity, thereby allowing the lungs to fill with air. (reverse action 1)

Motions 1. The subcostales’ line of pull upon ribs eight through ten creates one motion, which is to depress them. 2. Regarding their reverse action, the subcostales’ line of pull upon ribs ten through twelve creates one motion, which is to elevate them.

623

FIGURE 11-11

Posterior view of the subcostales bilaterally. The internal intercostals have been ghosted in on the left side.

Eccentric Antagonist Function 1. Restrain/slow elevation of ribs eight through ten or depression of ribs ten through twelve

Isometric Stabilization Function 1. Stabilize the lower five ribs

Isometric Stabilization Function Note • The subcostales’ primary function might be to stabilize ribs eight through ten by stopping them from elevating. This could help to stabilize the rib cage attachment of the diaphragm so that the diaphragm could more efficiently pull its dome (central tendon) down, increasing the superior to inferior volume of the thoracic cavity and therefore the lungs. This function would make the subcostales important as muscles of inspiration.

I N N E RVAT I O N Intercostal Nerves eight through eleven

A R T E R I A L S U P P LY The dorsal branches of the Posterior Intercostal Arteries (branches of the Aorta)

PA L PAT I O N

624

1. The subcostales are deep to the rib cage itself and are essentially not palpable. If pressure were to translate through to them, it would have to be applied with palpating fingers just lateral to the erector spinae’s lateral border, in the intercostal spaces between ribs eight through twelve.

RELATIONSHIP TO OTHER STRUCTURES The subcostales are deep to the rib cage and all the musculature overlying the rib cage in the lower posterior thoracic region, as well as the external and internal intercostal muscles and the intercostal neurovascular bundle. The subcostales are superficial to the pleural membrane of the lungs. The subcostales are located within the superficial back line myofascial meridian.

MISCELLANEOUS 1. The subcostales are variable in their presentation. They are usually well developed only in the lower thoracic region. Most often, there are three subcostales muscles running from rib eight to rib ten, rib nine to rib eleven, and rib ten to rib twelve (as presented earlier in the Attachment section and shown in the individual illustration).

625

REVIEW QUESTIONS 1. What is the general functional relationship between rib elevation/depression and breathing? ____________________________ ____________________________ 2. The muscle fibers of the internal intercostals are oriented in the same direction as the fibers of the ____________________________. What is the functional significance of this? ____________________________ ____________________________ 3. Given that the external intercostals are located in the anterior, posterior, and lateral trunk, what can be said for their role in breathing? ____________________________ ____________________________ ____________________________ 4. What is unique about the fiber direction of the transversus thoracis and the standard mover action it creates? ____________________________ ____________________________ ____________________________ 5. Describe the role of the diaphragm as it relates to belly/abdominal breathing. ____________________________ ____________________________ ____________________________ 6. Explain the relationship between breathing and performing joint actions requiring great strength. ____________________________ ____________________________ ____________________________ ____________________________ 7. The arcuate ligaments of the diaphragm are contiguous with fascial layers of what two pairs of muscles? ____________________________ ____________________________ 8. Aside from their standard movement actions, what other proposed function do the serratus posterior muscles have? Why would this be important? ____________________________ ____________________________ ____________________________ ____________________________ 9. Where these muscles overlap, place them in order from superficial to deep when looked at from a posterior perspective: levatores costarum, serratus posterior inferior, trapezius, external intercostals. ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ 10. What is the one largest obstacle to clear palpation of the subcostales? ____________________________ ____________________________ For answers to these questions, visit http://evolve.elsevier.com/Muscolino/muscular

626

627

THINK IT THROUGH Take a moment to consider the effects of posture on breathing. No one stands in anatomic position all day just breathing, so think about the various positions people find themselves in throughout the day. What possible effects, if any, do things like sitting, scoliosis, rounded shoulders, or an anteriorly tilted pelvis have on breathing? ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________

628

CHAPTER 12

629

Muscles of the Temporomandibular Joints CHAPTER OUTLINE Major muscles of mastication: Temporalis Masseter Lateral pterygoid Medial pterygoid Lesser muscles of mastication—the hyoid group: Hyoid Group Suprahyoids Digastric Mylohyoid Geniohyoid Stylohyoid Infrahyoids Sternohyoid Sternothyroid Thyrohyoid Omohyoid

OBJECTIVES After completing this chapter, the student should be able to perform the following for each of the muscles covered in the chapter: 1. Explain the general structure. 2. Explain the general function. 3. State the attachments. 4. State the standard mover actions. 5. State the reverse mover actions. 6. Discuss the line(s) of pull the muscle has and the motion(s) created. 7. State the eccentric antagonist functions. 8. State the isometric stabilization functions. 9. State the nervous innervation.

10. State the arterial supply. 11. Describe the starting position for palpation. 12. Describe the steps for palpation. 13. Discuss the muscle’s relationship to other body structures. 14. Discuss additional information that may help with palpation, assessment, and clinical decision-making. CHAPTER OVERVIEW

630

The muscles addressed in this chapter are the muscles whose principal function is usually considered to be movement of the mandible at the temporomandibular joints (TMJs). Some of these muscles are involved at other joints of the body. Principally, the muscles of the hyoid group are also involved in motions of the neck at the spinal joints. Overview of STRUCTURE Mastication is the act of chewing. Therefore the muscles of mastication are those that attach to and are involved in movement of the mandible at the TMJs. There are four major muscles of mastication: the temporalis, masseter, lateral pterygoid, and medial pterygoid. The eight muscles of the hyoid group are also involved in mastication and are therefore covered in this chapter. The hyoid group is composed of four suprahyoid muscles and four infrahyoid muscles. The major muscles of mastication are located in the head. The temporalis and masseter are superficial and the two pterygoids are deeper. The lesser muscles of mastication are the muscles of the hyoid group and are located in the anterior neck. Overview of FUNCTION The following general rules regarding actions can be stated for the functional groups of muscles of mastication at the TMJs: If a muscle attaches to the mandible and its other attachment is superior to the mandibular attachment, it can elevate the mandible at the TMJs. If a muscle attaches to the mandible and its other attachment is inferior to the mandibular attachment, it can depress the mandible at the TMJs. If a muscle attaches to the mandible and its other attachment is anterior to the mandibular attachment, it can protract the mandible at the TMJs. If a muscle attaches to the mandible and its other attachment is posterior to the mandibular attachment, it can retract the mandible at the TMJs. If a muscle attaches to the mandible and its other attachment is medial to the mandibular attachment, it can contralaterally deviate (do opposite side deviation of) the mandible at the TMJs. Reverse actions of the major muscles of mastication are unlikely because they would require movement of the entire head toward a fixed mandible (at the TMJs). Reverse actions of the suprahyoid muscles of the hyoid group occur when the mandible is fixed and the hyoid bone is moved superiorly toward the mandible.

I N N E RVAT I O N The major muscles of mastication are innervated by the trigeminal nerve (CN V). The hyoid muscles are innervated by the following nerves: the trigeminal nerve (CN V), the facial nerve (CN VII), the hypoglossal nerve (CN XII), and nerves from the cervical plexus.

A R T E R I A L S U P P LY The major muscles of mastication receive the majority of their arterial supply from the maxillary artery. The infrahyoid muscles receive their arterial supply from the superior thyroid artery. Arterial supply to the suprahyoid muscles is varied.

http://evolve.elsevier.com/Muscolino/muscular

631

632

Superficial Right Lateral View of the Muscles of the Head

FIGURE 12-1

Superficial right lateral view of the muscles of the head.

633

Views of the Major Muscles of Mastication

FIGURE 12-2

Right lateral view of the temporalis and masseter. The masseter has been ghosted in.

FIGURE 12-3 Views of the right lateral and medial pterygoids. A, Lateral view with the mandible partially cut away. B, Posterior view of the lateral and medial pterygoids with the cranial bones cut away.

634

635

Anterior Views of the Neck and Upper Chest Region

FIGURE 12-4 Anterior views of the neck and upper chest region. A, Superficial views; the platysma has been removed on the left side. B, Intermediate views with the head extended. The sternocleidomastoid (SCM) has been cut on the right side; the SCM and omohyoid have been removed and the sternohyoid has been cut on the left side.

636

Temporalis The name, temporalis, tells us that this muscle attaches onto the temporal bone. Derivation temporalis: L. refers to the temple Pronunciation tem-po-RA-lis

ATTACHMENTS Temporal Fossa the entire temporal fossa except the portion on the zygomatic bone to the Coronoid Process and the Ramus of the Mandible the anterior border, apex, posterior border, and internal surface of the coronoid process of the mandible, as well as the anterior border of the ramus of the mandible

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Elevates the mandible at the TMJs 2. Retracts the mandible at the TMJs

Reverse Mover Actions 1. Moves the temporal bone inferiorly toward the mandible 2. Moves the temporal bone anteriorly toward the mandible

TMJs = temporomandibular joints

Standard Mover Action Notes • The anterior fibers of the temporalis are oriented vertically from the cranium superiorly, to the mandible inferiorly. When the temporalis contracts, it pulls the mandible superiorly toward the cranium. Therefore the temporalis elevates the mandible at the TMJs. (action 1) • The posterior fibers of the temporalis are oriented horizontally from the cranium posteriorly, to the mandible anteriorly. When the temporalis contracts, it pulls the mandible posteriorly toward the cranium. Therefore the temporalis retracts the mandible at the TMJs. (action 2)

Reverse Mover Action Notes • Reverse actions of moving the temporal bone toward the mandible require the mandible to be fixed and the temporal bone and entire cranium to move toward the fixed mandible at the TMJs. These reverse actions do not commonly occur. When they do occur, they would be opposite in direction to the standard mover actions. Therefore the cranium would be pulled inferiorly and anteriorly. (reverse actions 1, 2)

637

FIGURE 12-5

Lateral view of the right temporalis. The masseter has been ghosted in.

Motions Because the temporalis has more than one line of pull, it can create more than one motion. 1. The anterior fibers have a vertical line of pull that creates the motion of elevation of the mandible. 2. The posterior fibers have a horizontal line of pull that creates the motion of retraction of the mandible. 3. The middle fibers have an oblique line of pull that creates one motion, which is a combination of elevation and retraction of the mandible.

Eccentric Antagonist Functions 1. Restrains/slows depression and protraction of the mandible

Isometric Stabilization Function 1. Stabilizes the mandible at the TMJs

Additional Note on Actions 1. Some sources state that the temporalis also contributes to side-to-side grinding by doing ipsilateral deviation of the mandible at the TMJs.

I N N E RVAT I O N The Trigeminal Nerve (CN V) deep temporal branches of the anterior trunk of the mandibular division of the trigeminal nerve

A R T E R I A L S U P P LY The Maxillary and Superficial Temporal Arteries (branches of the External Carotid Artery)

PA L PAT I O N 1. With the client supine, place palpating fingers over the temporal fossa.

638

2. Have the client alternately clench and relax the teeth and feel for the contraction and relaxation of the temporalis. In this manner the majority of the temporalis superior to the zygomatic arch can be easily palpated.

RELATIONSHIP TO OTHER STRUCTURES The superior portion of the temporalis is superficial (except for the auriculares anterior and superior, which are superficial to it). The inferior portion of the temporalis runs deep to the zygomatic arch. Inferior to the zygomatic arch, the temporalis is deep to the masseter. Deep to the superior portion of the temporalis are the cranial bones (frontal, parietal, temporal, and sphenoid). Deep to the inferior portion of the temporalis are the lateral pterygoid, the superficial head of the medial pterygoid, and a small part of the buccinator. The temporalis is involved with the deep front line myofascial meridian.

MISCELLANEOUS 1. The temporalis muscle is deep to thick fibrous fascia called the temporalis fascia. 2. The more superficial fibers of the temporalis actually attach into the temporal fascia. 3. A tight temporalis may be involved with tension headaches and with dysfunction of the temporomandibular joint (TMJ syndrome). 4. The temporal fossa is a fossa (depression) that overlies not only the temporal bone but also the frontal, parietal, zygomatic, and sphenoid bones. 5. The superficial temporal artery is superficial to the temporalis muscle, and its pulse can be palpated. 6. The temporal fossa is much deeper in carnivores, allowing for a much thicker and stronger temporalis muscle. This contributes to the strength of a carnivore’s bite.

639

Masseter The name, masseter, tells us that this muscle is involved with chewing. Derivation masseter: Gr. chewer Pronunciation MA-sa-ter

ATTACHMENTS Inferior Margins of Both the Zygomatic Bone and the Zygomatic Arch of the Temporal Bone to the Angle, Ramus, and Coronoid Process of the Mandible SUPERFICIAL LAYER: the inferior margins of the zygomatic bone and the zygomatic arch to the SUPERFICIAL LAYER: the angle and the inferior ½ of the external surface of the ramus of the mandible DEEP LAYER: the inferior margin and the deep surface of the zygomatic arch to the DEEP LAYER: the external surface of the coronoid process, and the superior ½ of the external surface of the ramus of the mandible

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Elevates the mandible at the TMJs 2. Protracts the mandible at the TMJs 3. Retracts the mandible at the TMJs

Reverse Mover Actions 1. Moves the cranium inferiorly toward the mandible 2. Moves the cranium posteriorly toward the mandible 3. Moves the cranium anteriorly toward the mandible

TMJs = temporomandibular joints

Standard Mover Action Notes • The fibers of the masseter are oriented vertically from the zygomatic bone and zygomatic arch of the temporal bone superiorly, to the mandible inferiorly. When the masseter contracts, it pulls the mandible superiorly toward the zygomatic bone and arch. Therefore the masseter elevates the mandible at the TMJs. (action 1) • The masseter is the prime mover of elevation of the mandible at the TMJs. (action 1) • The superficial layer of the masseter is somewhat oriented in a horizontal fashion from the zygomatic bone anteriorly, to the mandible posteriorly. When the superficial layer of the masseter contracts, it pulls the mandible anteriorly toward the zygomatic bone. Therefore the masseter protracts the mandible at the TMJs. (action 2)

640

FIGURE 12-6

Lateral views of the right masseter. A, The temporalis has been ghosted in. B, The superficial head of the masseter has been ghosted in.

• The deep layer of the masseter is somewhat oriented in a horizontal fashion from the zygomatic arch of the temporal bone posteriorly, to the mandible anteriorly. When the deep layer of the masseter contracts, it pulls the mandible posteriorly toward the zygomatic arch. Therefore the masseter retracts the mandible at the TMJs. (Note: Keep in mind that retraction can only occur if the mandible is first protracted. When the mandible is first protracted, the horizontal orientation of the fibers of the deep layer of the masseter increases.) (action 3)

Reverse Mover Action Note • Reverse actions of moving the cranium (temporal and zygomatic bones) toward the mandible require the mandible to be fixed and the entire cranium to move toward the fixed mandible at the TMJs. These reverse actions do not commonly occur. (reverse actions 1, 2, 3)

Motions Because the masseter has more than one line of pull, it can create more than one motion. 1. The superficial layer has one line of pull that creates one motion, which is a combination of elevation and protraction. 2. The deep layer has one line of pull that creates one motion, which is a combination of elevation

641

and retraction.

Eccentric Antagonist Function 1. Restrains/slows depression, retraction, and protraction of the mandible

Isometric Stabilization Function 1. Stabilizes the mandible at the TMJs

Additional Note on Actions 1. Some sources state that the masseter can also ipsilaterally deviate the mandible, contributing to side-to-side grinding.

I N N E RVAT I O N The Trigeminal Nerve (CN V) anterior trunk of the mandibular division of the trigeminal nerve

A R T E R I A L S U P P LY The Maxillary Artery (a branch of the External Carotid Artery) and the Transverse Facial Artery (a branch of the Superficial Temporal Artery)

PA L PAT I O N 1. With the client supine, place palpating fingers between the zygomatic arch and the angle of the mandible. 2. Have the client alternately clench the teeth and relax and feel for contraction and relaxation of the masseter. When the masseter contracts, the muscle may visibly bulge out.

RELATIONSHIP TO OTHER STRUCTURES The masseter is superficial in the cheek except for the platysma, the risorius, and the zygomaticus major (muscles of facial expression). The large parotid gland and parotid duct are superficial to the masseter. Deep to the masseter are the temporalis, part of the buccinator, and the ramus of the mandible. The masseter is involved with the deep front line myofascial meridian.

MISCELLANEOUS 1. The masseter is usually divided into two layers: a superficial layer and a deep layer. 2. Some sources further subdivide the deep layer of the masseter into two layers and therefore state that overall, the masseter has three layers: a superficial layer, a middle layer, and a deep layer. 3. The superficial layer of the masseter is the largest. 4. The masseter and medial pterygoid form a sling that supports the mandible. The masseter is superficial to the mandible; the medial pterygoid is deep to it. 5. The masseter may be involved with dysfunction of the temporomandibular joint (TMJ syndrome). 6. Proportional to its size, the masseter is stated by many sources to be the strongest muscle in the human body.

642

Lateral Pterygoid The name, lateral pterygoid, tells us that this muscle attaches to the sphenoid bone (the pterygoid process) and is lateral (lateral to the medial pterygoid muscle). Derivation lateral: L. side pterygoid: Gr. wing shaped Pronunciation LAT-er-al TER-i-goyd

ATTACHMENTS Entire Muscle: Sphenoid Bone to the Mandible and the Temporomandibular Joint (TMJ) SUPERIOR HEAD: the greater wing of the sphenoid to the SUPERIOR HEAD: the capsule and articular disc of the TMJ INFERIOR HEAD: the lateral surface of the lateral pterygoid plate of the pterygoid process of the sphenoid to the INFERIOR HEAD: the neck of the mandible

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Protracts the mandible at the TMJs 2. Contralaterally deviates the mandible at the TMJs

Reverse Mover Actions 1. Moves the cranium posteriorly toward the mandible 2. Moves the cranium laterally (ipsilateral deviation) toward the mandible

TMJs = temporomandibular joints

Standard Mover Action Notes • The lateral pterygoid attaches from the sphenoid anteriorly, to the mandible posteriorly (with its fibers running horizontally). When the lateral pterygoid contracts, it pulls the mandible anteriorly toward the sphenoid. Therefore the lateral pterygoid protracts the mandible at the TMJs. (action 1) • The lateral pterygoid attaches from the sphenoid medially, to the mandible laterally (with its fibers running horizontally). When the lateral pterygoid contracts, it pulls the mandible medially toward the sphenoid. By pulling one side of the mandible toward the sphenoid, the entire mandible is pulled toward the opposite side of the body. This movement is called lateral deviation of the mandible. Because the lateral pterygoid on one side of the body pulls the mandible toward the opposite side of the body, this action is called contralateral deviation of the mandible, and it occurs at the TMJs. (action 2)

643

FIGURE 12-7 Views of the right lateral pterygoid with the medial pterygoid ghosted in. A, Lateral view with the mandible partially cut away. B, Posterior view with the cranial bones partially cut away.

• Lateral deviation of the mandible at the TMJs is important for grinding and chewing food. (action 2)

Reverse Mover Action Notes • Reverse actions of moving the sphenoid bone toward the mandible require the mandible to be fixed and the sphenoid bone and entire cranium to move toward the fixed mandible at the TMJs. These reverse actions do not commonly occur. (reverse actions 1, 2)

Motion 1. The lateral pterygoid has one line of pull that creates one motion, which is a combination of protraction and contralateral deviation of the mandible.

Eccentric Antagonist Function 1. Restrains/slows retraction and ipsilateral deviation of the mandible

Isometric Stabilization Function

644

1. Stabilizes the mandible at the TMJs

Additional Notes on Actions 1. As protraction of the mandible occurs with opening the jaw, the articular disc of the TMJ must also protract to stay in proper alignment between the mandibular condyle and the mandibular fossa of the temporal bone. Given its attachment into the articular disc, the lateral pterygoid guides this movement of the articular disc. 2. Some sources report that the inferior belly of the lateral pterygoid can also depress the mandible at the TMJs. Given that its mandibular attachment is higher than the sphenoid attachment, this seems likely. 3. Some sources state that the superior belly of the lateral pterygoid can elevate the mandible at the TMJs. Given that its mandibular attachment is lower than the sphenoid attachment, this seems likely.

I N N E RVAT I O N The Trigeminal Nerve (CN V) lateral pterygoid nerve from the anterior trunk of the mandibular division of the trigeminal nerve

A R T E R I A L S U P P LY The Maxillary Artery (a branch of the External Carotid Artery)

PA L PAT I O N 1. With the client seated or supine, wearing a finger cot or glove, place palpating fingers along the external surfaces of the upper teeth until you reach the back molars. 2. Press posteriorly and superiorly (it may feel like your finger is in a little pocket; this is where peanut butter often gets stuck!), and then medially against the inside wall of the mouth and laterally against the condyle of the mandible. 3. Have the client protract the mandible and feel for the contraction of the lateral pterygoid.

RELATIONSHIP TO OTHER STRUCTURES Of the two pterygoid muscles, the lateral pterygoid is named lateral because its attachment onto the pterygoid process of the sphenoid bone is more lateral than the attachment of the medial pterygoid onto the pterygoid process of the sphenoid bone. Regarding the gross location of the bellies of these two muscles, the lateral pterygoid is generally lateral and superior in location relative to the medial pterygoid. The majority of the lateral pterygoid is deep to the zygomatic arch of the temporal bone and the coronoid process of the mandible. The lateral pterygoid is also deep to the masseter muscle and the inferior tendon of the temporalis. The superior part of the deep head of the medial pterygoid is deep to the lateral pterygoid. The lateral pterygoid may be involved with the deep front line myofascial meridian.

MISCELLANEOUS 1. The lateral pterygoid is sometimes known as the external pterygoid. 2. Both the lateral pterygoid and the medial pterygoid attach onto the lateral pterygoid plate of the pterygoid process of the sphenoid bone. The two pterygoids are so named because the lateral pterygoid attaches onto the lateral surface of the lateral pterygoid plate and the medial pterygoid attaches onto the medial surface of the lateral pterygoid plate. 3. The lateral pterygoid functions to protract the mandible and the articular disc of the temporomandibular joint (TMJ). It is important that the mandible and disc protract together when the jaw is opened. Therefore if the contraction of the lateral pterygoid is not precisely coordinated with the other muscles that move the mandible, the articular disc may become jammed between the two bones of the joint and dysfunction of the TMJ (TMJ syndrome) may occur. 4. Although all four major muscles of mastication (temporalis, masseter, and the lateral and medial

645

pterygoids) may be involved in TMJ syndrome, given the attachments of the lateral pterygoid directly into the capsule and articular disc of the TMJ, it is clear that hypertonicity of a lateral pterygoid could excessively pull on the soft tissue structures of the TMJ and therefore cause dysfunction of the TMJ (TMJ syndrome).

646

Medial Pterygoid The name, medial pterygoid, tells us that this muscle attaches to the sphenoid bone (the pterygoid process) and is medial (medial to the lateral pterygoid muscle). Derivation medial: L. toward the middle pterygoid: Gr. wing shaped Pronunciation MEE-dee-al TER-i-goyd

ATTACHMENTS Entire Muscle: Sphenoid Bone DEEP HEAD: the medial surface of the lateral pterygoid plate of the pterygoid process of the sphenoid, the palatine bone, and the tuberosity of the maxilla SUPERFICIAL HEAD: the palatine bone and the maxilla to the Internal Surface of the Mandible at the angle and the inferior border of the ramus of the mandible

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Elevates the mandible at the TMJs

Reverse Mover Actions 1. Moves the cranium inferiorly toward the mandible

2. Protracts the mandible at the TMJs

2. Moves the cranium posteriorly toward the mandible

3. Contralaterally deviates the mandible at the TMJs

3. Moves the cranium laterally (ipsilateral deviation) toward the mandible

TMJs = temporomandibular joints

Standard Mover Action Notes • The fibers of the medial pterygoid are oriented vertically from the sphenoid superiorly, to the mandible inferiorly. When the medial pterygoid contracts, it pulls the mandible superiorly toward the sphenoid. Therefore the medial pterygoid elevates the mandible at the TMJs. (action 1) • The medial pterygoid attaches from the sphenoid anteriorly, to the mandible posteriorly (with its fibers running somewhat horizontally). When the medial pterygoid contracts, it pulls the mandible anteriorly toward the sphenoid. Therefore the medial pterygoid protracts the mandible at the TMJs. (action 2)

647

FIGURE 12-8 Views of the right medial pterygoid with the lateral pterygoid ghosted in. A, Lateral view with the mandible partially cut away. B, Posterior view with the cranial bones partially cut away.

• The medial pterygoid attaches from the sphenoid medially, to the mandible laterally (with its fibers running somewhat horizontally). When the medial pterygoid contracts, it pulls the mandible medially toward the sphenoid. By pulling one side of the mandible toward the sphenoid, the entire mandible is pulled toward the opposite side of the body. This movement is called lateral deviation of the mandible. Because the medial pterygoid on one side of the body pulls the mandible toward the opposite side of the body, this action is called contralateral deviation of the mandible, and it occurs at the TMJs. (action 3) • Lateral deviation of the mandible at the TMJs is important for grinding and chewing food. (action 3)

Reverse Mover Action Notes • Reverse actions of moving the sphenoid bone toward the mandible require the mandible to be fixed and the sphenoid bone and entire cranium to move toward the fixed mandible at the TMJs. These reverse actions do not commonly occur. (reverse actions 1, 2, 3)

Motion 1. The medial pterygoid has one line of pull that creates one motion, which is a combination of

648

elevation, protraction, and contralateral deviation of the mandible.

Eccentric Antagonist Function 1. Restrains/slows depression, retraction, and ipsilateral deviation of the mandible

Isometric Stabilization Function 1. Stabilizes the mandible at the TMJs

Additional Note on Actions 1. The medial pterygoid and masseter are oriented very similarly, attaching inferiorly to the inferior angle of the mandible and running superiorly to the other attachment. Therefore they both elevate the mandible at the TMJs.

I N N E RVAT I O N The Trigeminal Nerve (CN V) medial pterygoid nerve from the mandibular division of the trigeminal nerve

A R T E R I A L S U P P LY The Maxillary Artery (a branch of the External Carotid Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating fingers on the angle of the mandible and then hook them under onto the internal surface of the mandible. 2. Have the client clench the teeth and feel for the contraction of the medial pterygoid. 3. To palpate from inside the mouth, wearing a finger cot or glove, place palpating finger along the internal surfaces of the lower teeth until you reach the back molars. 4. Press posterolaterally against the inside wall of the mouth, have the client protract the mandible, and feel for the contraction of the medial pterygoid.

RELATIONSHIP TO OTHER STRUCTURES Of the two pterygoid muscles, the medial pterygoid is named medial because its attachment onto the pterygoid process of the sphenoid bone is more medial than the attachment of the lateral pterygoid onto the pterygoid process of the sphenoid bone. Regarding the gross location of the bellies of these two muscles, the medial pterygoid is generally medial and inferior in location relative to the lateral pterygoid. The medial pterygoid is deep to the coronoid process, the ramus, and the angle of the mandible (and the zygomatic arch as well). The medial pterygoid is also deep to the masseter and the inferior tendon of the temporalis. From the lateral perspective, where they overlap, the medial pterygoid is deep to the lateral pterygoid. From the posterolateral perspective, the internal wall of the mouth is deep to the medial pterygoid. A number of small muscles of the palate and the pharynx lie close to the medial attachment of the medial pterygoid. The medial pterygoid is involved with the deep front line myofascial meridian.

MISCELLANEOUS 1. The medial pterygoid is sometimes known as the internal pterygoid. 2. The medial pterygoid is a fairly thick, quadrilateral (square) muscle. 3. The medial pterygoid is usually divided into a deep head and a superficial head. The deep head attaches onto the sphenoid; the superficial head attaches onto the palatine bone and the maxilla. 4. The deep head of the medial pterygoid is the larger of the two heads. 5. The direction of fibers of the medial pterygoid is essentially identical to the direction of the fibers of the masseter; in fact, these two muscles occupy the same position. The difference is that the

649

masseter is external (superficial) to the mandible, and the medial pterygoid is internal (deep) to the mandible. 6. The masseter and medial pterygoid form a sling that supports the mandible. 7. Both the medial pterygoid and the lateral pterygoid attach onto the lateral pterygoid plate of the pterygoid process of the sphenoid bone. The two pterygoids are so named because the medial pterygoid attaches onto the medial surface of the lateral pterygoid plate, and the lateral pterygoid attaches onto the lateral surface of the lateral pterygoid plate. 8. A tight medial pterygoid may be involved with dysfunction of the TMJ (TMJ syndrome).

650

Hyoid Group The hyoids are a group of eight muscles that are superficial in the anterior neck. They are subdivided into two groups of four, as follows: • The suprahyoids: digastric, mylohyoid, geniohyoid, stylohyoid • The infrahyoids: sternohyoid, sternothyroid, thyrohyoid, omohyoid

ATTACHMENTS All the hyoid muscles (except the sternothyroid) attach onto the hyoid bone. The suprahyoids are located superior to the hyoid bone. The infrahyoids are located inferior to the hyoid bone.

ACTIONS The hyoids are involved with movement of the mandible at the temporomandibular joints (TMJs). Most of the suprahyoids attach directly to the mandible and can depress it. The infrahyoids are also involved because they must stabilize the hyoid bone so that the suprahyoids’ contraction acts to depress the mandible. In this manner, all hyoid muscles can act synergistically to depress the mandible at the TMJs; hence they are placed in this chapter as muscles of mastication. The suprahyoids and infrahyoids may act synergistically to stabilize the hyoid bone as a stable base of attachment for movements of the tongue. Therefore the hyoid muscles are important in chewing, swallowing, and speech. As a group, because the hyoids cross the cervical spinal joints anteriorly with their fibers running vertically, they can all act synergistically to assist with flexion of the neck at the spinal joints. For this to occur, the hyoid bone and the mandible must be fixed (stabilized). The infrahyoids depress the hyoid bone; the suprahyoids elevate the hyoid bone. In this manner, the infrahyoids and the suprahyoids may be considered to be antagonistic to each other.

MISCELLANEOUS 1. The carotid sinus of the common carotid artery lies directly deep and lateral to the hyoid muscles midway up the neck. Given the neurologic reflex that occurs to lower blood pressure when the carotid sinus is pressed, manual therapy to this region must be done judiciously, especially with weak and/or elderly clients. 2. The hyoid muscles are located within the deep front line myofascial meridian.

I N N E RVAT I O N The hyoid muscles are innervated by the following nerves: the trigeminal nerve (CN V), the facial nerve (CN VII), the hypoglossal nerve (CN XII), and nerves from the cervical plexus.

A R T E R I A L S U P P LY The infrahyoid muscles receive their arterial supply from the superior thyroid artery. Arterial supply to the suprahyoid muscles is varied.

651

FIGURE 12-9 Anterior view of the hyoid muscle group. The sternohyoid, omohyoid, stylohyoid, and digastric have been removed on the left. The geniohyoid is deep to the mylohyoid and not seen.

652

SUPRAHYOIDS  

653

Digastric (of Hyoid Group) The name, digastric, tells us that this muscle has two bellies (gaster means belly). Derivation di: Gr. two gastric: Gr. belly Pronunciation di-GAS-trik

ATTACHMENTS POSTERIOR BELLY: Temporal Bone the mastoid notch of the temporal bone to the

Hyoid the central tendon is bound to the hyoid bone at the body and the greater cornu ANTERIOR BELLY: Mandible the inner surface of the inferior border (the digastric fossa) to the

Hyoid the central tendon is bound to the hyoid bone at the body and the greater cornu FUNCTIONS Concentric (Shortening) Mover Actions

TMJs = temporomandibular joints; AOJ = atlanto-occipital joint

Standard Mover Action Notes • The anterior belly of the digastric attaches superiorly and anteriorly to the mandible and inferiorly and posteriorly to the hyoid bone. If the hyoid bone is fixed, the digastric pulls the mandible inferiorly and posteriorly toward the hyoid bone. Therefore it depresses and retracts the mandible at the TMJs. (actions 1, 2) • The digastric is considered to be the prime mover of depression of the mandible at the TMJs. (action 1) • If the anterior belly of the digastric pulls inferiorly on the mandible, and elevators of the mandible

654

contract to fix the mandible to the cranium, then when the digastric contracts, it pulls the entire head and neck forward into flexion at the spinal joints. (action 3)

FIGURE 12-10

Views of the digastric. A, Anterior view of the digastric bilaterally with other hyoid muscles ghosted in on the client’s left side. B, Right lateral view.

• When the hyoid bone and mandible are fixed and the posterior belly of the digastric contracts, it pulls the temporal bone toward the hyoid bone. Because its line of pull is posterior to the AOJ, it extends the head at the AOJ. (action 4) • Even though one belly of the digastric may be primarily responsible for a certain action (as indicated in the above notes), its line of pull to create this action will not be efficient unless the other belly also contracts to stabilize the hyoid bone. (actions 1, 2, 3, 4)

Reverse Mover Action Note • The digastric is unusual in that it has two bellies. The anterior belly attaches inferiorly to the hyoid bone and superiorly to the mandible; the posterior belly attaches inferiorly to the hyoid bone and superiorly to the temporal bone. When the mandible and temporal bone are fixed (stabilized) and the digastric contracts, it pulls the hyoid bone superiorly. Movements of the hyoid bone are important in chewing, swallowing, and speech. (reverse action 1)

655

Motions 1. The digastric has one line of pull upon the mandible that creates one motion, which is a combination of depression and retraction of the mandible (as well as flexion of the head and neck). 2. The digastric has one line of pull upon the cranium that creates the motion of extension of the head. 3. The digastric has one line of pull upon the hyoid bone that creates one motion, which is elevation.

Eccentric Antagonist Functions 1. Restrains/slows elevation and protraction of the mandible 2. Restrains/slows extension of the head and neck 3. Restrains/slows flexion of the head 4. Restrains/slows depression of the hyoid bone

Isometric Stabilization Functions 1. Stabilizes the TMJs 2. Stabilizes the hyoid bone 3. Stabilizes the head and neck

Additional Notes on Actions 1. The digastric can also protract and retract the hyoid bone. The anterior belly of the digastric can protract the hyoid (i.e., draw the hyoid anteriorly), and the posterior belly of the digastric can retract the hyoid (i.e., draw the hyoid posteriorly). 2. All hyoid muscles are important in moving and/or fixing (stabilizing) the hyoid bone. These functions are necessary for chewing, swallowing, and speech. 3. All hyoid muscles can assist with flexion of the neck at the spinal joints.

I N N E RVAT I O N The Trigeminal Nerve (CN V) and the Facial Nerve (CN VII) anterior belly: mylohyoid branch of the inferior alveolar nerve of posterior trunk of the mandibular division of the trigeminal nerve (CN V) posterior belly: facial nerve (CN VII)

A R T E R I A L S U P P LY The Occipital, Posterior Auricular, and Facial Arteries (branches of the External Carotid Artery)

PA L PAT I O N 1. With the client supine, place palpating fingers between the sternocleidomastoid and the ramus of the mandible. 2. Ask the client to depress the mandible against gentle resistance and feel for the contraction of the digastric. It will be a pencil-thin muscle running horizontally. 3. Palpate as much of the digastric as possible. Note: Discerning the posterior belly of the digastric from the stylohyoid can be challenging.

RELATIONSHIP TO OTHER STRUCTURES The digastric runs an unusual course. The posterior belly attaches to the mastoid notch of the temporal bone (deep to the sternocleidomastoid). It then runs anteriorly and slightly inferiorly toward the hyoid bone. Near the hyoid bone, the digastric becomes tendinous (the central tendon). However, the digastric does not attach directly to the hyoid bone, but rather its central tendon is attached to the hyoid by a fibrous sling of tissue. From there, the anterior belly runs superiorly and anteriorly to the inner surface of the mandible. Except for the occipital attachment of the sternocleidomastoid and the platysma (which is superficial to all anterior neck muscles), the digastric is superficial for its entire course in the lateral and anterior neck. The submandibular salivary gland may also be superficial to the digastric.

656

The posterior belly of the digastric runs inferior to, and parallel to, the stylohyoid. The central tendon of the digastric perforates the attachment of the stylohyoid onto the hyoid bone. Deep to the posterior belly of the digastric is the transverse process of the atlas (C1). The digastric is located within the deep front line myofascial meridian.

MISCELLANEOUS 1. The digastric is one of the four suprahyoid muscles. The four suprahyoid muscles are the digastric, mylohyoid, geniohyoid, and stylohyoid. 2. The external carotid artery lies inferior and deep to the anterior belly of the digastric. Manual therapy to this region must be done judiciously. 3. The digastric is unusual in that it has two separate bellies: a posterior belly and an anterior belly. 4. The digastric’s two bellies are separated by its central tendon (also known as the intermediate tendon). Like the omohyoid (an infrahyoid muscle), the central tendon of the digastric is tethered (attached) to bone by a fibrous sling of tissue.

657

Mylohyoid (of Hyoid Group) The name, mylohyoid, tells us that this muscle attaches to the hyoid bone. Mylo, referring to the molar teeth, tells us that this muscle also attaches close to the molar teeth. Derivation mylo: Gr. mill (refers to the molar teeth) hyoid: Gr. refers to the hyoid bone Pronunciation MY-lo-HI-oyd

ATTACHMENTS Inner Surface of the Mandible the mylohyoid line of the mandible (from the symphysis menti to the molars) to the Hyoid the anterior surface of the body of the hyoid

FUNCTIONS Concentric (Shortening) Mover Actions

TMJs = temporomandibular joints

Standard Mover Action Notes • The mylohyoid attaches from the mandible superiorly, to the hyoid bone inferiorly (with its fibers running somewhat vertically). When the hyoid bone is fixed and the mylohyoid contracts, it pulls the mandible inferiorly toward the hyoid bone. Therefore the mylohyoid depresses the mandible at the TMJs. (action 1) • If the mylohyoid pulls inferiorly on the mandible, and elevators of the mandible contract to fix the mandible to the cranium, then when the mylohyoid contracts, it pulls the entire head and neck forward into flexion at the spinal joints. (action 2)

Reverse Mover Action Note • The mylohyoid attaches from the mandible superiorly, to the hyoid bone inferiorly (with its fibers running vertically). When the mandible is fixed and the mylohyoid contracts, it pulls the hyoid bone superiorly toward the mandible. Therefore the mylohyoid elevates the hyoid bone. Movements of the hyoid bone are important in chewing, swallowing, and speech. (reverse action 1)

Motions 1. The mylohyoid has one line of pull upon the head that creates one motion, which is a combination of depression of the mandible and flexion of the head (and neck).

658

FIGURE 12-11

Views of the mylohyoid. A, Anterior view of the mylohyoid bilaterally with the digastric and stylohyoid shown on the client’s left side. B, Right lateral view.

2. The mylohyoid has one line of pull upon the hyoid bone that creates one motion, which is elevation.

Eccentric Antagonist Functions 1. Restrains/slows elevation of the mandible 2. Restrains/slows extension of the head and neck 3. Restrains/slows depression of the hyoid bone

Isometric Stabilization Functions 1. Stabilizes the mandible at the TMJs 2. Stabilizes the hyoid bone 3. Stabilizes the head and neck

Additional Notes on Actions 1. Another function of the mylohyoid is to elevate the floor of the mouth during the first stage of swallowing.

659

2. Some sources state that the mylohyoid can retract the mandible at the TMJs. Given that the mandibular attachment is more anterior than the hyoid attachment, this seems likely. 3. All hyoid muscles are important in moving and/or fixing (stabilizing) the hyoid bone. These functions are necessary for chewing, swallowing, and speech. 4. All hyoid muscles can assist with flexion of the neck at the spinal joints.

I N N E RVAT I O N The Trigeminal Nerve (CN V) the mylohyoid branch of the inferior alveolar nerve of the posterior trunk of the mandibular division of the trigeminal nerve (CN V)

A R T E R I A L S U P P LY The Inferior Alveolar Artery (a branch of the Maxillary Artery)

PA L PAT I O N 1. With the client supine, place palpating fingers under the chin. 2. Ask the client to depress the mandible against resistance or push the tip of the tongue against the roof of the mouth and feel for the contraction of the mylohyoid.

RELATIONSHIP TO OTHER STRUCTURES The mylohyoid is a broad, flat muscle that forms the muscular floor of the oral cavity. Superior to the mylohyoid is the geniohyoid. Inferior to the mylohyoid is the anterior belly of the digastric. From the perspective of the underside of the mandible, the mylohyoid is superficial except for the anterior belly of the digastric and the platysma. The mylohyoid is located within the deep front line myofascial meridian.

MISCELLANEOUS 1. The mylohyoid is one of the four suprahyoid muscles. The four suprahyoid muscles are the digastric, mylohyoid, geniohyoid, and stylohyoid. 2. The fibers from the left and right mylohyoid muscles meet each other in the midline and form a median fibrous raphe. (A raphe is a seam of tissue formed by the union of the halves of a part.)

660

Geniohyoid (of Hyoid Group) The name, geniohyoid, tells us that this muscle attaches to the hyoid bone. Genio, referring to the chin, tells us that this muscle also attaches to the mandible. Derivation genio: Gr. chin hyoid: Gr. refers to the hyoid bone Pronunciation JEE-nee-o-HI-oyd

ATTACHMENTS Inner Surface of the Mandible the inferior mental spine of the mandible to the Hyoid the anterior surface of the body of the hyoid

FUNCTIONS Concentric (Shortening) Mover Actions

TMJs = temporomandibular joints

Standard Mover Action Notes • The geniohyoid attaches from the mandible superiorly, to the hyoid bone inferiorly (with its fibers running somewhat vertically). When the hyoid bone is fixed and the geniohyoid contracts, it pulls the mandible inferiorly toward the hyoid bone. Therefore the geniohyoid depresses the mandible at the TMJs. (action 1) • If the geniohyoid pulls inferiorly on the mandible, and elevators of the mandible contract to fix the mandible to the cranium, then when the geniohyoid contracts, it pulls the entire head and neck forward into flexion at the spinal joints. (action 2)

Reverse Mover Action Note • The geniohyoid attaches from the mandible superiorly, to the hyoid bone inferiorly (with its fibers running vertically). When the mandible is fixed and the geniohyoid contracts, it pulls the hyoid bone superiorly toward the mandible. Therefore the geniohyoid elevates the hyoid bone. Movements of the hyoid bone are important in chewing, swallowing, and speech. (reverse action 1)

Motions 1. The geniohyoid has one line of pull upon the head that creates one motion, which is a combination of depression of the mandible and flexion of the head (and neck).

661

FIGURE 12-12

Views of the geniohyoid. A, Anterior view of the geniohyoid bilaterally with the mylohyoid ghosted in on the client’s left side. B, Right lateral view.

2. The geniohyoid has one line of pull upon the hyoid bone that creates one motion, which is elevation.

Eccentric Antagonist Functions 1. Restrains/slows elevation of the mandible 2. Restrains/slows extension of the head and neck 3. Restrains/slows depression of the hyoid bone

Isometric Stabilization Functions 1. Stabilizes the mandible at the TMJs 2. Stabilizes the hyoid bone 3. Stabilizes the head and neck

Additional Notes on Actions 1. Another action of the geniohyoid is to protract the hyoid bone (draw the hyoid bone anteriorly). 2. Some sources state that the geniohyoid can retract the mandible at the TMJs. Given that the

662

mandibular attachment is more anterior than the hyoid attachment, this seems likely. 3. All hyoid muscles are important in moving and/or fixing (i.e., stabilizing) the hyoid bone. These functions are necessary for chewing, swallowing, and speech. 4. All hyoid muscles can assist with flexion of the neck at the spinal joints.

I N N E RVAT I O N The Hypoglossal Nerve (CN XII) a branch of C1 through the hypoglossal nerve

A R T E R I A L S U P P LY The Lingual Artery (a branch of the External Carotid Artery)

PA L PAT I O N 1. With the client supine, place palpating fingers on the underside of the chin in the midline. 2. Ask the client to depress the mandible against gentle resistance or push the tip of the tongue against the roof of the mouth and feel for the contraction of the geniohyoid. Note: It is difficult to discern the geniohyoid from the more superficial mylohyoid.

RELATIONSHIP TO OTHER STRUCTURES The two geniohyoid muscles are two pencil-thin muscles that lie next to each other in the midline, sandwiched between the mylohyoid and the genioglossus muscles. The mylohyoids are inferior to the geniohyoids; the genioglossus muscles (muscles that move the tongue) (_______ see the Evolve website) are superior to the geniohyoids. From the perspective of the underside of the mandible, the geniohyoid is deep to the mylohyoid, the anterior belly of the digastric, and the platysma muscles. The geniohyoid is located within the deep front line myofascial meridian.

MISCELLANEOUS 1. The geniohyoid is one of the four suprahyoid muscles. The four suprahyoid muscles are the digastric, mylohyoid, geniohyoid, and stylohyoid. 2. The left and right geniohyoid muscles occasionally blend together. 3. The inferior mental spines are bony landmarks of the mandible that are on the internal (posterior) side, directly behind the symphysis menti (the midline of the mandible).

663

Stylohyoid (of Hyoid Group) The name, stylohyoid, tells us that this muscle attaches from the styloid process (of the temporal bone) to the hyoid bone. Derivation stylo: Gr. refers to the styloid process hyoid: Gr. refers to the hyoid bone Pronunciation STI-lo-HI-oyd

ATTACHMENTS Styloid Process of the Temporal Bone the posterior surface to the Hyoid at the junction of the body and the greater cornu of the hyoid bone

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Elevates the hyoid bone

Reverse Mover Actions 1. Extends the head at the AOJ

AOJ = atlanto-occipital joint

Standard Mover Action Note • The stylohyoid attaches from the temporal bone superiorly, to the hyoid bone inferiorly (with its fibers running vertically). When the stylohyoid contracts, it pulls the hyoid bone superiorly toward the temporal bone. Therefore the stylohyoid elevates the hyoid. Movements of the hyoid bone are important in chewing, swallowing, and speech. (action 1)

Reverse Mover Action Note • When the hyoid bone is fixed and the stylohyoid contracts, it pulls the temporal bone and entire cranium toward the hyoid bone. Because its line of pull is posterior to the AOJ, it extends the head at the AOJ. (reverse action 1)

Motions 1. The stylohyoid has one line of pull upon the hyoid bone that creates one motion, which is elevation. 2. The stylohyoid has one line of pull upon the head that creates one motion, which is extension.

Eccentric Antagonist Functions 1. Restrains/slows depression of the hyoid bone 2. Restrains/slows flexion of the head

664

FIGURE 12-13

Views of the stylohyoid. A, Anterior view of the stylohyoid bilaterally with the digastric ghosted in on the client’s left side. B, Right lateral view.

Isometric Stabilization Functions 1. Stabilizes the hyoid bone 2. Stabilizes the head at the AOJ

Additional Notes on Actions 1. The stylohyoid can also retract the hyoid bone. 2. All hyoid muscles are important in moving and/or fixing (stabilizing) the hyoid bone. These functions are necessary for chewing, swallowing, and speech. 3. All hyoid muscles can assist with flexion of the neck at the spinal joints. The stylohyoid assists by stabilizing the hyoid bone.

I N N E RVAT I O N The Facial Nerve (CN VII) the stylohyoid branch

665

A R T E R I A L S U P P LY The Occipital, Posterior Auricular, and Facial Arteries (branches of the External Carotid Artery)

PA L PAT I O N 1. With the client supine, place palpating fingers between the sternocleidomastoid and the posterior ramus of the mandible (i.e., over the styloid process of the temporal bone). Keep your pressure light to moderate because the styloid process of the temporal bone is a delicate structure. 2. Ask the client to swallow and feel for the stylohyoid to contract. 3. Palpate as much of the stylohyoid as possible. It is a pencil-thin muscle located next to the digastric. Note: Discerning the stylohyoid from the posterior belly of the digastric can be challenging.

RELATIONSHIP TO OTHER STRUCTURES The stylohyoid is superior to, and runs parallel to, the posterior belly of the digastric. Except for the platysma, which is superficial to all anterior neck muscles (and the submandibular salivary gland), the stylohyoid is superficial in the superolateral neck. The attachment of the stylohyoid onto the hyoid bone is the same location where the digastric attaches (via its fibrous sling attachment that holds the central tendon of the digastric to the hyoid bone). The attachment of the stylohyoid onto the hyoid bone is perforated by the central tendon of the digastric. Deep to the stylohyoid is the transverse process of the atlas (C1). The stylohyoid is located within the deep front line myofascial meridian.

MISCELLANEOUS 1. The stylohyoid is one of the four suprahyoid muscles. The four suprahyoid muscles are the digastric, mylohyoid, geniohyoid, and stylohyoid. 2. The external carotid artery lies inferior and deep to the stylohyoid. Manual therapy to this region must be done judiciously. 3. There are two other small muscles that attach to the styloid process of the temporal bone: the styloglossus and the stylopharyngeus (_______ see the Evolve website), muscles involved with movements of the tongue and pharynx.

666

INFRAHYOIDS  

667

Sternohyoid (of Hyoid Group) The name, sternohyoid, tells us that this muscle attaches from the sternum to the hyoid bone. Derivation sterno: L. refers to the sternum hyoid: Gr. refers to the hyoid Pronunciation STER-no-HI-oyd

ATTACHMENTS Sternum the posterior surface of both the manubrium of the sternum and the medial clavicle to the Hyoid the inferior surface of the body of the hyoid

FUNCTIONS Concentric (Shortening) Mover Actions

Standard Mover Action Notes • The sternohyoid attaches from the hyoid bone superiorly, to the sternum inferiorly (with its fibers running vertically). When the sternohyoid contracts, it pulls the hyoid bone inferiorly toward the sternum. Therefore the sternohyoid depresses the hyoid bone. Movements of the hyoid bone are important in chewing, swallowing, and speech. (action 1) • If the inferior attachment of the sternohyoid stays fixed and the hyoid bone is pulled inferiorly, and the suprahyoids contract to fix the hyoid bone to the mandible, and elevators of the mandible contract to fix the mandible to the cranium, the sternohyoid can assist in flexing the neck and head at the spinal joints. This makes sense given that it crosses the cervical vertebrae anteriorly with a vertical direction to its fibers. (action 2)

Reverse Mover Action Note • If the hyoid bone is fixed and the sternohyoid contracts, its pull would be exerted on its inferior attachment, the sternum, thereby pulling it superiorly. Given how small the sternohyoid is and how much resistance there is to the sternum lifting (the rib cage would have to move with it), this reverse action would not be very powerful. However, it may play a role in lifting the rib cage when breathing in. In this manner, the sternohyoid may be considered to be an accessory muscle of breathing. (reverse action 1)

668

FIGURE 12-14

Anterior view of the sternohyoid bilaterally. The omohyoid has been ghosted in on the client’s left side.

Motions 1. The sternohyoid has one line of pull upon the neck that creates one motion, which is a combination of depression of the hyoid bone and flexion of the neck (and head). 2. The sternohyoid has one line of pull upon the sternum that creates one motion, which is elevation.

Eccentric Antagonist Functions 1. Restrains/slows elevation of the hyoid 2. Restrains/slows extension of the neck and head 3. Restrains/slows depression of the sternum

Isometric Stabilization Functions 1. Stabilizes the hyoid bone 2. Stabilizes the sternum 3. Stabilizes the temporomandibular joints (TMJs) 4. Stabilizes the neck

Isometric Function Note • The sternohyoid can indirectly assist stabilization of the TMJs by stabilizing the hyoid bone when the suprahyoid muscles contract. With the hyoid stabilized, the suprahyoids can exert their pull on the mandible, thereby stabilizing the TMJs.

Additional Notes on Actions 1. If the sternohyoid stabilizes the hyoid bone, and the suprahyoid muscles contract, they will act to depress the mandible at the temporomandibular joints (TMJs). Therefore, via its stabilization of the hyoid, the sternohyoid can assist in depressing the mandible. In this manner, all infrahyoid muscles and all suprahyoid muscles can assist in depressing the mandible at the TMJs. 2. All hyoid muscles are important in moving and/or fixing (stabilizing) the hyoid bone. These functions are necessary for chewing, swallowing, and speech. 3. All hyoid muscles can assist with flexion of the neck at the spinal joints.

669

I N N E RVAT I O N The Cervical Plexus ansa cervicalis (C1, C3)

A R T E R I A L S U P P LY The Superior Thyroid Artery (a branch of the External Carotid Artery)

PA L PAT I O N 1. With the client supine, place palpating fingers superior to the manubrium of the sternum and slightly lateral to midline. Make sure that you stay medial to the sternocleidomastoid. 2. Gently resist the client from depressing the mandible and feel for the contraction of the sternohyoid. 3. Palpate the sternohyoid superiorly toward the hyoid bone (using delicate pressure over the thyroid gland that is superficial in the anterior lower neck).

RELATIONSHIP TO OTHER STRUCTURES Nearly the entire sternohyoid is superficial in the anterior neck (except for the platysma, which is superficial to all anterior neck muscles). However, the inferior belly of the sternohyoid is deep to the sternocleidomastoid. The inferior attachment of the sternohyoid is deep to the sternum and clavicle. The inferior portion of the sternohyoid lies directly medial to the sternocleidomastoid. The superior portion of the sternohyoid lies medial to the omohyoid. The sternohyoid lies anterior to, and just lateral to, the midline of the trachea. Deep to the sternohyoid are the sternothyroid and thyrohyoid. The sternohyoid is located within the deep front line myofascial meridian.

MISCELLANEOUS 1. The sternohyoid is one of the four infrahyoid muscles. The four infrahyoid muscles are the sternohyoid, sternothyroid, thyrohyoid, and omohyoid. 2. The carotid sinus of the common carotid artery lies slightly lateral to the sternohyoid (between the sternohyoid and the sternocleidomastoid, midway up the neck). Given the neurologic reflex that occurs to lower blood pressure when the carotid sinus is pressed, manual therapy to this region must be done judiciously, especially with weak and/or elderly clients.

670

Sternothyroid (of Hyoid Group) The name, sternothyroid, tells us that this muscle attaches from the sternum to the thyroid cartilage. Derivation sterno: L. refers to the sternum thyroid: Gr. refers to the thyroid cartilage Pronunciation STER-no-THI-royd

ATTACHMENTS Sternum the posterior surface of both the manubrium of the sternum and the cartilage of the first rib to the Thyroid Cartilage the lamina of the thyroid cartilage

FUNCTIONS Concentric (Shortening) Mover Actions

Standard Mover Action Notes • The sternothyroid attaches from the thyroid cartilage superiorly, to the sternum inferiorly (with its fibers running vertically). When the sternothyroid contracts, it pulls the thyroid cartilage inferiorly toward the sternum. Therefore the sternothyroid depresses the thyroid cartilage. Movements of the thyroid cartilage are important in chewing, swallowing, and speech. (action 1) • If the inferior attachment of the sternothyroid stays fixed and the thyroid cartilage is pulled inferiorly, and the thyrohyoid contracts to fix the thyroid cartilage to the hyoid bone, and the suprahyoids contract to fix the hyoid bone to the mandible, and elevators of the mandible contract to fix the mandible to the cranium, then the sternothyroid can assist in flexing the neck and head at the spinal joints. This makes sense given that it crosses the cervical vertebrae anteriorly with a vertical direction to its fibers. Although this sounds complicated, it effectively requires only that the hyoid group contract simultaneously with elevators of the mandible. (action 2)

Reverse Mover Action Note • If the thyroid cartilage is fixed and the sternothyroid contracts, its pull would be exerted on its inferior attachment, the sternum, thereby pulling it superiorly. Given how small the sternothyroid is and how much resistance there is to the sternum lifting (the rib cage would have to move with it), this reverse action would not be very powerful. However, it may play a role when the rib cage has to be lifted when breathing in. In this manner, the sternothyroid may be considered to be an accessory muscle of breathing. (reverse action 1)

671

FIGURE 12-15

Anterior view of the sternothyroid bilaterally. The sternohyoid and thyrohyoid have been ghosted in.

Motions 1. The sternothyroid has one line of pull upon the neck that creates one motion, which is a combination of depression of the thyroid cartilage and flexion of the neck (and head). 2. The sternothyroid has one line of pull upon the sternum that creates one motion, which is elevation.

Eccentric Antagonist Functions 1. Restrains/slows elevation of the thyroid cartilage 2. Restrains/slows extension of the neck and head 3. Restrains/slows depression of the sternum

Isometric Stabilization Functions 1. Stabilizes the thyroid cartilage 2. Stabilizes the hyoid bone 3. Stabilizes the sternum 4. Stabilizes the temporomandibular joints (TMJs) 5. Stabilizes the neck

Isometric Function Notes • The sternothyroid can play a role in stabilizing the hyoid bone by stabilizing the thyroid cartilage when the thyrohyoid contracts. This allows the contraction force of the thyrohyoid to be exerted on the hyoid bone. • The sternothyroid can indirectly assist stabilization of the TMJs by stabilizing the thyroid cartilage and hyoid bone when the suprahyoid muscles contract. With the hyoid stabilized, the suprahyoids can exert their pull on the mandible, thereby stabilizing the TMJs.

Additional Notes on Actions 1. If the sternothyroid stabilizes the thyroid cartilage and hyoid bone, and the suprahyoid muscles contract, they will act to depress the mandible at the temporomandibular joints (TMJs). Therefore, via its stabilization of the hyoid, the sternothyroid can assist in depressing the mandible. In this

672

manner, all infrahyoid muscles and all suprahyoid muscles can assist in depressing the mandible at the TMJs. 2. All hyoid muscles are important in moving and/or fixing (stabilizing) the hyoid bone. These functions are necessary for chewing, swallowing, and speech. 3. All hyoid muscles can assist with flexion of the neck at the spinal joints.

I N N E RVAT I O N The Cervical Plexus ansa cervicalis (C1, C3)

A R T E R I A L S U P P LY The Superior Thyroid Artery (a branch of the External Carotid Artery)

PA L PAT I O N 1. The sternothyroid is best palpated along with the sternohyoid (see the Palpation section for this muscle on page 435). Keep in mind that the sternothyroid does not extend superiorly beyond the thyroid cartilage, as does the sternohyoid.

RELATIONSHIP TO OTHER STRUCTURES Most of the sternothyroid lies directly deep to the sternohyoid and the omohyoid. However, part of the sternothyroid is superficial (except for the platysma, which is superficial to all anterior neck muscles) just above the sternum. The sternothyroid lies anterior to, and just lateral to, the midline of the trachea. Deep to the sternothyroid is the trachea. The inferior attachment of the sternothyroid is deep to the sternum and first rib. The sternothyroid is located within the deep front line myofascial meridian.

MISCELLANEOUS 1. The sternothyroid is one of the four infrahyoid muscles. The four infrahyoid muscles are the sternohyoid, sternothyroid, thyrohyoid, and omohyoid. 2. The sternothyroid is the only hyoid muscle that does not attach onto the hyoid bone. 3. The carotid sinus of the common carotid artery lies slightly lateral to the sternothyroid (between the sternothyroid and the sternocleidomastoid, midway up the neck). Given the neurologic reflex that occurs to lower blood pressure when the carotid sinus is pressed, manual therapy to this region must be done judiciously, especially with weak and/or elderly clients.

673

Thyrohyoid (of Hyoid Group) The name, thyrohyoid, tells us that this muscle attaches from the thyroid cartilage to the hyoid bone. Derivation thyro: Gr. refers to the thyroid cartilage hyoid: Gr. refers to the hyoid bone Pronunciation THI-ro-HI-oyd

ATTACHMENTS Thyroid Cartilage the lamina of the thyroid cartilage to the Hyoid the inferior surface of the greater cornu of the hyoid

FUNCTIONS Concentric (Shortening) Mover Actions

Standard Mover Action Notes • The thyrohyoid attaches from the hyoid bone superiorly, to the thyroid cartilage inferiorly (with its fibers running vertically). When the thyroid cartilage is fixed (stabilized) and the thyrohyoid contracts, it pulls the hyoid bone inferiorly toward the thyroid cartilage. Therefore the thyrohyoid depresses the hyoid bone. Movements of the hyoid bone are important in chewing, swallowing, and speech. (action 1) • If the thyroid cartilage attachment of the thyrohyoid stays fixed and the hyoid bone is pulled inferiorly, and the suprahyoids contract to fix the hyoid bone to the mandible, and elevators of the mandible contract to fix the mandible to the cranium, then the thyrohyoid can assist in flexing the neck and head at the spinal joints. This makes sense given that it crosses the cervical vertebrae anteriorly with a vertical direction to its fibers. (action 2)

Reverse Mover Action Note • The thyrohyoid attaches from the thyroid cartilage inferiorly, to the hyoid bone superiorly (with its fibers running vertically). When the hyoid bone is fixed (stabilized) and the thyrohyoid contracts, it pulls the thyroid cartilage superiorly toward the hyoid bone. Therefore the thyrohyoid elevates the thyroid cartilage. Movements of the thyroid cartilage are important in chewing, swallowing, and speech. (reverse action 1)

674

FIGURE 12-16

Anterior view of the thyrohyoid bilaterally. The sternothyroid has been ghosted in on the client’s left side.

Motions 1. The thyrohyoid has one line of pull upon its upper attachment that creates one motion, which is a combination of depression of the hyoid bone and flexion of the neck (and head). 2. The thyrohyoid has one line of pull upon the thyroid cartilage (its lower attachment) that creates one motion, which is elevation.

Eccentric Antagonist Functions 1. Restrains/slows elevation of the hyoid 2. Restrains/slows depression of the thyroid cartilage 3. Restrains/slows extension of the neck and head

Isometric Stabilization Functions 1. Stabilizes the hyoid bone and thyroid cartilage 2. Stabilizes the temporomandibular joints (TMJs) 3. Stabilizes the neck

Isometric Function Note • The thyrohyoid can indirectly assist stabilization of the TMJs by stabilizing the hyoid bone when the suprahyoid muscles contract. With the hyoid stabilized, the suprahyoids can exert their pull on the mandible, thereby stabilizing the TMJs.

Additional Notes on Actions 1. If the thyrohyoid stabilizes the hyoid bone, and the suprahyoid muscles contract, they will act to depress the mandible at the temporomandibular joints (TMJs). Therefore, via its stabilization of the hyoid, the thyrohyoid can assist in depressing the mandible. In this manner, all infrahyoid muscles and all suprahyoid muscles can assist in depressing the mandible at the TMJs. 2. All hyoid muscles are important in moving and/or fixing (stabilizing) the hyoid bone. These functions are necessary for chewing, swallowing, and speech. 3. All hyoid muscles can assist with flexion of the neck at the spinal joints.

675

I N N E RVAT I O N The Hypoglossal Nerve (CN XII) a branch of C1 through the hypoglossal nerve

A R T E R I A L S U P P LY The Superior Thyroid Artery (a branch of the External Carotid Artery)

PA L PAT I O N 1. The thyrohyoid is best palpated along with the sternohyoid (see the Palpation section for this muscle on page 435). Keep in mind that the thyrohyoid does not extend inferiorly beyond the thyroid cartilage, as does the sternohyoid.

RELATIONSHIP TO OTHER STRUCTURES The inferior part of the thyrohyoid lies directly deep to the sternohyoid and omohyoid. However, its superior part is superficial (except for the platysma, which is superficial to all anterior neck muscles). The thyrohyoid lies anterior to, and lateral to, the midline of the thyroid cartilage. It is inferior to the hyoid bone. Deep to the thyrohyoid is the thyroid cartilage. The thyrohyoid is located within the deep front line myofascial meridian.

MISCELLANEOUS 1. The thyrohyoid is one of the four infrahyoid muscles. The four infrahyoid muscles are the sternohyoid, sternothyroid, thyrohyoid, and omohyoid. 2. The carotid sinus of the common carotid artery lies directly lateral to the thyrohyoid (between the thyrohyoid and the sternocleidomastoid, superior in the neck). Given the neurologic reflex that occurs to lower blood pressure when the carotid sinus is pressed, manual therapy to this region must be done judiciously, especially with weak and/or elderly clients. 3. The thyrohyoid can be considered to be an upward continuation of the sternothyroid muscle.

676

Omohyoid (of Hyoid Group) The name, omohyoid, tells us that this muscle attaches from the scapula (omo means shoulder, referring to the scapula) to the hyoid bone. Derivation omo: Gr. shoulder hyoid: Gr. refers to the hyoid bone Pronunciation O-mo-HI-oyd

ATTACHMENTS INFERIOR BELLY: Scapula the superior border to the

Clavicle the central tendon is bound to the clavicle SUPERIOR BELLY: Clavicle the central tendon is bound to the clavicle to the

Hyoid the inferior surface of the body of the hyoid FUNCTIONS Concentric (Shortening) Mover Actions

Standard Mover Action Notes • The omohyoid attaches from the hyoid bone superiorly, to the clavicle inferiorly (with a continuation of its fibers to the scapula). Therefore its fibers run vertically. When the scapula and the clavicle are fixed (stabilized) and the omohyoid contracts, it pulls the hyoid bone inferiorly toward the clavicle. Therefore the omohyoid depresses the hyoid bone. Movements of the hyoid bone are important in chewing, swallowing, and speech. (action 1) • If the inferior attachments of the omohyoid stay fixed and the hyoid bone is pulled inferiorly, and the suprahyoids contract to fix the hyoid bone to the mandible, and elevators of the mandible contract to fix the mandible to the cranium, then the omohyoid can assist in flexing the neck and head at the spinal joints. This makes sense given that it crosses the cervical vertebrae anteriorly with a vertical direction to its fibers. (action 2)

Reverse Mover Action Note • The omohyoid attaches from the hyoid bone superiorly, to the scapula inferiorly. When the hyoid bone is fixed (stabilized) and the omohyoid contracts, it pulls the scapula superiorly toward the

677

hyoid bone. Therefore the omohyoid elevates the scapula at the scapulocostal joint. (reverse action 1)

FIGURE 12-17

Anterior view of the omohyoid bilaterally. The sternohyoid has been ghosted in on the client’s left side.

Motions 1. The omohyoid has one line of pull upon the neck that creates one motion, which is a combination of depression of the hyoid bone and flexion of the neck (and head). 2. The omohyoid has one line of pull upon the scapula that creates one motion, which is elevation.

Eccentric Antagonist Functions 1. Restrains/slows elevation of the hyoid 2. Restrains/slows depression of the scapula 3. Restrains/slows extension of the neck and head

Isometric Stabilization Functions 1. Stabilizes the hyoid bone 2. Stabilizes the scapula 3. Stabilizes the clavicle 4. Stabilizes the temporomandibular joints (TMJs)

Isometric Function Note • The omohyoid can indirectly assist stabilization of the TMJs by stabilizing the hyoid bone when the suprahyoid muscles contract. With the hyoid stabilized, the suprahyoids can exert their pull on the mandible, thereby stabilizing the TMJs.

Additional Notes on Actions 1. If the omohyoid stabilizes the hyoid bone, and the suprahyoid muscles contract, they will act to depress the mandible at the temporomandibular joints (TMJs). Therefore, via its stabilization of the hyoid, the omohyoid can assist in depressing the mandible. In this manner, all infrahyoid muscles

678

and all suprahyoid muscles can assist in depressing the mandible at the TMJs. 2. All hyoid muscles are important in moving and/or fixing (stabilizing) the hyoid bone. These functions are necessary for chewing, swallowing, and speech. 3. All hyoid muscles can assist with flexion of the neck at the spinal joints. 4. Even though the omohyoid has two bellies that could theoretically contract separately, its line of pull to create an action will not be efficient unless both bellies contract together.

I N N E RVAT I O N The Cervical Plexus ansa cervicalis (C1-C3)

A R T E R I A L S U P P LY The Superior Thyroid Artery (a branch of the External Carotid Artery) and the Transverse Cervical Artery (a branch of the Thyrocervical Trunk)

PA L PAT I O N 1. With the client supine, place palpating fingers lateral to the sternocleidomastoid, just superior to the clavicle, and feel for the fibers of the omohyoid running nearly horizontally. Make sure you are not palpating the scalenes, which are deep to the omohyoid (and have fibers running more vertically). 2. To engage the omohyoid, ask the client to depress the mandible against mild resistance and feel for its contraction. 3. Palpate as much of the omohyoid as possible.

RELATIONSHIP TO OTHER STRUCTURES The omohyoid runs an unusual course. The inferior belly of the omohyoid attaches onto the superior border of the scapula, just superior to the supraspinatus (near the scapular notch). From the scapula, the omohyoid runs anteriorly and slightly superiorly toward the clavicle, deep to the trapezius and superficial to the scalenes. Near the medial end of the clavicle, the omohyoid becomes tendinous (the central tendon). However, it does not attach directly to the clavicle, but rather its central tendon is attached to the clavicle by a fibrous sling of tissue. At this point, the omohyoid is deep to the sternocleidomastoid and superficial to the sternothyroid. Its superior belly then runs superiorly and attaches to the hyoid bone, just lateral to the sternohyoid. Except for the platysma, the omohyoid is superficial in two locations: (1) slightly inferior to the hyoid bone and superior to the sternocleidomastoid in the anterior neck and (2) between the sternocleidomastoid and the trapezius in the inferolateral neck (within the posterior triangle of the neck). The omohyoid is located within the deep front line myofascial meridian.

MISCELLANEOUS 1. The omohyoid is one of the four infrahyoid muscles. The four infrahyoid muscles are the sternohyoid, sternothyroid, thyrohyoid, and omohyoid. 2. The carotid sinus of the common carotid artery lies slightly lateral to the omohyoid (between the omohyoid and the sternocleidomastoid, midway up the neck). Given the neurologic reflex that occurs to lower blood pressure when the carotid sinus is pressed, manual therapy to this region must be done judiciously, especially with weak and/or elderly clients. 3. The omohyoid is unusual in that it has two separate bellies: a superior belly and an inferior belly. 4. The omohyoid’s two bellies are separated by its central tendon (also known as the intermediate tendon). Like the digastric (a suprahyoid muscle), the omohyoid’s central tendon is tethered (i.e., attached) to bone by a fibrous sling of tissue.

679

680

REVIEW QUESTIONS 1. The major muscles of mastication are innervated by what nerve? ____________________________ 2. What structure(s) is (are) found deep to the superior portion of the temporalis? ____________________________ ____________________________ 3. The _______ is the prime mover of elevation of the mandible at the temporomandibular joints. 4. Placement of palpation fingers between the zygomatic arch and the angle of the mandible is the starting position for palpation of what muscle? ____________________________ 5. Explain the role of the lateral pterygoid as it relates to protraction of the mandible at the temporomandibular joints. ____________________________ ____________________________ ____________________________ 6. Describe the motion created by the medial pterygoid. ____________________________ ____________________________ 7. All the hyoid muscles attach to the hyoid bone except the_______. 8. Stabilizing the hyoid bone would require the suprahyoids and infrahyoids to act_______ ____________________________ 9. Name the two hyoid muscles that have central tendons tethered to bone by a fibrous sling. ____________________________ ____________________________ 10. Because of their anatomic location, care must be exercised when palpating the hyoid muscles because of what neurologic reflex? ____________________________ ____________________________ For answers to these questions, visit http://evolve.elsevier.com/Muscolino/muscular

681

THINK IT THROUGH Take a moment to consider the importance of a stabilized hyoid bone. Given the number of functions that require this bone to be stabilized, what might the potential problems or consequences be if a client’s ability to do so were compromised? ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________

682

CHAPTER 13

683

Muscles of Facial Expression CHAPTER OUTLINE Scalp: Occipitofrontalis Temporoparietalis Auricularis group Eye: Orbicularis oculi Levator palpebrae superioris Corrugator supercilii Nose: Procerus Nasalis Depressor septi nasi Mouth: Levator labii superioris alaeque nasi Levator labii superioris Zygomaticus minor Zygomaticus major Levator anguli oris Risorius Depressor anguli oris Depressor labii inferioris Mentalis Buccinator Orbicularis oris Platysma

OBJECTIVES After completing this chapter, the student should be able to perform the following for each of the muscles covered in the chapter: 1. Explain the general structure. 2. Explain the general function 3. State the attachments. 4. State the standard mover actions. 5. Discuss the line(s) of pull the muscle has and the motion(s) created. 6. State the nervous innervation. 7. State the arterial supply. 8. Describe the starting position for palpation. 9. Describe the steps for palpation.

684

10. Discuss the muscle’s relationship to other body structures. 11. Discuss additional information that may help with palpation, assessment, and clinical decision-making. CHAPTER OVERVIEW The muscles of facial expression can be subdivided into four groups: muscles of facial expression of the scalp, eye, nose, and mouth. Overview of STRUCTURE Some sources do not include the muscles of the scalp in the muscles of facial expression. Although they are the least active with facial expression, they can be considered to be involved; this is especially true of the occipitofrontalis. The platysma of the neck is included here as a muscle of fascial expression of the mouth. Some sources treat this muscle as a neck muscle because it is primarily located in the neck, or as a muscle of mastication because it can move the mandible at the temporomandibular joints (TMJs). The levator labii superioris alaeque nasi is a facial expression muscle of both the nose and the mouth. The orbicularis oris encircles the mouth. All other muscles of the mouth radiate out from the mouth like spokes of a wheel. The modiolus is a fibromuscular condensation approximately ¼ inch (0.5 cm) lateral to the angle of the mouth. Six muscles of the mouth attach into the modiolus: the zygomaticus major, levator anguli oris, risorius, depressor anguli oris, buccinator, and orbicularis oris. Overview of FUNCTION All the facial muscles move the fascia and/or skin of the face and scalp. Therefore they all contribute to facial expressions, which are important for displaying emotions. Although there is certainly some universality of facial expressions expressing emotions, there can be variations from one culture to another. Further, many of these muscles may act in concert with others to add to the spectrum of facial expressions displayed. Some sources state that there are more than 1,800 separate facial expressions that can be created with combinations of the muscles of facial expression. The levator labii superioris alaeque nasi, levator labii superioris, levator anguli oris, and zygomaticus minor and major all elevate the upper lip. The zygomaticus minor, zygomaticus major, risorius, depressor anguli oris, depressor labii inferioris, and platysma all draw the lip(s) and/or the angle (corner) of the mouth laterally. The depressor anguli oris, depressor labii inferioris, mentalis, and platysma all depress the lower lip. Most muscles of facial expression are also functionally important for dilating or constricting (opening or closing) the apertures (openings) of the face (mouth, nostrils, eyes, and ears); this is functionally important to our physiology by allowing or blocking the intake of food, air, light, and sound. Long-standing contraction of a facial expression muscle creates wrinkles in the skin of the face that run perpendicular to the direction of fibers of the underlying muscle. Botox injections temporarily eliminate/remove these wrinkles because Botox paralyzes the muscle, preventing it from contracting. Because the muscle is paralyzed, Botox also decreases the ability to contract the muscle and create facial expressions to convey emotion.

I N N E RVAT I O N The facial muscles (except the levator palpebrae superioris) are innervated by the facial nerve (CN VII).

A R T E R I A L S U P P LY Most muscles of facial expression receive the majority of their arterial supply from the facial artery.

685

http://evolve.elsevier.com/Muscolino/muscular

686

Superficial Right Lateral View of the Muscles of the Head

FIGURE 13-1

Superficial right lateral view of the muscles of the head.

687

Anterior Views of the Muscles of the Head

FIGURE 13-2 Superficial and intermediate anterior views of the muscles of the head. The platysma has been ghosted in on the right side. Note: Acronyms used on the person’s left side are defined on the right side.

688

Posterior View of the Muscles of the Head

FIGURE 13-3

Superficial posterior view of the muscles of the head.

689

Facial Landmarks

FIGURE 13-4

Facial landmarks. A and B, Anterior views of the face. C, Anterolateral view of the nose. D, Lateral view of the right ear.

690

SCALP  

691

Occipitofrontalis (of Epicranius) The name, occipitofrontalis, tells us that this muscle lies over the occipital and frontal bones. Derivation occipitofrontalis: L. refers to the occiput and the frontal bone Pronunciation ok-SIP-i-to-fron-TA-lis

ATTACHMENTS OCCIPITALIS: Occipital Bone and the Temporal Bone the lateral ⅔ of the highest nuchal line of the occipital bone and the mastoid area of the temporal bone to the

Galea Aponeurotica FRONTALIS: Galea Aponeurotica to the

Fascia and Skin overlying the Frontal Bone FUNCTIONS Concentric Mover Actions 1. Draws the Scalp Posteriorly (Elevation of the Eyebrow) 2. Draws the Scalp Anteriorly

FIGURE 13-5 The occipitofrontalis. A, Lateral view of the right occipitofrontalis. The trapezius and sternocleidomastoid have been ghosted in. B, Expression of elevating the eyebrows created by the bilateral contraction of the occipitofrontalis.

692

Mover Action Notes • The occipitofrontalis attaches from the occipital and temporal bones posteriorly, to the fascia and skin overlying the frontal bone anteriorly. The posterior attachment, which is bone, is more fixed than the anterior attachment, which is soft tissue. Therefore when the posterior attachment is fixed, and the occipitofrontalis contracts, it pulls the anterior attachment toward the posterior attachment. When this occurs, the entire scalp moves posteriorly. This pulls on the fascia and skin located superior to the eye, causing the eyebrow to elevate and the skin of the forehead to wrinkle. (action 1) • The frontalis belly of the occipitofrontalis attaches from the fascia and skin overlying the frontal bone to the galea aponeurotica posteriorly. When the anterior attachment is fixed and the frontalis contracts, it pulls the posterior attachment (the galea aponeurotica) toward the anterior attachment. Therefore the scalp is drawn anteriorly. When this occurs, the skin of the forehead may also wrinkle. (action 2)

Motion 1. The occipitofrontalis has one line of pull so its motion is its action, drawing the scalp posteriorly (which elevates the eyebrow).

I N N E RVAT I O N The Facial Nerve (CN VII) occipitalis: posterior auricular branch of the facial nerve frontalis: temporal branches of the facial nerve

A R T E R I A L S U P P LY Occipitalis: the Occipital and Posterior Auricular Arteries (branches of the External Carotid Artery) Frontalis: supraorbital and supratrochlear branches of the Ophthalmic Artery (a branch of the Internal Carotid Artery)

PA L PAT I O N 1. With the client prone or supine, place palpating fingers over the occipital bone and feel for the occipitalis, over the parietal bone and feel for the galea aponeurotica, and over the frontal bone and feel for the frontalis. 2. Ask the client to wrinkle the skin of the forehead, and feel for the contraction of the muscle.

RELATIONSHIP TO OTHER STRUCTURES The occipitalis is directly superior to the most superficial muscles of the posterior neck that attach into the superior nuchal line and the mastoid process, namely, the trapezius and the sternocleidomastoid. The frontalis is superior to and even blends into the procerus, the corrugator supercilii, and the orbicularis oculi. Lateral to the frontalis and the galea aponeurotica is the temporoparietalis, and deep to that, the temporalis. The occipitofrontalis is located within the superficial back line myofascial meridian.

MISCELLANEOUS 1. The occipitofrontalis attaches into the galea aponeurotica; the temporoparietalis also attaches into the galea aponeurotica. The occipitofrontalis and the temporoparietalis together are known as the epicranius. (Note: The galea aponeurotica is also known as the epicranial aponeurosis.) 2. The occipitofrontalis can be considered to be two separate muscles: the occipitalis and the frontalis. 3. Elevation of the eyebrows often accompanies glancing upward. Elevation of the eyebrows is associated with the expressions of surprise, shock, horror, fright, or recognition. 4. The occipitofrontalis is located within the scalp. The scalp consists of five layers: the skin,

693

subcutaneous tissue, the epicranius and its aponeurosis (the galea aponeurotica), loose connective tissue, and the pericranium. Of these layers, the skin, the subcutaneous tissue, and the galea aponeurotica are firmly connected to each other. 5. The left and right frontalis muscles blend into each other in the midline of the head. The left and right occipitalis muscles usually have a gap between them that is filled in with an extension of the galea aponeurotica. 6. The occipitofrontalis is often ignored or only worked lightly during bodywork. It is a muscle like any other in the body, and moderate or even deeper work may be done to benefit the client. Because tension headaches often involve the occipitofrontalis, this muscle should be evaluated in any client complaining of headaches, especially tension headaches.

694

Temporoparietalis (of Epicranius) The name, temporoparietalis, tells us that this muscle lies over the temporal and parietal bones. Derivation temporoparietalis: L. refers to the temporal and parietal bones Pronunciation TEM-po-ro-pa-RI-i-TAL-is

ATTACHMENTS Fascia Superior to the Ear to the Lateral Border of the Galea Aponeurotica

FUNCTIONS Concentric Mover Actions 1. Elevates the Ear 2. Tightens the Scalp

Mover Action Notes • The temporoparietalis attaches from the fascia superior to the ear inferiorly, to the galea aponeurotica superiorly (with its fibers running vertically). When the temporoparietalis contracts, it pulls the fascia that is superior to the ear superiorly toward the galea aponeurotica, which causes the ear to elevate. (action 1) • Because the fibers of the temporoparietalis attach into the galea aponeurotica, when the temporoparietalis contracts it exerts a pull on the galea aponeurotica, which causes the scalp to tighten. (action 2)

Motion 1. The temporoparietalis has one line of pull so its motion is its action, tightening the scalp and elevating the ear.

I N N E RVAT I O N The Facial Nerve (CN VII) temporal branch

A R T E R I A L S U P P LY The Superficial Temporal and Posterior Auricular Arteries (branches of the External Carotid Artery)

PA L PAT I O N 1. With the client prone or supine, place palpating fingers 1 to 2 inches (2.5 to 5 cm) superior and slightly anterior to the ear. 2. Have the client contract the temporoparietalis to elevate the ear (if able to) and feel for the contraction of the temporoparietalis. Be sure that you are superior enough so that you are on the temporoparietalis and not on the auricularis superior, which can also elevate the ear.

695

FIGURE 13-6

Lateral view of the right temporoparietalis.

RELATIONSHIP TO OTHER STRUCTURES The temporoparietalis is superficial and lies between the frontalis and the auricularis anterior and auricularis superior. The temporoparietalis is involved with the deep front line myofascial meridian.

MISCELLANEOUS 1. The temporoparietalis attaches into the galea aponeurotica; the occipitofrontalis also attaches into the galea aponeurotica. The occipitofrontalis and the temporoparietalis together are known as the epicranius. (Note: The galea aponeurotica is also known as the epicranial aponeurosis.) 2. The temporoparietalis is located within the scalp. The scalp consists of five layers: the skin, subcutaneous tissue, the epicranius and its aponeurosis (the galea aponeurotica), loose connective tissue, and the pericranium. Of these layers, the skin, the subcutaneous tissue, and the galea aponeurotica are firmly connected to each other. 3. The degree of development of the temporoparietalis varies. In some individuals, it is very thin; in others, it is nonexistent. 4. In addition to the galea aponeurotica, the temporoparietalis often attaches directly into the belly of the frontalis muscle.

696

Auricularis Group There are three auricularis muscles: the auricular anterior, auricular superior, and auricularis posterior. The name, auricularis, tells us that these muscles are involved with the ear. Anterior, superior, and posterior tell us their location relative to the ear. Derivation auricularis: L. ear anterior: L. before, in front of superior: L. upper, higher than posterior: L. behind, toward the back Pronunciation aw-RIK-u-la-ris an-TEE-ri-or sue-PEE-ri-or pos-TEE-ri-or

ATTACHMENTS AURICULARIS ANTERIOR: Galea Aponeurotica the lateral margin to the

Anterior Ear the spine of the helix AURICULARIS SUPERIOR: Galea Aponeurotica the lateral margin to the

Superior Ear the superior aspect of the cranial surface AURICULARIS POSTERIOR: Temporal Bone the mastoid area of the temporal bone to the

Posterior Ear the ponticulus of the eminentia conchae FUNCTIONS Concentric Mover Actions 1. Draws the Ear Anteriorly (auricularis anterior) 2. Elevates the Ear (auricularis superior) 3. Draws the Ear Posteriorly (auricularis posterior) 4. Tightens and Moves the scalp (auricularis anterior and superior)

Mover Action Notes • The auricularis anterior attaches from the ear posteriorly, to the galea aponeurotica anteriorly (with its fibers running horizontally). When the auricularis anterior contracts, it pulls the ear toward the more anterior attachment. Therefore the auricularis anterior draws the ear anteriorly. (action 1)

697

FIGURE 13-7

Lateral view of the right auricularis muscles.

• The auricularis superior attaches from the ear inferiorly, to the galea aponeurotica superiorly (with its fibers running vertically). When the auricularis superior contracts, it pulls the ear toward the more superior attachment; therefore the auricularis superior elevates the ear. (Note: The auricularis anterior also has a slight vertical orientation to its fibers; therefore it can also help elevate the ear.) (action 2) • The auricularis posterior attaches from the ear anteriorly, to the temporal bone posteriorly (with its fibers running horizontally). When the auricularis posterior contracts, it pulls the ear toward the more posterior attachment. Therefore the auricularis posterior draws the ear posteriorly. (action 3) • If the auricular (ear) attachment is more fixed, the auricularis anterior and superior could pull on the galea aponeurotica, thereby tightening and moving the scalp. (action 4)

Motions 1. Each of the auricularis muscles has one line of pull so its motion is its action: drawing the ear anteriorly (auricularis anterior), elevating the ear (auricularis superior), and drawing the ear posteriorly (auricularis posterior); and tightening the scalp (for auricularis anterior and superior).

I N N E RVAT I O N The Facial Nerve (CN VII) Auricularis anterior and superior: temporal branches Auricularis posterior: posterior auricular branch

A R T E R I A L S U P P LY The Superficial Temporal and Posterior Auricular Arteries (branches of the External Carotid Artery)

PA L PAT I O N 1. With the client prone or supine, place palpating fingers directly anterior, superior, or posterior to

698

the ear. 2. Ask the client to move the ear anteriorly, posteriorly, or superiorly, palpating in the respective area and feeling for the contraction of the corresponding muscle. Keep in mind that many people cannot consciously “will” these muscles to contract.

RELATIONSHIP TO OTHER STRUCTURES The auricularis muscles are located superficially in the scalp. The auricularis anterior and superior are located inferior to the temporoparietalis. The auricularis posterior is located just superior to the cranial attachment of the sternocleidomastoid. The auricularis muscles are involved with the deep front line myofascial meridian.

MISCELLANEOUS 1. The auricularis anterior is the smallest of the three auricularis muscles; the auricularis superior is the largest. 2. One, two, or all three of the auricularis muscles are nonfunctional in many people. 3. The spine of the helix is the cartilage in the helix of the ear. 4. The eminentia conchae is the cartilage in the concha of the ear, which forms an eminence on the cranial surface of the ear. The ponticulus of the eminentia conchae is a ridge found on the eminentia conchae that is the attachment site for the auricularis posterior muscle. 5. Although the auricularis muscles in humans are poorly formed and often nonfunctional, the analogous muscles in dogs (and many other animals) are highly developed. This is clear when one sees how a dog can direct its ears toward the location from which a sound originates.

699

EYE  

700

Orbicularis Oculi The name, orbicularis oculi, tells us that this muscle encircles the eye. Derivation orbicularis: L. a small circle oculi: L. refers to the eye Pronunciation or-BIK-you-la-ris OK-you-lie

ATTACHMENTS Medial Side of the Eye to the Medial Side of the Eye (returns to the same attachment, encircling the eye) ORBITAL PART: the nasal part of the frontal bone, the frontal process of the maxilla, and the medial palpebral ligament to the ORBITAL PART: returns to the same attachment (these fibers encircle the eye) PALPEBRAL PART: the medial palpebral ligament to the PALPEBRAL PART: the lateral palpebral ligament (these fibers run through the connective tissue of the eyelids) LACRIMAL PART: the lacrimal bone to the LACRIMAL PART: the medial palpebral raphe (these fibers are deeper in the eye socket)

FUNCTIONS Concentric Mover Actions 1. Closes and Squints the Eye (orbital part) 2. Depresses the Upper Eyelid (palpebral part) 3. Elevates the Lower Eyelid (palpebral part) 4. Retraction of the Lower Eyelid (lacrimal part) 5. Assists in Tear Transport and Drainage (lacrimal part)

Mover Action Notes • The fiber direction of the orbital part of the orbicularis oculi is circular around the eye. When the orbital part of the orbicularis oculi contracts, it acts as a circular sphincter muscle that closes in around the eye, not only forcing the two eyelids together but also closing in the tissue above and below the eye. This is often termed forceful closure of the eye, or more commonly, squinting. (Note: To understand how a circular sphincter muscle works, the following reasoning applies: if a linear muscle shortens, its length decreases. When that same linear muscle is arranged in a circular fashion and shortens, the length of the line you have to make the circle decreases and therefore the size of the circle lessens, which can close in on whatever structure is being surrounded by it.) (action 1)

701

FIGURE 13-8

The orbicularis oculi. A, Anterior view of the right orbicularis oculi. B, Anterolateral view of the expression created by the contraction of the right orbicularis oculi.

• The palpebral part of the orbicularis oculi has fibers that are arranged in an arc-like fashion in the upper eyelid. (The direction of the fibers is a horizontal arc with the convexity oriented superiorly.) When the fibers contract, the arc flattens down and the upper eyelid is depressed, gently closing the eye from above. (action 2) • The palpebral part of the orbicularis oculi has fibers that are arranged in an upside-down, arc-like fashion in the lower eyelid. (The direction of the fibers is a horizontal arc with the convexity oriented inferiorly.) When the fibers contract, the arc flattens upward and the lower eyelid is elevated, gently closing the eye from below. (action 3) • The lacrimal part of the orbicularis oculi is located deeper in the eye socket (with its fibers running horizontally from anterior to posterior). When the lacrimal part contracts, it pulls on the medial palpebral raphe, causing the lower eyelid to be retracted, and thereby pulled against the surface of the eye (this also prevents eversion of the lower eyelid). Holding the lower eyelid against the surface of the eye helps to direct (transport) tear fluid toward the medial corner of the eye where it can be drained into the lacrimal sac. When the lacrimal part of the orbicularis oculi contracts, it also exerts a pulls on the lacrimal sac that dilates it and increases its ability to drain tears from the surface of the eye. (actions 4, 5)

702

Motions Because the orbicularis oculi has more than one line of pull, it can create more than one motion. 1. The orbital and palpebral parts of the orbicularis oculi essentially have one line of pull and therefore one motion, which is to close the eye (which involves depressing the upper eyelid and elevating the lower eyelid). 2. The lacrimal part of the orbicularis oculi has one line of pull and therefore one motion, which is to pull the lower eyelid posteriorly against the eye.

I N N E RVAT I O N The Facial Nerve (CN VII) temporal and zygomatic branches

A R T E R I A L S U P P LY The Branches of the Facial Artery and Superficial Temporal Artery (both branches of the External Carotid Artery)

PA L PAT I O N 1. To palpate the orbital part, with the client supine, place palpating fingers inferior, lateral, or superior to the eye. 2. Ask the client to forcefully close the eye and feel for the contraction of the orbicularis oculi. 3. To palpate the palpebral part, place palpating fingers gently on the upper and lower eyelids. 4. Ask the client to gently close the eye and feel for its contraction.

RELATIONSHIP TO OTHER STRUCTURES The orbicularis oculi is superficial and encircles the eye. The orbicularis oculi is inferior to the frontalis and the corrugator supercilii and superior to the levator labii superioris alaeque nasi, levator labii superioris, zygomaticus minor, and zygomaticus major. It is lateral to the procerus and nasalis and medial to the temporoparietalis and the temporalis. Some fibers of the levator palpebrae superioris pierce through the palpebral part of the orbicularis oculi to attach into the skin of the upper eyelid. The orbicularis oculi is involved with the deep front line myofascial meridian.

MISCELLANEOUS 1. The palpebral part of the orbicularis oculi is under both conscious and unconscious control and may contract reflexively to close the eye (for protection and as part of blinking). 2. Superiorly, the orbital part of the orbicularis oculi blends in with fibers of the frontalis and the corrugator supercilii. Inferiorly, the orbital part of the orbicularis oculi blends in with fibers of the zygomaticus minor, levator labii superioris, and levator labii superioris alaeque nasi. 3. Some fibers of the orbital part may blend into the skin, deep to the eyebrow, creating the depressor supercilii muscle. 4. If the entire orbicularis oculi contracts, the eye will close forcefully (i.e., the eyelids and the surrounding tissue close in around the eye) and the skin of the eyelids and surrounding area (forehead, temple, and cheek) will be drawn medially toward the attachment at the medial eye. This action creates a facial expression in which the amount of light entering the eye decreases and wrinkles radiating out from the lateral eye form; these wrinkles are called crow’s feet. 5. The medial and lateral palpebral raphes are where the tissue from the upper and lower eyelids come together at the corners (canthi) of the eye. The medial and lateral palpebral ligaments are small ligaments located directly next to the raphes in the corners of the eye. (A raphe is a seam of tissue formed by the union of the halves of a part.) 6. When the tissue located superior to the eye is pulled down around the eye by the contraction of the orbicularis oculi, it helps shield the eye from bright sunlight. The corrugator supercilii and the procerus can also assist with this function of shielding the eye from bright sunlight. 7. Given that the lacrimal part of the orbicularis oculi helps drain tears from the surface of the eye into the lacrimal sac, weakness or flaccid paralysis of the lacrimal part of the orbicularis oculi results

703

in excessive spilling of tears over the lower eyelid (i.e., crying).

704

Levator Palpebrae Superioris The name, levator palpebrae superioris, tells us that this muscle elevates the upper eyelid. Derivation levator: L. lifter palpebrae: L. eyelid superioris: L. upper Pronunciation LE-vay-tor pal-PEE-bree su-PEE-ri-OR-is

ATTACHMENTS Sphenoid Bone the anterior surface of the lesser wing of the sphenoid to the Upper Eyelid the fascia and skin of the upper eyelid

FUNCTIONS Concentric Mover Action 1. Elevates the Upper Eyelid

Mover Action Note • The levator palpebrae superioris attaches from the sphenoid bone superiorly, to the upper eyelid inferiorly. When the levator palpebrae superioris contracts, it pulls the upper eyelid superiorly toward the sphenoid bone. Therefore the levator palpebrae superioris elevates the upper eyelid (action 1).

Motion 1. The levator palpebrae superioris has one line of pull so its motion is its action, elevating the upper eyelid.

I N N E RVAT I O N The Oculomotor Nerve (CN III)

A R T E R I A L S U P P LY The Ophthalmic Artery (a branch of the Internal Carotid Artery)

PA L PAT I O N 1. With the client supine, have the client close the eye. 2. Gently place your palpating finger on the client’s upper eyelid. Then ask the client to open the eye and feel for the contraction of the levator palpebrae superioris.

RELATIONSHIP TO OTHER STRUCTURES The levator palpebrae superioris begins in the orbital socket, deep to the orbicularis oculi. Some of its fibers pierce through the orbicularis oculi to attach into the skin of the eyelid, superficial to the orbicularis oculi. The levator palpebrae superioris is superior to, and somewhat conjoined to, the superior rectus muscle of the eye.

705

The levator palpebrae superioris is involved with the deep front line myofascial meridian.

FIGURE 13-9 The levator palpebrae superioris. A, Lateral view of the right levator palpebrae superioris. B, Anterolateral view of the right levator palpebrae superioris. C, Anterior view of the expression created by the bilateral contraction of the levator palpebrae superioris.

706

Corrugator Supercilii The name, corrugator supercilii, tells us that this muscle wrinkles the skin of the eyebrow. Derivation corrugator: L. to wrinkle together supercilii: L. refers to the eyebrow Pronunciation KOR-u-gay-tor su-per-SIL-i-eye

ATTACHMENTS Inferior Frontal Bone the medial end of the superciliary arch of the frontal bone to the Fascia and Skin Superior to the Eyebrow

FUNCTIONS Concentric Mover Action 1. Draws the Eyebrow Inferomedially

Mover Action Note • The corrugator supercilii attaches to the region of the frontal bone next to the nasal bone. From there, its fibers run superiorly and laterally to attach into the skin superior to the eyebrow. Because the frontal bone attachment is more fixed, when the corrugator supercilii contracts, it pulls the skin deep to the eyebrow inferomedially toward the frontal bone attachment (toward the other eyebrow). When both corrugator supercilii muscles contract, both eyebrows are pulled inferomedially toward each other. (action 1)

Motion 1. The corrugator supercilii has one line of pull so its motion is its action, drawing the eyebrow inferomedially.

I N N E RVAT I O N The Facial Nerve (CN VII) temporal branch

A R T E R I A L S U P P LY The Supratrochlear and Supraorbital Arteries (branches of the Ophthalmic Artery)

PA L PAT I O N 1. With the client supine, place palpating fingers over the middle to medial portion of the eyebrow. 2. Ask the client to frown, drawing the eyebrow medially and inferiorly, and feel for the contraction of the corrugator supercilii. 3. Continue palpating the corrugator supercilii inferomedially toward its frontal bone attachment.

707

FIGURE 13-10 The corrugator supercilii. A, Anterior view of the right corrugator supercilii. B, Anterior view of the expression created by the bilateral contraction of the corrugator supercilii.

RELATIONSHIP TO OTHER STRUCTURES The corrugator supercilii is lateral to the procerus. The corrugator supercilii is deep to the frontalis. The corrugator supercilii lies toward the superior end of the orbicularis oculi. Where these two muscles overlap, the corrugator supercilii is deep to the orbicularis oculi. The corrugator supercilii is involved with the deep front line and superficial back line myofascial meridians.

MISCELLANEOUS 1. Some fibers of the corrugator supercilii blend in with fibers of the frontalis and the orbicularis oculi. 2. The action of drawing the eyebrows inferiorly and medially is involved in frowning. It is also useful in shielding the eyes from bright sunlight. (Note: The orbicularis oculi and the procerus can also assist with this function of shielding the eyes from bright sunlight.) 3. When the corrugator supercilii contracts, it causes vertical wrinkles superior and medial to the

708

eyes.

709

NOSE  

710

Procerus The name, procerus, tells us that this muscle helps create the expression of superiority of a nobleman or prince. Derivation procerus: L. a chief noble, prince Pronunciation pro-SAIR-rus

ATTACHMENTS Fascia and Skin over the Nasal Bone to the Fascia and Skin Medial to the Eyebrow

FUNCTIONS Concentric Mover Actions 1. Wrinkles the Skin of the Nose Upward 2. Draws Down the Medial Eyebrow

Mover Action Notes • The procerus attaches from the fascia and skin over the nose to the fascia and skin medial to the eyebrow (with its fibers running vertically). When the superior attachment is fixed and the procerus contracts, it pulls the fascia and skin of the nose superiorly, which causes the skin of the nose to wrinkle. (action 1) • The procerus attaches from the fascia and skin over the nose to the fascia and skin medial to the eyebrow (with its fibers running vertically). When the inferior attachment is fixed and the procerus contracts, it pulls the medial eyebrow inferiorly (downward) toward the nose. Therefore the procerus draws down the medial eyebrow (this also causes the skin over the nose to wrinkle). (action 2)

Motions 1. The procerus has one line of pull upon its lower attachment on the nose, so its motion is its action, wrinkling the skin of the nose upward. 2. The procerus has one line of pull upon its upper attachment on the eyebrow, so its motion is its action, drawing down the medial eyebrow.

I N N E RVAT I O N The Facial Nerve (CN VII) superior buccal branches

A R T E R I A L S U P P LY The Facial Artery (a branch of the External Carotid Artery)

711

FIGURE 13-11

The procerus. A, Anterior view of the right procerus. B, Anterior view of the expression created by the bilateral contraction of the procerus.

PA L PAT I O N 1. With the client supine, place palpating fingers directly superior to the bridge of the nose. 2. Ask the client to wrinkle the nose upward and/or draw the medial eyebrows down with a look of disdain as in frowning, and feel for the contraction of the procerus. 3. Palpate the entire procerus.

RELATIONSHIP TO OTHER STRUCTURES The procerus is located superior to the nasalis, inferior to the frontalis, and medial to the corrugator supercilii and the orbicularis oculi. The procerus is involved with the deep front line and superficial back line myofascial meridians.

MISCELLANEOUS 1. The procerus often blends with the frontalis superiorly and the nasalis inferiorly. 2. The action of wrinkling the skin of the nose and/or drawing down the medial eyebrows can

712

create the look of frowning or disdain that a person may make to convey an air of superiority (hence the name procerus, meaning chief noble or prince). 3. Bringing the medial eyebrows down is part of the facial expression of frowning, but it also helps shield the eyes from bright sunlight. (Note: The orbicularis oculi and the corrugator supercilii can also assist with this function of shielding the eyes from bright sunlight.)

713

Nasalis The name, nasalis, tells us that this muscle is involved with the nose. Derivation nasalis: L. nose Pronunciation nay-SA-lis

ATTACHMENTS Maxilla to the Cartilage of the Nose and the Opposite-Side Nasalis Muscle ALAR PART: the maxilla, lateral to the lower part of the nose to the ALAR PART: the alar cartilage of the nose TRANSVERSE PART: the maxilla, lateral to the upper part of the nose to the TRANSVERSE PART: the opposite-side nasalis over the upper cartilage of the nose

FUNCTIONS Concentric Mover Actions 1. Flares the Nostril 2. Constricts the Nostril

Mover Action Notes • The alar part of the nasalis pulls directly on the lower part of the alar cartilage of the nose from the maxillary attachment, which is more lateral (the fibers are running somewhat horizontally). Therefore the lower part of the nose is pulled laterally, flaring the nostril and increasing the aperture for breathing. (action 1) • The transverse part of each nasalis attaches into the opposite-side nasalis over the upper cartilage of the nose. When the transverse part of the nasalis contracts, it pulls the common midline attachment at the upper part of the nose down and in. This results in a constriction of the nose, which narrows the airway when breathing. (action 2)

Motions Because the nasalis has more than one line of pull, it can create more than one motion. 1. The alar part has one line of pull and therefore creates one motion, which is flaring the nostril. 2. The transverse part has one line of pull and therefore creates one motion, which is constricting the nostril.

714

FIGURE 13-12

The nasalis. A, Anterior view of the right nasalis. B, Anterior view of the expression created by the bilateral contraction of the alar part of the nasalis.

I N N E RVAT I O N The Facial Nerve (CN VII) superior buccal branches

A R T E R I A L S U P P LY The Facial Artery (a branch of the External Carotid Artery)

PA L PAT I O N 1. With the client supine, place palpating fingers over the cartilage of the nose, as well as the skin just lateral to the cartilage of the nose. 2. Have the client flare the nostrils as if taking in a deep breath and feel for the contraction of the (lower) alar part of the nasalis. Then have the client constrict the nostrils and palpate the (upper) transverse part of the nasalis.

715

RELATIONSHIP TO OTHER STRUCTURES The nasalis is inferior to the procerus, medial to the levator labii superioris alaeque nasi, superior to the orbicularis oris, and superolateral to the depressor septi nasi. The nasalis is involved with the deep front line and superficial back line myofascial meridians.

MISCELLANEOUS 1. The alar part of the nasalis is sometimes called the dilatator naris. The transverse part of the nasalis is sometimes called the compressor naris. 2. The maxillary attachments of the transverse and alar parts of the nasalis often partially blend together. 3. Superiorly, the nasalis often blends in with the procerus. 4. The muscle directly inferomedial to the nasalis, the depressor septi nasi, is sometimes considered to be a part of the alar portion (dilatator nasi) of the nasalis. 5. The action of flaring the nostrils to increase the aperture for breathing in is important for deep inspiration. This action can also be associated with facial expressions during emotional states.

716

Depressor Septi Nasi The name, depressor septi nasi, tells us that this muscle depresses the nasal septum. (The septum is the midline cartilage of the nose.) Derivation depressor: L. depressor septi: L. refers to the nasal septum nasi: L. refers to the nose Pronunciation dee-PRES-or SEP-ti NAY-zi

ATTACHMENTS Maxilla the incisive fossa of the maxilla to the Cartilage of the Nose the septum and the alar cartilage of the nose

FUNCTIONS Concentric Mover Action 1. Constricts the Nostril

Mover Action Note • The depressor septi nasi attaches from the maxilla inferiorly, to the cartilage of the nose superiorly (with its fibers running vertically). Given that the maxillary attachment is fixed, when the depressor septi nasi contracts, it pulls the cartilage of the nose inferiorly toward the maxilla. More specifically, the septum of the nose will be depressed and the alar cartilage will be depressed and pulled medially. These actions cause the nostril to constrict, which narrows the airway when breathing. (action 1)

Motion 1. The depressor septi nasi has one line of pull so its motion is its action, constricting the nostril.

I N N E RVAT I O N The Facial Nerve (CN VII) superior buccal branches

A R T E R I A L S U P P LY The Facial Artery (a branch of the External Carotid Artery)

PA L PAT I O N 1. With the client supine, place palpating fingers directly inferior to the nose. 2. Ask the client to try to pull the middle of the nose down toward the mouth and/or to constrict the nostrils and feel for the contraction of the depressor septi nasi.

717

FIGURE 13-13 The depressor septi nasi. A, Anterior view of the right depressor septi nasi. B, Anterior view of the expression created by the bilateral contraction of the depressor septi nasi.

RELATIONSHIP TO OTHER STRUCTURES The depressor septi nasi is superior to the orbicularis oris, and where they overlap, the depressor septi nasi is deep to the orbicularis oris. The depressor septi nasi is inferior and medial to the nasalis (alar part). The depressor septi nasi is involved with the deep front line myofascial meridian.

MISCELLANEOUS 1. The depressor septi nasi is sometimes simply known as the depressor septi. 2. The depressor septi nasi is sometimes considered to be a part of the alar portion of the nasalis. 3. The action of constricting the nostrils can be associated with facial expressions during emotional states.

718

719

MOUTH  

720

Levator Labii Superioris Alaeque Nasi The name, levator labii superioris alaeque nasi, tells us that this muscle elevates the upper lip and is involved with the ala (cartilage of the nostril of the nose). Derivation levator: L. lifter labii: L. refers to the lip superioris: L. upper alaeque: L. refers to the ala (alar cartilage) nasi: L. refers to the nose Pronunciation le-VAY-tor LAY-be-eye soo-PEE-ri-o-ris a-LEE-kwe NAY-si

ATTACHMENTS Maxilla the frontal process of the maxilla near the nasal bone to the Upper Lip and the Nose LATERAL SLIP: the muscular substance of the lateral part of the upper lip MEDIAL SLIP: the alar cartilage and the fascia and skin of the nose

FUNCTIONS Concentric Mover Actions 1. Elevates the Upper Lip 2. Flares the Nostril 3. Everts the Upper Lip

Mover Action Notes • The lateral slip of the levator labii superioris alaeque nasi attaches from the upper lip inferiorly and has a bony attachment near the eye superiorly (with its fibers running vertically). Because the superior attachment is into bone, it is more fixed than the other soft tissue attachment. When the levator labii superioris alaeque nasi contracts, it pulls the upper lip superiorly toward the other attachment. Therefore the levator labii superioris alaeque nasi elevates the upper lip. (action 1)

721

FIGURE 13-14 The levator labii superioris alaeque nasi (LLSAN). A, Anterior view of the right LLSAN. The levator labii superioris and the orbicularis oris have been ghosted in. B, Anterior view of the expression created by the bilateral contraction of the LLSAN.

• The medial slip of the levator labii superioris alaeque nasi attaches from the alar cartilage and the fascia and skin of the nose medially, to attach onto the maxilla laterally (with its fibers running somewhat horizontally). Because the lateral attachment is into bone, it is more fixed than the other soft tissue attachment. When the levator labii superioris alaeque nasi contracts, it pulls the skin and alar cartilage of the nose toward the other attachment. Therefore the cartilage of the nose is pulled laterally, flaring the nostril and increasing the aperture for breathing. (action 2) • When the inferior attachment of the lateral slip of the levator labii superioris alaeque nasi is pulled superiorly toward the superior attachment, the lower margin of the upper lip is not only pulled superiorly, it is also pulled away from the mouth, curling the upper lip. This curling or pulling away of the upper lip from the face is called eversion of the upper lip. (action 3)

Motions Because the levator labii superior alaeque nasi has more than one line of pull, it can create more than one motion. 1. The lateral slip has one line of pull and therefore creates one motion, which is a combination of elevation and eversion of the upper lip.

722

2. The medial slip has one line of pull and therefore creates one motion, which is flaring the nostril.

I N N E RVAT I O N The Facial Nerve (CN VII) buccal branches

A R T E R I A L S U P P LY The Infraorbital Artery (a branch of the Maxillary Artery)

PA L PAT I O N 1. With the client supine, place palpating fingers just lateral to the nose. 2. Ask the client to flare the nostrils and/or elevate the upper lip to show you the upper teeth, and feel for the contraction of the levator labii superioris alaeque nasi. Try to distinguish it from the nasalis medially and the levator labii superioris laterally.

RELATIONSHIP TO OTHER STRUCTURES The levator labii superioris alaeque nasi is located lateral to the nasalis and medial (and somewhat superficial) to the levator labii superioris. The levator labii superioris alaeque nasi is also medial to the zygomaticus minor. The levator labii superioris alaeque nasi is medial and inferior to the orbicularis oculi. The levator labii superioris alaeque nasi is superior to the orbicularis oris. The levator labii superioris alaeque nasi is involved with the deep front line myofascial meridian.

MISCELLANEOUS 1. Some sources consider the levator labii superioris alaeque nasi muscle to be the angular head of the levator labii superioris. 2. The three main elevators of the upper lip are the levator labii superioris alaeque nasi, the levator labii superioris, and the zygomaticus minor. These three muscles were once considered to be three individual heads (named angularis, infraorbitalis, and zygomaticus, respectively) of the musculus quadratus labii superioris. 3. The levator labii superioris alaeque nasi blends into the levator labii superioris and the orbicularis oris. 4. In addition to increasing the aperture for breathing, flaring the nostrils can also be part of the look of anger. 5. Contraction of the lateral slip of the levator labii superioris alaeque nasi alone will elevate the upper lip, as in showing someone your upper teeth. This action, along with the contraction of other facial muscles, can contribute to the facial expression of a smile or express smugness, contempt, or disdain.

723

Levator Labii Superioris The name, levator labii superioris, tells us that this muscle elevates the upper lip. Derivation levator: L. lifter labii: L. refers to the lip superioris: L. upper Pronunciation le-VAY-tor LAY-be-eye soo-PEE-ri-O-ris

ATTACHMENTS Maxilla at the inferior orbital margin of the maxilla to the Upper Lip the muscular substance of the upper lip

FUNCTIONS Concentric Mover Actions 1. Elevates the Upper Lip 2. Everts the Upper Lip

Mover Action Notes • The levator labii superioris attaches from the upper lip inferiorly, to attach onto the maxilla superiorly (with its fibers running vertically). The superior attachment is into bone and is therefore more fixed than the other attachment, which is into soft tissue. When the levator labii superioris contracts, it pulls the upper lip superiorly toward the maxilla. Therefore the levator labii superioris elevates the upper lip. (action 1) • When the inferior attachment of the levator labii superioris is pulled superiorly toward the superior attachment, the lower margin of the upper lip is not only pulled superiorly, it is also pulled away from the mouth, curling the upper lip. This curling or pulling away of the upper lip from the face is called eversion of the upper lip. (action 2)

Motion 1. The levator labii superioris has one line of pull and therefore creates one motion, which is a combination of elevation and eversion of the upper lip.

724

FIGURE 13-15 The levator labii superioris (LLS). A, Anterior view of the right LLS. The levator labii superioris alaeque nasi and the orbicularis oris have been ghosted in. B, Anterior view of the expression created by the bilateral contraction of the levator labii superioris.

I N N E RVAT I O N The Facial Nerve (CN VII) buccal branches

A R T E R I A L S U P P LY The Facial Artery (a branch of the External Carotid Artery)

PA L PAT I O N 1. With the client supine, place palpating fingers just superior to the upper lip approximately ½ to 1 inch (1-2 cm) medial to the corner of the mouth. 2. Ask the client to elevate the upper lip to show you the upper gums and feel for the contraction of the levator labii superioris. Try to distinguish it from the levator labii superioris alaeque nasi medially and the zygomaticus minor laterally.

725

RELATIONSHIP TO OTHER STRUCTURES The levator labii superioris is between the levator labii superioris alaeque nasi (medially) and the zygomaticus minor (laterally). The levator labii superioris is inferior to the orbicularis oculi; where they overlap, the levator labii superioris is deep to the orbicularis oculi. The levator labii superioris is superior to the orbicularis oris. When the levator labii superioris meets the orbicularis oris, the fibers of the levator labii superioris run deep to and blend into the orbicularis oris. The levator labii superioris is involved with the deep front line myofascial meridian.

MISCELLANEOUS 1. Some sources consider the levator labii superioris alaeque nasi muscle to be the angular head of the levator labii superioris. 2. The three main elevators of the upper lip are the levator labii superioris alaeque nasi, the levator labii superioris, and the zygomaticus minor. These three muscles were once considered to be three individual heads (named angularis, infraorbitalis, and zygomaticus, respectively) of the musculus quadratus labii superioris. 3. The levator labii superioris blends in with the levator labii superioris alaeque nasi and the orbicularis oris. 4. Contraction of the levator labii superioris alone will elevate the upper lip, as in showing someone your upper teeth. This action, along with the contraction of other facial muscles, can contribute to the facial expression of a smile or express smugness, contempt, or disdain.

726

Zygomaticus Minor The name, zygomaticus minor, tells us that this muscle attaches to the zygomatic bone and is small (smaller than the zygomaticus major). Derivation zygomaticus: Gr. refers to the zygomatic bone minor: L. smaller Pronunciation ZI-go-MAT-ik-us MY-nor

ATTACHMENTS Zygomatic Bone near the zygomaticomaxillary suture to the Upper Lip the muscular substance of the upper lip

FUNCTIONS Concentric Mover Actions 1. Elevates the Upper Lip 2. Everts the Upper Lip

Mover Action Notes • The zygomaticus minor attaches from the upper lip inferiorly, to the zygomatic bone superiorly (with its fibers running vertically). The maxillary attachment is into bone and is therefore more fixed than the other attachment, which is into soft tissue. When the zygomaticus minor contracts, it pulls the upper lip superiorly toward the zygomatic bone. Therefore the zygomaticus minor elevates the upper lip. (action 1) • When the inferior attachment of the zygomaticus minor is pulled superiorly toward the superior attachment, the lower margin of the upper lip is not only pulled superiorly, it is also pulled away from the mouth, curling the upper lip. This curling or pulling away of the upper lip from the face is called eversion of the upper lip. (action 2)

Motion 1. The zygomaticus minor has one line of pull and therefore creates one motion, which is a combination of elevation and eversion of the upper lip.

I N N E RVAT I O N The Facial Nerve (CN VII) buccal branches

A R T E R I A L S U P P LY The Facial Artery (a branch of the External Carotid Artery)

727

FIGURE 13-16 The zygomaticus minor. A, Anterior view of the right zygomaticus minor. The zygomaticus major and the orbicularis oris have been ghosted in. B, Anterior view of the expression created by the bilateral contraction of the zygomaticus minor.

PA L PAT I O N 1. With the client supine, place palpating fingers just superior to the upper lip, approximately ½ to 1 inch (1-2 cm) medial to the angle of the mouth. 2. Have the client elevate the upper lip to show you the upper teeth and feel for the contraction of the zygomaticus minor. Try to distinguish it from the levator labii superioris and levator labii superioris alaeque nasi medially and the zygomaticus major laterally.

RELATIONSHIP TO OTHER STRUCTURES The zygomaticus minor is lateral to the levator labii superioris alaeque nasi and the levator labii superioris and medial to the zygomaticus major. The zygomaticus minor is superior to the orbicularis oris and inferior to the orbicularis oculi. The zygomaticus minor is superficial to the levator anguli oris. The zygomaticus minor is involved with the deep front line myofascial meridian.

728

MISCELLANEOUS 1. The zygomaticus minor blends with the levator labii superioris. 2. The three main elevators of the upper lip are the levator labii superioris alaeque nasi, the levator labii superioris, and the zygomaticus minor. These three muscles were once considered to be three individual heads (named angularis, infraorbitalis, and zygomaticus, respectively) of the musculus quadratus labii superioris. 3. Contraction of the zygomaticus minor alone will elevate the upper lip, as in showing someone your upper teeth. This action, along with the contraction of other facial muscles, can contribute to the facial expression of a smile or express smugness, contempt, or disdain. 4. Contraction of the zygomaticus minor also increases the nasolabial sulcus.

729

Zygomaticus Major The name, zygomaticus major, tells us that this muscle attaches to the zygomatic bone and is large (larger than the zygomaticus minor). Derivation zygomaticus: Gr. refers to the zygomatic bone major: L. larger Pronunciation ZI-go-MAT-ik-us MAY-jor

ATTACHMENTS Zygomatic Bone near the zygomaticotemporal suture to the Angle of the Mouth the modiolus, just lateral to the angle of the mouth

FUNCTIONS Concentric Mover Actions 1. Elevates the Angle of the Mouth 2. Draws Laterally the Angle of the Mouth

Mover Action Notes • The zygomaticus major attaches from the zygomatic bone superiorly, to the angle (corner) of the mouth inferiorly (with its fibers running vertically). The zygomatic attachment is into bone and is therefore more fixed than the other attachment, which is into soft tissue. When the zygomaticus major contracts, it pulls the angle of the mouth superiorly toward the zygomatic bone. Therefore the zygomaticus major elevates the angle of the mouth. (action 1) • The zygomaticus major attaches from the zygomatic bone laterally, to the angle (corner) of the mouth medially (with its fibers running somewhat horizontally). The zygomatic attachment is into bone and is therefore more fixed than the other attachment, which is into soft tissue. When the zygomaticus major contracts, it pulls the angle of the mouth toward the zygomatic bone. Therefore the zygomaticus major draws laterally the angle of the mouth. (action 2)

Motion 1. The zygomaticus major has one line of pull and therefore creates one motion, which is a combination of elevating and drawing laterally the angle of the mouth.

730

FIGURE 13-17 The zygomaticus major. A, Anterior view of the right zygomaticus major. The zygomaticus minor and the orbicularis oris have been ghosted in. B, Anterior view of the expression created by the bilateral contraction of the zygomaticus major.

I N N E RVAT I O N The Facial Nerve (CN VII) buccal branches

A R T E R I A L S U P P LY The Facial Artery (a branch of the External Carotid Artery)

PA L PAT I O N 1. With the client supine, place palpating fingers superior and lateral to the angle of the mouth. 2. Have the client smile by drawing the angle of the mouth both superiorly and laterally and feel for the contraction of the belly of the zygomaticus major.

RELATIONSHIP TO OTHER STRUCTURES 731

The zygomaticus major is lateral to the zygomaticus minor. The zygomaticus major is superior to the risorius and the orbicularis oris. The zygomaticus major is superficial to the buccinator and the masseter. The zygomaticus major is involved with the deep front line myofascial meridian.

MISCELLANEOUS 1. The zygomaticus major blends in with the levator anguli oris and the orbicularis oris. 2. The action of elevating the angle of the mouth and drawing it laterally contributes to smiling and laughing. 3. Contraction of the zygomaticus major also increases the nasolabial sulcus. 4. Six muscles attach into the modiolus: the zygomaticus major, levator anguli oris, risorius, depressor anguli oris, buccinator, and orbicularis oris. 5. The modiolus is a fibromuscular condensation approximately ¼ inch (0.5 cm) lateral to the angle of the mouth (see page 448).

732

Levator Anguli Oris The name, levator anguli oris, tells us that this muscle elevates the angle of the mouth. Derivation levator: L. lifter anguli: L. refers to the angle oris: L. mouth Pronunciation le-VAY-tor ANG-you-lie O-ris

ATTACHMENTS Maxilla the canine fossa of the maxilla (just inferior to the infraorbital foramen) to the Angle of the Mouth the modiolus, just lateral to the angle of the mouth

FUNCTIONS Concentric Mover Action 1. Elevates the Angle of the Mouth

Mover Action Note • The levator anguli oris attaches from the maxilla superiorly to the tissue at the angle (corner) of the mouth inferiorly (with its fibers running vertically). The maxillary attachment is into bone and is therefore more fixed than the other attachment, which is into soft tissue. When the levator anguli oris contracts, it pulls the angle of the mouth superiorly toward the maxilla. Therefore the levator anguli oris elevates the angle of the mouth. (action 1)

Motion 1. The levator anguli oris has one line of pull and therefore creates one motion, which is its action of elevation of the angle of the mouth.

I N N E RVAT I O N The Facial Nerve (CN VII) buccal branches

A R T E R I A L S U P P LY The Facial Artery (a branch of the External Carotid Artery)

PA L PAT I O N 1. With the client supine, place palpating fingers just superior to the angle (corner) of the mouth. 2. Have the client elevate the angle of the mouth straight superiorly, attempting to show you the canine tooth, and feel for the contraction of the belly of the levator anguli oris. Try to distinguish it from the levator labii superioris, the zygomaticus major, and the zygomaticus minor.

733

FIGURE 13-18 The right levator anguli oris. A, Anterior view. The orbicularis oris has been ghosted in. B, Anterior view of the expression created by the unilateral contraction of the right levator anguli oris.

RELATIONSHIP TO OTHER STRUCTURES Where they overlap, the levator anguli oris is deep to the levator labii superioris, the zygomaticus minor, and the zygomaticus major. The levator anguli oris is superficial between the zygomaticus minor and the zygomaticus major. The inferior attachment of the levator anguli oris is superficial to the buccinator. The levator anguli oris is superior to the orbicularis oris and inferior to the orbicularis oculi. The levator anguli oris is involved with the deep front line myofascial meridian.

MISCELLANEOUS 1. The levator anguli oris is also known as the caninus (kay-NI-nus). This name is given because the contraction of the levator anguli oris can result in the teeth, especially the canine tooth, becoming visible. 2. At the attachment near the angle of the mouth (the modiolus), fibers of the levator anguli oris blend in with the orbicularis oris, the zygomaticus major, and the depressor anguli oris. 3. Although the action of the levator anguli oris may contribute to a smile, its action alone

734

(unilaterally or bilaterally) can manifest a sneer. Bilateral contraction of this muscle can also reproduce the typical Dracula expression, wherein the canine teeth are exposed. 4. Contraction of the levator anguli oris also increases the nasolabial sulcus. 5. Six muscles attach into the modiolus: the zygomaticus major, the levator anguli oris, the risorius, the depressor anguli oris, the buccinator, and the orbicularis oris. 6. The modiolus is a fibromuscular condensation approximately ¼ inch (0.5 cm) lateral to the angle of the mouth (see page 448).

735

Risorius The name, risorius, tells us that this muscle is involved with laughing. Derivation risorius: L. laughing Pronunciation ri-ZOR-ee-us

ATTACHMENTS Fascia and Skin Superficial to the Masseter to the Angle of the Mouth

the modiolus, just lateral to the angle of the mouth

FUNCTIONS Concentric Mover Action 1. Draws Laterally the Angle of the Mouth

Mover Action Note • The risorius attaches from the fascia and skin superficial to the masseter laterally, to the angle (corner) of the mouth medially (with its fibers running somewhat horizontally). If the lateral attachment is the more fixed attachment and the risorius contracts, it pulls the angle of the mouth laterally. Therefore the risorius draws laterally the angle of the mouth. (action 1)

Motion 1. The risorius has one line of pull and therefore creates one motion, which is its action of drawing laterally the angle of the mouth.

I N N E RVAT I O N The Facial Nerve (CN VII) buccal branches

A R T E R I A L S U P P LY The Facial Artery (a branch of the External Carotid Artery)

PA L PAT I O N 1. With the client supine, place palpating fingers directly lateral to the angle of the mouth. 2. Ask the client to draw the angle (corner) of the mouth directly lateral and feel for the contraction of the belly of the risorius. Be sure that you are not palpating too superiorly onto the zygomaticus major, which can also help draw the angle of the mouth laterally.

RELATIONSHIP TO OTHER STRUCTURES The risorius is inferior to the zygomaticus major and lateral to the orbicularis oris.

736

FIGURE 13-19 The risorius. A, Anterior view of the right risorius. The orbicularis oris has been ghosted in. B, Anterior view of the expression created by the bilateral contraction of the risorius.

The risorius is superior to the depressor anguli oris and the platysma. Where these muscles overlap, the risorius is superficial. The risorius is superficial to the buccinator. The risorius is involved with the deep front line myofascial meridian.

MISCELLANEOUS 1. The lateral attachment of the risorius varies greatly in its presentation. 2. The medial attachment of the risorius also varies, often attaching approximately ¼ inch (0.5 cm) inferior to the angle of the mouth. 3. Drawing the angle of the mouth laterally is involved with grinning, smiling, and laughing. 4. Six muscles attach into the modiolus: the zygomaticus major, levator anguli oris, risorius, depressor anguli oris, buccinator, and orbicularis oris. 5. The modiolus is a fibromuscular condensation approximately ¼ inch (0.5 cm) lateral to the angle of the mouth (see page 448).

737

738

Depressor Anguli Oris The name, depressor anguli oris, tells us that this muscle depresses the angle of the mouth. Derivation depressor: L. depressor anguli: L. refers to the angle oris: L. mouth Pronunciation dee-PRES-or ANG-you-lie OR-is

ATTACHMENTS Mandible the oblique line of the mandible, inferior to the mental foramen to the Angle of the Mouth the modiolus, just lateral to the angle of the mouth

FUNCTIONS Concentric Mover Actions 1. Depresses the Angle of the Mouth 2. Draws Laterally the Angle of the Mouth

Mover Action Notes • The depressor anguli oris attaches from the mandible inferiorly, to the tissue at the angle (corner) of the mouth superiorly (with its fibers running vertically). The mandibular attachment is into bone and is therefore more fixed than the other attachment, which is into soft tissue. When the depressor anguli oris contracts, it pulls the angle of the mouth inferiorly toward the mandible. Therefore the depressor anguli oris depresses the angle of the mouth. (action 1) • The depressor anguli oris attaches from the mandible laterally, into the angle (corner) of the mouth medially (with its fibers running somewhat horizontally). The mandibular attachment is into bone and is therefore more fixed than the other attachment, which is into soft tissue. When the depressor anguli oris contracts, it pulls the angle of the mouth laterally toward the mandible. Therefore the depressor anguli oris draws laterally the angle of the mouth. (action 2)

Motion 1. The depressor anguli oris has one line of pull and therefore creates one motion, which is a combination of depressing and drawing laterally the angle of the mouth.

739

FIGURE 13-20 The depressor anguli oris. A, Anterior view of the right depressor anguli oris. The orbicularis oris has been ghosted in. B, Anterior view of the expression created by the bilateral contraction of the depressor anguli oris.

I N N E RVAT I O N The Facial Nerve (CN VII) mandibular branch

A R T E R I A L S U P P LY The Facial Artery (a branch of the External Carotid Artery)

PA L PAT I O N 1. With the client supine, place palpating fingers slightly lateral and inferior to the angle of the mouth. 2. Have the client draw the angle of the mouth inferiorly (and perhaps slightly laterally) and feel for the contraction of the belly of the depressor anguli oris. It may be difficult to precisely discern this muscle from the nearby depressor labii inferioris.

740

RELATIONSHIP TO OTHER STRUCTURES The depressor anguli oris is lateral to the depressor labii inferioris. Where these two muscles overlap, the depressor anguli oris is superficial to the depressor labii inferioris. The depressor anguli oris is inferior to the orbicularis oris and the risorius. The depressor anguli oris is superior to the platysma. The depressor anguli oris is involved with the deep front line myofascial meridian.

MISCELLANEOUS 1. The depressor anguli oris blends into the platysma. 2. Occasionally, some fibers of the depressor anguli oris blend into the opposite-side depressor anguli oris and/or the same-side levator anguli oris. 3. Both the depressor anguli oris and the depressor labii inferioris arise from the oblique line of the mandible. On the oblique line, the depressor anguli oris attaches more laterally than the depressor labii inferioris. 4. The actions of the depressor anguli oris contribute to the facial expression of sadness or uncertainty. 5. Six muscles attach into the modiolus: the zygomaticus major, levator anguli oris, risorius, depressor anguli oris, buccinator, and orbicularis oris. 6. The modiolus is a fibromuscular condensation approximately ¼ inch (0.5 cm) lateral to the angle of the mouth (see page 448).

741

Depressor Labii Inferioris The name, depressor labii inferioris, tells us that this muscle depresses the lower lip. Derivation depressor: L. depressor labii: L. refers to the lip inferioris: L. lower Pronunciation dee-PRES-or LAY-be-eye in-FEE-ri-OR-is

ATTACHMENTS Mandible the oblique line of the mandible, between the symphysis menti and the mental foramen to the Lower Lip the midline of the lower lip

FUNCTIONS Concentric Mover Actions 1. Depresses the Lower Lip 2. Draws Laterally the Lower Lip 3. Everts the Lower Lip

Mover Action Notes • The depressor labii inferioris attaches from the mandible inferiorly, into the lower lip superiorly (with its fibers running vertically). The mandibular attachment is into bone and is therefore more fixed than the other attachment, which is into soft tissue. When the depressor labii inferioris contracts, it pulls the lower lip inferiorly toward the mandible. Therefore the depressor labii inferioris depresses the lower lip. (action 1) • The depressor labii inferioris attaches from the mandible laterally, into the lower lip medially (with its fibers running somewhat horizontally). The mandibular attachment is into bone and is therefore more fixed than the other attachment, which is into soft tissue. When the depressor labii inferioris contracts, it pulls the lower lip laterally toward the mandible. Therefore the depressor labii inferioris draws laterally the lower lip. (action 2) • When the superior attachment of the depressor labii inferioris is pulled inferiorly toward the mandible, the upper margin of the lower lip is not only pulled inferiorly, it is also pulled away from the mouth, curling the lower lip. This curling or pulling away of the lower lip from the face is called eversion of the lower lip. (action 3)

742

FIGURE 13-21 The depressor labii inferioris. A, Anterior view of the right depressor labii inferioris. The orbicularis oris has been ghosted in. B, Anterior view of the expression created by the bilateral contraction of the depressor labii inferioris.

Motion 1. The depressor labii inferioris has one line of pull and therefore creates one motion, which is a combination of depressing, drawing laterally, and everting the lower lip.

I N N E RVAT I O N The Facial Nerve (CN VII) mandibular branch

A R T E R I A L S U P P LY The Facial Artery (a branch of the External Carotid Artery)

PA L PAT I O N 1. With the client supine, place palpating fingers inferior to the lower lip, slightly lateral from the center.

743

2. Have the client draw the lower lip inferiorly and slightly laterally and feel for the contraction of the depressor labii inferioris. It may be difficult to precisely discern the depressor labii inferioris from the nearby mentalis and the depressor anguli oris.

RELATIONSHIP TO OTHER STRUCTURES The depressor labii inferioris is lateral to the mentalis. Where these two muscles overlap, the depressor labii inferioris is superficial. The depressor labii inferioris is medial to the depressor anguli oris. Where these two muscles overlap, the depressor labii inferioris is deeper. The depressor labii inferioris is inferior to the orbicularis oris and superior to the platysma. The depressor labii inferioris is involved with the deep front line myofascial meridian.

MISCELLANEOUS 1. The depressor labii inferioris blends with the opposite side depressor labii inferioris and the orbicularis oris at the lip. Inferiorly, the depressor labii inferioris blends with the platysma. 2. Both the depressor labii inferioris and the depressor anguli oris arise from the oblique line of the mandible. On the oblique line, the depressor labii inferioris attaches more medially than the depressor anguli oris. 3. The actions of the depressor labii inferioris can contribute to the facial expressions of sorrow, doubt, and irony.

744

Mentalis The name, mentalis, tells us that this muscle is related to the chin. Derivation mentalis: L. the chin Pronunciation men-TA-lis

ATTACHMENTS Mandible the incisive fossa of the mandible to the Fascia and Skin of the Chin

FUNCTIONS Concentric Mover Actions 1. Elevates the Lower Lip 2. Everts and Protracts the Lower Lip 3. Wrinkles the Skin of the Chin

Mover Action Notes • The mentalis attaches from the mandible superiorly and attaches into the fascia and skin of the chin inferiorly (with its fibers running vertically). The mandibular attachment is into bone and is therefore more fixed than the other attachment, which is into soft tissue. When the mentalis contracts, it pulls the fascia and skin of the chin superiorly toward the mandible. When this occurs, the skin of the chin is pulled into the lower lip, pushing the lower lip superiorly. Therefore the mentalis elevates the lower lip. (action 1) • When the mentalis pulls superiorly on the fascia and skin of the chin, the lower lip is elevated. As the mentalis continues to contract, the upper margin of the lower lip is forced away from the mouth anteriorly. This action is called eversion of the lower lip. As the mentalis continues to contract, the entire lower lip is forced away from the mouth. This action is called protraction (or protrusion) of the lower lip. Therefore the mentalis everts and protracts the lower lip. (action 2) • When the mentalis contracts and pulls superiorly on the fascia and skin of the chin, the skin of the chin is wrinkled. (action 3)

Motion 1. The mentalis has one line of pull and therefore creates one motion, which is a combination of elevating, everting, and protracting the lower lip, as well as wrinkling the skin of the chin.

745

FIGURE 13-22

The mentalis. A, Right lateral view. B, Anterior view of the expression created by the bilateral contraction of the mentalis.

I N N E RVAT I O N The Facial Nerve (CN VII) mandibular branch

A R T E R I A L S U P P LY The Facial Artery (a branch of the External Carotid Artery)

PA L PAT I O N 1. With the client supine, place palpating fingers inferior to the midline of the lower lip, just slightly lateral from the center. Be sure that you are inferior to the orbicularis oris and medial to the depressor labii inferioris. 2. Have the client stick out the lower lip as if pouting and feel for the contraction of the mentalis.

RELATIONSHIP TO OTHER STRUCTURES 746

The mentalis is medial to the depressor labii inferioris. Where these two muscles overlap, the mentalis is deeper. The mentalis is also medial to the depressor anguli oris. The mentalis is inferior to the orbicularis oris and superior to the platysma. The mentalis is involved with the deep front line myofascial meridian.

MISCELLANEOUS 1. The actions of the mentalis are involved in manifesting the facial expressions of doubt, pouting, or disdain. 2. Elevating, everting, and protracting the lower lip are also useful when drinking. 3. When the mentalis contracts, it also raises the mentolabial sulcus.

747

Buccinator The name, buccinator, tells us that this muscle is found in the cheek region. Derivation buccinator: L. trumpeter, refers to the cheek Pronunciation BUK-sin-A-tor

ATTACHMENTS Maxilla and the Mandible the external surfaces of the alveolar processes of the mandible and the maxilla (opposite the molars), and the pterygomandibular raphe to the Lips deeper into the musculature of the lips, and the modiolus, just lateral to the angle of the mouth

FUNCTIONS Concentric Mover Action 1. Compresses the Cheek against the Teeth

Mover Action Note • Posteriorly, the fibers of the buccinator arise from the maxilla and the mandible (and the pterygomandibular raphe between them). From there, the buccinator fibers travel anteriorly through the tissue of the cheek (running horizontally) to attach into the lips. The posterior attachments are into bone and are therefore more fixed than the anterior attachment, which is into soft tissue. When the buccinator contracts, the tissue of the cheek and the lips is pulled posteriorly and compressed against the teeth. (action 1)

Motion 1. The buccinator has one line of pull and therefore creates one motion, which is its action of compressing the cheek against the teeth.

I N N E RVAT I O N The Facial Nerve (CN VII) buccal branches

A R T E R I A L S U P P LY The Maxillary and Facial Arteries (branches of the External Carotid Artery)

PA L PAT I O N 1. With the client supine, place palpating fingers on the cheek, anterior (medial) to the ramus of the mandible. 2. Have the client take in a breath, purse the lips, and press the lips against the teeth as if expelling air to play the trumpet, and feel for the contraction of the buccinator.

748

FIGURE 13-23 The buccinator. A, Right lateral view. The masseter has been ghosted in. B, Anterior view of the expression created by the bilateral contraction of the buccinator.

RELATIONSHIP TO OTHER STRUCTURES The anterior (medial) part of the buccinator is superficial and located in the tissue of the cheek. The posterior (lateral) part of the buccinator is deeper and located posterior (deep) to the ramus of the mandible. The anterior (medial) part of the buccinator is deep to the levator anguli oris, zygomaticus major, risorius, and depressor anguli oris. Deep to the buccinator is the mucosa of the cheek. The buccinator is involved with the deep front line myofascial meridian.

MISCELLANEOUS 1. The buccinator has three posterior parts that all converge into the anterior attachment. These three parts come from the maxilla, the mandible, and the pterygomandibular raphe. 2. The buccinator’s central posterior attachment is into the pterygomandibular raphe. (A raphe is a seam of tissue formed by the union of the halves of a part.) Essentially, the pterygomandibular raphe is composed of fibrous connective tissue that bridges the pterygoid process of the sphenoid

749

bone to the mandible, hence, its name. 3. The pterygomandibular raphe is located deep near the sphenoid bone, posterior to the maxilla. More specifically, the pterygomandibular raphe runs from the hamulus of the medial pterygoid plate of the sphenoid bone to the posterior end of the mylohyoid line of the mandible. (The pterygomandibular raphe also serves as an attachment site for the superior pharyngeal constrictor muscle ( See Evolve website). The pterygomandibular raphe can be thought of as the intersection of the buccinator and the superior pharyngeal constrictor muscle.) 4. The parotid duct pierces through the buccinator to enter the mouth. 5. The action of compressing the cheeks against the teeth by the two buccinators working bilaterally is important for forcefully expelling air from the mouth. If one is forcefully expelling air through tightly closed lips, it is the buccinator that expels the air and keeps the cheeks from distending. 6. The buccinator is the muscle that contracts when a musician blows air into a brass or woodwind instrument. In fact, the Latin word for trumpeter is buccinator. 7. The buccinators are also important with whistling, blowing up a balloon, and with helping to keep food from lingering in the vestibule of the mouth (between the teeth and the cheeks). 8. The buccinators are the muscles responsible for the expression made (puckering the cheeks) when a person eats something sour, such as biting into a lemon. 9. Six muscles attach into the modiolus: the zygomaticus major, levator anguli oris, risorius, depressor anguli oris, buccinator, and orbicularis oris. 10. The modiolus is a fibromuscular condensation approximately ¼ inch (0.5 cm) lateral to the angle of the mouth (see page 448).

750

Orbicularis Oris The name, orbicularis oris, tells us that this muscle encircles the mouth. Derivation orbicularis: L. a small circle oris: L. mouth Pronunciation or-BIK-you-LA-ris OR-is

ATTACHMENTS Orbicularis oris is a muscle that, in its entirety, surrounds the mouth. In more detail, there are four parts to the orbicularis oris: two on the left (upper and lower) and two on the right (upper and lower). Therefore there is one part in each of the four quadrants. Each of these four parts of the orbicularis oris anchors to the modiolus on that side. From there, the fibers traverse through the tissue of the upper or the lower lips. At the midline, the fibers on each side interlace with each other, thereby attaching into each other.

FUNCTIONS Concentric Mover Actions 1. Closes the Mouth 2. Protracts the Lips

Mover Action Notes • The fiber direction of the orbicularis oris is circular around the mouth. When the orbicularis oris contracts, it acts like a circular sphincter muscle that closes in around the mouth, forcing the two lips together. (Note: To understand how a circular sphincter muscle works, the following reasoning applies: if a linear muscle shortens, its length decreases. When that same linear muscle is arranged in a circular fashion and shortens, the length of the line you have to make the circle decreases and therefore the size of the circle lessens, which can close in on whatever structure is being surrounded by it.) (action 1) • After closure of the mouth occurs, if the orbicularis oris continues to contract, the lips are pushed against each other harder and push out anteriorly. This action is called protraction (or protrusion) of the lips. (action 2)

Motion 1. The orbicularis oris has one line of pull and therefore creates one motion, which is to close the mouth and protract the lips.

751

FIGURE 13-24

The orbicularis oris. A, Anterior view. B, Anterior view of the expression created by the contraction of orbicularis oris.

I N N E RVAT I O N The Facial Nerve (CN VII) buccal and mandibular branches

A R T E R I A L S U P P LY The Facial Artery (A Branch of the External Carotid Artery)

PA L PAT I O N 1. With the client supine, wearing a finger cot or glove, place palpating fingers on the tissue of the lips. 2. Have the client pucker up the lips and feel for the contraction of the orbicularis oris.

RELATIONSHIP TO OTHER STRUCTURES The orbicularis oris surrounds the mouth. The following muscles radiate outward from the

752

orbicularis oris like spokes from a wheel: the depressor septi nasi, levator labii superioris alaeque nasi, levator labii superioris, zygomaticus minor, levator anguli oris, zygomaticus major, risorius, buccinator, depressor anguli oris, depressor labii inferioris, mentalis, and platysma. The orbicularis oris is involved with the deep front line myofascial meridian.

MISCELLANEOUS 1. In even more detail, in each of the four quadrants, the orbicularis oris has two layers, the pars peripheralis and the pars marginalis. Therefore the orbicularis oris actually has eight parts. 2. The orbicularis oris in humans is particularly well developed. This is necessary for the intricacies of speech. 3. Contraction of the orbicularis oris can also draw the angles (corners) of the mouth medially. This occurs because as the fibers of both sides of the orbicularis oris contract, they create a force that pulls the modiolus attachments toward each other. 4. The fibers of the orbicularis oris are reinforced by fibers of other muscles that blend into it. The levator labii superioris alaeque nasi, levator labii superioris, levator anguli oris, zygomaticus major, buccinator, depressor anguli oris, and depressor labii inferioris all blend into the orbicularis oris. 5. The contraction of the orbicularis oris causes the lips to close and protrude as in puckering the lips or whistling. 6. Six muscles attach into the modiolus: the zygomaticus major, levator anguli oris, risorius, depressor anguli oris, buccinator, and orbicularis oris. 7. The modiolus is a fibromuscular condensation approximately ¼ inch (0.5 cm) lateral to the angle of the mouth (see page 448).

753

Platysma The name, platysma, tells us that this muscle is broad and flat in shape. Derivation platysma: Gr. broad, plate Pronunciation pla-TIZ-ma

ATTACHMENTS Subcutaneous Fascia of the Superior Chest the pectoral and deltoid fascia to the Mandible and the Subcutaneous Fascia of the Lower Face

FUNCTIONS Concentric Mover Actions 1. Draws Up the Skin of the Superior Chest and Neck, Creating Ridges of Skin of the Neck 2. Depresses and Draws Laterally the Lower Lip 3. Depresses the Mandible at the Temporomandibular Joints

Mover Action Notes • When both attachments of the platysma are fixed (i.e., the mandible is not allowed to move and the fascia of the chest is pulled taut and can only move just so far) and the platysma is contracted forcefully, the fibers of the platysma (attempting to move the attachments toward each other) tense, creating ridges of soft tissue in the skin of the neck. These ridges are usually easily visible. (The lower lip will also be seen to move). Note: Some sources describe this as wrinkling the skin of the neck. (action 1) • The platysma attaches to the fascia of the lower lip. From there, its fibers run primarily inferiorly, and a bit laterally, toward the fascia of the superior chest. When the superior attachment to the fascia of the inferior face moves, the lower lip and angle (corner) of the mouth are drawn inferiorly and the angle of the mouth is drawn laterally. This creates the facial expression of horror, surprise, or disgust. (action 2) • Given the attachment directly onto the mandible (and the attachment into the fascia overlying the mandible) and the fact that these fibers that attach into the mandible run vertically down to the chest, the platysma can pull the mandible down toward the chest, thus depressing the mandible at the temporomandibular joints (TMJs). (action 3)

754

FIGURE 13-25

The platysma. A, Anterior view of the right platysma. B, Anterior view of the expression created by the bilateral contraction of the platysma.

Motion 1. The platysma has one line of pull and therefore creates one motion, which is to wrinkle the skin of the neck and upper chest (if the superior attachment is not fixed, this same line of pull will also depress and draw laterally the lower lip, and depress the mandible).

Additional Note on Actions 1. Some sources state that the platysma can assist in flexion of the head and neck. Given that it crosses the spinal joints of the cervicocranial region anteriorly, this seems likely (but would require the mandible to remain fixed and not depress, so that the pull of the platysma would transfer to the head at the atlanto-occipital joint and then the neck at the spinal joints).

I N N E RVAT I O N Facial Nerve (CN VII) cervical branch

755

A R T E R I A L S U P P LY The Facial Artery (a branch of the External Carotid Artery) and the transverse cervical artery (a branch of the thyrocervical trunk)

PA L PAT I O N 1. With the client seated or supine, place palpating fingers on the anterolateral neck. 2. Ask the client to forcefully contract the platysma by depressing and drawing the lower lip laterally, while keeping the mandible fixed in a position of slight depression. Observe and feel for the ridges of skin of the neck caused by the contraction of the platysma.

RELATIONSHIP TO OTHER STRUCTURES The platysma is superficial in the chest and neck. In the face, it is superficial to the depressor anguli oris, the depressor labii inferioris, and the risorius. The clavicle and parts of the deltoid, pectoralis major, sternocleidomastoid, infrahyoids, and suprahyoids are all deep to the platysma. The platysma is involved with the superficial front line and superficial front arm line myofascial meridians.

MISCELLANEOUS 1. The skeletal action of depression of the mandible at the temporomandibular joints (TMJs) by the platysma is extremely weak. 2. The platysma on one side blends with the contralateral platysma. 3. The platysma often blends with the other facial muscles in the lower face. 4. The platysma in humans is considered to be a remnant of a broader fascial muscle called the panniculus carnosus found in four-legged mammals. The panniculus carnosus is what enables a horse to shake off flies from its skin and it is the same muscle that enables a cat to raise the hair on its back. 5. When the platysma contracts and the ridges or wrinkling of the skin of the neck occurs, it is reminiscent of the title character from the film The Creature from the Black Lagoon.

756

REVIEW QUESTIONS 1. Why is it functionally important for muscles of facial expression to be able to dilate or constrict the apertures of the face? ____________________________ ____________________________ ____________________________ 2. What two muscles attach into the galea aponeurotica? What is the name given to this collective structure? ____________________________ ____________________________ ____________________________ 3. Which of the auricularis muscles is located just superior to the cranial attachment of the sternocleidomastoid? ____________________________ 4. Explain the importance of the lacrimal portion of the orbicularis oculi to good eye health. ____________________________ ____________________________ ____________________________ ____________________________ 5. What three muscles have actions that would help to shield the eyes from bright sunlight (squinting)? ____________________________ ____________________________ ____________________________ 6. What are the three main elevators of the upper lip? ____________________________ ____________________________ ____________________________ 7. Describe the modiolus and its approximate location. Why is this structure important? ____________________________ ____________________________ ____________________________ ____________________________ 8. With the exception of the_______, the facial muscles are innervated by the _______ nerve. 9. Bilateral contraction of what muscle can reproduce the typical Dracula expression, wherein the canine teeth are exposed? ____________________________ 10. The parotid duct pierces through what muscle to enter the mouth? ____________________________ For answers to these questions, visit http://evolve.elsevier.com/Muscolino/muscular

757

THINK IT THROUGH After reading this chapter, there is no doubt that the muscles of facial expression are important to the human experience. From verbal and nonverbal communication to breathing and eye protection, these muscles are responsible for a large array of tasks. What might be the role of a manual therapist as it relates to dysfunction of these muscles? ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________

758

PA R T 4

The Skeletal Muscles of the Lower Extremity OUTLINE Chapter 14: Muscles of the Hip Joint Chapter 15: Muscles of the Knee Joint Chapter 16: Muscles of the Ankle and Subtalar Joints Chapter 17: Extrinsic Muscles of the Toe Joints Chapter 18: Intrinsic Muscles of the Toe Joints

759

CHAPTER 14

760

Muscles of the Hip Joint CHAPTER OUTLINE Hip Joint Flexors: Psoas major Iliacus Tensor fasciae latae (TFL) Sartorius Adductor group: Pectineus Adductor longus Gracilis Adductor brevis Adductor magnus Gluteal group: Gluteus maximus Gluteus medius Gluteus minimus Deep lateral rotator group: Piriformis Superior gemellus Obturator internus Inferior gemellus Obturator externus Quadratus femoris

OBJECTIVES After completing this chapter, the student should be able to perform the following for each of the muscles covered in the chapter: 1. Explain the general structure. 2. Explain the general function. 3. State the attachments. 4. State the standard mover actions. 5. State the reverse mover actions. 6. Discuss the line(s) of pull the muscle has and the motion(s) created. 7. State the eccentric antagonist functions. 8. State the isometric stabilization functions. 9. State the nervous innervation.

10. State the arterial supply. 11. Describe the starting position for palpation. 12. Describe the steps for palpation. 761

13. Discuss the muscle’s relationship to other body structures. 14. Discuss additional information that may help with palpation, assessment, and clinical decision-making. CHAPTER OVERVIEW The muscles addressed in this chapter are the muscles whose principal function is usually considered to be movement of the hip joint. Other muscles in the body can also move the hip joint, but they are placed in different chapters because their primary function is usually considered to be at another joint. These muscles are the hamstring group and rectus femoris of the quadriceps femoris group; they are covered in Chapter 15. Overview of STRUCTURE Structurally, muscles of the hip joint are generally classified as being anterior, posterior, medial, or lateral. Actually, most hip joint muscles lie somewhere between, for example, anterolateral or anteromedial. The psoas major, iliacus, tensor fasciae latae, and sartorius are hip flexors and are located anteriorly (the rectus femoris of the quadriceps femoris group, also located anteriorly, is covered in Chapter 15). The adductor muscles of the hip joint are located medially. The gluteal group is located primarily laterally. The deep lateral rotator group is a group of six muscles that are deeply situated in the posterior buttock and are oriented horizontally. (The hamstring group, covered in Chapter 15, crosses the hip joint posteriorly with a vertical orientation.)

C o m p a r t m e n t s o f t h e Pe l v i s a n d T h i g h : The musculature of the pelvis and thigh are not as clearly compartmentalized as some other regions of the body. Following is the general layout of the musculature of these two regions of the body. Pelvis musculature is usually divided into anterior, lateral, and posterior compartments. • The anterior compartment contains the iliacus and psoas major (and psoas minor). • The lateral compartment contains the gluteus medius, gluteus minimus, and tensor fasciae latae (TFL) (as well as part of the gluteus maximus). • The posterior compartment contains the gluteus maximus, the posterior aspects of the gluteus medius and gluteus minimus, the deep lateral rotator group (piriformis, gemelli superior and inferior, obturators internus and externus, and quadratus femoris), as well as the coccygeus and levator ani of the pelvic floor. Thigh musculature is usually divided into anterior (flexor), medial (adductor), and posterior (extensor) compartments. • The anterior compartment contains the TFL, quadriceps femoris, sartorius, iliacus, and psoas major. • The medial compartment contains the pectineus, adductor longus, gracilis, adductor brevis, and adductor magnus. • The posterior compartment contains the hamstrings (as well as the distal attachments of most of the adductor group and quadriceps femoris group muscles). Notes: • The pectineus is a transitional muscle between the anterior and medial groups of the thigh. • The adductor magnus is a transitional muscle between the medial and posterior groups of the thigh. • The quadriceps femoris musculature is primarily located in the anterior thigh, but also wraps into the medial and lateral thigh to attach into the linea aspera of the posterior thigh. • The iliotibial band (ITB) is a fibrous fascial thickening in the lateral thigh of the fascia latae (the fascial membrane that envelops the entire thigh) and acts as a distal tendon of the TFL and gluteus maximus (and also acts to stabilize the lateral knee joint). Overview of FUNCTION

762

The following general rules regarding actions can be stated for the functional groups of muscles of the hip joint: If a muscle crosses the hip joint anteriorly with a vertical direction to its fibers, it can flex the thigh at the hip joint by moving the anterior surface of the thigh toward the anterior surface of the pelvis. Or it can anteriorly tilt the pelvis at the hip joint by moving the anterior surface of the pelvis toward the anterior surface of the thigh. If a muscle crosses the hip joint posteriorly with a vertical direction to its fibers, it can extend the thigh at the hip joint by moving the posterior surface of the thigh toward the posterior surface of the pelvis. Or it can posteriorly tilt the pelvis at the hip joint by moving the posterior surface of the pelvis toward the posterior surface of the thigh. If a muscle crosses the hip joint laterally with a vertical direction to its fibers, it can abduct the thigh at the hip joint by moving the lateral surface of the thigh toward the lateral surface of the pelvis. Or it can depress (laterally tilt) the same-side (ipsilateral) pelvis at the hip joint by moving the lateral surface of the pelvis toward the lateral surface of the thigh. If a muscle crosses the hip joint medially, it can adduct the thigh at the hip joint by moving the medial surface of the thigh toward the medial surface of the pelvis. Or it can elevate the sameside (ipsilateral) pelvis at the hip joint by moving the medial surface of the pelvis toward the medial surface of the thigh. Medial rotators of the thigh wrap around the femur from medial to lateral, anterior to the hip joint. They can also ipsilaterally rotate the pelvis at the hip joint. Lateral rotators of the thigh wrap around the femur from medial to lateral, posterior to the hip joint. They can also contralaterally rotate the pelvis at the hip joint. Reverse actions are common at the hip joint and tend to occur when the foot is planted on the ground causing the distal attachment to be fixed and therefore the proximal attachment to be mobile and move toward the distal attachment (closed chain kinematics). The reverse actions wherein the pelvis moves at the hip joint are often as important as, if not more important than, the typically thought of standard mover actions of the thigh at the hip joint.

http://evolve.elsevier.com/Muscolino/muscular

763

Anterior Views of the Muscles of the Hip Joint— Superficial and Intermediate Views

FIGURE 14-1

Anterior views of the muscles of the hip joint. A, Superficial view on the right and an intermediate view on the left.

764

Anterior Views of the Muscles of the Hip Joint—Deep Views

FIGURE 14-1

B, Deep view on the right and deeper view on the left.

765

Posterior Views of the Muscles of the Hip Joint— Superficial and Intermediate Views

FIGURE 14-2

Posterior views of the muscles of the hip joint. A, Superficial view on the left and intermediate view on the right.

766

Posterior Views of the Muscles of the Hip Joint—Deep Views

FIGURE 14-2

B, Deep view on the left and deeper view on the right.

767

Medial View of the Muscles of the Right Hip Joint— Superficial View

FIGURE 14-3

Medial views of the muscles of the right hip joint. A, Superficial.

768

Medial View of the Muscles of the Right Hip Joint— Deep View

FIGURE 14-3

769

B, Deep.

Lateral View of the Muscles of the Right Hip Joint— Superficial View

FIGURE 14-4

Lateral views of the muscles of the right hip joint. A, Superficial.

770

Lateral View of the Muscles of the Right Hip Joint— Deep View

FIGURE 14-4

771

B, Deep.

Transverse Plane Cross Sections of the Right Thigh

FIGURE 14-5 Transverse plane cross sections of the right thigh. A, Proximal. B, Middle. C, Distal. Perspective: Top is anterior; bottom is posterior; right is lateral; left is medial.

772

Psoas Major (of Iliopsoas) The name, psoas major, tells us that this muscle is located in the loin (low back) area and is large (larger than the psoas minor). Derivation psoas: Gr. loin (low back) major: L. larger Pronunciation SO-as MAY-jor

ATTACHMENTS Anterolateral Lumbar Spine anterolaterally on the bodies of T12-L5 and the intervertebral discs between, and anteriorly on the TPs of L1-L5 to the Lesser Trochanter of the Femur

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions

Reverse Mover Actions

1. Flexes the thigh at the hip joint

1. Flexes the trunk at the spinal joints

2. Posteriorly tilts the pelvis at the LS joint

2. Anteriorly tilts the pelvis at the hip joint 3. Contralaterally rotates the trunk and pelvis

3. Laterally rotates the thigh at the hip joint 4. Elevates the same-side pelvis at the LS joint

4. Laterally flexes the trunk at the spinal joints

LS joint = lumbosacral joint

Standard Mover Action Notes • The psoas major crosses the hip joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the thigh at the hip joint. (action 1) • The iliopsoas is the prime mover (most powerful muscle) of flexion of the thigh (and anterior tilt of the pelvis) at the hip joint. (action 1) • If the trunk is fixed and the psoas major pulls the thigh toward the trunk anteriorly, but the pelvis is fixed to the thigh, the psoas major pulls the thigh/pelvis as a unit toward the anterior trunk and can posteriorly tilt the pelvis at the LS joint. (action 2) • The psoas major crosses the hip joint anteriorly in such a way that it wraps around from the vertebral column to attach onto the lesser trochanter of the femur (with its fibers running somewhat horizontally in the transverse plane). When the psoas major contracts, it pulls the lesser trochanter anterolaterally and laterally rotates the thigh at the hip joint. (action 3)

773

FIGURE 14-6

Anterior view of the psoas major bilaterally. The left iliacus has been drawn in and the rectus abdominis has been ghosted in.

• Lateral rotation of the thigh at the hip joint is a very weak action of the psoas major. (action 3) • The psoas major crosses the spinal joints laterally (with its fibers running vertically in the frontal plane); therefore when the spinal attachment is fixed, it pulls upward on the femoral attachment. If the femur is fixed to the pelvis, the pelvis will be elevated at the LS joint. (action 4)

Reverse Mover Action Notes • The psoas major crosses the spinal joints anteriorly (with its fibers running vertically in the sagittal plane); therefore when the femoral attachment is fixed, the psoas major flexes the trunk at the spinal joints. (reverse action 1) • There is controversy about whether the psoas major flexes or extends the trunk at the spinal joints. Its line of pull passes anteriorly to the lower lumbar spinal joints, so it certainly flexes the lower lumbar spine. However, as it ascends, it may pass posteriorly to the upper spinal joints that it crosses; therefore it would extend the vertebrae at these joints. Keep in mind that the degree of lumbar lordosis would affect the line of pull of this muscle relative to the joints it crosses. (reverse action 1) • When the trunk is fixed to the pelvis and the psoas major contracts (with the femoral attachment fixed), the psoas major pulls the spinal attachment anteriorly and inferiorly toward the femurs,

774

causing the pelvis to anteriorly tilt at the hip joint. An excessively anteriorly tilted pelvis results in a hyperlordotic lumbar spine. (reverse action 2) • When the psoas major crosses the spinal joints, it attaches from anterolaterally on the vertebral column to then attach further anteriorly onto the femur (with its fibers running somewhat horizontally in the transverse plane). When the femoral attachment is fixed and the psoas major contracts, it pulls the vertebrae, causing the anterior surface of the vertebrae to rotate toward the opposite side of the body from the side on which the psoas major is attached. Therefore the psoas major contralaterally rotates the trunk at the spinal joints. (reverse action 3) • When the trunk is fixed to the pelvis, and the psoas major contracts, it pulls on the spinal attachment and rotates it in the transverse plane. The trunk and the pelvis move as a unit, and the pelvis rotates toward the opposite side of the body from the side on which the psoas major is attached. Therefore the psoas major contralaterally rotates the pelvis at the hip joint. (reverse action 3) • The psoas major crosses the spinal joints laterally (with its fibers running vertically in the frontal plane); therefore when the femoral attachment is fixed, the psoas major laterally flexes the trunk at the spinal joints. (reverse action 4)

Motions 1. The psoas major has one line of pull upon the thigh in an oblique plane and therefore creates one motion, which is a combination of flexion and lateral rotation of the thigh at the hip joint. 2. Regarding its reverse action pull on the trunk, the psoas major has one line of pull in an oblique plane and therefore creates one motion, which is a combination of flexion, lateral flexion, and contralateral rotation of the trunk at the spinal joints.

Eccentric Antagonist Functions 1. Restrains/slows thigh extension and pelvic posterior tilt at the hip joint 2. Restrains/slows thigh medial rotation and pelvic ipsilateral rotation at the hip joint 3. Restrains/slows lumbar spinal extension 4. Restrains/slows lumbar spinal lateral flexion to the opposite side 5. Restrains/slows ipsilateral rotation of the lumbar spine 6. Restrains/slows anterior tilt and depression of the same-side pelvis at the LS joint

Eccentric Antagonist Function Note • A force of lateral rotation of the thigh at the hip joint prevents medial rotation of the entire lower extremity (thigh, leg, and talus) if the weight-bearing foot overly pronates (if the arch of the foot drops).

Isometric Stabilization Functions 1. Stabilizes the lumbar spine at the spinal joints 2. Stabilizes the pelvis at the LS, sacroiliac, and hip joints 3. Stabilizes the thigh at the hip joint

Isometric Stabilization Function Note • Because the psoas major lies so close to the lumbar spine, its major stabilization function is at the spine.

Additional Notes on Actions 1. In anatomic position, the moment arm (lever arm) for the psoas major for flexion of the thigh at the hip joint is not very large. However, as the thigh flexes, its moment arm leverage increases. For this reason, the action of hip joint flexion by the psoas major is strongest between approximately 45 and 60 degrees. 2. There is controversy about the psoas major’s frontal plane motion of the thigh at the hip joint. In anatomic position, it is likely a weak adductor. But if the thigh is first abducted or laterally rotated, the line of pull of the psoas major passes lateral to the frontal plane axis for motion and the psoas major becomes an abductor. 3. There is some controversy about the psoas major’s transverse plane motion at the hip joint. Some

775

sources have asserted that it can medially rotate the thigh instead of laterally rotate it. Looking at the line of pull of the muscle relative to the axis for transverse plane motion makes it fairly clear that the psoas major laterally rotates the thigh at the hip joint. Indeed, the belief that the psoas major can medially rotate is increasingly falling out of favor. 4. There is a great deal of controversy regarding whether the psoas major flexes or extends the lumbar spine in the sagittal plane. To determine this, we must look at where the line of pull of the psoas major is relative to the axis of movement for each of the spinal joints that it crosses. Generally, the line of pull of the psoas major crosses anteriorly to the mediolateral axis of motion of the lumbar spinal joints; therefore it pulls the vertebrae anteriorly. For this reason, the psoas major is considered to be a flexor of the lumbar spine. This is certainly true for the L5-S1 spinal joint. However, as we look further up the lumbar spine, the line of pull of the psoas major moves increasingly posterior. By the T12-L1 spinal joint, the psoas major’s line of pull actually crosses posteriorly to the joint, thereby causing extension of the spine at that level (i.e., extension of T12 on L1). Another factor to consider is that if the posture of the lumbar spine changes, the line of pull of the psoas major relative to the axis of motion of the spinal joints changes. For example, if the lordotic curve of the lumbar spine increases, the line of pull of the psoas major will move farther posterior relative to the axis of motion for the spinal joints and the ability of the psoas major to extend the trunk at the lumbar spinal joints will increase. In this case the psoas major becomes an extensor of the lumbar spine. Similarly, if the lordosis of the lumbar spine decreases, the line of pull of the psoas major will move farther anterior relative to the axis of motion for the spinal joints and the ability of the psoas major to flex the trunk at the lumbar spinal joints will increase. Therefore, once a postural distortion of the lumbar spine in the sagittal plane is present (hyperlordosis/swayback or hypolordosis/rounded back), the psoas major tends to amplify it. 5. The term psoas paradox is used to describe the sagittal plane extension effect of the psoas major upon the spine. Even though its pull for extension is not that strong, the psoas major seems to create greater spinal extension than would otherwise be expected. One reason proffered for this is that as the lower lumbar spine is pulled into flexion, the nervous system may order the upper lumbar spine into greater extension as a compensation to bring the center of weight of the body back posteriorly to be balanced over the pelvis. The determination for whether psoas paradox compensation occurs is probably based on the flexibility/rigidity of the upper lumbar spine. In other words, people with spinal flexibility will have a greater ability to engage in psoas paradox compensatory motion. 6. Following is a detailed examination of how the concept of psoas paradox occurs at the segmental joint level. The presence of psoas paradox is based on whether or not the vertebrae superior to the vertebra that is being moved are fixed to it or not. If we accept that the psoas major crosses anteriorly to the axis of movement of whatever spinal joint it is crossing, a concentric contraction of the psoas major causes that vertebra to be pulled anteriorly; this will result in flexion of that vertebra on the vertebra that is inferior to it. Let’s use the L3 vertebra as an example. When the psoas major contracts and pulls on L3, it will flex L3 on L4 at the L3-L4 spinal joint. If the vertebra directly superior to it, L2, is fixed to L3 (perhaps by deep muscular contraction), L2 will move along with L3 and the lumbar spine will flex at the L3-L4 spinal joint. However, if L2 is not fixed to L3, the psoas major will pull L3 anteriorly and L2 will now be relatively posterior, thus causing L2 to be extended on L3 at the L2-L3 spinal joint. In this scenario, the psoas major is still flexing L3 at the L3L4 spinal joint, but L2 is now extending at the L2-L3 spinal joint. Consequently, the pull of the psoas major flexes the vertebra to which it is attached; however, the force of gravity on the weight of the vertebra directly superior causes it to extend. The danger of extension in the lumbar spine is that it increases the lordotic curve and may result in what is commonly called swayback. 7. Another reason for the psoas major’s ability to create lumbar spinal extension is due to its indirect effect upon lumbar spinal posture via pelvis posture. The psoas major acts primarily as a flexor of the thigh at the hip joint. Thigh flexors are also anterior tilters of the pelvis at the hip joint. And in closed chain posture (with the foot on the floor), a tight psoas major would play out its pull on the pelvis, not the thigh. As the pelvis’ anterior tilt increases, the lordotic curve of extension of the lumbar spine increases. 8. Because the psoas major’s line of pull passes so closely to the axes for sagittal plane motion of the spine (at least when the spine is in anatomic position), its effect upon the spine is likely less for movement than it is for stability. 9. As a generalization, it can probably be stated that the major function of the psoas major is to stabilize the lumbar spine as the thigh flexes at the hip joint.

776

I N N E RVAT I O N Lumbar Plexus L1, L2, L3

A R T E R I A L S U P P LY The Lumbar Arteries (branches of the Aorta) and the Iliolumbar Artery (a branch of the Internal Iliac Artery)

PA L PAT I O N 1. With the client supine with a pillow under the knees, place palpating hand on the abdomen between the iliac crest and the twelfth rib (lateral to the rectus abdominis, approximately halfway between the ASIS and the umbilicus). 2. Palpate slowly but deeply with even pressure directed posteromedially toward the spine. 3. Ask the client to flex the thigh at the hip joint a few degrees and feel for the contraction of the psoas major. 4. The distal belly of the psoas major is also palpable in the proximal anterior thigh between the pectineus and the sartorius. Note: Be careful with palpation in this region because the femoral nerve, artery, and vein lie over the iliopsoas and pectineus here.

RELATIONSHIP TO OTHER STRUCTURES The psoas major is deep in the abdomen and lies anteromedially to the quadratus lumborum. Distally, the psoas major tendon is joined by the iliacus tendon to attach onto the lesser trochanter of the femur. The psoas major lies deep to the inguinal ligament and directly anterior to the hip joint. The psoas minor lies directly anterior to the belly of the psoas major. The psoas major is located within the deep front line myofascial meridian.

MISCELLANEOUS 1. The psoas major and the iliacus muscle are sometimes considered to be the iliopsoas muscle because of their common distal attachment onto the lesser trochanter of the femur. 2. The proximal attachment of the psoas major on the spine arises by five separate slips of tissue. 3. The psoas major is divided by some sources into upper and lower fibers. The upper fibers tend to pass posterior to the mediolateral axis of sagittal plane motion of the spine and cause extension, whereas the lower fibers tend to pass anterior to the mediolateral axis for sagittal plane motion of the spine and cause flexion. Other sources divide the psoas major into anterior and posterior fibers. The attachments onto the vertebral bodies comprise the anterior fibers; the attachments onto the transverse processes comprise the posterior fibers. 4. The psoas major has been found to have fascial attachments into the diaphragm, sacroiliac joint, and the pelvic floor. Therefore, the psoas major could help to stabilize all these structures. 5. The psoas major muscle is actually a triangular-shaped muscle, which is apparent when viewing it in a quadruped, but less apparent when viewing it in a human (biped). 6. With regard to posture, a chronically tight psoas major anteriorly tilts the pelvis at the hip joints, causing the lumbar curve to increase (hyperlordosis, also known as swayback). Straight-legged sit-ups tend to disproportionately strengthen the psoas major in comparison to the anterior abdominal wall muscles. To avoid this, it is recommended to do curl-ups, wherein the hip and knee joints are flexed and the trunk “curls” up (i.e., spinal flexion, not the pelvis anteriorly tilting at the hip joints) approximately 30 degrees. With the hip joint flexed to 90 degrees, the psoas major is slackened and will not be as readily engaged if the curl-up is restricted to approximately 30 degrees. 7. Because the psoas major’s line of pull passes so closely to the mediolateral axes for sagittal plane motion of the spine (at least when the spine is in anatomic position), the psoas major creates a great deal of compression upon the spine. This has the positive effect of adding to stability, but can also compress the intervertebral discs, aggravating pathologic disc bulges/herniations. 8. The roots of the lumbar plexus of nerves enter the psoas major muscle directly; the lumbar plexus itself is located within the belly of the psoas major, and the branches of the lumbar plexus then

777

emerge from the psoas major muscle. Therefore a tight psoas major may entrap these nerves. 9. Tenderloin (also known as filet mignon) is the psoas major of a cow or pig.

778

Iliacus (of Iliopsoas) The name, iliacus, tells us that this muscle attaches onto the ilium. Derivation iliacus: L. refers to the ilium Pronunciation i-lee-AK-us

ATTACHMENTS Internal Ilium the upper ⅔ of the iliac fossa, and the anterior inferior iliac spine (AIIS) and the sacral ala to the Lesser Trochanter of the Femur

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes the thigh at the hip joint 2. Laterally rotates the thigh at the hip joint

Reverse Mover Actions 1. Anteriorly tilts the pelvis at the hip joint 2. Contralaterally rotates the pelvis at the hip joint

Standard Mover Action Notes • The iliacus crosses the hip joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the thigh at the hip joint. (action 1) • The iliopsoas is the prime mover (most powerful muscle) of flexion of the thigh (and anterior tilt of the pelvis) at the hip joint. (action 1) • The iliacus crosses the hip joint anteriorly in such a way that it wraps around from the internal ilium to attach onto the lesser trochanter of the femur (with its fibers running somewhat horizontally in the transverse plane). When the iliacus contracts, it pulls the lesser trochanter anterolaterally and laterally rotates the thigh at the hip joint. (action 2) • Lateral rotation of the thigh at the hip joint is a very weak action of the iliacus. (action 2)

Reverse Mover Action Notes • When the thigh is fixed and the iliacus contracts, it pulls the anterior surface of the pelvis toward the anterior thigh. Therefore it anteriorly tilts the pelvis at the hip joint. (reverse action 1) • The iliacus crosses the hip joint anteriorly (with its fibers running somewhat horizontally in the transverse plane) in such a way that it wraps around from the femur to attach laterally onto the pelvis. When the femur is fixed and the iliacus contracts, it rotates the pelvis (in the transverse plane) away from the side of the body on which the iliacus is attached. Therefore the iliacus contralaterally rotates the pelvis at the hip joint. (reverse action 2)

779

FIGURE 14-7

Anterior view of the iliacus bilaterally. The left psoas major has been drawn in and the rectus abdominis has been ghosted in.

Motions 1. The iliacus has one line of pull upon the thigh in an oblique plane and therefore creates one motion, which is a combination of flexion and lateral rotation of the thigh at the hip joint. 2. Regarding its reverse action pull on the pelvis, the iliacus has one line of pull in an oblique plane and therefore creates one motion, which is a combination of anterior tilt and contralateral rotation of the pelvis at the hip joint.

Eccentric Antagonist Functions 1. Restrains/slows thigh extension and pelvic posterior tilt at the hip joint 2. Restrains/slows thigh medial rotation and pelvic ipsilateral rotation at the hip joint

Isometric Stabilization Functions 1. Stabilizes the thigh and pelvis at the hip joint

Isometric Stabilization Function Note

780

• A force of lateral rotation of the thigh at the hip joint prevents medial rotation of the entire lower extremity (thigh, leg, and talus) if the weight-bearing foot overly pronates (if the arch of the foot drops).

Additional Note on Actions 1. Some sources state that the iliacus can abduct the thigh at the hip joint. This is more likely to occur if the thigh is first abducted or laterally rotated because this would cause the iliacus’ line of pull to move lateral to the anteroposterior axis of frontal plane motion of the thigh, thereby affording it the ability to create abduction.

I N N E RVAT I O N The Femoral Nerve L2, L3

A R T E R I A L S U P P LY The Iliolumbar Artery (a branch of the Internal Iliac Artery) and the Obturator Artery (a branch of the Internal Iliac Artery)

PA L PAT I O N 1. With the client supine with the thighs slightly passively flexed and laterally rotated at the hip joints (this can be accomplished by placing a small pillow under the client’s knees), place palpating fingers on the anterior iliac crest and palpate into the iliac fossa by curling your fingertips around the iliac crest. 2. Have the client flex the thigh at the hip joint and feel for the contraction of the iliacus. 3. The distal belly of the iliacus is also somewhat palpable in the proximal anterior thigh between the pectineus and the sartorius. Note: Be careful with palpation in the anterior thigh region, because the femoral nerve, artery, and vein lie over the iliopsoas and pectineus here.

RELATIONSHIP TO OTHER STRUCTURES Distally, the iliacus tendon joins the psoas major tendon to attach onto the lesser trochanter of the femur. The iliacus lies deep to the inguinal ligament and directly anterior to the hip joint. Distal to the inguinal ligament, the fibers of the distal belly of the iliacus lie lateral to the fibers of the distal psoas major. The iliacus is located within the deep front line myofascial meridian.

MISCELLANEOUS 1. The iliacus and the psoas major muscle are sometimes considered to be the iliopsoas muscle because of their common distal attachment onto the lesser trochanter of the femur. 2. The majority of the fibers of the distal iliacus actually attach into the psoas major’s tendon (deep on the posterior side) to then attach onto the lesser trochanter. 3. With regard to posture, a chronically tight iliacus anteriorly tilts the pelvis, causing the lumbar curve to increase (hyperlordosis, also known as swayback). Straight-legged sit-ups tend to disproportionately strengthen the iliacus in comparison to the anterior abdominal wall muscles. To avoid this, it is recommended to do curl-ups, wherein the hip and knee joints are flexed and the trunk “curls” up (i.e., spinal flexion, not the pelvis anteriorly tilting at the hip joints) approximately 30 degrees. With the hip joint flexed to 90 degrees, the iliacus is slackened and will not be as readily engaged if the curl-up is restricted to approximately 30 degrees.

781

Tensor Fasciae Latae (TFL) The name, tensor fasciae latae, tells us that this muscle tenses the fascia lata. The fascia lata is the broad covering of fascia that envelops the musculature of the thigh. Derivation tensor: L. stretcher fasciae: L. band/bandage latae: L. broad, refers to the side Pronunciation TEN-sor FASH-ee-a LA-tee

782

ATTACHMENTS Anterior Superior Iliac Spine (ASIS) and the anterior iliac crest to the Iliotibial Band (ITB) ⅓ of the way down the thigh

783

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions

Reverse Mover Actions

1. Flexes the thigh at the hip joint

1. Anteriorly tilts the pelvis at the hip joint

2. Abducts the thigh at the hip joint

2. Depresses the same-side pelvis at the hip joint 3. Ipsilaterally rotates the pelvis at the hip joint

3. Medially rotates the thigh at the hip joint 4. Extends the leg at the knee joint

4. Extends the thigh at the knee joint

Standard Mover Action Notes • The TFL crosses the hip joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the thigh at the hip joint. (action 1) • The TFL crosses the hip joint laterally (with its fibers running vertically in the frontal plane); therefore it abducts the thigh at the hip joint. (action 2) • The TFL crosses the hip joint laterally in such a way that it wraps from anteriorly on the pelvis to posteriorly into the ITB (with its fibers running somewhat horizontally in the transverse plane). When the TFL pulls on the iliotibial band, it pulls this lateral attachment anteromedially, causing the anterior thigh to face medially. Therefore the TFL medially rotates the thigh at the hip joint. (action 3) • Because of its pull via the ITB (which attaches to the proximal anterolateral tibia), the TFL crosses the knee joint anteriorly (with a vertical orientation to its pull in the sagittal plane); therefore it extends the leg at the knee joint. (action 4)

784

FIGURE 14-8

Lateral view of the right tensor fasciae latae (TFL). The gluteus maximus has been ghosted in. ITB, Iliotibial band.

Reverse Mover Action Notes • If the TFL contracts and the femur is fixed, it pulls the anterior pelvis toward the anterior thigh. Therefore the TFL anteriorly tilts the pelvis at the hip joint. (reverse action 1) • If the TFL contracts and the femur is fixed, it pulls the lateral pelvis toward the lateral thigh. Therefore the TFL depresses (laterally tilts) the same-side pelvis at the hip joint. Note: Depressing one side of the pelvis causes the other side to elevate. (reverse action 2) • The TFL crosses the hip joint in such a way that it wraps from medially on the pelvis to laterally into the ITB (with its fibers running somewhat horizontally in the transverse plane). When the iliotibial band attachment is fixed and the TFL contracts, it pulls on the pelvis, causing the anterior pelvis to face toward the same side of the body on which the TFL is attached. Therefore the TFL ipsilaterally rotates the pelvis at the hip joint. (reverse action 3) • If the leg is fixed, the TFL can extend the thigh at the knee joint via its ITB attachment, which crosses the knee joint anteriorly (with a vertical orientation to its fibers in the sagittal plane). (reverse action 4)

Motions 1. The TFL has one line of pull upon the thigh in an oblique plane and therefore creates one motion, which is a combination of flexion, abduction, and medial rotation of the thigh at the hip joint, as well as extension of the leg at the knee joint. 2. Regarding its reverse action pull on the pelvis, the TFL has one line of pull in an oblique plane and therefore creates one motion, which is a combination of anterior tilt, same-side depression, and

785

ipsilateral rotation of the pelvis at the hip joint.

Eccentric Antagonist Functions 1. Restrains/slows thigh extension and pelvic posterior tilt at the hip joint 2. Restrains/slows thigh adduction and same-side pelvic elevation at the hip joint 3. Restrains/slows thigh lateral rotation and pelvic contralateral rotation at the hip joint 4. Restrains/slows knee joint flexion

Isometric Stabilization Functions 1. Stabilizes the thigh and pelvis at the hip joint 2. Stabilizes the knee joint

Isometric Stabilization Function Notes • Same-side pelvic depression force on the support limb side prevents depression of pelvis to the opposite side (swing limb side) when walking. This is likely the most important function of the TFL. • Given that both the TFL and the gluteus maximus attach into the ITB and the ITB crosses the knee joint anterolaterally, both of these muscles in effect cross the knee joint anteriorly and therefore, theoretically, can extend the leg at the knee joint. However, there is controversy over their ability to actually do this. Certainly, extension of the leg at the knee joint is not one of their major actions. It is likely that the role of these two muscles and the ITB crossing the knee is primarily to help stabilize the lateral side of the knee joint.

Additional Notes on Actions 1. The anteromedial fibers of the TFL are more active with flexion and abduction of the thigh at the hip joint and anterior tilt and depression of the pelvis at the hip joint. 2. The posterolateral fibers of the TFL are more active with medial rotation of the thigh at the hip joint and ipsilateral rotation of the pelvis at the hip joint. 3. Some sources state that the TFL, via its ITB attachment, can laterally rotate the leg at the knee joint.

I N N E RVAT I O N The Superior Gluteal Nerve L4, L5, S1

A R T E R I A L S U P P LY The Superior Gluteal Artery (a branch of the Internal Iliac Artery) and the Deep Femoral Artery (a major branch of the Femoral Artery)

PA L PAT I O N 1. With the client supine, place palpating fingers just distal and slightly lateral to the anterior superior iliac spine (ASIS). 2. Have the client actively hold the thigh in a position of flexion and medial rotation at the hip joint and palpate for the engagement of the TFL. Resistance can be added. 3. Continue palpating the TFL distally and slightly posteriorly toward the ITB attachment.

786

RELATIONSHIP TO OTHER STRUCTURES The TFL is posterior to the sartorius. The TFL is superficial to the anterior fibers of the gluteus medius and anterior to the middle fibers of the gluteus medius. The TFL is superficial to the vastus lateralis. At its proximal attachment, the TFL is superficial to the proximal attachment of the rectus femoris. The TFL is located within the lateral line and spiral line myofascial meridians.

787

MISCELLANEOUS 1. There are two muscles that attach into the ITB: the TFL and the gluteus maximus. Given that the TFL attaches into the ITB from one direction and the gluteus maximus attaches into the ITB from the opposite direction, they have opposite actions of rotation at the hip joint. 2. A chronically tight TFL can create the postural conditions of a functional short lower extremity (usually called a short leg) and a compensatory scoliosis. When the TFL is tight, it pulls on and depresses (laterally tilts) the pelvis toward the thigh on that side. This results in a functional short leg (as opposed to a structural short leg, wherein the femur and/or the tibia on one side is actually shorter than on the other side). Further, depressing the pelvis on one side creates an unlevel sacrum for the spine to sit on, and a compensatory scoliosis must occur to return the head to a level position. (Note: The head must be level for proper proprioceptive balance in the inner ear and for the eyes to be level for visual proprioception.) 3. The ITB is a thickening of the fascia lata in the lateral thigh. 4. If the TFL is tight, it can increase tension in the ITB, thereby increasing the likelihood of ITB friction syndrome at the greater trochanter or lateral condyle of the femur.

Sartorius The name, sartorius, tells us that this muscle performs the four actions necessary to create a cross-legged position that a “sartor” (Latin for tailor) sits in to do his or her work. These actions are flexion, abduction, and lateral rotation of the thigh at the hip joint and flexion of the leg at the knee joint. Derivation sartorius: L. tailor Pronunciation sar-TOR-ee-us

ATTACHMENTS Anterior Superior Iliac Spine (ASIS) to the Pes Anserine Tendon (at the Proximal Anteromedial Tibia)

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes the thigh at the hip joint

Reverse Mover Actions

2. Abducts the thigh at the hip joint

1. Anteriorly tilts the pelvis at the hip joint 2. Depresses the same-side pelvis at the hip joint

3. Laterally rotates the thigh at the hip joint

3. Contralaterally rotates the pelvis at the hip joint

4. Flexes the leg at the knee joint 5. Medially rotates the leg at the knee joint

4. Flexes the thigh at the knee joint 5. Laterally rotates the thigh at the knee joint

Standard Mover Action Notes • The sartorius crosses the hip joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the thigh at the hip joint. (action 1) • The sartorius crosses the hip joint laterally (with its fibers running vertically in the frontal plane); therefore it abducts the thigh at the hip joint. (action 2) • The sartorius crosses the hip joint medially in such a way that it wraps from anteriorly on the pelvis to posteriorly on the tibia/leg (with its fibers running somewhat horizontally in the transverse plane). When the leg is fixed to the thigh and the sartorius pulls the leg, it rotates the thigh anterolaterally, causing the anterior thigh to face laterally. Therefore the sartorius laterally rotates the thigh at the hip joint. (action 3)

788

• The sartorius crosses the knee joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the leg at the knee joint. (action 4) • The sartorius crosses the knee joint medially from posterior to anterior (with its fibers running somewhat horizontally in the transverse plane) to attach into the pes anserine tendon at the medial tibia. When the sartorius pulls at the tibial attachment, the tibial attachment rotates posteromedially, causing the anterior tibia to face somewhat medially. Therefore the sartorius medially rotates the leg at the knee joint. (action 5)

FIGURE 14-9

Anterior view of the sartorius bilaterally. The tensor fasciae latae (TFL) and iliotibial band (ITB) have been ghosted in.

Reverse Mover Action Notes • With the distal attachment fixed, the sartorius, by pulling inferiorly on the anterior pelvis, anteriorly tilts the pelvis at the hip joint. (reverse action 1) • With the distal attachment fixed, the sartorius, by pulling inferiorly on the lateral pelvis, depresses (laterally tilts) the pelvis on that side at the hip joint. Note: Depression of one side of the pelvis causes the other side to elevate. (reverse action 2) • The sartorius crosses the hip joint in such a way that it wraps from laterally on the pelvis to medially onto the tibia (with its fibers running somewhat horizontally in the transverse plane). When the tibial attachment is fixed and the sartorius contracts, it pulls on the pelvis, causing the anterior pelvis to face the opposite side of the body from the side on which the sartorius is attached. Therefore the sartorius contralaterally rotates the pelvis at the hip joint. (reverse action 3)

789

• The sartorius crosses the knee joint posteriorly (with its fibers running vertically in the sagittal plane). If the distal attachment is fixed, it flexes the thigh at the knee joint. (reverse action 4) • Any muscle that medially rotates the leg at the knee joint can laterally rotate the thigh at the knee joint if the distal (leg) attachment is fixed. (reverse action 5)

Motions 1. The sartorius has one line of pull upon the thigh in an oblique plane and therefore creates one motion, which is a combination of flexion, abduction, and lateral rotation of the thigh at the hip joint (as well as flexion of the leg at the knee joint). 2. Regarding its reverse action pull on the pelvis, the sartorius has one line of pull in an oblique plane and therefore creates one motion, which is a combination of anterior tilt, same-side depression, and contralateral rotation of the pelvis at the hip joint.

Eccentric Antagonist Functions 1. Restrains/slows extension, adduction, and medial rotation of the thigh at the hip joint 2. Restrains/slows posterior tilt, same-side elevation, and ipsilateral rotation of the pelvis at the hip joint 3. Restrains/slows knee joint extension 4. Restrains/slows lateral rotation of the leg and medial rotation of the thigh at the knee joint

Isometric Stabilization Functions 1. Stabilizes the thigh and pelvis at the hip joint 2. Stabilizes the knee joint

Isometric Stabilization Function Notes • Same-side pelvic depression force on the support limb side prevents depression of the pelvis to the opposite side (swing limb side) when walking. • The distal tendon of the sartorius (along with the gracilis and semitendinosus muscles—the three pes anserine muscles) helps stabilize the medial knee joint against lateral to medial (valgus) forces that would buckle the knee joint medially.

Additional Note on Actions 1. All three pes anserine muscles (sartorius, gracilis, and semitendinosus) flex and medially rotate the leg at the knee joint.

I N N E RVAT I O N The Femoral Nerve L2, L3

A R T E R I A L S U P P LY The Femoral Artery (the continuation of the External Iliac Artery)

PA L PAT I O N 1. With the client supine, place palpating fingers just distal and slightly medial to the anterior superior iliac spine (ASIS). 2. Have the client actively hold the thigh in a position of flexion and lateral rotation at the hip joint and palpate for the engagement of the sartorius. Resistance can be added. 3. Continue palpating the sartorius distally toward the pes anserine attachment.

RELATIONSHIP TO OTHER STRUCTURES The sartorius is superficial for its entire length. Proximally, the sartorius is located between the tensor fasciae latae (which is lateral to it) and the iliopsoas (which is medial to it). Deep to the sartorius are the rectus femoris, the vastus medialis, and the adductor longus.

790

Of the three muscles that attach into the pes anserine tendon (sartorius, gracilis, semitendinosus), the sartorius’ attachment is the most anterior and proximal. The sartorius is located within the superficial front line and ipsilateral functional line myofascial meridians.

MISCELLANEOUS 1. The sartorius is one of three muscles that attach into the pes anserine tendon. The other two muscles that attach here are the gracilis and the semitendinosus. Pes anserine means goose foot. 2. Think SGS: Of the muscles that attach into the pes anserine, the sartorius attaches the most anterior and proximal of the three, the gracilis is in the middle, and the semitendinosus attaches the most posterior and distal. 3. The sartorius is the longest muscle in the human body. 4. The medial border of the sartorius is the lateral border of the femoral triangle of the thigh. The femoral triangle is located between the medial borders of the sartorius and adductor longus and contains the femoral nerve, artery, and vein. 5. The lateral femoral cutaneous nerve sometimes pierces the sartorius. This can lead to entrapment of this nerve, causing meralgia paresthetica.

Adductor Group These muscles are grouped together, because they all adduct the thigh at the hip joint. There are five adductor muscles of the thigh: the pectineus, gracilis, adductor brevis, adductor longus, and adductor magnus.

ATTACHMENTS Anatomically, the adductor muscle group of the thigh makes up the majority of the musculature of the medial thigh. Their relative anatomic relationships are as follows: Superficially, from the anterior perspective, from lateral to medial, one will see the pectineus, then the adductor longus, then the gracilis. The adductor brevis is deep to the adductor longus. The adductor magnus is the deepest (most posterior) of the entire group. All three adductor muscles attach onto the linea aspera of the femur. The muscles of the adductor group are located within and/or involved with the deep front line, front functional line, and spiral line myofascial meridians.

FUNCTIONS The adductors all cross the hip joint medially, with their fibers running from proximal and medial on the pelvic bone to distal and lateral on the lower extremity. Therefore they all adduct the thigh at the hip joint. Their reverse action is to elevate the same-side (ipsilateral) pelvis at the hip joint. This will also depress the opposite-side (contralateral) pelvis at the hip joint. Four of the five adductors can also flex the thigh at the hip joint because they are anterior to the hip joint. The adductor magnus extends the thigh at the hip joint because it is posterior to the hip joint. Beyond 60 degrees of flexion of the thigh at the hip joint, the adductors’ line of pull relative to the hip joint is posterior and they can all do extension of the thigh at the hip joint. There is some controversy about the role of all three adductors (adductor longus, adductor brevis, and adductor magnus) regarding rotation of the thigh at the hip joint. Some sources state that these three adductor muscles medially rotate the thigh at the hip joint; other sources state that they laterally rotate the thigh at the hip joint. Much of the confusion arises because of the difference between the shaft of the femur and the mechanical axis of the femur. Usually, the mechanical axis of a long bone runs through its shaft. However, because of the change in angulation between the neck and the shaft of the femur and the natural curved shape of the femoral shaft (convex anteriorly), the mechanical axis of the femur lies posterior to its shaft. (The mechanical axis can be determined by drawing a line from the center of the femoral head to the midpoint between the femoral condyles.) When one first looks at the attachment of these three adductors onto the linea aspera of the femur, it seems that their attachment site is posterior to the axis of the femur, and therefore they should laterally rotate the femur. However, considering that the mechanical axis is posterior to the shaft of the femur, the attachment of the adductors onto the

791

linea aspera is actually anterior to the mechanical axis of the femur. For this reason, the weight of the evidence favors the adductors’ role as medial rotators of the thigh at the hip joint.

MISCELLANEOUS 1. When the adductor muscles are strained and pain is felt at their proximal attachment, it is usually called a groin pull in lay terms. 2. The gracilis muscle is also known as the adductor gracilis.

I N N E RVAT I O N The adductors are innervated by the obturator nerve, except the pectineus, which is innervated by the femoral nerve. (The adductor magnus is innervated by the obturator nerve and the sciatic nerve.)

A R T E R I A L S U P P LY The adductors receive the majority of their blood supply from the deep femoral artery.

Anterior Views of the Adductors of the Thigh—Superficial and Deep Views

792

FIGURE 14-10

Views of the adductor group. A, Anterior views. Superficial view on the right (the sartorius has been ghosted in) and deep view on the left.

Medial View of the Adductors of the Thigh

793

FIGURE 14-10

B, Medial view of the right thigh.

Posterior View of the Adductors of the Thigh

794

FIGURE 14-10

C, Posterior view.

Pectineus (of Adductor Group) The name, pectineus, means comb. This muscle has a comblike appearance because its muscle fibers form a flat surface as they leave the pubic bone. Derivation pectineus: L. comb Pronunciation pek-TIN-ee-us

ATTACHMENTS Pubis the pectineal line on the superior pubic ramus to the Proximal Posterior Shaft of the Femur the pectineal line of the femur

795

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes the thigh at the hip joint 2. Adducts the thigh at the hip joint 3. Medially rotates the thigh at the hip joint

Reverse Mover Actions 1. Anteriorly tilts the pelvis at the hip joint 2. Elevates the same-side pelvis at the hip joint 3. Ipsilaterally rotates the pelvis at the hip joint

Standard Mover Action Notes • The pectineus crosses the hip joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the thigh at the hip joint. (action 1) • The pectineus crosses the hip joint medially (with its fibers running somewhat horizontally in the frontal plane); therefore it adducts the thigh at the hip joint. (action 2) • The pectineus is oriented somewhat horizontally in the transverse plane, attaching from the pubic bone to the posterior shaft of the femur. Because the pectineus attaches to the posterior femur anterior to the mechanical axis for rotation (due to the sagittal plane bowing of the shape of the femur from proximal to distal), it medially rotates the thigh at the hip joint. (action 3)

Reverse Mover Action Notes • With the distal femoral attachment fixed, the pectineus, by pulling inferiorly on the anterior pelvis, anteriorly tilts the pelvis at the hip joint. (reverse action 1) • With the distal femoral attachment fixed, the pectineus pulls the medial aspect of the pelvic bone inferiorly toward the medial thigh, resulting in elevation of the same-side pelvis at the hip joint. Note: Elevation of one side of the pelvis causes the other side to depress. (reverse action 2) • All muscles that medially rotate the thigh at the hip joint can ipsilaterally rotate the pelvis at the hip joint (if the thigh is fixed). (reverse action 3)

796

FIGURE 14-11

Anterior view of the right pectineus. The adductor longus has been cut and ghosted in.

Motions 1. The pectineus has one line of pull upon the thigh in an oblique plane and therefore creates one motion, which is a combination of flexion, adduction, and medial rotation of the thigh at the hip joint. 2. Regarding its reverse action pull on the pelvis, the pectineus has one line of pull in an oblique plane and therefore creates one motion, which is a combination of anterior tilt, same-side elevation, and ipsilateral rotation of the pelvis at the hip joint.

Eccentric Antagonist Functions 1. Restrains/slows extension, abduction, and lateral rotation of the thigh at the hip joint 2. Restrains/slows posterior tilt, same-side depression, and contralateral rotation of the pelvis at the hip joint

Isometric Stabilization Functions 1. Stabilizes the thigh and pelvis at the hip joint

Additional Notes on Actions 1. All five members of the adductors of the thigh group can, as their name implies, adduct the thigh (and elevate the same-side pelvis) at the hip joint. 2. If the thigh is sufficiently flexed at the hip joint (at least 45 degrees of flexion of more), the line of pull of the pectineus may change to be posterior to the sagittal plane (mediolateral) axis of motion.

797

If this occurs, the pectineus becomes an extensor of the thigh at the hip joint.

I N N E RVAT I O N The Femoral Nerve L2, L3

A R T E R I A L S U P P LY The Femoral Artery (the continuation of the External Iliac Artery) and the Deep Femoral Artery (a major branch of the Femoral Artery) and the Obturator Artery (a branch of the Internal Iliac Artery)

PA L PAT I O N 1. With the client supine, first locate the adductor longus tendon at the pubic bone (it is the most prominent tendon in the groin region). 2. Once located, drop laterally off the adductor longus and you are on the pectineus. 3. To bring out the pectineus, ask the client to adduct and/or flex the thigh at the hip joint against resistance. Keep in mind that these actions will cause all the thigh adductors to contract. (Note: Be careful with palpation in the proximal anterior thigh, because the femoral nerve, artery, and vein lie over the iliopsoas and pectineus here.) 4. The pectineus can be challenging to palpate because it sits a bit deeper than the adjacent adductor longus and iliopsoas.

RELATIONSHIP TO OTHER STRUCTURES In the proximal anteromedial thigh, part of the pectineus is superficial and lies medial to the iliopsoas and lateral to the adductor longus. The lateral part of the pectineus lies deep to the iliopsoas. From the anterior perspective, the obturator externus and the quadratus femoris are directly deep to the pectineus. The femoral nerve, artery, and vein lie over the lateral aspect of the pectineus. The pectineus is located within the deep front line myofascial meridian.

MISCELLANEOUS 1. Although some sources do not include it, the pectineus belongs in the adductor group of muscles (adductor longus, brevis, magnus, and gracilis). Note the similarity of the direction of fibers of the pectineus to the direction of fibers of the adductor longus. 2. The pectineus is a transitional muscle between the flexor muscles of the thigh and the adductor group of the thigh. 3. Do not confuse the pectineal line of the pubis (which is along the superior pubic ramus and is also known as the pecten of the pubis) with the pectineal line of the femur (which runs on the posterior femur between the lesser trochanter and the linea aspera of the femur).

798

Adductor Longus (of Adductor Group) The name, adductor longus, tells us that this muscle is an adductor and is long (longer than the adductor brevis). Derivation adductor: L. a muscle that adducts a body part longus: L. longer Pronunciation ad-DUK-tor LONG-us

799

ATTACHMENTS Pubis the anterior body to the Linea Aspera of the Femur the middle ⅓ at the medial lip

800

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Adducts the thigh at the hip joint 2. Flexes the thigh at the hip joint 3. Medially rotates the thigh at the hip joint

Reverse Mover Actions 1. Elevates the same-side pelvis at the hip joint 2. Anteriorly tilts the pelvis at the hip joint 3. Ipsilaterally rotates the pelvis at the hip joint

Standard Mover Action Notes • The adductor longus crosses the hip joint medially (with its fibers running somewhat horizontally in the frontal plane); therefore it adducts the thigh at the hip joint. (action 1) • The adductor longus crosses the hip joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the thigh at the hip joint. (action 2) • The adductor longus is oriented somewhat horizontally in the transverse plane, attaching from the pubic bone to the posterior shaft of the femur. Because the adductor longus attaches to the posterior femur anterior to the mechanical axis for rotation (due to the sagittal plane bowing of the shape of the femur from proximal to distal), it medially rotates the thigh at the hip joint. (action 3)

Reverse Mover Action Notes • With the distal femoral attachment fixed, the adductor longus pulls the medial aspect of the pelvic bone inferiorly toward the medial thigh, resulting in elevation of the same-side pelvis at the hip joint. Note: Elevation of one side of the pelvis causes the other side to depress. (reverse action 1) • With the distal femoral attachment fixed, the adductor longus, by pulling inferiorly on the anterior pelvis, anteriorly tilts the pelvis at the hip joint. (reverse action 2) • All muscles that medially rotate the thigh at the hip joint can ipsilaterally rotate the pelvis at the hip joint (if the thigh is fixed). (reverse action 3)

801

FIGURE 14-12

Anterior view of the right adductor longus. The pectineus has been cut and ghosted in.

Motions 1. The adductor longus has one line of pull upon the thigh in an oblique plane and therefore creates one motion, which is a combination of adduction, flexion, and medial rotation of the thigh at the hip joint. 2. Regarding its reverse action pull on the pelvis, the adductor longus has one line of pull in an oblique plane and therefore creates one motion, which is a combination of same-side elevation, anterior tilt, and ipsilateral rotation of the pelvis at the hip joint.

Eccentric Antagonist Functions 1. Restrains/slows abduction, extension, and lateral rotation of the thigh at the hip joint 2. Restrains/slows same-side depression, posterior tilt, and contralateral rotation of the pelvis at the hip joint

Isometric Stabilization Functions 1. Stabilizes the thigh and pelvis at the hip joint

Additional Notes on Actions 1. All five members of the adductors of the thigh group can, as their name implies, adduct the thigh

802

(and elevate the same-side pelvis) at the hip joint. 2. Although the major sagittal plane action of the adductor longus is flexion of the thigh at the hip joint, if the thigh is flexed far enough in front of the body (at least 45 degrees of flexion of more), the adductor longus’ line of pull is now posterior to the sagittal plane (mediolateral) axis of motion of the hip joint and it is now able to extend the thigh at the hip joint. This is important during the gait cycle to begin extension of the lower extremity that is flexed and in front of the body.

I N N E RVAT I O N The Obturator Nerve L2, L3, L4

A R T E R I A L S U P P LY The Femoral Artery (the continuation of the External Iliac Artery) and the Deep Femoral Artery (a major branch of the Femoral Artery) and the Obturator Artery (a branch of the Internal Iliac Artery)

PA L PAT I O N 1. With the client supine, place palpating hand on the proximal anteromedial thigh, very close to the pubic bone. 2. Ask the client to actively adduct the thigh at the hip joint and feel for the proximal tendon of the adductor longus. It will be the most prominent tendon in the proximal anteromedial thigh. 3. Once located, try to follow the adductor longus distally as far as possible. At a certain point, the adductor longus will be posterior (deep) to the sartorius.

803

RELATIONSHIP TO OTHER STRUCTURES Much of the adductor longus is superficial in the proximal anteromedial thigh. The adductor longus is medial to the pectineus and lateral to the gracilis. From the anterior perspective, the adductor brevis is directly deep to the adductor longus. (The adductor magnus is directly deep to the adductor brevis.) All three adductors attach distally onto the linea aspera. The attachment of the adductor longus on the linea aspera is the most medial of the three adductor muscles. The vastus medialis attaches onto the medial lip of the linea aspera, medial to the adductor longus. The adductor longus is located within the deep front line and front functional line myofascial meridians.

804

MISCELLANEOUS 1. The adductor longus has the most prominent proximal tendon in the groin region, which can serve as a useful landmark for locating the pectineus, gracilis, and adductor magnus. 2. The attachment of the adductor longus at the linea aspera often blends with the attachment of the vastus medialis. 3. The medial border of the adductor longus is the medial border of the femoral triangle of the thigh. The femoral triangle is located between the medial borders of the sartorius and adductor longus and contains the femoral nerve, artery, and vein.

Gracilis (of Adductor Group) The name, gracilis, tells us that the shape of this muscle is slender and graceful. Derivation gracilis: L. slender, graceful Pronunciation gra-SIL-is

ATTACHMENTS Pubis the anterior body and the inferior ramus to the Pes Anserine Tendon (at the Proximal Anteromedial Tibia)

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Adducts the thigh at the hip joint 2. Flexes the thigh at the hip joint 3. Flexes the leg at the knee joint 4. Medially rotates the leg at the knee joint 5. Medially rotates the thigh at the hip joint

Reverse Mover Actions 1. Elevates the same-side pelvis at the hip joint 2. Anteriorly tilts the pelvis at the hip joint 3. Flexes the thigh at the knee joint 4. Laterally rotates the thigh at the knee joint 5. Ipsilaterally rotates the pelvis at the hip joint

Standard Mover Action Notes • The gracilis crosses the hip joint medially (with its fibers running somewhat horizontally in the frontal plane); therefore it adducts the thigh at the hip joint. This is the major action of the gracilis. (action 1) • The gracilis crosses the hip joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the thigh at the hip joint. (action 2) • The gracilis crosses the knee joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the leg at the knee joint. (action 3) • The gracilis crosses the knee joint medially from posterior to anterior (with its fibers running somewhat horizontally in the transverse plane) to attach into the pes anserine tendon at the medial tibia. When the gracilis pulls at the tibial attachment, the tibial attachment rotates posteromedially, causing the anterior tibia to face somewhat medially. Therefore the gracilis medially rotates the leg at the knee joint. (action 4) • If the knee joint is extended so that it does not allow rotation (and/or if the leg is fixed to the thigh), then when the gracilis pulls the leg into medial rotation, the thigh will follow and medially rotate at the hip joint. (action 5)

805

FIGURE 14-13

Anterior view of the right gracilis. The adductor longus and sartorius have been cut and ghosted in.

Reverse Mover Action Notes • With the distal attachment fixed, the gracilis pulls the medial aspect of the pelvic bone inferiorly toward the medial thigh, resulting in elevation of the same-side pelvis at the hip joint. Note: Elevation of one side of the pelvis causes the other side to depress. (reverse action 1) • With the distal attachment fixed, the gracilis, by pulling inferiorly on the anterior pelvis, anteriorly tilts the pelvis at the hip joint. (reverse action 2) • The gracilis crosses the knee joint posteriorly (with its fibers running vertically in the sagittal plane). If the distal attachment is fixed and the pelvis is fixed to the thigh, the gracilis flexes the thigh at the knee joint. (reverse action 3) • If the distal end of the gracilis on the tibia is fixed, the reverse action of medial rotation of the leg at the knee joint is lateral rotation of the thigh at the knee joint. (reverse action 4) • All muscles that medially rotate the thigh at the hip joint can ipsilaterally rotate the pelvis at the hip joint (if the thigh is fixed). (reverse action 5)

Motions 1. The gracilis has one line of pull upon the thigh in an oblique plane and therefore creates one motion, which is a combination of adduction, flexion, and medial rotation of the thigh at the hip joint (as well as flexion of the leg at the knee joint).

806

2. Regarding its reverse action pull on the pelvis, the gracilis has one line of pull in an oblique plane and therefore creates one motion, which is a combination of same-side elevation, anterior tilt, and ipsilateral rotation of the pelvis at the hip joint.

Eccentric Antagonist Functions 1. Restrains/slows abduction, extension, and lateral rotation of the thigh at the hip joint 2. Restrains/slows same-side depression, posterior tilt, and contralateral rotation of the pelvis at the hip joint 3. Restrains/slows knee joint extension 4. Restrains/slows lateral rotation of the leg and medial rotation of the thigh at the knee joint

Isometric Stabilization Functions 1. Stabilizes the thigh and pelvis at the hip joint 2. Stabilizes the knee joint

Isometric Stabilization Function Note • The distal tendon of the gracilis (along with the sartorius and semitendinosus muscles – the three pes anserine muscles) helps stabilize the medial knee joint against lateral to medial (valgus) forces that would buckle the knee joint medially.

Additional Notes on Actions 1. All five members of the adductors of the thigh group can, as their name implies, adduct the thigh (and elevate the same-side pelvis) at the hip joint. 2. All three pes anserine muscles (sartorius, gracilis, and semitendinosus) flex and medially rotate the leg at the knee joint. 3. As with the pectineus, adductor longus, and adductor brevis, if the thigh is flexed far enough in front of the body (at least 45 degrees of flexion of more), the gracilis’ line of pull is now posterior to the sagittal plane axis of motion of the hip joint and it is now able to extend the thigh at the hip joint.

I N N E RVAT I O N The Obturator Nerve L2, L3

A R T E R I A L S U P P LY The Deep Femoral Artery (a major branch of the Femoral Artery) and the Obturator Artery (a branch of the Internal Iliac Artery)

PA L PAT I O N 1. With the client supine with the thighs on the table and the legs hanging off the table (the leg is flexed to 90 degrees at the knee joint), locate the adductor longus tendon at the pubic bone (it is the most prominent tendon in the groin region). 2. Then drop immediately off it posteriorly and you are on the gracilis. 3. Ask the client to actively flex the leg at the knee joint against the resistance of the table and the gracilis will engage. 4. Once located, continue palpating the gracilis distally toward the tibia.

RELATIONSHIP TO OTHER STRUCTURES The gracilis is located in the medial thigh and is superficial for its entire course. Proximally, the adductor longus is anterior and lateral to the gracilis. More distally, the sartorius is anterior to the gracilis. Proximally, the adductor magnus is posterior to the gracilis. More distally, the semimembranosus and the semitendinosus are posterior to the gracilis. The gracilis is one of three muscles that attach into the pes anserine tendon, and it attaches between

807

the sartorius and the semitendinosus on the tibia. The gracilis is located within the deep front line myofascial meridian.

MISCELLANEOUS 1. The gracilis is also known as the adductor gracilis. 2. The gracilis is one of three muscles that attach into the pes anserine tendon. The other two muscles that attach here are the sartorius and the semitendinosus. Pes anserine means goose foot. 3. Think SGS: Of the muscles that attach into the pes anserine, the sartorius attaches the most anterior and proximal of the three, the gracilis is in the middle, and the semitendinosus attaches the most posterior and distal. 4. The gracilis is the only member of the adductor group that crosses the knee joint. 5. The gracilis is the second longest muscle in the human body. (The sartorius is the longest.) 6. The curve of the gracilis is an artifact of evolution. In bent-kneed quadrupeds, the gracilis runs in a straight line passing posterior to the knee joint. As our knee joints extended (straightened out) with evolution, the gracilis stayed posterior to the knee joint due to fascia that held it down.

808

Adductor Brevis (of Adductor Group) The name, adductor brevis, tells us that this muscle is an adductor and is short (shorter than the adductor longus). Derivation adductor: L. a muscle that adducts a body part brevis: L. shorter Pronunciation ad-DUK-tor BRE-vis

809

ATTACHMENTS Pubis the inferior ramus to the Linea Aspera of the Femur the proximal ⅓

810

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions

Reverse Mover Actions 1. Elevates the same-side pelvis at the hip joint

1. Adducts the thigh at the hip joint 2. Flexes the thigh at the hip joint 3. Medially rotates the thigh at the hip joint

2. Anteriorly tilts the pelvis at the hip joint 3. Ipsilaterally rotates the pelvis at the hip joint

Standard Mover Action Notes • The adductor brevis crosses the hip joint medially (with its fibers running somewhat horizontally in the frontal plane); therefore it adducts the thigh at the hip joint. (action 1) • The adductor brevis crosses the hip joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the thigh at the hip joint. (action 2) • Although the major sagittal plane action of the adductor brevis is flexion of the thigh at the hip joint, if the thigh is flexed far enough in front of the body, the adductor brevis’ line of pull is now posterior to the sagittal plane mediolateral axis of motion of the hip joint and it is now able to extend the thigh at the hip joint. This is important during the gait cycle to begin extension of the lower extremity that is flexed and in front of the body. (action 2) • The adductor brevis is oriented somewhat horizontally in the transverse plane, attaching from the pubic bone to the posterior shaft of the femur. Because the adductor brevis attaches to the posterior femur anterior to the mechanical axis for rotation (due to the sagittal plane bowing of the shape of the femur from proximal to distal), it medially rotates the thigh at the hip joint. (action 3)

FIGURE 14-14

Anterior view of the adductor brevis bilaterally. The adductor longus has been cut and ghosted in on the left.

Reverse Mover Action Notes 811

• With the distal femoral attachment fixed, the adductor brevis pulls the medial aspect of the pelvic bone inferiorly toward the medial thigh, resulting in elevation of the same-side pelvis at the hip joint. Note: Elevation of one side of the pelvis causes the other side to depress. (reverse action 1) • With the distal femoral attachment fixed, the adductor brevis, by pulling inferiorly on the anterior pelvis, anteriorly tilts the pelvis at the hip joint. (reverse action 2) • All muscles that medially rotate the thigh at the hip joint can ipsilaterally rotate the pelvis at the hip joint (if the thigh is fixed). (reverse action 3)

Motions 1. The adductor brevis has one line of pull upon the thigh in an oblique plane and therefore creates one motion, which is a combination of adduction, flexion, and medial rotation of the thigh at the hip joint. 2. Regarding its reverse action pull on the pelvis, the adductor brevis has one line of pull in an oblique plane and therefore creates one motion, which is a combination of same-side elevation, anterior tilt, and ipsilateral rotation of the pelvis at the hip joint.

Eccentric Antagonist Functions 1. Restrains/slows abduction, extension, and lateral rotation of the thigh at the hip joint 2. Restrains/slows same-side depression, posterior tilt, and contralateral rotation of the pelvis at the hip joint

Isometric Stabilization Functions 1. Stabilizes the thigh and pelvis at the hip joint

Additional Notes on Actions 1. All five members of the adductors of the thigh group can, as their name implies, adduct the thigh (and elevate the same-side pelvis) at the hip joint. 2. Although the major sagittal plane action of the adductor brevis is flexion of the thigh at the hip joint, if the thigh is flexed far enough in front of the body (at least 45 degrees of flexion of more), the adductor brevis’ line of pull is now posterior to the sagittal plane axis of motion of the hip joint and it is now able to extend the thigh at the hip joint. This is important during the gait cycle to begin extension of the lower extremity that is flexed and in front of the body.

I N N E RVAT I O N The Obturator Nerve L2, L3

A R T E R I A L S U P P LY The Femoral Artery (the continuation of the External Iliac Artery) and the Deep Femoral Artery (a major branch of the Femoral Artery) and the Obturator Artery (a branch of the Internal Iliac Artery)

PA L PAT I O N 1. With the client supine, place palpating hand on the proximal anteromedial thigh, very close to the pubic bone. 2. Ask the client to actively adduct the thigh at the hip joint and feel for the proximal tendon of the adductor longus. It will be the most prominent tendon in the proximal anteromedial thigh. 3. Once located, have the client relax and try to palpate deep to the adductor longus for the adductor brevis. (Note: It is very difficult to discern the adductor brevis from the adductor longus.)

812

813

RELATIONSHIP TO OTHER STRUCTURES From the anterior perspective, the adductor brevis is deep to the adductor longus and superficial to the adductor magnus. All three adductors attach distally onto the linea aspera. The adductor brevis attaches onto the linea aspera between the attachments of the adductor longus and adductor magnus. The adductor brevis is located within the deep front line and front functional line myofascial meridians.

814

MISCELLANEOUS 1. The adductor brevis is usually entirely deep (from the anterior perspective) to the adductor longus. However, sometimes a small part of it is superficial between the adductor longus and the gracilis.

Adductor Magnus (of Adductor Group) The name, adductor magnus, tells us that this muscle is an adductor and is large (larger than the adductor longus and the adductor brevis). Derivation adductor: L. a muscle that adducts a body part magnus: L. great, larger Pronunciation ad-DUK-tor MAG-nus

ATTACHMENTS Pubis and Ischium to the Linea Aspera of the Femur ANTERIOR HEAD: inferior pubic ramus and the ramus of the ischium to the ANTERIOR HEAD: gluteal tuberosity, linea aspera, and medial supracondylar line of the femur POSTERIOR HEAD: ischial tuberosity to the POSTERIOR HEAD: adductor tubercle of the femur

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Adducts the thigh at the hip joint

Reverse Mover Actions 1. Elevates the same-side pelvis at the hip joint

2. Extends the thigh at the hip joint 3. Flexes the thigh at the hip joint

2. Posteriorly tilts the pelvis at the hip joint 3. Anteriorly tilts the pelvis at the hip joint

4. Medially rotates the thigh at the hip joint

4. Ipsilaterally rotates the pelvis at the hip joint

Standard Mover Action Notes • The adductor magnus crosses the hip joint medially (with its fibers running somewhat horizontally in the frontal plane); therefore it adducts the thigh at the hip joint. (action 1) • The adductor magnus crosses the hip joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it extends the thigh at the hip joint. (action 2) • Some sources state that the most anterior fibers (often termed the adductor minimus) of the adductor magnus can flex the thigh at the hip joint. This would be explained by their pubic attachment being slightly anterior to the femoral attachment. (action 3)

815

FIGURE 14-15

Posterior view of the right adductor magnus.

• The adductor magnus is oriented somewhat horizontally in the transverse plane, attaching from the pelvic bone to the posterior shaft of the femur. Because the adductor magnus attaches to the posterior femur anterior to the mechanical axis for rotation (due to the sagittal plane bowing of the shape of the femur from proximal to distal), it medially rotates the thigh at the hip joint. (action 4)

Reverse Mover Action Notes • With the distal femoral attachment fixed, the adductor magnus pulls the medial aspect of the pelvic bone inferiorly toward the medial thigh, resulting in elevation of the same-side pelvis at the hip joint. Note: Elevation of one side of the pelvis causes the other side to depress. (reverse action 1) • With the distal femoral attachment fixed, the adductor magnus, by pulling inferiorly on the posterior pelvis, posteriorly tilts the pelvis at the hip joint. (reverse action 2) • All muscles that flex the thigh at the hip joint can anteriorly tilt the pelvis at the hip joint if the distal femoral attachment is fixed. (reverse action 3) • All muscles that medially rotate the thigh at the hip joint can ipsilaterally rotate the pelvis at the hip joint (if the distal femoral attachment is fixed). (reverse action 4)

Motions

816

Because the adductor magnus has more than one line of pull, it can create more than one motion. 1. The posterior head of the adductor magnus has one line of pull upon the thigh in an oblique plane and therefore creates one motion, which is a combination of adduction, extension, and medial rotation of the thigh at the hip joint. 2. The anterior head of the adductor magnus has one line of pull upon the thigh in an oblique plane and therefore creates one motion, which is a combination of adduction, flexion, and medial rotation of the thigh at the hip joint. 3. Regarding its reverse action pull on the pelvis, the posterior head of the adductor magnus has one line of pull in an oblique plane and therefore creates one motion, which is a combination of posterior tilt, same-side elevation, and ipsilateral rotation of the pelvis at the hip joint. 4. Regarding its reverse action pull on the pelvis, the anterior head of the adductor magnus has one line of pull in an oblique plane and therefore creates one motion, which is a combination of anterior tilt, same-side elevation, and ipsilateral rotation of the pelvis at the hip joint.

Eccentric Antagonist Functions 1. Restrains/slows abduction, flexion, extension, and lateral rotation of the thigh at the hip joint 2. Restrains/slows same-side depression, anterior tilt, posterior tilt, and contralateral rotation of the pelvis at the hip joint

Isometric Stabilization Functions 1. Stabilizes the thigh and pelvis at the hip joint

Additional Notes on Actions 1. All five members of the adductors of the thigh group can, as their name implies, adduct the thigh (and elevate the same-side pelvis) at the hip joint. 2. The adductor magnus is the only member of the adductor group whose major sagittal plane actions are extension of the thigh and posterior tilt of the pelvis at the hip joint.

I N N E RVAT I O N The Obturator Nerve and the Sciatic Nerve the obturator nerve innervates the anterior head the tibial branch of the sciatic nerve innervates the posterior head L2, L3, L4

A R T E R I A L S U P P LY Anterior Head The Femoral Artery (the continuation of the External Iliac Artery) and the Deep Femoral Artery (a major branch of the Femoral Artery) and the Obturator Artery (a branch of the Internal Iliac Artery) Posterior Head The Deep Femoral Artery (a major branch of the Femoral Artery) and the Inferior Gluteal Artery (a branch of the Internal Iliac Artery) and the Obturator Artery (a branch of the Internal Iliac Artery) and branches of the Popliteal Artery (the continuation of the Femoral Artery)

PA L PAT I O N 1. With the client supine with thighs on the table and legs hanging off the table, place your palpating fingers on the proximal medial thigh and ask the client to flex the leg at the knee joint against the resistance of the table. 2. This will engage the gracilis and medial hamstrings but not the adductor magnus, which is located between them. 3. To engage the adductor magnus, ask the client to either adduct the thigh at the hip joint against your resistance or to extend the thigh at the hip joint against the resistance of the table.

RELATIONSHIP TO OTHER STRUCTURES 817

From the anterior perspective, the adductor magnus is deep to the pectineus, adductor longus, and the adductor brevis. (There is a small portion of the adductor magnus that is superficial from the anterior perspective between the sartorius, adductor longus, and the gracilis.) From the posterior perspective, the adductor magnus is deep to all three hamstring muscles. Although the adductor magnus is primarily deep from the anterior and posterior perspectives, there is a large portion of it that is superficial medially. All three adductors attach distally onto the linea aspera. The adductor longus and adductor brevis attach directly medial to the adductor magnus on the linea aspera of the femur. The gluteus maximus and the short head of the biceps femoris attach directly lateral to the adductor magnus onto the femur. (They attach onto the gluteal tuberosity and the linea aspera of the femur, respectively.) The obturator externus and the quadratus femoris lie directly proximal to the adductor magnus. The adductor magnus is located within the deep front line and involved with the spiral line myofascial meridians.

MISCELLANEOUS 1. The adductor magnus has an anterior head and a posterior head. 2. The anterior head of the adductor magnus consists of two sections. The first section is often called the adductor minimus (it is also called the horizontal fibers); the second section is called the oblique fibers. 3. The posterior head of the adductor magnus is also called the ischiocondylar section, because it attaches from the ischial tuberosity to the adductor tubercle, which is on the medial condyle of the femur. 4. The anterior head of the adductor magnus arises from the inferior ramus of the pubis and the ramus of the ischium. 5. The anterior and posterior heads of the adductor magnus (the oblique fibers of the anterior head and the ischiocondylar section) are separated distally by a hiatus called the adductor hiatus. 6. The femoral artery and vein from the anterior thigh pass through the adductor hiatus, becoming the popliteal artery and vein in the distal posterior thigh. 7. The position of the adductor magnus in the medial thigh is such that from the anterior perspective it forms a floor that the other adductors sit on and from the posterior perspective it forms a floor that the hamstrings sit on. 8. The adductor magnus is a transitional muscle between the adductor group and the hamstring group. 9. Like the hamstring muscles, the adductor magnus attaches to the ischial tuberosity and can extend the thigh at the hip joint. For this reason, the adductor magnus (or more specifically the posterior head of the adductor magnus) is sometimes referred to as the fourth hamstring.

818

Gluteal Group There are three muscles in the gluteal group: the gluteus maximus, medius, and minimus. • All three gluteal muscles cross the hip joint, so they can move the thigh at the hip joint and/or move the pelvis at the hip joint. • The gluteus medius and minimus are primarily important for stabilizing the pelvis when walking.

FIGURE 14-16

Right lateral views of the gluteal muscles. A, Superficial view. The gluteus minimus is not seen. B, Deep view. The gluteus medius has been ghosted in.

819

Gluteus Maximus (of Gluteal Group) The name, gluteus maximus, tells us that this muscle is located in the gluteal (i.e., buttock) region and is large (larger than the gluteus medius and the gluteus minimus). Derivation gluteus: Gr. buttocks maximus: L. greatest Pronunciation GLOO-tee-us MAX-i-mus

820

ATTACHMENTS Posterior Iliac Crest, the Posterolateral Sacrum, and the Coccyx and the sacrotuberous ligament, the thoracolumbar fascia, and the fascia over the gluteus medius to the Iliotibial Band (ITB) and the Gluteal Tuberosity of the Femur

821

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions

Reverse Mover Actions

1. Extends the thigh at the hip joint

1. Posteriorly tilts the pelvis at the hip joint

2. Laterally rotates the thigh at the hip joint

2. Contralaterally rotates the pelvis at the hip joint 3. Depresses the same-side pelvis at the hip joint (upper ⅓)

3. Abducts the thigh at the hip joint (upper ⅓) 4. Adducts the thigh at the hip joint (lower ⅔) 5. Extends the leg at the knee joint

4. Elevates the same-side pelvis at the hip joint (lower ⅔) 5. Extends the thigh at the knee joint

Standard Mover Action Notes • The gluteus maximus crosses the hip joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it extends the thigh at the hip joint. (action 1) • The gluteus maximus wraps around the posterior pelvis to attach laterally onto the iliotibial band and femur (with its fibers running somewhat horizontally in the transverse plane). When the gluteus maximus contracts, it pulls this lateral attachment posteromedially, causing the anterior surface of the thigh to face laterally. Therefore the gluteus maximus laterally rotates the thigh at the hip joint. (action 2) • If a person is standing and pinches the buttocks together (i.e., contracts the gluteus maximus muscles), an interesting postural effect occurs. The contraction of the gluteus maximus muscles should cause lateral rotation of the thighs at the hip joints. However, because of the friction between the bottom of the feet and the floor, the thighs cannot freely laterally rotate. Therefore the rotatory force on the thighs is translated all the way to the talus of the foot, which laterally rotates relative to the calcaneus at the subtalar joint. Lateral rotation is a component action of foot supination, which lifts up the arches of the feet. A conclusion from this might be that if a person’s gluteus maximus muscles are well developed and therefore have a stronger resting baseline tone, the arches of their feet may gain extra support. (action 2)

FIGURE 14-17

Posterior view of the right gluteus maximus. The tensor fasciae latae, fascia over the gluteus medius, and iliotibial band (ITB) have been ghosted in.

822

• The gluteus maximus, albeit the largest extensor and/or lateral rotator of the thigh at the hip joint, only contracts when forceful extension and/or lateral rotation of the thigh is required, such as running, jumping, or climbing stairs. (actions 1, 2) • The upper ⅓ of the gluteus maximus crosses the hip joint from medial to lateral above the center of the joint (with its fibers running vertically in the frontal plane). Therefore this portion of the gluteus maximus abducts the thigh at the hip joint. (Note the similarity of the direction of these fibers of the gluteus maximus to the direction of fibers of the nearby gluteus medius.) (action 3) • The lower ⅔ of the gluteus maximus crosses the hip joint from medial to lateral below the center of the joint (with its fibers running somewhat horizontally in the frontal plane). Therefore this portion of the gluteus maximus adducts the thigh at the hip joint. (action 4) • Because of its pull via the iliotibial band (which attaches to the proximal anterolateral tibia), the gluteus maximus crosses the knee joint anteriorly (with a vertical orientation to its pull in the sagittal plane). Therefore the gluteus maximus extends the leg at the knee joint. (action 5)

Reverse Mover Action Notes • When the thigh is fixed, the gluteus maximus, by pulling down on the posterior pelvis, posteriorly tilts the pelvis at the hip joint. This action is important during walking, running, and returning to an upright position from a stooped position. (reverse action 1) • The gluteus maximus crosses the hip joint posteriorly (with its fibers running somewhat horizontally in the transverse plane). When the femoral attachment is fixed and the gluteus maximus contracts, it pulls on the pelvis, causing the anterior pelvis to face the opposite side of the body from the side on which the gluteus maximus is attached. Therefore the gluteus maximus contralaterally rotates the pelvis at the hip joint. (reverse action 2) • Contralateral rotation of the pelvis at the hip joint is important whenever a foot is planted on the ground and the pelvis is rotated to the opposite side, such as when planting and cutting in sports. (reverse action 2) • The upper ⅓ of the gluteus maximus’ fibers cross the hip joint laterally. If the distal attachment is fixed, the lateral surface of the pelvis will be pulled down toward the lateral surface of the thigh. Therefore, the upper ⅓ of the gluteus maximus depresses the same-side (ipsilateral) pelvis at the hip joint. This action is important because it prevents depression of the pelvis to the opposite side when walking. (reverse action 3) • The lower ⅔ of the gluteus maximus’ fibers cross the hip joint on the medial side (below the center of the joint). If the distal attachment is fixed, the medial pelvis is pulled down toward the medial thigh, causing elevation of the same-side pelvis at the hip joint. (reverse action 4) • Via its iliotibial band attachment, the gluteus maximus crosses the knee joint anteriorly (with its fibers running vertically in the sagittal plane). If the distal attachment is fixed, it extends the thigh at the knee joint. (reverse action 5)

Motions Because the gluteus maximus has more than one line of pull, it can create more than one motion. 1. The upper fibers have one line of pull in an oblique plane and therefore create one motion, which is a combination of extension, abduction, and lateral rotation of the thigh at the hip joint (as well as extension of the leg at the knee joint). 2. The lower fibers have one line of pull in an oblique plane and therefore create one motion, which is a combination of extension, adduction, and lateral rotation of the thigh at the hip joint (as well as extension of the leg at the knee joint). 3. Regarding their reverse action pull upon the pelvis, the upper fibers of the gluteus maximus have one line of pull, so they create one motion, which is a combination of posterior tilt, contralateral rotation, and same-side depression of the pelvis at the hip joint. 4. Regarding their reverse action pull upon the pelvis, the lower fibers of the gluteus maximus have one line of pull, so they create one motion, which is a combination of posterior tilt, contralateral rotation, and same-side elevation of the pelvis at the hip joint.

Eccentric Antagonist Functions 1. Restrains/slows flexion, medial rotation, adduction, and abduction of the thigh at the hip joint

823

2. Restrains/slows anterior tilt, ipsilateral rotation, same-side elevation and same-side depression of the pelvis at the hip joint 3. Restrains/slows knee joint flexion

Isometric Stabilization Functions 1. Stabilizes the thigh and pelvis at the hip joint 2. Stabilizes the knee joint 3. Stabilizes the subtalar joint

Isometric Stabilization Function Notes • Given that both the gluteus maximus and the tensor fasciae latae attach into the iliotibial band and the iliotibial band crosses the knee joint anterolaterally, both of these muscles in effect cross the knee joint anteriorly and therefore, theoretically, can extend the leg at the knee joint. However, there is controversy over their ability to actually do this. Certainly, extension of the leg at the knee joint is not one of their major actions. It is likely that the role of these two muscles and the iliotibial band crossing the knee joint is primarily to help stabilize the knee joint. • Lateral rotation of the thigh at the hip joint acts to prevent medial rotation of the thigh and entire lower extremity, including the talus at the subtalar joint. This can stabilize the subtalar joint and prevent excessive pronation (dropping of the arch) of the foot.

Additional Note on Actions 1. If the thigh is first flexed to 90 degrees, the gluteus maximus would have a horizontal line of pull that could create horizontal extension (horizontal abduction) of the thigh at the hip joint.

I N N E RVAT I O N The Inferior Gluteal Nerve L5, S1, S2

A R T E R I A L S U P P LY The Superior Gluteal Artery and the Inferior Gluteal Artery (branches of the Internal Iliac Artery)

PA L PAT I O N 1. With the client prone, place your palpating hand on the posterior gluteal region, just lateral to the sacrum. 2. Have the client laterally rotate and extend the thigh at the hip joint and feel for the contraction of the gluteus maximus. Resistance can be added to the distal thigh. 3. Palpate the gluteus maximus distally and laterally to its distal attachment on the iliotibial band and femur.

824

RELATIONSHIP TO OTHER STRUCTURES The gluteus maximus is superficial in the posterior pelvis and covers the posteroinferior portion of the gluteus medius. The gluteus maximus also covers the entire piriformis, superior gemellus, obturator internus, inferior gemellus, obturator externus, quadratus femoris, and ischial tuberosity. The attachment of the gluteus maximus onto the gluteal tuberosity of the femur is between the vastus lateralis and adductor magnus attachments. The gluteus maximus is located within the lateral line and back functional line myofascial meridians.

825

MISCELLANEOUS 1. The gluteus maximus has deeper fibers located superiorly that cross from the sacrum to the iliac crest. Therefore these fibers directly cross the sacroiliac joint and can function to stabilize it. Likely because of their sacroiliac joint stabilization function, these deeper superior fibers are often the site of hypertonic myofascial trigger points. 2. Two muscles attach into the iliotibial band (ITB): the gluteus maximus and the tensor fasciae latae (TFL). Given that the gluteus maximus attaches into the ITB from one direction and the TFL attaches into the ITB from the opposite direction, they have opposite actions of rotation at the hip joint. 3. It can be helpful to think of the gluteus maximus as the speed skater’s muscle. The gluteus maximus is powerful in extending, abducting, and laterally rotating the thigh at the hip joint, which are all actions that are necessary when speed skating. 4. The gluteus maximus is the largest muscle in the human body.

Gluteus Medius (of Gluteal Group) The name, gluteus medius, tells us that this muscle is located in the gluteal (i.e., buttock) region and is medium sized (smaller than the gluteus maximus and larger than the gluteus minimus). Derivation gluteus: Gr. buttocks medius: L. middle Pronunciation GLOO-tee-us MEED-ee-us

ATTACHMENTS External Ilium inferior to the iliac crest and between the anterior and posterior gluteal lines to the Greater Trochanter of the Femur the lateral surface

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions

Reverse Mover Actions

1. Abducts the thigh at the hip joint (entire muscle)

1. Depresses the same-side pelvis at the hip joint (entire muscle)

2. Extends the thigh at the hip joint (posterior fibers)

2. Posteriorly tilts the pelvis at the hip joint (posterior fibers)

3. Flexes the thigh at the hip joint (anterior fibers)

3. Anteriorly tilts the pelvis at the hip joint (anterior fibers)

4. Laterally rotates the thigh at the hip joint (posterior fibers)

4. Contralaterally rotates the pelvis at the hip joint (posterior fibers) 5. Ipsilaterally rotates the pelvis at the hip joint (anterior fibers)

5. Medially rotates the thigh at the hip joint (anterior fibers)

Standard Mover Action Notes • The gluteus medius crosses the hip joint laterally above the center of the joint (with its fibers running vertically in the frontal plane). Therefore the gluteus medius abducts the thigh at the hip joint. (action 1) • The posterior fibers of the gluteus medius cross the hip joint posteriorly (running vertically in the sagittal plane); therefore they extend the thigh at the hip joint. (action 2) • The anterior fibers of the gluteus medius cross the hip joint anteriorly (running vertically in the sagittal plane); therefore they flex the thigh at the hip joint. (action 3) • The posterior fibers of the gluteus medius wrap around the posterior pelvis to attach laterally

826

onto the greater trochanter (running somewhat horizontally in the transverse plane). When the posterior fibers contract, they pull the greater trochanter posteromedially, causing the anterior surface of the thigh to face laterally. Therefore the gluteus medius laterally rotates the thigh at the hip joint. Note the similarity of the direction of posterior fibers of the gluteus medius to the direction of fibers of the neighboring piriformis. (action 4) • The anterior fibers of the gluteus medius wrap around the anterior pelvis to attach laterally onto the greater trochanter (running somewhat horizontally in the transverse plane). When the anterior fibers contract, they pull the greater trochanter anteromedially, causing the anterior surface of the thigh to face medially. Therefore the gluteus medius medially rotates the thigh at the hip joint. Note the similarity of the direction of anterior fibers of the gluteus medius to the direction of fibers of the neighboring tensor fasciae latae. (action 5)

FIGURE 14-18

Lateral view of the right gluteus medius. The piriformis has been ghosted in.

Reverse Mover Action Notes • When the femoral attachment is fixed, the gluteus medius, by pulling inferiorly on the pelvis laterally, depresses (i.e., laterally tilts) the same-side (ipsilateral) pelvis at the hip joint. Note: Depression of one side of the pelvis causes the other side of the pelvis to elevate. (reverse action 1) • Ipsilateral pelvic depression force on the support-limb side when walking prevents depression of the pelvis to the opposite unsupported swing-limb side. (reverse action 1) • When the femoral attachment is fixed and the posterior fibers of the gluteus medius contract, they pull inferiorly on the posterior pelvis, posteriorly tilting the pelvis at the hip joint. (reverse action 2) • When the femoral attachment is fixed and the anterior fibers of the gluteus medius contract, they pull inferiorly on the anterior pelvis, anteriorly tilting the pelvis at the hip joint. (reverse action 3) • The posterior fibers of the gluteus medius cross the hip joint posteriorly (running somewhat horizontally in the transverse plane). When the femoral attachment is fixed and the posterior fibers of the gluteus medius contract, they pull on the pelvis, causing the anterior pelvis to face

827

the opposite side of the body from the side on which the gluteus medius is attached. Therefore the posterior fibers of the gluteus medius contralaterally rotate the pelvis at the hip joint. (reverse action 4) • The anterior fibers of the gluteus medius cross the hip joint anteriorly (with their fibers running somewhat horizontally in the transverse plane). When the femoral attachment is fixed and the anterior fibers of the gluteus medius contract, they pull on the pelvis, causing the anterior pelvis to face the same side of the body on which the gluteus medius is attached. Therefore the anterior fibers of the gluteus medius ipsilaterally rotate the pelvis at the hip joint. (reverse action 5)

Motions Because the gluteus medius has more than one line of pull, it can create more than one motion. 1. The middle fibers of the gluteus medius have one line of pull, essentially in one cardinal plane (the frontal plane) and therefore have one motion, which is a cardinal plane action, abduction of the thigh at the hip joint. 2. The posterior fibers of the gluteus medius have one line of pull in an oblique plane and therefore create one motion, which is a combination of extension, abduction, and lateral rotation of the thigh at the hip joint. 3. The anterior fibers of the gluteus medius have one line of pull in an oblique plane and therefore create one motion, which is a combination of flexion, abduction, and medial rotation of the thigh at the hip joint. 4. Regarding their reverse action upon the pelvis, the middle fibers of the gluteus medius have one line of pull, essentially in one cardinal plane (the frontal plane) and therefore have one motion, its cardinal plane action, same-side depression of the pelvis at the hip joint. 5. Regarding their reverse action pull upon the pelvis, the posterior fibers of the gluteus medius have one line of pull in an oblique plane and therefore create one motion, which is a combination of posterior tilt, same-side depression, and contralateral rotation of the pelvis at the hip joint. 6. Regarding their reverse action pull upon the pelvis, the anterior fibers of the gluteus medius have one line of pull in an oblique plane and therefore create one motion, which is a combination of anterior tilt, same-side depression, and ipsilateral rotation of the pelvis at the hip joint.

Eccentric Antagonist Functions 1. Restrains/slows adduction, flexion, extension, medial rotation, and lateral rotation of the thigh at the hip joint 2. Restrains/slows same-side elevation, anterior tilt, posterior tilt, ipsilateral rotation, and contralateral rotation of the pelvis at the hip joint

Isometric Stabilization Functions 1. Stabilizes the thigh and pelvis at the hip joint 2. Stabilizes the subtalar joint

Isometric Stabilization Function Notes • Same-side (ipsilateral) pelvic depression (lateral tilt) force by the gluteus medius is actually its most important function. When one foot is lifted off the floor, the pelvis should fall to that side because it is now unsupported. However, this is prevented by the gluteus medius on the (opposite) support-limb side, which contracts and creates a force of ipsilateral depression of the pelvis. Depressing the pelvis on the support-limb side prevents the pelvis from falling (depressing) to the other unsupported swing-limb side. Therefore the pelvis remains level. With every step that a person takes when walking, contraction of the gluteus medius on the support side occurs. Therefore, the gluteus medius is important and necessary for proper gait by isometrically contracting to stabilize the pelvis. • The gluteus medius contracts to create a force of same-side pelvic depression (lateral tilt) not only when a foot is lifted off the floor to walk (see note above) but also when weight is simply shifted to one foot. Therefore the habitual practice of standing with all or most of the body weight on one side tends to cause the gluteus medius on that side to become overused and tight. • Thigh lateral rotation action prevents medial rotation of the thigh and entire lower extremity, including the talus at the subtalar joint, if the foot overly pronates (if the arch of the foot

828

collapses).

Additional Notes on Actions 1. Note how the gluteus medius fans around the hip joint. It crosses the hip joint posteriorly, laterally, and anteriorly. Therefore some sources consider the gluteus medius to have three sections: posterior, middle, and anterior. This orientation is similar to the orientation of the deltoid to the glenohumeral joint. Therefore both of these muscles can do the same actions at their respective joints. The gluteus medius can abduct, extend, flex, laterally rotate, and medially rotate the thigh at the hip joint. The deltoid can abduct, extend, flex, laterally rotate, and medially rotate the arm at the glenohumeral joint 2. Because the posterior portion of the gluteus medius is the thickest part, its actions are the strongest. Therefore the strongest actions of the gluteus medius are abduction, extension, and lateral rotation of the thigh at the hip joint.

I N N E RVAT I O N The Superior Gluteal Nerve L4, L5, S1

A R T E R I A L S U P P LY The Superior Gluteal Artery (a branch of the Internal Iliac Artery)

PA L PAT I O N 1. With the client side lying, place your palpating fingers immediately distal to the middle of the iliac crest. 2. Have the client abduct the thigh into the air and feel for the contraction of the gluteus medius. Resistance can be added. 3. The posterior and anterior fibers of the gluteus medius are deep to the gluteus maximus and tensor fasciae latae, respectively, and can be difficult to discern from these overlying muscles.

RELATIONSHIP TO OTHER STRUCTURES The posterior ⅓ of the gluteus medius is deep to the gluteus maximus. A portion of the anterior gluteus medius is deep to the tensor fasciae latae. The middle portion of the gluteus medius is superficial. The anterior fibers of the gluteus medius lie next to and deep to the tensor fasciae latae (with essentially an identical fiber direction), and the posterior fibers of the gluteus medius lie next to the piriformis (with essentially an identical fiber direction). Deep to the gluteus medius is the gluteus minimus. The gluteus medius is located within the lateral line myofascial meridian.

MISCELLANEOUS 1. There is usually a thick layer of fascia overlying the gluteus medius muscle called the gluteal fascia or the gluteal aponeurosis. 2. A chronically tight gluteus medius can create the postural conditions of a functional short lower extremity (usually called a short leg) and a compensatory scoliosis. When the gluteus medius is tight, it pulls on and depresses (laterally tilts) the pelvis toward the thigh on that side. This results in a functional short leg (as opposed to a structural short leg, wherein the femur and/or the tibia on one side is actually shorter than on the other side). Further, depressing the pelvis on one side creates an unlevel sacrum for the spine to sit on and a compensatory scoliosis must occur to return the head to a level position. (Note: The head must be level for proper proprioceptive balance in the inner ear and for the eyes to be level for visual proprioception.) 3. Understanding the role of the gluteus medius as a same-side pelvis depressor whenever a person lifts a foot off the floor or simply shifts his or her weight to one side gives us another easy way to palpate the gluteus medius. Stand and rock your weight back and forth from one foot to the other while palpating both gluteus medius muscles. The gluteus medius muscle on the support-limb side

829

(the side that you are bearing weight on) will clearly be felt as it contracts. 4. Because the gluteus medius has the same actions at the hip joint that the deltoid has at the glenohumeral joint, the gluteus medius is sometimes known as the deltoid of the hip.

830

Gluteus Minimus (of Gluteal Group) The name, gluteus minimus, tells us that this muscle is located in the gluteal (i.e., buttock) region and is small (smaller than the gluteus maximus and the gluteus medius). Derivation gluteus: Gr. buttocks minimus: L. least Pronunciation GLOO-tee-us MIN-i-mus

831

ATTACHMENTS External Ilium between the anterior and inferior gluteal lines to the Greater Trochanter of the Femur the anterior surface

832

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions

Reverse Mover Actions

1. Abducts the thigh at the hip joint (entire muscle)

1. Depresses the same-side pelvis at the hip joint (entire muscle)

2. Flexes the thigh at the hip joint (anterior fibers)

2. Anteriorly tilts the pelvis at the hip joint (anterior fibers)

3. Extends the thigh at the hip joint (posterior fibers) 4. Medially rotates the thigh at the hip joint (anterior fibers)

3. Posteriorly tilts the pelvis at the hip joint (posterior fibers) 4. Ipsilaterally rotates the pelvis at the hip joint (anterior fibers)

5. Laterally rotates the thigh at the hip joint (posterior fibers)

5. Contralaterally rotates the pelvis at the hip joint (posterior fibers)

Standard Mover Action Notes • The gluteus minimus has the same standard (and reverse) mover actions as the gluteus medius. One difference is that the thickest and most powerful aspect of the gluteus minimus is its anterior aspect. Therefore its actions of abduction, flexion, and medial rotation are its most powerful actions. The other difference is that the gluteus medius fans out more anteriorly and posteriorly around the hip joint; therefore it is much more powerful than the gluteus minimus because of its greater size and greater coverage around the joint. (actions 1, 2, 3, 4, 5) • The gluteus minimus crosses the hip joint laterally above the center of the joint (with its fibers running vertically in the frontal plane). Therefore the gluteus minimus abducts the thigh at the hip joint. (action 1)

FIGURE 14-19

Lateral view of the right gluteus minimus. The piriformis has been ghosted in.

• The anterior fibers of the gluteus minimus cross the hip joint anteriorly (running vertically in the

833

sagittal plane); therefore they flex the thigh at the hip joint. (action 2) • The posterior fibers of the gluteus minimus cross the hip joint posteriorly (running vertically in the sagittal plane); therefore they extend the thigh at the hip joint. (action 3) • The anterior fibers of the gluteus minimus wrap around the anterior pelvis to attach laterally onto the greater trochanter (running somewhat horizontally in the transverse plane). When the anterior fibers contract, they pull the greater trochanter anteromedially, causing the anterior surface of the thigh to face medially. Therefore the gluteus minimus medially rotates the thigh at the hip joint. Note the similarity of the direction of anterior fibers of the gluteus minimus to the direction of fibers of the neighboring tensor fasciae latae. (action 4) • The posterior fibers of the gluteus minimus wrap around the posterior pelvis to attach laterally onto the greater trochanter (running somewhat horizontally in the transverse plane). When the posterior fibers contract, they pull the greater trochanter posteromedially, causing the anterior surface of the thigh to face laterally. Therefore the gluteus minimus laterally rotates the thigh at the hip joint. Note the similarity of the direction of posterior fibers of the gluteus minimus to the direction of fibers of the neighboring piriformis. (action 1)

Reverse Mover Action Notes • The gluteus minimus has the same standard and reverse mover actions as the gluteus medius. The only difference is that the thickest and most powerful aspect of the gluteus minimus is its anterior aspect. Therefore its reverse actions of same-side depression, anterior tilt, and ipsilateral rotation of the pelvis are its most powerful reverse actions. (reverse actions 1, 2, 3, 4, 5) • When the femoral attachment is fixed, the gluteus minimus, by pulling inferiorly on the pelvis laterally, depresses (i.e., laterally tilts) the same-side (ipsilateral) pelvis at the hip joint. Note: Depression of one side of the pelvis causes the other side of the pelvis to elevate. (reverse action 1) • Ipsilateral pelvic depression force on the support-limb side when walking prevents depression of the pelvis to the opposite unsupported swing-limb side. (reverse action 1) • When the femoral attachment is fixed and the anterior fibers of the gluteus minimus contract, they pull inferiorly on the anterior pelvis, anteriorly tilting the pelvis at the hip joint. (reverse action 2) • When the femoral attachment is fixed and the posterior fibers of the gluteus minimus contract, they pull inferiorly on the posterior pelvis, posteriorly tilting the pelvis at the hip joint. (reverse action 3) • The anterior fibers of the gluteus minimus cross the hip joint anteriorly (with their fibers running somewhat horizontally in the transverse plane). When the femoral attachment is fixed and the anterior fibers of the gluteus minimus contract, they pull on the pelvis, causing the anterior pelvis to face the same side on which the gluteus minimus is attached. Therefore the anterior fibers of the gluteus minimus ipsilaterally rotate the pelvis at the hip joint. (reverse action 4) • The posterior fibers of the gluteus minimus cross the hip joint posteriorly (running somewhat horizontally in the transverse plane). When the femoral attachment is fixed and the posterior fibers of the gluteus minimus contract, they pull on the pelvis, causing the anterior pelvis to face the opposite side of the body from the side on which the gluteus minimus is attached. Therefore the posterior fibers of the gluteus minimus contralaterally rotate the pelvis at the hip joint. (reverse action 5)

Motions Because the gluteus minimus has more than one line of pull, it can create more than one motion. 1. The middle fibers of the gluteus minimus have one line of pull, essentially in one cardinal plane (the frontal plane) and therefore have one motion, which is a cardinal plane action, abduction of the thigh at the hip joint. 2. The posterior fibers of the gluteus minimus have one line of pull in an oblique plane and therefore create one motion, which is a combination of extension, abduction, and lateral rotation of the thigh at the hip joint. 3. The anterior fibers of the gluteus minimus have one line of pull in an oblique plane and therefore create one motion, which is a combination of flexion, abduction, and medial rotation of the thigh at the hip joint.

834

4. Regarding their reverse action upon the pelvis, the middle fibers of the gluteus minimus have one line of pull, essentially in one cardinal plane (the frontal plane) and therefore have one motion, its cardinal plane action, same-side depression of the pelvis at the hip joint. 5. Regarding their reverse action pull upon the pelvis, the posterior fibers of the gluteus minimus have one line of pull in an oblique plane and therefore create one motion, which is a combination of posterior tilt, same-side depression, and contralateral rotation of the pelvis at the hip joint. 6. Regarding their reverse action pull upon the pelvis, the anterior fibers of the gluteus minimus have one line of pull in an oblique plane and therefore create one motion, which is a combination of anterior tilt, same-side depression, and ipsilateral rotation of the pelvis at the hip joint.

Eccentric Antagonist Functions 1. Restrains/slows adduction, extension, flexion, lateral rotation, and medial rotation of the thigh at the hip joint 2. Restrains/slows same-side elevation, posterior tilt, anterior tilt, contralateral rotation, and ipsilateral rotation of the pelvis at the hip joint

Isometric Stabilization Functions 1. Stabilizes the thigh and pelvis at the hip joint 2. Stabilizes the subtalar joint

Isometric Stabilization Function Notes • As with the gluteus medius, same-side (ipsilateral) pelvic depression (lateral tilt) force by the gluteus minimus is actually its most important function because it stabilizes the pelvis by preventing it from depressing (falling) to the unsupported side when walking. • The gluteus minimus also contracts to stabilize the pelvis when a person has the habitual practice of standing with all or most of their body weight on one side. Overuse for this function can cause the gluteus minimus to become tight. • Thigh lateral rotation action prevents medial rotation of the thigh and entire lower extremity, including the talus at the subtalar joint, if the foot overly pronates (if the arch of the foot collapses).

Additional Note on Actions 1. Like the gluteus medius, the gluteus minimus fans around the hip joint and has three sections: anterior, middle, and posterior. This orientation is similar to the orientation of the deltoid to the glenohumeral joint. Therefore both of these muscles can do the same actions at their respective joints. The gluteus minimus can abduct, flex, extend, medially rotate, and laterally rotate the thigh at the hip joint. The deltoid can abduct, flex, extend, medially rotate, and laterally rotate the arm at the glenohumeral joint.

I N N E RVAT I O N The Superior Gluteal Nerve L4, L5, S1

A R T E R I A L S U P P LY The Superior Gluteal Artery (a branch of the Internal Iliac Artery)

PA L PAT I O N 1. It is extremely difficult to differentiate the gluteus minimus from the gluteus medius because the gluteus medius entirely overlies the gluteus minimus and they have identical actions. The thickest part of the gluteus minimus is the anterior portion. 2. To palpate, follow the same procedure as for the gluteus medius and try to palpate deeper for the gluteus minimus. 3. If the superficial gluteus medius is relaxed and the gluteus minimus is very tight, it may be

835

possible to feel and distinguish the gluteus minimus.

836

RELATIONSHIP TO OTHER STRUCTURES The gluteus minimus is deep to the gluteus medius. Deep to the gluteus minimus are the joint capsule of the hip joint and the ilium. The gluteus minimus is directly superior to the piriformis. The gluteus minimus is involved with the lateral line myofascial meridian.

837

MISCELLANEOUS 1. A chronically tight gluteus minimus can contribute to the related biomechanical postural conditions of a functional short lower extremity (usually called a short leg) with a compensatory scoliosis (see Miscellaneous section of gluteus medius).

Deep Lateral Rotator Group Deep to the gluteus maximus, there is a second layer of muscles that laterally rotates the thigh at the hip joint. These muscles are usually grouped together and called the deep lateral rotators or the deep six. The deep lateral rotator muscles are the following (from superior to inferior): piriformis, superior gemellus, obturator internus, inferior gemellus, obturator externus, and quadratus femoris.

ATTACHMENTS On observation, it is clear that all the deep lateral rotators have a nearly identical direction of fibers. They lie approximately horizontal in the transverse plane, and they attach laterally onto or near the greater trochanter of the femur. From a posterior perspective, all these muscles are at the same depth (except for the obturator externus, which lies deep to the quadratus femoris and is either entirely covered or nearly entirely covered by it). The piriformis and obturator internus both arise from the internal surface of the pelvis. All the other muscles of the deep lateral rotator group arise from the external surface of the pelvis.

FUNCTIONS When the deep lateral rotators of the thigh pull the femur toward their more medial attachment in the posterior buttock region, they cause lateral rotation of the thigh at the hip joint. A force of lateral rotation of the thigh prevents medial rotation of the thigh and entire lower extremity, including the talus at the subtalar joint, if the foot overly pronates (if the arch of the foot collapses). When the femoral attachment of the deep lateral rotators of the thigh is fixed, the pelvis rotates instead of the femur. This rotation causes the pelvis to rotate away from the side of the body on which these muscles are attached. Therefore these muscles contralaterally rotate the pelvis at the hip joint. (Note: All muscles that laterally rotate the thigh at the hip joint can also contralaterally rotate the pelvis at the hip joint.) This reverse action of contralateral rotation of the pelvis at the hip joint is important when a person is walking or running and plants the foot to change the direction of movement. In sports, this is called planting and cutting. An important function of the deep lateral rotator group is to stabilize the hip joint. Their line of pull is largely horizontal, pulling the femoral head into the acetabulum. In this regard they are analogous to the rotator cuff group of the glenohumeral joint.

MISCELLANEOUS 1. The two largest muscles of the deep lateral rotator group are the piriformis and quadratus femoris. 2. The gluteus maximus can also laterally rotate the thigh at the hip joint, but it is superficial to this group. 3. Although it is at the same depth, the gluteus medius is usually not included in this group. The posterior fibers of the gluteus medius have the same direction as the piriformis, which lies directly inferior to it, and these fibers laterally rotate the thigh at the hip joint. 4. The posterior fibers of the gluteus minimus can also laterally rotate the thigh at the hip joint, but the gluteus minimus is considered to be at a third deeper layer of musculature in the posterior pelvis. 5. As a rule, because of their horizontal orientation, the deep lateral rotators do not fit well into the

838

longitudinally oriented myofascial meridians. They may be considered to be involved with the deep front line myofascial meridian.

I N N E RVAT I O N The deep lateral rotators are innervated by branches of the lumbosacral plexus, except for the obturator externus, which is innervated by the obturator nerve.

A R T E R I A L S U P P LY The deep lateral rotators receive their arterial supply from the superior and inferior gluteal arteries and the obturator artery.

839

Posterior Views of the Deep Lateral Rotator Group

FIGURE 14-20 Views of the deep lateral rotator group. The deep lateral rotator group is shown on the left; the gluteus minimus has been ghosted in. The quadratus femoris has been cut on the right to show the obturator externus.

Piriformis (of Deep Lateral Rotator Group) The name, piriformis, tells us that this muscle is shaped like a pear. Derivation piriformis: L. pear shaped Pronunciation pi-ri-FOR-mis

ATTACHMENTS Anterior Sacrum and the anterior surface of the sacrotuberous ligament to the Greater Trochanter of the Femur the superomedial surface

FUNCTIONS Concentric (Shortening) Mover Actions

840

Standard Mover Action Notes • The piriformis attaches from the sacrum medially and wraps around to the greater trochanter of the femur laterally (with its fibers running horizontally in the transverse plane). When the piriformis contracts, it pulls the greater trochanter posteromedially, causing the anterior surface of the thigh to face laterally. Therefore the piriformis laterally rotates the thigh at the hip joint. (action 1) • When the thigh is already flexed, the orientation of the line of pull of the piriformis relative to the hip joint changes. The fibers (running horizontally) can now pull the femur away from the midline in the frontal plane. Therefore the piriformis horizontally extends the thigh at the hip joint. Note: Horizontal extension is also known as horizontal abduction, hence the piriformis is often said to abduct the hip joint. (action 2)

FIGURE 14-21 Views of the piriformis. A, Posterior view of the piriformis bilaterally. The gluteus medius and superior gemellus have been ghosted in on the left. B, Anterior view of the right piriformis, showing its attachment onto the anterior surface of the sacrum.

• When the thigh is already flexed, the orientation of the line of pull of the piriformis relative to the hip joint changes. When the thigh is not in flexion, the fibers of the piriformis wrap around the posterior side of the femur to attach onto the greater trochanter. However, if the thigh is

841

sufficiently flexed (sources state a minimum of 60 degrees is needed), the fibers of the piriformis now wrap around the anterior side of the femur to attach onto the greater trochanter. Given this direction of fibers relative to the hip joint, the piriformis now pulls the greater trochanter anteromedially instead of posteromedially. Therefore the piriformis medially rotates the thigh at the hip joint instead of laterally rotating the thigh at the hip joint. The best way to visualize this is to place a string where the piriformis attaches, flex the thigh to approximately 90 degrees, and look from above at where the string is located relative to the hip joint before and after the thigh is flexed. Note: The more superior fibers of the piriformis would be more active with regard to the action of medial rotation. (action 3)

Reverse Mover Action Notes • The piriformis crosses the hip joint posteriorly (with its fibers running somewhat horizontally in the transverse plane). When the femoral attachment is fixed and the piriformis contracts, it pulls on the pelvis, causing the anterior pelvis to face the opposite side of the body from the side to which the piriformis is attached. Therefore the piriformis contralaterally rotates the pelvis at the hip joint. (reverse action 1) • Contralateral rotation of the pelvis at the hip joint is important whenever a foot is planted on the ground and the pelvis is rotated to the opposite side, such as when planting and cutting in sports. (reverse action 1) • If the piriformis changes its line of pull at the hip joint to become a medial rotator of the thigh, then its reverse action changes to be ipsilateral rotation of the pelvis at the hip joint. (reverse action 2)

Motions 1. When in anatomic position, the piriformis has one line of pull in the transverse plane, and therefore its motion is its cardinal plane joint action, lateral rotation of the thigh at the hip joint. 2. Regarding its anatomic position reverse action pull on the pelvis, the piriformis has one line of pull in the transverse plane, and therefore its motion is its cardinal plane joint action, contralateral rotation of the pelvis at the hip joint. 3. Note: When the thigh is first flexed to approximately 60 degrees or more, the piriformis has one line of pull that creates a combination of medial rotation and horizontal extension (horizontal abduction) of the thigh at the hip joint.

Eccentric Antagonist Functions 1. Restrains/slows medial rotation, horizontal flexion (horizontal adduction), and lateral rotation of the thigh at the hip joint 2. Restrains/slows ipsilateral rotation and contralateral rotation of the pelvis at the hip joint

Isometric Stabilization Functions 1. Stabilizes the thigh and pelvis at the hip joint 2. Stabilizes the sacrum at the sacroiliac and lumbosacral joints 3. Stabilizes the subtalar joint

Isometric Stabilization Function Note • A force of lateral rotation of the thigh prevents medial rotation of the thigh and the entire lower extremity, including the talus at the subtalar joint, if the foot overly pronates (in other words, if the arch of the foot collapses). Therefore, the piriformis can assist in stabilization of the subtalar joint.

Additional Notes on Actions 1. All six members of the deep lateral rotator group can, as their name implies, laterally rotate the thigh (and contralaterally rotate the pelvis) at the hip joint. 2. The piriformis, superior gemellus, obturator internus, and inferior gemellus can all horizontally extend (horizontally abduct) the thigh at the hip joint if the thigh is flexed. 3. The line of pull of the piriformis has a small vertical component in the sagittal plane that crosses posterior to the hip joint, therefore, the piriformis likely has a very weak component action of

842

extension of the thigh at the hip joint.

I N N E RVAT I O N Nerve to Piriformis (of the Lumbosacral Plexus) L5, S1, S2

A R T E R I A L S U P P LY The Superior and Inferior Gluteal Arteries (branches of the Internal Iliac Artery)

PA L PAT I O N 1. With the client prone, place palpating hand just lateral to the sacrum, at a point halfway between the posterior superior iliac spine (PSIS) and the apex of the sacrum. 2. Flex the client’s leg at the knee joint to 90 degrees. Then have the client laterally rotate the thigh at the hip joint against gentle resistance and feel for the contraction of the piriformis. (Note: Lateral rotation of the thigh at the hip joint involves the client’s foot moving medially, toward the opposite side of the body.) 3. Continue palpating the piriformis laterally toward the greater trochanter of the femur.

RELATIONSHIP TO OTHER STRUCTURES The piriformis is deep to the gluteus maximus. The piriformis is located inferior/distal to the gluteus medius. Laterally in the buttock, the piriformis is located superior/proximal to the superior gemellus. Medially in the buttock, the piriformis is located superior/proximal to the coccygeus muscle and the sacrospinous ligament. Directly inferior/distal to the medial (sacral) attachment of the piriformis is the sacrotuberous ligament. The piriformis is involved with the deep front line myofascial meridian.

MISCELLANEOUS 1. Probably the most common method to stretch the piriformis is to have the client supine with the foot flat on the table (i.e., the thigh flexed at the hip joint and the leg flexed at the knee joint); then horizontally flex (horizontally adduct) the client’s thigh toward the opposite side of the body. 2. The piriformis can change from being a lateral rotator of the thigh at the hip joint to a medial rotator of the thigh at the hip joint (if the thigh is first flexed at the hip joint); therefore the method of stretching the piriformis varies with the position of the client’s thigh. If the client’s thigh is flexed, lateral rotation must be used to stretch the piriformis. If the client’s thigh is not flexed, medial rotation would be used. The thigh must be flexed to at least 60 degrees for the piriformis to become a medial rotator of the thigh. 3. The piriformis sometimes blends with the gluteus medius. 4. The piriformis often protectively tightens when the client’s sacroiliac joint is sprained. 5. The relationship of the sciatic nerve to the piriformis varies. The sciatic nerve normally exits from the pelvis between the piriformis and the superior gemellus. However, in approximately 10% to 20% of individuals, the common fibular portion of the sciatic nerve (occasionally even the entire sciatic nerve) may pierce the piriformis muscle, exiting through the middle of it. Some sources believe this makes the sciatic nerve more susceptible to being compressed if the piriformis is tight; others do not. When the piriformis does compress the sciatic nerve, regardless of the relationship between the piriformis and the sciatic nerve, this condition is called piriformis syndrome and can result in symptoms of sciatica.

843

Superior Gemellus (of Deep Lateral Rotator Group) The name, superior gemellus, tells us that this muscle is the more superior muscle of a pair of similar muscles. Derivation superior: L. upper gemellus: L. twin Pronunciation su-PEE-ree-or jee-MEL-us

ATTACHMENTS Ischial Spine to the Greater Trochanter of the Femur

the medial surface

FUNCTIONS Concentric (Shortening) Mover Actions

Standard Mover Action Notes • The superior gemellus wraps around the posterior pelvis to attach laterally onto the greater trochanter of the femur (with its fibers running horizontally in the transverse plane). When the superior gemellus contracts, it pulls the greater trochanter posteromedially, causing the anterior surface of the thigh to face laterally. Therefore the superior gemellus laterally rotates the thigh at the hip joint. (Note the similarity of the direction of fibers of the superior gemellus to the direction of fibers of the piriformis.) (action 1) • As with the piriformis and other deep lateral rotators, if the thigh is already flexed, the orientation of the line of pull of the superior gemellus to the femur changes. The fibers (running horizontally) can now pull the femur away from the midline in the frontal plane. Therefore the superior gemellus horizontally extends (i.e., horizontally abducts) the thigh at the hip joint. (action 2)

Reverse Mover Action Note • The superior gemellus crosses the hip joint posteriorly (with its fibers running somewhat horizontally in the transverse plane). When the femoral attachment is fixed and the superior gemellus contracts, it pulls on the pelvis, causing the anterior pelvis to face the opposite side of the body from the side to which the superior gemellus is attached. Therefore the superior gemellus contralaterally rotates the pelvis at the hip joint. Contralateral rotation of the pelvis is functionally important when a person is walking or running and changes direction. (reverse action 1)

844

FIGURE 14-22

Posterior view of the superior gemellus bilaterally. The piriformis and obturator internus have been ghosted in on the left.

Motions 1. The superior gemellus has one line of pull in the transverse plane, and therefore its motion is its cardinal plane joint action, lateral rotation of the thigh at the hip joint. 2. Regarding its reverse action upon the pelvis, the superior gemellus has one line of pull in the transverse plane, and therefore its motion is its cardinal plane joint action, contralateral rotation of the pelvis at the hip joint.

Eccentric Antagonist Functions 1. Restrains/slows medial rotation and horizontal flexion (horizontal adduction) of the thigh at the hip joint 2. Restrains/slows ipsilateral rotation of the pelvis at the hip joint

Isometric Stabilization Functions 1. Stabilizes the thigh and pelvis at the hip joint 2. Stabilizes the subtalar joint

Isometric Stabilization Function Note • A force of lateral rotation of the thigh at the hip joint prevents medial rotation of the thigh and the entire lower extremity, including the talus at the subtalar joint, if the foot overly pronates (in other words, if the arch of the foot collapses).

Additional Notes on Actions 1. All six members of the deep lateral rotator group can, as their name implies, laterally rotate the thigh (and contralaterally rotate the pelvis) at the hip joint. 2. The piriformis, superior gemellus, obturator internus, and inferior gemellus can all horizontally extend (horizontally abduct) the thigh at the hip joint if the thigh is flexed.

I N N E RVAT I O N Nerve to Obturator Internus (of the Lumbosacral Plexus) L5, S1

845

A R T E R I A L S U P P LY The Inferior Gluteal Artery (a branch of the Internal Iliac Artery)

PA L PAT I O N 1. With the client prone, place palpating fingers just inferior to the lateral aspect of the piriformis. 2. Flex the client’s leg at the knee joint to 90 degrees. 3. Then have the client laterally rotate the thigh at the hip joint against gentle resistance and feel for the contraction of the superior gemellus. It is difficult to discern the superior gemellus from the other nearby deep lateral rotators. (Note: Lateral rotation of the thigh at the hip joint involves the client’s foot moving medially, toward the opposite side of the body.)

RELATIONSHIP TO OTHER STRUCTURES The superior gemellus lies between the piriformis (which is superior to it) and the obturator internus (which is inferior to it). The sciatic nerve normally exits the pelvis between the piriformis and the superior gemellus. The superior gemellus is involved with the deep front line myofascial meridian.

MISCELLANEOUS 1. The lateral tendons of the superior gemellus, obturator internus, and inferior gemellus usually blend together.

846

Obturator Internus (of Deep Lateral Rotator Group) The name, obturator internus, tells us that this muscle attaches to the internal surface of the obturator foramen. Derivation obturator: L. to stop up, obstruct (refers to the obturator foramen) internus: L. inner Pronunciation ob-too-RAY-tor in-TER-nus

ATTACHMENTS Internal Surface of the Pelvic Bone Surrounding the Obturator Foramen the internal surfaces of the margin of the obturator foramen, the obturator membrane, the ischium, the pubis, and the ilium to the Greater Trochanter of the Femur the medial surface

FUNCTIONS Concentric (Shortening) Mover Actions

Standard Mover Action Notes • The obturator internus wraps around the posterior pelvis to attach laterally onto the greater trochanter of the femur (with its fibers running horizontally in the transverse plane). When the obturator internus contracts, it pulls the greater trochanter posteromedially, causing the anterior surface of the thigh to face laterally. Therefore the obturator internus laterally rotates the thigh at the hip joint. (Note the similarity of the direction of fibers of the obturator internus to the direction of fibers of the other deep lateral rotators.) (action 1) • As with the piriformis and other deep lateral rotators, if the thigh is already flexed, the orientation of the line of pull of the obturator internus to the femur changes. The fibers (running horizontally) can now pull the femur away from the midline in the frontal plane. Therefore the obturator internus horizontally extends (i.e., horizontally abducts) the thigh at the hip joint. (action 2)

Reverse Mover Action Note • The obturator internus crosses the hip joint posteriorly (with its fibers running somewhat horizontally in the transverse plane). When the femoral attachment is fixed and the obturator internus contracts, it pulls on the pelvis, causing the anterior pelvis to face the opposite side of the body from the side of the body to which the obturator internus is attached. Therefore the obturator internus contralaterally rotates the pelvis at the hip joint. Contralateral rotation of the pelvis is functionally important when a person is walking or running and changes direction. (reverse action 1)

847

FIGURE 14-23

Posterior view of the obturator internus bilaterally. The superior gemellus and inferior gemellus have been ghosted in on the left.

Motions 1. The obturator internus has one line of pull in the transverse plane, and therefore its motion is its cardinal plane joint action, lateral rotation of the thigh at the hip joint. 2. Regarding its reverse action upon the pelvis, the obturator internus has one line of pull in the transverse plane, and therefore its motion is its cardinal plane joint action, contralateral rotation of the pelvis at the hip joint.

Eccentric Antagonist Functions 1. Restrains/slows medial rotation and horizontal flexion of the thigh at the hip joint 2. Restrains/slows ipsilateral rotation of the pelvis at the hip joint

Isometric Stabilization Functions 1. Stabilizes the thigh and pelvis at the hip joint 2. Stabilizes the subtalar joint

Isometric Stabilization Function Note • A force of lateral rotation of the thigh at the hip joint prevents medial rotation of the thigh and the entire lower extremity, including the talus at the subtalar joint, if the foot overly pronates (in other words, if the arch of the foot collapses).

Additional Notes on Actions 1. All six members of the deep lateral rotator group can, as their name implies, laterally rotate the thigh (and contralaterally rotate the pelvis) at the hip joint. 2. The piriformis, superior gemellus, obturator internus, and inferior gemellus can all horizontally extend (horizontally abduct) the thigh at the hip joint if the thigh is flexed.

I N N E RVAT I O N Nerve to Obturator Internus (of the Lumbosacral Plexus) L5, S1

A R T E R I A L S U P P LY

848

The Superior and Inferior Gluteal Arteries (branches of the Internal Iliac Artery) and the Obturator Artery (a branch of the Internal Iliac Artery)

PA L PAT I O N 1. With the client prone, place palpating fingers inferior to the piriformis and the superior gemellus. 2. Flex the client’s leg at the knee joint to 90 degrees. Then have the client laterally rotate the thigh at the hip joint against gentle resistance and feel for the contraction of the obturator internus. It is difficult to discern the obturator internus from the other nearby deep lateral rotators. (Note: Lateral rotation of the thigh at the hip joint involves the client’s foot moving medially, toward the opposite side of the body.)

RELATIONSHIP TO OTHER STRUCTURES The obturator internus begins inside the pelvis and exits the pelvis through the lesser sciatic foramen. It wraps around the ischium between the ischial spine and the ischial tuberosity to join the other lateral rotators of the thigh. The obturator internus lies between the two gemelli muscles. It is directly inferior to the superior gemellus and directly superior to the inferior gemellus. The obturator internus is involved with the deep front line myofascial meridian.

MISCELLANEOUS 1. Obturator means to stop up or obstruct. The obturator foramen is obstructed by the obturator membrane, as well as by the obturator internus and obturator externus. 2. The lateral tendons of the superior gemellus, obturator internus, and inferior gemellus usually blend together. 3. The obturator internus has a much larger pelvic attachment than the obturator externus. 4. The obturator internus has a tendon that makes an abrupt turn of 90 degrees or more. (Other muscles that do this are the fibularis longus, tibialis posterior, flexor digitorum longus, flexor hallucis longus, tensor palati, and superior oblique.) 5. If the opportunity to attend a cadaver lab workshop occurs, it can be an invaluable experience to actually see and feel the muscles and other tissues of the body that are abstractly studied in books. In cadaver dissection, the obturator internus can usually be readily identified and discerned from the other muscles of the deep lateral rotators of the thigh group by the shiny appearance of its lateral tendon. 6. The obturator internus is multipennate.

849

Inferior Gemellus (of Deep Lateral Rotator Group) The name, inferior gemellus, tells us that this muscle is the more inferior muscle of a pair of similar muscles. Derivation inferior: L. lower gemellus: L. twin Pronunciation in-FEE-ree-or jee-MEL-us

ATTACHMENTS Ischial Tuberosity the superior aspect to the Greater Trochanter of the Femur the medial surface

FUNCTIONS Concentric (Shortening) Mover Actions

Standard Mover Action Notes • The inferior gemellus wraps around the posterior pelvis to attach laterally onto the greater trochanter (with its fibers running horizontally in the transverse plane). When the inferior gemellus contracts, it pulls the greater trochanter posteromedially, causing the anterior surface of the thigh to face laterally. Therefore the inferior gemellus laterally rotates the thigh at the hip joint. (Note the similarity of the direction of fibers of the inferior gemellus to the direction of fibers of the other deep lateral rotators.) (action 1) • As with the piriformis and other deep lateral rotators, if the thigh is already flexed, the orientation of the line of pull of the inferior gemellus to the femur changes. The fibers (running horizontally) can now pull the femur away from the midline in the frontal plane. Therefore the inferior gemellus horizontally extends (i.e., horizontally abducts) the thigh at the hip joint. (action 2)

Reverse Mover Action Note • The inferior gemellus crosses the hip joint posteriorly (with its fibers running somewhat horizontally in the transverse plane). When the femoral attachment is fixed, and the inferior gemellus contracts, it pulls on the pelvis, causing the anterior pelvis to face the opposite side of the body from the side to which the inferior gemellus is attached. Therefore the inferior gemellus contralaterally rotates the pelvis at the hip joint. Contralateral rotation of the pelvis is functionally important when a person is walking or running and changes direction. (reverse action 1)

850

FIGURE 14-24

Posterior view of the inferior gemellus bilaterally. The obturator internus and quadratus femoris have been ghosted in on the left.

Motions 1. The inferior gemellus has one line of pull in the transverse plane, and therefore its motion is its cardinal plane joint action, lateral rotation of the thigh at the hip joint. 2. Regarding its reverse action upon the pelvis, the inferior gemellus has one line of pull in the transverse plane, and therefore its motion is its cardinal plane joint action, contralateral rotation of the pelvis at the hip joint.

Eccentric Antagonist Functions 1. Restrains/slows medial rotation and horizontal flexion (horizontal adduction) of the thigh at the hip joint 2. Restrains/slows ipsilateral rotation of the pelvis at the hip joint

Isometric Stabilization Functions 1. Stabilizes the thigh and pelvis at the hip joint 2. Stabilizes the subtalar joint

Isometric Stabilization Function Note • A force of lateral rotation of the thigh at the hip joint prevents medial rotation of the thigh and the entire lower extremity, including the talus at the subtalar joint, if the foot overly pronates (in other words, if the arch of the foot collapses).

Additional Notes on Actions 1. All six members of the deep lateral rotator group can, as their name implies, laterally rotate the thigh (and contralaterally rotate the pelvis) at the hip joint. 2. The piriformis, superior gemellus, obturator internus, and inferior gemellus can all horizontally extend (horizontally abduct) the thigh at the hip joint if the thigh is flexed.

I N N E RVAT I O N Nerve to Quadratus Femoris (of the Lumbosacral Plexus) L5, S1

A R T E R I A L S U P P LY The Inferior Gluteal Artery (a branch of the Internal Iliac Artery) and the Obturator Artery (a branch of the Internal Iliac Artery)

851

PA L PAT I O N 1. With the client prone, place palpating fingers just lateral and slightly superior to the superior margin of the ischial tuberosity. 2. Flex the client’s leg at the knee joint to 90 degrees. Then have the client laterally rotate the thigh at the hip joint against gentle resistance and feel for the contraction of the inferior gemellus. It is difficult to discern the inferior gemellus from the other nearby deep lateral rotators. (Note: Lateral rotation of the thigh at the hip joint involves the client’s foot moving medially, toward the opposite side of the body.)

RELATIONSHIP TO OTHER STRUCTURES The inferior gemellus is inferior to the obturator internus. The inferior gemellus is superior to the obturator externus and the quadratus femoris. The inferior gemellus is involved with the deep front line myofascial meridian.

MISCELLANEOUS 1. The lateral tendons of the superior gemellus, obturator internus, and inferior gemellus usually blend together.

852

Obturator Externus (of Deep Lateral Rotator Group) The name, obturator externus, tells us that this muscle attaches to the external surface of the obturator foramen. Derivation obturator: L. to stop up, obstruct (refers to the obturator foramen) externus: L. outer Pronunciation ob-too-RAY-tor ex-TER-nus

ATTACHMENTS External Surface of the Pelvic Bone Surrounding the Obturator Foramen the external surfaces of the margin of the obturator foramen on the ischium and the pubis, and the obturator membrane to the Trochanteric Fossa of the Femur

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions

Reverse Mover Actions

1. Laterally rotates the thigh at the hip joint 2. Adducts the thigh at the hip joint

1. Contralaterally rotates the pelvis at the hip joint 2. Elevates the same-side pelvis at the hip joint

3. Horizontally extends (horizontally abducts) the thigh at the hip joint

3. Contralaterally rotates the pelvis at the hip joint

Standard Mover Action Notes • The obturator externus wraps around the posterior pelvis to attach laterally onto the femur (with its fibers running horizontally in the transverse plane). When the obturator externus contracts, it pulls the greater trochanter posteromedially, causing the anterior surface of the thigh to face laterally. Therefore the obturator externus laterally rotates the thigh at the hip joint. (Note the similarity of the direction of fibers of the obturator externus to the direction of fibers of the other deep lateral rotators.) (action 1) • The obturator externus attaches far enough distally to be below the center of the hip joint. Therefore it can adduct the thigh at the hip joint. (action 2) • As with the piriformis and other deep lateral rotators, if the thigh is already flexed, the orientation of the line of pull of the obturator externus to the femur changes. The fibers (running horizontally) can now pull the femur away from the midline in the frontal plane. Therefore the obturator externus horizontally extends (i.e., horizontally abducts) the thigh at the hip joint. (action 3)

853

FIGURE 14-25

Posterior view of the obturator externus bilaterally. The inferior gemellus and quadratus femoris (cut) have been ghosted in on the left.

Reverse Mover Action Notes • The obturator externus crosses the hip joint posteriorly (with its fibers running somewhat horizontally in the transverse plane). When the femoral attachment is fixed and the obturator externus contracts, it pulls on the pelvis, causing the anterior pelvis to face the opposite side of the body from the side to which the obturator externus is attached. Therefore the obturator externus contralaterally rotates the pelvis at the hip joint. Contralateral rotation of the pelvis is functionally important when a person is walking or running and changes direction. (reverse actions 1, 3) • With the distal femoral attachment fixed, the obturator externus pulls the medial aspect of the pelvic bone inferiorly toward the medial thigh, resulting in elevation of the same-side pelvis at the hip joint. Note: Elevation of one side of the pelvis causes the other side to depress. (reverse action 2)

Motions 1. The obturator externus has one line of pull upon the thigh in an oblique plane and therefore creates one motion, which is a combination of lateral rotation and adduction of the thigh at the hip joint. 2. Regarding its reverse action pull on the pelvis, the obturator externus has one line of pull in an oblique plane and therefore creates one motion, which is a combination of contralateral rotation and same-side elevation of the pelvis at the hip joint.

Eccentric Antagonist Functions 1. Restrains/slows medial rotation and abduction of the thigh at the hip joint 2. Restrains/slows ipsilateral rotation and depression of the same-side pelvis at the hip joint

Isometric Stabilization Functions 1. Stabilizes the thigh and pelvis at the hip joint 2. Stabilizes the subtalar joint

Isometric Stabilization Function Note • A force of lateral rotation of the thigh at the hip joint prevents medial rotation of the thigh and the entire lower extremity, including the talus at the subtalar joint, if the foot overly pronates (in other words, if the arch of the foot collapses).

Additional Note on Actions

854

1. All six members of the deep lateral rotator group can, as their name implies, laterally rotate the thigh (and contralaterally rotate the pelvis) at the hip joint.

I N N E RVAT I O N The Obturator Nerve L3, L4

A R T E R I A L S U P P LY The Obturator Artery (a branch of the Internal Iliac Artery)

PA L PAT I O N 1. With the client prone, place palpating fingers slightly lateral to the superior margin of the ischial tuberosity. 2. Flex the client’s leg at the knee joint to 90 degrees. Then have the client laterally rotate the thigh at the hip joint against gentle resistance and feel for the contraction of the obturator externus. It is difficult to discern the obturator externus from the other nearby deep lateral rotators. (Note: Lateral rotation of the thigh at the hip joint will involve the client’s foot moving medially, toward the opposite side of the body.)

RELATIONSHIP TO OTHER STRUCTURES The obturator externus is directly inferior to the inferior gemellus. From the posterior perspective, the obturator externus is deep to the quadratus femoris and is either entirely covered or nearly entirely covered by it. From the anterior perspective, the obturator externus is directly deep to the pectineus. The obturator externus is involved with the deep front line myofascial meridian.

MISCELLANEOUS 1. Obturator means to stop up or obstruct. The obturator foramen is obstructed by the obturator membrane, as well as by the obturator internus and obturator externus. 2. The obturator externus is the only muscle of the deep lateral rotator group that is not visible in the second layer of the posterior pelvic muscles. It is either entirely covered or nearly entirely covered by the quadratus femoris. When the obturator externus is visible in this layer, it is located between the inferior gemellus and the quadratus femoris. 3. The obturator externus is the only deep lateral rotator that is not innervated by the lumbosacral plexus. It is innervated by the obturator nerve.

855

Quadratus Femoris (of Deep Lateral Rotator Group) The name, quadratus femoris, tells us that this muscle is square in shape and attaches to the femur. Derivation quadratus: L. squared femoris: L. refers to the femur Pronunciation kwod-RATE-us FEM-o-ris

ATTACHMENTS Ischial Tuberosity the lateral border to the Intertrochanteric Crest of the Femur

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions

Reverse Mover Actions

1. Laterally rotates the thigh at the hip joint 2. Adducts the thigh at the hip joint

1. Contralaterally rotates the pelvis at the hip joint 2. Elevates the same-side pelvis at the hip joint

3. Horizontally extends (horizontally abducts) the thigh at the hip joint

3. Contralaterally rotates the pelvis at the hip joint

Standard Mover Action Notes • The quadratus femoris wraps around the posterior pelvis to attach laterally onto the femur (with its fibers running horizontally in the transverse plane). When the quadratus femoris contracts, it pulls the greater trochanter posteromedially, causing the anterior surface of the thigh to face laterally. Therefore the quadratus femoris laterally rotates the thigh at the hip joint. (Note the similarity of the direction of fibers of the quadratus femoris to the direction of fibers of the other deep lateral rotators.) (action 1) • The quadratus femoris attaches sufficiently inferior on the pelvis and distal on the femur to cross the hip joint medially below the center of the joint (with its fibers running horizontally in the frontal plane). When the quadratus femoris contracts, it pulls the lateral attachment (i.e., the thigh) medially in the frontal plane. Therefore the quadratus femoris adducts the thigh at the hip joint. (action 2) • As with the piriformis and other deep lateral rotators, if the thigh is already flexed, the orientation of the line of pull of the quadratus femoris to the femur changes. The fibers (running horizontally) can now pull the femur away from the midline in the frontal plane. Therefore the quadratus femoris horizontally extends (i.e., horizontally abducts) the thigh at the hip joint. (action 3)

856

FIGURE 14-26

Posterior view of the quadratus femoris bilaterally. The inferior gemellus and adductor magnus have been ghosted in on the left.

Reverse Mover Action Notes • The quadratus femoris crosses the hip joint posteriorly (with its fibers running somewhat horizontally in the transverse plane). When the femoral attachment is fixed and the quadratus femoris contracts, it pulls on the pelvis, causing the anterior pelvis to face the opposite side of the body from the side to which the quadratus femoris is attached. Therefore the quadratus femoris contralaterally rotates the pelvis at the hip joint. (reverse actions 1, 3) • Contralateral rotation of the pelvis at the hip joint is important whenever a foot is planted on the ground and the pelvis is rotated to the opposite side, such as when planting and cutting in sports. (reverse actions 1, 3) • With the distal femoral attachment fixed, the quadratus femoris pulls the medial aspect of the pelvic bone inferiorly toward the medial thigh, resulting in elevation of the same-side pelvis at the hip joint. Note: Elevation of one side of the pelvis causes the other side to depress. (reverse action 2)

Motions 1. The quadratus femoris has one line of pull upon the thigh in an oblique plane and therefore creates one motion, which is a combination of lateral rotation and adduction of the thigh at the hip joint. 2. Regarding its reverse action pull on the pelvis, the quadratus femoris has one line of pull in an oblique plane and therefore creates one motion, which is a combination of contralateral rotation and same-side elevation of the pelvis at the hip joint.

Eccentric Antagonist Functions 1. Restrains/slows medial rotation and abduction of the thigh at the hip joint 2. Restrains/slows ipsilateral rotation and depression of the same-side pelvis at the hip joint

Isometric Stabilization Functions 1. Stabilizes the thigh and pelvis at the hip joint 2. Stabilizes the subtalar joint

Isometric Stabilization Functions Note • A force of lateral rotation of the thigh at the hip joint prevents medial rotation of the thigh and the entire lower extremity, including the talus at the subtalar joint, if the foot overly pronates (in other words, if the arch of the foot collapses).

857

Additional Notes on Actions 1. All six members of the deep lateral rotator group can, as their name implies, laterally rotate the thigh (and contralaterally rotate the pelvis) at the hip joint. 2. If the thigh is in a position of flexion at the hip joint, the quadratus femoris can extend the thigh back to anatomical position.

I N N E RVAT I O N Nerve to Quadratus Femoris (of the Lumbosacral Plexus) L5, S1

A R T E R I A L S U P P LY The Inferior Gluteal Artery (a branch of the Internal Iliac Artery) and the Obturator Artery (a branch of the Internal Iliac Artery)

PA L PAT I O N 1. With the client prone, place palpating fingers on the lateral side of the ischial tuberosity. 2. Flex the client’s leg at the knee joint to 90 degrees. Then have the client laterally rotate the thigh at the hip joint against gentle resistance and feel for the contraction of the quadratus femoris. (Note: Lateral rotation of the thigh at the hip joint will involve the client’s foot moving medially, toward the opposite side of the body.) 3. Be aware that the sciatic nerve usually courses over the quadratus femoris, close to the ischial tuberosity.

RELATIONSHIP TO OTHER STRUCTURES The quadratus femoris is directly inferior to the inferior gemellus and directly superior to the adductor magnus. From the posterior perspective, the quadratus femoris is superficial to and either entirely covers or nearly entirely covers the obturator externus. The sciatic nerve runs vertically, superficial to the quadratus femoris. The quadratus femoris is involved with the deep front line myofascial meridian.

MISCELLANEOUS 1. The quadratus femoris is a fairly massive muscle; it is usually larger than the superior gemellus, obturator internus, and inferior gemellus combined. It is often larger than the piriformis.

858

REVIEW QUESTIONS 1. Due to its fascial attachments, the psoas major could help to stabilize what three structures? ____________________________ ____________________________ ____________________________ 2. When palpating the iliacus, the distal belly can be found in the _______ thigh between the _______ and the _______ muscles. 3. The tensor fasciae latae and the sartorius share several actions of the thigh at the hip joint. What action(s), if any, can be of use during palpation to distinguish these two muscles? ____________________________ ____________________________ ____________________________ 4. Describe the boundaries of the femoral triangle and what is contained inside of this area. ____________________________ ____________________________ ____________________________ 5. Is it possible for the adductor muscle group to perform extension of the thigh at the hip joint? If so, how? ____________________________ ____________________________ ____________________________ 6. Explain the palpation process for the adductor magnus. ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ 7. What is the relationship between the gluteus maximus and the arches of the foot? ____________________________ ____________________________ ____________________________ ____________________________ 8. What is the most important function of the gluteus medius? Why is this important? ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ 9. Explain the functional importance of contralateral rotation of the pelvis at the hip joint. ____________________________ ____________________________ ____________________________ ____________________________ 10. The piriformis, as an example, is a muscle that changes its actions based upon its relationship to anatomic position. Describe how the position of the body changes the mover action(s) of the piriformis. ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ For answers to these questions, visit http://evolve.elsevier.com/Muscolino/muscular

859

860

THINK IT THROUGH Spend a few moments thinking about the importance of a stable, level, balanced pelvis. The muscles covered in this chapter, among others, influence the position of the pelvis. Consider the consequences of chronically tight pelvic musculature on the overall posture of the body. What might you see in a client with such a problem? Would the posture be significantly different if instead the imbalance were due to functionally weak pelvic musculature? ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________

861

CHAPTER 15

862

Muscles of the Knee Joint CHAPTER OUTLINE Quadriceps femoris group: Rectus femoris Vastus lateralis Vastus medialis Vastus intermedius Articularis genus: Hamstring group: Biceps femoris Semitendinosus Semimembranosus Popliteus

OBJECTIVES After completing this chapter, the student should be able to perform the following for each of the muscles covered in the chapter: 1. Explain the general structure. 2. Explain the general function. 3. State the attachments. 4. State the standard mover actions. 5. State the reverse mover actions. 6. Discuss the line(s) of pull the muscle has and the motion(s) created. 7. State the eccentric antagonist functions. 8. State the isometric stabilization functions. 9. State the nervous innervation.

10. State the arterial supply. 11. Describe the starting position for palpation. 12. Describe the steps for palpation. 13. Discuss the muscle’s relationship to other body structures. 14. Discuss additional information that may help with palpation, assessment, and clinical decision-making. CHAPTER OVERVIEW The muscles addressed in this chapter are the muscles whose principal function is usually considered to be movement of the knee joint. Other muscles in the body can also move the knee joint, but they are placed in different chapters because their primary function is usually considered to be at another joint. These muscles are the sartorius and gracilis (covered in Chapter 14) and the gastrocnemius and plantaris (covered in Chapter 16). Note: The hamstring group and the rectus femoris of the quadriceps femoris group (covered in this chapter) also cross the hip joint and therefore move the thigh and pelvis at the hip joint.

863

Overview of STRUCTURE Structurally, muscles of the knee joint are generally classified as being either anterior or posterior. The quadriceps femoris group and the articularis genus are located anteriorly. The hamstring group and the popliteus are located posteriorly.

Compartments of the Thigh: The musculature of the thigh is not as clearly compartmentalized as some other regions of the body. Following is the general layout of the musculature of the thigh. Thigh musculature is usually divided into anterior (flexor), medial (adductor), and posterior (extensor) compartments. • The anterior compartment contains the tensor fasciae latae (TFL), quadriceps femoris, sartorius, iliacus, and psoas major. • The medial compartment contains the pectineus, adductor longus, gracilis, adductor brevis, and adductor magnus. • The posterior compartment contains the hamstrings (as well as the distal attachments of most of the adductor group and quadriceps femoris group muscles). Notes: • The pectineus is a transitional muscle between the anterior and medial groups of the thigh. • The adductor magnus is a transitional muscle between the medial and posterior groups of the thigh. • The quadriceps femoris musculature is primarily located in the anterior thigh but also wraps into the medial and lateral thigh to attach into the linea aspera of the posterior thigh. • The iliotibial band (ITB) is a fibrous fascial thickening in the lateral thigh of the fascia latae (the fascial membrane that envelops the entire thigh) and acts as a distal tendon of the TFL and gluteus maximus (and also acts to stabilize the lateral knee joint). Overview of FUNCTION The following general rules regarding actions can be stated for the functional groups of muscles of the knee joint: If a muscle crosses the knee joint anteriorly with a vertical direction to its fibers, it can extend the leg at the knee joint by moving the anterior surface of the leg toward the anterior surface of the thigh. If a muscle crosses the knee joint posteriorly with a vertical direction to its fibers, it can flex the leg at the knee joint by moving the posterior surface of the leg toward the posterior surface of the thigh. If a muscle wraps around the knee joint, it can rotate the knee joint (the knee joint can only rotate if it is first flexed). Medial rotators attach to the medial side of the leg. The biceps femoris is the only lateral rotator and attaches to the lateral side of the leg. Reverse actions are common at the knee joint and tend to occur when the foot is planted on the ground (closed chain kinematics), causing the distal attachment to be fixed and therefore the proximal attachment (the thigh) to be mobile and move toward the distal attachment (the leg). The reverse action of extension of the leg at the knee joint is extension of the thigh at the knee joint in which the anterior surface of the thigh moves toward the anterior surface of the leg. This occurs every time we stand up from a seated position. The reverse action of flexion of the leg at the knee joint is flexion of the thigh at the knee joint in which the posterior surface of the thigh moves toward the posterior surface of the leg. The reverse action of medial rotation of the leg at the knee joint is lateral rotation of the thigh at the knee joint; the reverse action of lateral rotation of the leg at the knee joint is medial rotation of the thigh at the knee joint.

http://evolve.elsevier.com/Muscolino/muscular

864

865

Anterior Views of the Muscles of the Knee Joint

FIGURE 15-1

Anterior views of the muscles of the knee joint. A, Superficial and intermediate views.

866

FIGURE 15-1

B, Deeper views.

867

Posterior Views of the Muscles of the Knee Joint

FIGURE 15-2

Posterior views of the muscles of the knee joint. A, Superficial and intermediate views.

868

FIGURE 15-2

B, Deeper views.

869

Lateral Views of the Muscles of the Right Knee Joint

FIGURE 15-3

Lateral views of the muscles of the right knee joint. A, Superficial. B, Deep.

870

Medial Views of the Muscles of the Right Knee Joint

FIGURE 15-4

Medial views of the muscles of the right knee joint. A, Superficial. B, Deep.

871

Transverse Plane Cross Sections of the Muscles of the Right Thigh

FIGURE 15-5

Transverse plane cross sections of the muscles of the right thigh. A, Proximal. B, Middle. C, Distal.

872

Quadriceps Femoris Group (Quads) • The quadriceps femoris are a group of muscles that wrap around nearly the entire shaft of the femur and are superficial in the anterior thigh. • There are four quadriceps femoris muscles: the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius.

ATTACHMENTS These muscles are grouped together as the quadriceps femoris, because they all attach distally onto the patella and then onto the tibial tuberosity via the patellar ligament. The patella is a sesamoid bone that formed within the distal tendon of the quadriceps femoris group. Therefore the patellar ligament is actually a continuation of the distal tendon of the quadriceps femoris. The quadriceps femoris have additional distal fibers (primarily from the vastus lateralis, vastus medialis, and vastus intermedius) called retinacular fibers that attach onto the lateral and medial condyles of the tibia. Keep in mind that vastus quadriceps femoris muscles attach onto the linea aspera. Therefore although these muscles are superficial anteriorly, they are also located in the lateral, medial, and posterior thigh. The names of the quadriceps femoris muscles generally refer to where they are located relative to each other. The vastus lateralis is more lateral, the vastus medialis is more medial, and the vastus intermedius is between the other two. The rectus femoris is straight (rectus means straight) up and down (proximal to distal) over the femur. From the anterior perspective, the rectus femoris is the most superficial of the quadriceps femoris muscles. All four quadriceps femoris muscles are located within the superficial front line myofascial meridian.

FUNCTIONS As a group, all four quadriceps femoris muscles extend the leg at the knee joint. Because it is the only quadriceps femoris muscle that crosses the hip joint, the rectus femoris is the only one that can move the thigh at the hip joint and/or move the pelvis at the hip joint. The reason that the quadriceps femoris are so large and strong is not just to move the leg into extension at the knee joint but rather to do the reverse action, in other words, move the thigh into extension at the knee joint. This happens every time a person stands up from a seated position. To move the thigh at the knee joint requires moving the entire body along with the thigh; hence the quadriceps femoris group needs to be very large and strong.

MISCELLANEOUS 1. If the quadriceps femoris group is considered to be one muscle, it is the largest muscle in the human body (being appreciably larger than the gluteus maximus).

I N N E RVAT I O N The quadriceps femoris group is innervated by the femoral nerve.

A R T E R I A L S U P P LY The quadriceps femoris group receives its blood supply from the femoral artery and the deep femoral artery.

873

874

Views of the Quadriceps Femoris Group

FIGURE 15-6

Views of the quadriceps femoris group. A, Anterior views; superficial on the right and deep on the left. B, Lateral view. C, Medial view.

875

Rectus Femoris (of Quadriceps Femoris Group) The name, rectus femoris, tells us that the fibers of this muscle run straight up and down (proximal to distal) on the femur. Derivation rectus: L. straight femoris: L. refers to the femur Pronunciation REK-tus FEM-o-ris

ATTACHMENTS Anterior Inferior Iliac Spine (AIIS) and just superior to the brim of the acetabulum to the Tibial Tuberosity via the Patella and the Patellar Ligament and the tibial condyles via the retinacular fibers

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions

Reverse Mover Actions

1. Extends the leg at the knee joint

1. Extends the thigh at the knee joint

2. Flexes the thigh at the hip joint

2. Anteriorly tilts the pelvis at the hip joint

Standard Mover Actions Notes • The rectus femoris crosses the knee joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it extends the leg at the knee joint. (action 1) • The rectus femoris crosses the hip joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the thigh at the hip joint. (action 2) • The rectus femoris is the only member of the quadriceps femoris group that crosses the hip joint. Therefore it is the only member that can flex the thigh (and anteriorly tilt the pelvis) at the hip joint. (action 2)

Reverse Mover Actions Notes • If the distal tibial attachment is fixed, the rectus femoris pulls the anterior surface of the femur toward the anterior surface of the tibia. Therefore the rectus femoris extends the thigh at the knee joint. (reverse action 1) • The reason that the quadriceps femoris are so large and strong is not just to move the leg into extension at the knee joint but rather to do the reverse action, in other words, move the thigh into extension at the knee joint. This happens every time a person stands up from a seated position. To move the thigh at the knee joint requires moving the entire body along with the thigh; hence the quadriceps femoris group needs to be very large and strong. (reverse action 1)

876

FIGURE 15-7

Anterior views of the rectus femoris bilaterally. The rest of the quadriceps femoris group has been ghosted in on the left.

• With the distal attachment fixed, the rectus femoris pulls the anterior pelvis toward the anterior surface of the femur. Therefore it anteriorly tilts the pelvis at the hip joint. (reverse action 2)

Motions 1. The rectus femoris has one line of pull upon the leg and thigh in the sagittal plane, so it creates one motion at the knee and hip joints, which is a combination of extension of the leg at the knee joint and flexion of the thigh at the hip joint. 2. Regarding its reverse action pull on the pelvis, the rectus femoris has one line of pull in the sagittal plane, and therefore its motion is its cardinal plane joint action, anterior tilt of the pelvis at the hip joint.

Eccentric Antagonist Functions 1. Restrains/slows knee joint flexion 2. Restrains/slows thigh extension and pelvic posterior tilt at the hip joint

Major Isometric Stabilization Functions 1. Stabilizes the knee joint (tibiofemoral and patellofemoral joints) 2. Stabilizes the pelvis and thigh at the hip joint

Isometric Function Note • Strengthening the quadriceps femoris group is a major factor in knee joint stabilization for

877

physical rehabilitation work.

Additional Notes on Actions 1. As the rectus femoris extends the leg at the knee joint, it also pulls the patella superiorly at the patellofemoral joint. 2. Some sources state that the rectus femoris can abduct the thigh at the hip joint. Given that its line of pull is slightly lateral to the anteroposterior axis through the hip joint for frontal plane motion, this action seems likely. 3. All four members of the quadriceps femoris group can extend the leg (and thigh) at the knee joint. Only the rectus femoris crosses and moves the hip joint.

I N N E RVAT I O N The Femoral Nerve L2, L3, L4

A R T E R I A L S U P P LY The Femoral Artery (the continuation of the External Iliac Artery) and the Deep Femoral Artery (a major branch of the Femoral Artery)

PA L PAT I O N 1. With the client supine with a pillow under the knees, place palpating hand just proximal to the patella. 2. Resist the client from extending the leg at the knee joint and feel for the contraction of the rectus femoris. 3. Continue palpating the rectus femoris toward the anterior inferior iliac spine (AIIS).

RELATIONSHIP TO OTHER STRUCTURES The rectus femoris is superficial for its entire course except proximally, where it is deep to the sartorius and the tensor fasciae latae. Deep to the rectus femoris is the vastus intermedius. The rectus femoris is primarily located between the vastus lateralis (laterally) and the vastus medialis (medially), but it slightly overlies the two. The rectus femoris is located within the superficial front line myofascial meridian.

MISCELLANEOUS 1. The proximal attachment of the rectus femoris onto the anterior inferior iliac spine (AIIS) is known as the straight tendon. 2. The proximal attachment of the rectus femoris that attaches just superior to the brim of the acetabulum, is known as the reflected tendon. 3. Because of the difference in leverage, the rectus femoris is more powerful at the knee joint than at the hip joint. 4. The rectus femoris is bipennate.

878

Vastus Lateralis (of Quadriceps Femoris Group) The name, vastus lateralis, tells us that this muscle is vast in size and located laterally. Derivation vastus: L. vast lateralis: L. lateral Pronunciation VAS-tus lat-er-A-lis

ATTACHMENTS Linea Aspera of the Femur the lateral lip of the linea aspera of the femur, and the intertrochanteric line and gluteal tuberosity of the femur to the Tibial Tuberosity via the Patella and the Patellar Ligament and the tibial condyles via the retinacular fibers

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extends the leg at the knee joint

Reverse Mover Actions 1. Extends the thigh at the knee joint

Standard Mover Actions Note • The vastus lateralis crosses the knee joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it extends the leg at the knee joint. (action 1)

Reverse Mover Actions Notes • If the distal tibial attachment is fixed, the vastus lateralis pulls the anterior surface of the femur toward the anterior surface of the tibia. Therefore the vastus lateralis extends the thigh at the knee joint. (reverse action 1) • The reason that the quadriceps femoris are so large and strong is not just to move the leg into extension at the knee joint but rather to do the reverse action, in other words, move the thigh into extension at the knee joint. This happens every time a person stands up from a seated position. To move the thigh at the knee joint requires moving the entire body along with the thigh; hence the quadriceps femoris group needs to be very large and strong. (reverse action 1)

Motion 1. The vastus lateralis has one line of pull in the sagittal plane, and therefore its motion is its cardinal plane joint action, extension of the knee joint.

Eccentric Antagonist Function 1. Restrains/slows knee joint flexion

879

FIGURE 15-8 Views of the vastus lateralis. A, Anterior views of the vastus lateralis bilaterally. The rest of the quadriceps femoris group has been ghosted in on the left. B, Right lateral view. The rectus femoris has been drawn in.

Isometric Stabilization Function 1. Stabilizes the knee joint (tibiofemoral and patellofemoral joints)

Isometric Function Note • Strengthening the quadriceps femoris group is a major factor in knee joint stabilization for physical rehabilitation work.

Additional Notes on Actions 1. As the vastus lateralis extends the leg at the knee joint, it also pulls the patella superiorly/proximally and laterally at the patellofemoral joint. 2. The fibers of the vastus lateralis are oriented somewhat horizontally, which creates a line of pull on the patella that can pull it slightly laterally at the patellofemoral joint, in addition to proximally, when it contracts to extend the leg at the knee joint. Similarly, the vastus medialis can pull the patella slightly medially as the leg extends at the knee joint. The counterbalancing forces of the vastus lateralis and the vastus medialis help ensure that the patella tracks correctly on the femur at

880

the patellofemoral joint as the knee (tibiofemoral) joint extends and flexes. 3. All four members of the quadriceps femoris group can extend the leg (and thigh) at the knee joint.

I N N E RVAT I O N The Femoral Nerve L2, L3, L4

A R T E R I A L S U P P LY The Femoral Artery (the continuation of the External Iliac Artery) and the Deep Femoral Artery (a major branch of the Femoral Artery) and branches of the Popliteal Artery (the continuation of the Femoral Artery)

PA L PAT I O N 1. With the client supine with a pillow under the knees, place palpating hand just distal to the greater trochanter. 2. Have the client extend the leg at the knee joint against your resistance and feel for the contraction of the vastus lateralis. 3. Continue palpating the vastus lateralis toward the patella in the lateral, posterolateral, and anterolateral thigh.

RELATIONSHIP TO OTHER STRUCTURES Anteriorly, the vastus lateralis is lateral and partially deep to the rectus femoris. In the lateral thigh, the vastus lateralis is deep to the tensor fasciae latae and the iliotibial band (ITB). Posteriorly, the vastus lateralis is superficial between the iliotibial band and the biceps femoris of the hamstring group. From the lateral perspective, the vastus intermedius and the femur are deep to the vastus lateralis. The vastus lateralis is located within the back functional line and involved with the superficial front line myofascial meridians.

MISCELLANEOUS 1. The vastus lateralis is the largest of the four quadriceps femoris muscles. 2. Pain attributed to the ITB is often caused by tightness of the vastus lateralis, which is deep to the ITB. 3. The vastus lateralis is pennate.

881

Vastus Medialis (of Quadriceps Femoris Group) The name, vastus medialis, tells us that this muscle is vast in size and located medially. Derivation vastus: L. vast medialis: L. medial Pronunciation VAS-tus mee-dee-A-lis

ATTACHMENTS Linea Aspera of the Femur the medial lip of the linea aspera, and the intertrochanteric line and the medial supracondylar line of the femur to the Tibial Tuberosity via the Patella and the Patellar Ligament and the tibial condyles via the retinacular fibers

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extends the leg at the knee joint

Reverse Mover Actions 1. Extends the thigh at the knee joint

Standard Mover Actions Note • The vastus medialis crosses the knee joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it extends the leg at the knee joint. (action 1)

Reverse Mover Actions Notes • If the distal tibial attachment is fixed, the vastus medialis pulls the anterior surface of the femur toward the anterior surface of the tibia. Therefore the vastus medialis extends the thigh at the knee joint. (reverse action 1) • The reason that the quadriceps femoris are so large and strong is not just to move the leg into extension at the knee joint but rather to do the reverse action, in other words, move the thigh into extension at the knee joint. This happens every time a person stands up from a seated position. To move the thigh at the knee joint requires moving the entire body along with the thigh; hence the quadriceps femoris group needs to be very large and strong. (reverse action 1)

Motion 1. The vastus medialis has one line of pull in the sagittal plane, and therefore its motion is its cardinal plane joint action, extension of the knee joint.

Eccentric Antagonist Function 1. Restrains/slows knee joint flexion

882

FIGURE 15-9

Anterior views of the vastus medialis bilaterally. The rest of the quadriceps femoris group has been ghosted in on the left.

Isometric Stabilization Function 1. Stabilizes the knee joint (tibiofemoral and patellofemoral joints)

Isometric Function Note • Strengthening the quadriceps femoris group is a major factor in knee joint stabilization for physical rehabilitation work.

Additional Notes on Actions 1. As the vastus medialis extends the leg at the knee joint, it also pulls the patella superiorly/proximally and medially at the patellofemoral joint. 2. The fibers of the vastus medialis are oriented somewhat horizontally, which creates a line of pull on the patella that can pull it slightly medially at the patellofemoral joint, in addition to proximally, when it contracts to extend the leg at the knee joint. Similarly, the vastus lateralis can pull the patella slightly laterally as the leg extends at the knee joint. The counterbalancing forces of the vastus medialis and the vastus lateralis help ensure that the patella tracks correctly on the femur at the patellofemoral joint as the knee (tibiofemoral) joint extends and flexes. 3. All four members of the quadriceps femoris group can extend the leg (and thigh) at the knee joint.

I N N E RVAT I O N

883

The Femoral Nerve L2, L3, L4

A R T E R I A L S U P P LY The Femoral Artery (the continuation of the External Iliac Artery)

PA L PAT I O N 1. With the client supine with a pillow under the knees, place palpating hand just proximal and medial to the patella. 2. Have the client extend the leg at the knee joint against your resistance and feel for the contraction of the vastus medialis. 3. Continue palpating the vastus medialis proximally as far as possible.

RELATIONSHIP TO OTHER STRUCTURES Anteriorly, the vastus medialis is medial and slightly deep to the rectus femoris. It is also deep to the sartorius. The vastus medialis is anterior to the adductor group. From the medial perspective, the femur is deep to the vastus medialis. The vastus medialis is involved with the superficial front line myofascial meridian.

MISCELLANEOUS 1. The most distal aspect of the vastus medialis is the bulkiest and may form a bulge in well-toned individuals. 2. Some sources refer to the upper fibers of the vastus medialis as the vastus medialis longus (VML) and the lower fibers as the vastus medialis oblique (VMO) because of the drastic difference in the direction of the upper fibers compared with the lower fibers. 3. A common dysfunction of the patellofemoral joint is for the patella to track laterally as the knee (tibiofemoral) joint extends. Physical rehabilitation is often directed toward trying to preferentially strengthen the vastus medialis (specifically the VMO fibers) over the vastus lateralis; however, there is controversy as to whether this is possible. 4. The vastus medialis is pennate.

884

Vastus Intermedius (of Quadriceps Femoris Group) The name, vastus intermedius, tells us that this muscle is vast in size and located between the two other vastus muscles. Derivation vastus: L. vast inter: L. between medius: L. middle Pronunciation VAS-tus in-ter-MEE-dee-us

ATTACHMENTS Anterior Shaft and Linea Aspera of the Femur the anterior and lateral surfaces of the femur and the lateral lip of the linea aspera to the Tibial Tuberosity via the Patella and the Patellar Ligament and the tibial condyles via the retinacular fibers

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extends the leg at the knee joint

Reverse Mover Actions 1. Extends the thigh at the knee joint

Standard Mover Actions Notes • The vastus intermedius crosses the knee joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it extends the leg at the knee joint. (action 1)

Reverse Mover Actions Notes • If the distal tibial attachment is fixed, the vastus intermedius pulls the anterior surface of the femur toward the anterior surface of the tibia. Therefore the vastus intermedius extends the thigh at the knee joint. (reverse action 1) • The reason that the quadriceps femoris are so large and strong is not just to move the leg into extension at the knee joint but rather to do the reverse action, in other words, move the thigh into extension at the knee joint. This happens every time a person stands up from a seated position. To move the thigh at the knee joint requires moving the entire body along with the thigh; hence the quadriceps femoris group needs to be very large and strong. (reverse action 1)

Motion 1. The vastus intermedius has one line of pull in the sagittal plane, and therefore its motion is its cardinal plane joint action, extension of the knee joint.

885

FIGURE 15-10 Anterior views of the vastus intermedius bilaterally. The rest of the quadriceps femoris group has been ghosted in on the left side (the rectus femoris has been cut).

Eccentric Antagonist Function 1. Restrains/slows knee joint flexion

Isometric Stabilization Function 1. Stabilizes the knee joint (tibiofemoral and patellofemoral joints)

Isometric Function Note • Strengthening the quadriceps femoris group is a major factor in knee joint stabilization for physical rehabilitation work.

Additional Notes on Actions 1. As the vastus intermedius extends the leg at the knee joint, it also pulls the patella superiorly/proximally and somewhat laterally at the patellofemoral joint. 2. All four members of the quadriceps femoris group can extend the leg (and thigh) at the knee joint.

I N N E RVAT I O N The Femoral Nerve L2, L3, L4

A R T E R I A L S U P P LY The Deep Femoral Artery (a major branch of the Femoral Artery)

PA L PAT I O N

886

1. With the client supine with a pillow under the knees, place palpating hand just proximal to the patella. 2. If the rectus femoris can be lifted and/or moved aside, the distal vastus intermedius may be palpated deep to the rectus femoris when approached from either the medial or the lateral side. 3. To feel the vastus intermedius deep to the rectus femoris, make sure that the direction of your pressure is oriented toward the middle of the femur.

RELATIONSHIP TO OTHER STRUCTURES The vastus intermedius is deep to the rectus femoris and the vastus lateralis. From the anterior perspective, a small muscle called the articularis genus and the femur are deep to the vastus intermedius. From the lateral perspective, the femur is deep to the vastus intermedius. The vastus medialis is involved with the superficial front line myofascial meridian.

MISCELLANEOUS 1. The vastus intermedius somewhat blends into the vastus lateralis and the vastus medialis. 2. The vastus intermedius sometimes blends with the articularis genus. 3. The vastus intermedius is pennate.

887

Articularis Genus The name, articularis genus, tells us that this muscle is involved with the knee joint. Derivation articularis: L. refers to a joint genu: L. referes to the knee Pronunciation ar-TIK-you-LA-ris JEH-new

ATTACHMENTS Anterior Distal Femoral Shaft to the Knee Joint Capsule

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Tenses and pulls the knee joint capsule proximally

Reverse Mover Actions 1. The reverse action of moving the femur is unlikely to occur

Standard Mover Action Notes • The articularis genus (with its fibers oriented vertically) pulls its distal attachment, the joint capsule of the knee joint, toward its proximal attachment, the anterior distal shaft of the femur. (action 1) • The action of the articularis genus tensing and pulling the knee joint capsule proximally couples with the contraction of the quadriceps femoris group contracting and pulling the patella proximally when the knee joint extends. Pulling the knee joint capsule proximally when the patella moves proximally prevents the capsule from being pinched between the patella and femur. (action 1)

Motion 1. The articularis genu has one line of pull in the sagittal plane, and therefore its motion is its cardinal plane joint action, tensing and pulling the knee joint capsule proximally.

Eccentric Antagonist Function 1. Restrains/slows distal movement of the knee joint capsule

Isometric Stabilization Function 1. Stabilizes the position of the knee joint capsule

888

FIGURE 15-11

Anterior view of the right articularus genus.

I N N E RVAT I O N The Femoral Nerve L2, L3, L4

A R T E R I A L S U P P LY The Deep Femoral Artery (a major branch of the Femoral Artery)

PA L PAT I O N 1. The articularis genus is a small muscle deep to the rectus femoris and vastus intermedius and is extremely difficult, if not impossible, to palpate and distinguish from the adjacent musculature.

RELATIONSHIP TO OTHER STRUCTURES The articularis genus is deep to the vastus intermedius. Deep to the articularis genus is the femur. The articularis genus is involved with the superficial front line myofascial meridian.

MISCELLANEOUS 1. The articularis genus is sometimes a distinct muscle and sometimes it blends with the vastus intermedius.

889

Hamstring Group The hamstrings are a group of muscles in the posterior thigh. There are three hamstring muscles: the biceps femoris, semitendinosus, and semimembranosus.

ATTACHMENTS These muscles are grouped together as the hamstrings, because they all attach proximally onto the ischial tuberosity. The semitendinosus and the semimembranosus are located medially in the posterior thigh and are sometimes referred to as the medial hamstrings. The biceps femoris is located laterally in the posterior thigh and is sometimes referred to as the lateral hamstrings. (Hamstrings is plural because the biceps femoris has two heads.) The semitendinosus and long head of the biceps femoris are superficial; the semimembranosus and short head of the biceps femoris are deeper. All three hamstring muscles are located within the superficial back line myofascial meridian.

FUNCTIONS As a group, all three hamstrings flex the leg (or thigh) at the knee joint. Because of the difference in leverage, the hamstrings are more powerful at the hip joint than they are at the knee joint. As a group, all three hamstrings (except the short head of the biceps femoris) extend the thigh at the hip joint and/or posteriorly tilt the pelvis at the hip joint.

MISCELLANEOUS 1. The hamstrings, as a group, were given this name because butchers used to hang the carcass of a pig by the hamstring tendons.

I N N E RVAT I O N The three hamstrings are innervated by the sciatic nerve. They are all innervated by the tibial branch of the sciatic nerve except for the short head of the biceps femoris, which is innervated by the common fibular branch of the sciatic nerve.

A R T E R I A L S U P P LY The upper ⅓ of the hamstrings receives its arterial supply from the inferior gluteal artery and the obturator artery. The middle ⅓ of the hamstrings receives its arterial supply from perforating branches of the deep femoral artery. The distal ⅓ of the hamstrings receives its arterial supply from the popliteal artery.

890

Posterior Views of the Hamstring Group

FIGURE 15-12

Posterior views of the right hamstring group. A, Superficial. B, Deep.

891

Biceps Femoris (of Hamstring Group) The name, biceps femoris, tells us that this muscle has two heads and lies over the femur. Derivation biceps: L. two heads femoris: L. refers to the femur Pronunciation BY-seps FEM-o-ris

ATTACHMENTS LONG HEAD: Ischial Tuberosity and the sacrotuberous ligament SHORT HEAD: Linea Aspera and the lateral supracondylar line of the femur to the Head of the Fibula and the lateral tibial condyle

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes the leg at the knee joint

Reverse Mover Actions 1. Flexes the thigh at the knee joint

2. Extends the thigh at the hip joint 3. Laterally rotates the leg at the knee joint

2. Posteriorly tilts the pelvis at the hip joint 3. Medially rotates the thigh at the knee joint

4. Laterally rotates the thigh at the hip joint

4. Contralaterally rotates the pelvis at the hip joint

5. Adducts the thigh at the hip joint

5. Elevates the same-side pelvis at the hip joint

Standard Mover Action Notes • The biceps femoris crosses the knee joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the leg at the knee joint. (action 1) • The long head of the biceps femoris crosses the hip joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it extends the thigh at the hip joint. The short head cannot extend the thigh at the hip joint because it does not cross the hip joint. (action 2) • The biceps femoris crosses the knee joint laterally from posterior to anterior (with its fibers running somewhat horizontally in the transverse plane) and attaches to the lateral leg. When the biceps femoris pulls at the leg attachment, the attachment is pulled posteriorly, causing the anterior leg to face somewhat laterally. Therefore the biceps femoris laterally rotates the leg at the knee joint. (Note: The knee joint can only rotate if it is first flexed.) (action 3)

892

FIGURE 15-13 Posterior views of the right biceps femoris. A, The long and short heads of the biceps femoris are drawn in. The semitendinosus has been ghosted in. B, The short head of the biceps femoris. The semimembranosus has been ghosted in.

• The biceps femoris is the only muscle that can laterally rotate the leg (and medially rotate the thigh) at the knee joint. (action 3) • The long head of the biceps femoris crosses the hip joint laterally, wrapping around the thigh from posteriorly on the pelvis to more anteriorly onto the leg (with its fibers running somewhat horizontally in the transverse plane). If the leg is fixed to the thigh and the long head of the biceps femoris pulls on the leg, the leg and thigh are pulled posterolaterally, causing the anterior thigh to face laterally. Therefore the biceps femoris laterally rotates the thigh at the hip joint. (action 4) • The long head of the biceps femoris crosses the hip joint posteriorly (with its fibers running somewhat horizontally in the frontal plane) below the center of the hip joint from medially on the pelvis to laterally on the leg. Therefore when the biceps femoris pulls its lateral attachment (the leg) medially, it adducts the thigh at the hip joint. (action 5)

Reverse Mover Action Notes • Reverse actions of the biceps femoris usually occur when the foot is planted on the ground (closed chain kinematics), making the distal attachment relatively more fixed so that the proximal attachment moves instead. (reverse actions 1, 2, 3, 4, 5)

893

• The biceps femoris crosses the knee joint posteriorly (with its fibers running vertically in the sagittal plane). If the distal attachment is fixed, the thigh flexes toward the leg at the knee joint. (reverse action 1) • With the distal attachment fixed, the long head of the biceps femoris, by pulling inferiorly on the posterior pelvis, posteriorly tilts the pelvis at the hip joint. The short head does not cross the hip joint; therefore it cannot move the pelvis at the hip joint. (reverse action 2) • The reverse action of lateral rotation of the leg at the knee joint is medial rotation of the thigh at the knee joint. (reverse action 3) • The long head of the biceps femoris runs slightly horizontally (in the transverse plane) across the hip joint. If the distal attachment is fixed, the pelvis will be pulled such that its anterior surface comes to face the opposite side of the body from the side to which the biceps femoris is attached. Therefore the biceps femoris contralaterally rotates the pelvis at the hip joint. (reverse action 4) • With the distal attachment fixed, the long head of the biceps femoris pulls inferiorly and laterally on the ischial tuberosity, causing the iliac crest on that side to elevate. Therefore the long head of the biceps femoris elevates the same-side pelvis at the hip joint. Note: If one side of the pelvis elevates, the other side depresses. (reverse action 5)

Motions 1. The biceps femoris has one line of pull upon the leg and thigh in an oblique plane and therefore creates one motion, which is a combination of flexion and lateral rotation of the leg at the knee joint, and extension, lateral rotation, and adduction of the thigh at the hip joint. 2. Regarding its reverse action pull on the pelvis, the biceps femoris has one line of pull in an oblique plane and therefore creates one motion, which is posterior tilt along with contralateral rotation and same-side elevation of the pelvis.

Eccentric Antagonist Functions 1. Restrains/slows knee joint extension and medial rotation of the leg and lateral rotation of the thigh at the knee joint 2. Restrains/slows flexion, medial rotation, and abduction of the thigh at the hip joint 3. Restrains/slows anterior tilt, ipsilateral rotation, and same-side depression of the pelvis at the hip joint

Isometric Stabilization Functions 1. Stabilizes the thigh and pelvis at the hip joint 2. Stabilizes the knee joint

Additional Notes on Actions 1. All three hamstring muscles (biceps femoris, semitendinosus, and semimembranosus) flex the knee joint. 2. All hamstring musculature (except the short head of the biceps femoris) extends the thigh (and posteriorly tilts the pelvis) at the hip joint.

I N N E RVAT I O N The Sciatic Nerve the tibial nerve and the common fibular nerve; L5, S1, S2

A R T E R I A L S U P P LY Long Head The Inferior Gluteal Artery (a branch of the Internal Iliac Artery) and perforating branches of the Deep Femoral Artery (a major branch of the Femoral Artery) and the Obturator Artery (a branch of the Internal Iliac Artery) and branches of the Popliteal Artery (the continuation of the Femoral Artery) Short Head Perforating branches of the Deep Femoral Artery (a major branch of the Femoral Artery) and branches of the Popliteal Artery (the continuation of the Femoral Artery)

894

PA L PAT I O N 1. With the client prone with the leg partially flexed at the knee joint, place palpating hand just distal and slightly lateral to the ischial tuberosity. 2. Resist the client from performing further flexion of the leg at the knee joint and palpate the biceps femoris toward the head of the fibula.

RELATIONSHIP TO OTHER STRUCTURES The biceps femoris is a lateral hamstring muscle. The biceps femoris is superficial in the posterolateral thigh, except proximally where it is deep to the gluteus maximus. The proximal attachment of the short head of the biceps femoris begins immediately distal to the femoral attachment of the gluteus maximus. All fibers of the short head of the biceps femoris are deep to the long head except distally near the knee, where some of the fibers of the short head are superficial, lateral to the long head of the biceps femoris. The biceps femoris is just lateral to the semitendinosus and just medial (and also superficial) to the vastus lateralis. The biceps femoris is located within the superficial back line and spiral line myofascial meridians.

MISCELLANEOUS 1. The proximal attachment of the biceps femoris’ long head blends with the proximal attachment of the semitendinosus. 2. Some sources state that the short head of the biceps femoris is not a true hamstring muscle because it does not attach to the ischial tuberosity, does not cross the hip joint, and is not innervated by the tibial nerve branch of the sciatic nerve.

Semitendinosus (of Hamstring Group) The name, semitendinosus, tells us that this muscle has a long, slender (distal) tendon. Derivation semitendinosus: L. refers to its long tendon Pronunciation SEM-i-TEN-di-NO-sus

ATTACHMENTS Ischial Tuberosity to the Pes Anserine Tendon (at the Proximal Anteromedial Tibia)

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes the leg at the knee joint

Reverse Mover Actions 1. Flexes the thigh at the knee joint

2. Extends the thigh at the hip joint 3. Medially rotates the leg at the knee joint

2. Posteriorly tilts the pelvis at the hip joint 3. Laterally rotates the thigh at the knee joint

4. Medially rotates the thigh at the hip joint

4. Ipsilaterally rotates the pelvis at the hip joint

5. Adducts the thigh at the hip joint

5. Elevates the same-side pelvis at the hip joint

Standard Mover Actions Notes • The semitendinosus crosses the knee joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the leg at the knee joint. (action 1)

895

• The semitendinosus crosses the hip joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it extends the thigh at the hip joint. (action 2) • The semitendinosus crosses the knee joint medially from posterior to anterior (with its fibers running somewhat horizontally in the transverse plane) to attach into the pes anserine tendon at the medial tibia. When the semitendinosus pulls at the leg attachment, the attachment is pulled posteriorly, causing the anterior tibia to face somewhat medially. Therefore the semitendinosus medially rotates the leg at the knee joint. (Note: The knee joint can only rotate if it is first flexed.) (action 3) • The semitendinosus crosses the hip joint medially, wrapping around the thigh from posteriorly on the pelvis to more anteriorly onto the leg (with its fibers running somewhat horizontally in the transverse plane). If the leg is fixed to the thigh, and the semitendinosus pulls on the leg, the thigh rotates posteromedially, causing the anterior thigh to face medially. Therefore the semitendinosus medially rotates the thigh at the hip joint. (action 4)

FIGURE 15-14

Posterior view of the right semitendinosus. The biceps femoris has been ghosted in.

• The semitendinosus crosses the hip joint posteriorly (with its fibers running somewhat horizontally in the frontal plane) from medially on the pelvis to slightly laterally on the leg. Therefore when the semitendinosus pulls its lateral attachment (the leg) medially, it adducts the thigh at the hip joint. (action 5)

Reverse Mover Actions Notes • Reverse actions of the semitendinosus usually occur when the foot is planted on the ground (closed chain kinematics), making the distal attachment relatively more fixed so that the proximal

896

attachment moves instead. (reverse actions 1, 2, 3, 4, 5) • The semitendinosus crosses the knee joint posteriorly (with its fibers running vertically in the sagittal plane). If the distal attachment is fixed, the thigh flexes toward the leg at the knee joint. (reverse action 1) • With the distal attachment fixed, the semitendinosus, by pulling inferiorly on the posterior pelvis, posteriorly tilts the pelvis at the hip joint. (reverse action 2) • The reverse action of medial rotation of the leg at the knee joint is lateral rotation of the thigh at the knee joint. (reverse action 3) • The semitendinosus runs slightly horizontally (in the transverse plane) across the hip joint. If the distal attachment is fixed, the pelvis will be pulled such that its anterior surface comes to face the same side of the body as the side to which the semitendinosus is attached. Therefore the semitendinosus ipsilaterally rotates the pelvis at the hip joint. (reverse action 4) • With the distal attachment fixed, the semitendinosus pulls inferiorly and laterally on the ischial tuberosity, causing the iliac crest on that side to elevate. Therefore the semitendinosus elevates the same-side pelvis at the hip joint. Note: If one side of the pelvis elevates, the other side depresses. (reverse action 5)

Motions 1. The semitendinosus has one line of pull upon the leg and thigh in an oblique plane and therefore creates one motion, which is a combination of flexion and medial rotation of the leg at the knee joint, and extension, medial rotation, and adduction of the thigh at the hip joint. 2. Regarding its reverse action pull on the pelvis, the semitendinosus has one line of pull in an oblique plane and therefore creates one motion, which is posterior tilt along with ipsilateral rotation and same-side elevation of the pelvis.

Eccentric Antagonist Functions 1. Restrains/slows knee joint extension and lateral rotation of the leg and medial rotation of the thigh at the knee joint 2. Restrains/slows flexion, lateral rotation, and abduction of the thigh at the hip joint 3. Restrains/slows anterior tilt, contralateral rotation, and same-side depression of the pelvis at the hip joint

Isometric Stabilization Functions 1. Stabilizes the thigh and pelvis at the hip joint 2. Stabilizes the knee joint

Isometric Function Note • The distal tendon of the semitendinosus (along with the sartorius and gracilis muscles) helps stabilize the medial knee joint against lateral to medial (valgus) forces that would buckle the knee joint medially.

Additional Notes on Actions 1. All three hamstring muscles (biceps femoris, semitendinosus, and semimembranosus) flex the knee joint. 2. All hamstring musculature (except the short head of the biceps femoris) extends the thigh (and posteriorly tilts the pelvis) at the hip joint. 3. All three pes anserine muscles (sartorius, gracilis, and semitendinosus) flex and medially rotate the leg at the knee joint (or flex and laterally rotate the thigh at the knee joint).

I N N E RVAT I O N The Sciatic Nerve the tibial nerve; L5, S1, S2

A R T E R I A L S U P P LY The Inferior Gluteal Artery (a branch of the Internal Iliac Artery) and perforating branches of the

897

Deep Femoral Artery (a major branch of the Femoral Artery) and the Obturator Artery (a branch of the Internal Iliac Artery) and branches of the Popliteal Artery (the continuation of the Femoral Artery)

PA L PAT I O N 1. With the client prone with the leg partially flexed at the knee joint, place palpating hand just distal and slightly medial to the ischial tuberosity. 2. Resist the client from performing further flexion of the leg at the knee joint and palpate the semitendinosus toward the pes anserine tendon.

RELATIONSHIP TO OTHER STRUCTURES The semitendinosus is the more superficial medial hamstring muscle. The proximal attachment of the semitendinosus is deep to the gluteus maximus. The biceps femoris is lateral to the semitendinosus. More distally, a portion of the semimembranosus is lateral to the semitendinosus. Medial to the semitendinosus is the adductor magnus and a portion of the semimembranosus. The majority of the semimembranosus is deep to the semitendinosus. Of the three muscles that attach into the pes anserine tendon, the semitendinosus’ attachment is the most posterior and distal. The semitendinosus is located within the superficial back line myofascial meridian.

MISCELLANEOUS 1. The semitendinosus is named for its long distal tendon. 2. The semitendinosus is one of three muscles that attach into the pes anserine tendon. The other two muscles that attach here are the sartorius and the gracilis. 3. Think SGS: Of the muscles that attach into the pes anserine, the sartorius attaches the most anteriorly and proximally of the three, the gracilis is in the middle, and the semitendinosus attaches the most posteriorly and distally. 4. Pes anserine means goose foot. 5. The proximal tendon of the semitendinosus blends with the proximal tendon of the biceps femoris. 6. The semitendinosus often has a fibrous septum that divides it into distinct proximal and distal portions.

898

Semimembranosus (of Hamstring Group) The name, semimembranosus, tells us that this muscle has a flattened, membranous (proximal) attachment. Derivation semimembranosus: L. refers to its flattened, membranous tendon Pronunciation SEM-i-MEM-bra-NO-sus

ATTACHMENTS Ischial Tuberosity to the Posterior Surface of the Medial Condyle of the Tibia

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes the leg at the knee joint

Reverse Mover Actions 1. Flexes the thigh at the knee joint

2. Extends the thigh at the hip joint 3. Medially rotates the leg at the knee joint

2. Posteriorly tilts the pelvis at the hip joint 3. Laterally rotates the thigh at the knee joint

4. Medially rotates the thigh at the hip joint

4. Ipsilaterally rotates the pelvis at the hip joint

5. Adducts the thigh at the hip joint

5. Elevates the same-side pelvis at the hip joint

Standard Mover Actions Notes • The semimembranosus crosses the knee joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the leg at the knee joint. (action 1) • The semimembranosus crosses the hip joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it extends the thigh at the hip joint. (action 2) • The semimembranosus crosses the knee joint medially from posterior to anterior (with its fibers running somewhat horizontally in the transverse plane) to attach into the posterior surface of the medial tibial condyle. When the semimembranosus pulls at the leg attachment, the attachment is pulled posteriorly, causing the anterior tibia to face somewhat medially. Therefore the semimembranosus medially rotates the leg at the knee joint. (Note: The knee joint can only rotate if it is first flexed.) (action 3) • The semimembranosus crosses the hip joint medially, wrapping around the thigh from posteriorly on the pelvis to more anteriorly onto the leg (with its fibers running somewhat horizontally in the transverse plane). If the leg is fixed to the thigh, and the semimembranosus pulls on the leg, the thigh rotates posteromedially, causing the anterior thigh to face medially. Therefore the semimembranosus medially rotates the thigh at the hip joint. (action 4)

899

FIGURE 15-15

Posterior view of the right semimembranosus. The proximal and distal tendons of the semitendinosus have been cut and ghosted in.

• The semimembranosus crosses the hip joint posteriorly (with its fibers running somewhat horizontally in the frontal plane) from medially on the pelvis to slightly laterally on the leg. Therefore when the semimembranosus pulls its lateral attachment (the leg) medially, it adducts the thigh at the hip joint. (action 5)

Reverse Mover Actions Notes • Reverse actions of the semimembranosus usually occur when the foot is planted on the ground (closed chain kinematics), making the distal attachment relatively more fixed so that the proximal attachment moves instead. (reverse actions 1, 2, 3, 4, 5) • The semimembranosus crosses the knee joint posteriorly (with its fibers running vertically in the sagittal plane). If the distal attachment is fixed, the thigh flexes toward the leg at the knee joint. (reverse action 1) • With the distal attachment fixed, the semimembranosus, by pulling inferiorly on the posterior pelvis, posteriorly tilts the pelvis at the hip joint. (reverse action 2) • The reverse action of medial rotation of the leg at the knee joint is lateral rotation of the thigh at the knee joint. (reverse action 3) • The semimembranosus runs slightly horizontally (in the transverse plane) across the hip joint. If the distal attachment is fixed, the pelvis will be pulled such that its anterior surface comes to face the same side of the body to which the semimembranosus is attached. Therefore the semimembranosus ipsilaterally rotates the pelvis at the hip joint. (reverse action 4) • With the distal attachment fixed, the semimembranosus pulls inferiorly and laterally on the ischial tuberosity, causing the iliac crest on that side to elevate. Therefore the semimembranosus elevates the same-side pelvis at the hip joint. Note: If one side of the pelvis elevates, the other side

900

depresses. (reverse action 5)

Motions 1. The semimembranosus has one line of pull upon the leg and thigh in an oblique plane and therefore creates one motion, which is a combination of flexion and medial rotation of the leg at the knee joint, and extension, medial rotation, and adduction of the thigh at the hip joint. 2. Regarding its reverse action pull on the pelvis, the semimembranosus has one line of pull in an oblique plane and therefore creates one motion, which is posterior tilt along with ipsilateral rotation and same-side elevation of the pelvis.

Eccentric Antagonist Functions 1. Restrains/slows knee joint extension and lateral rotation of the leg and medial rotation of the thigh at the knee joint 2. Restrains/slows flexion, lateral rotation, and abduction of the thigh at the hip joint 3. Restrains/slows anterior tilt, contralateral rotation, and same-side depression of the pelvis at the hip joint

Isometric Stabilization Functions 1. Stabilizes the thigh and pelvis at the hip joint 2. Stabilizes the knee joint

Additional Notes on Actions 1. All three hamstring muscles (biceps femoris, semitendinosus, and semimembranosus) flex the knee joint. 2. All hamstring musculature (except the short head of the biceps femoris) extends the thigh (and posteriorly tilts the pelvis) at the hip joint.

I N N E RVAT I O N The Sciatic Nerve the tibial nerve; L5, S1, S2

A R T E R I A L S U P P LY The Inferior Gluteal Artery (a branch of the Internal Iliac Artery) and perforating branches of the Deep Femoral Artery (a major branch of the Femoral Artery) and the Obturator Artery (a branch of the Internal Iliac Artery) and branches of the Popliteal Artery (the continuation of the Femoral Artery)

PA L PAT I O N 1. With the client prone with the leg partially flexed at the knee joint, place palpating hand on the posteromedial thigh. 2. Resist the client from performing further flexion of the leg at the knee joint and feel for the contraction of the semimembranosus. It is medial to the semitendinosus and on either side of the distal tendon of the semitendinosus. (Keep in mind that this will also make the semitendinosus and the biceps femoris contract.)

RELATIONSHIP TO OTHER STRUCTURES The semimembranosus is the deeper medial hamstring muscle. The semimembranosus is generally deep to the semitendinosus. However, part of it is superficial, and found medial to the semitendinosus. More distally, the muscle belly of the semimembranosus is superficial and located on both sides of the distal tendon of the semitendinosus. The proximal attachment of the semimembranosus is deep to the gluteus maximus. Even though the semimembranosus is a medial hamstring muscle, its proximal attachment on the ischial tuberosity is located more laterally than the proximal attachments of the semitendinosus

901

and biceps femoris. Superior to the proximal attachment of the semimembranosus on the ischial tuberosity are the medial attachments of the quadratus femoris and the inferior gemellus. Deep to the semimembranosus from the posterior perspective is the adductor magnus. The semimembranosus is located within the superficial back line myofascial meridian.

MISCELLANEOUS 1. The semimembranosus is named for its flattened, membranous proximal tendon. 2. The semimembranosus is the largest of the three hamstring muscles. 3. The semimembranosus also attaches into the medial meniscus of the knee joint. 4. The medial meniscus attachment of the semimembranosus facilitates the posterior movement of the medial meniscus during knee flexion. This helps to prevent impingement of the medial meniscus between the femur and tibia during flexion of the knee joint. (Note: The popliteus has the same action with regard to the lateral meniscus.)

902

Popliteus The name, popliteus, tells us that this muscle is located in the posterior knee. Derivation popliteus: L. ham of the knee (refers to the posterior knee) Pronunciation pop-LIT-ee-us

ATTACHMENTS Distal Posterolateral Femur the lateral surface of the lateral condyle of the femur to the Proximal Posteromedial Tibia

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Medially rotates the leg at the knee joint 2. Flexes the leg at the knee joint

Reverse Mover Actions 1. Laterally rotates the thigh at the knee joint 2. Flexes the thigh at the knee joint

Standard Mover Actions Notes • At the posterior knee, the popliteus wraps around the knee joint from the lateral femur to the medial tibia (with its fibers running horizontally in the transverse plane). When the popliteus contracts, it pulls the tibial attachment posterolaterally toward the femoral attachment. This causes the anterior leg to face somewhat medially. Therefore the popliteus medially rotates the leg at the knee joint. (action 1) • The popliteus crosses the knee joint posteriorly (with its fibers running somewhat vertically in the sagittal plane); therefore it flexes the leg at the knee joint. (action 2)

Reverse Mover Actions Notes • Reverse actions of the popliteus usually occur when the foot is planted on the ground (closed chain kinematics), making the distal attachment relatively more fixed so that the proximal attachment, the thigh moves instead. (reverse actions 1, 2) • Because the popliteus crosses the knee joint horizontally in the transverse plane, it can rotate the knee joint. When its distal attachment on the leg is fixed (e.g., when the foot is planted on the ground), instead of rotating the leg medially, the popliteus pulls on the thigh, causing its anterior surface to face laterally. Therefore the popliteus laterally rotates the thigh at the knee joint. (reverse action 1) • The popliteus crosses the knee joint posteriorly (with its fibers running vertically in the sagittal plane). If the distal attachment is fixed, the thigh will flex toward the leg at the knee joint. (reverse action 2)

903

FIGURE 15-16

Posterior view of the right popliteus. The soleus and cut distal tendon of the semimembranosus have been ghosted in.

Motions 1. The popliteus has one line of pull upon the leg in an oblique plane and therefore creates one motion, which is a combination of medial rotation and flexion of the leg at the knee joint. 2. Regarding its reverse action pull on the thigh, the popliteus has one line of pull in an oblique plane and therefore creates one motion, which is a combination of lateral rotation and flexion of the thigh at the knee joint.

Eccentric Antagonist Functions 1. Restrains/slows lateral rotation of the leg and medial rotation of the thigh at the knee joint 2. Restrains/slows knee joint extension

Isometric Stabilization Function 1. Stabilizes the knee joint

Additional Note on Actions 1. To flex a fully extended knee joint, medial rotation of the leg at the knee joint and/or lateral rotation of the thigh at the knee joint is required. Of all muscles that can do these actions, the

904

popliteus is considered to be the most important at creating this initial knee joint rotation and is said to unlock the extended knee joint.

I N N E RVAT I O N The Tibial Nerve L4, L5, S1

A R T E R I A L S U P P LY Branches of the Popliteal Artery (the continuation of the Femoral Artery)

PA L PAT I O N 1. With the client seated with the feet flat on the floor, locate the tibial tuberosity and slide around medially until you are on the medial border of the tibia; curl your fingertips around to the posterior side of the tibial shaft. 2. Have the client medially rotate the leg at the knee joint and feel for the contraction of the popliteus. 3. Continue palpating the popliteus (deep to the gastrocnemius) toward its femoral attachment.

RELATIONSHIP TO OTHER STRUCTURES The popliteus is deep to the plantaris and the lateral head of the gastrocnemius. The popliteus is proximal to the soleus. Deep to the popliteus are the femur and the tibia. The proximal tendon of the popliteus arises from the femur within the joint capsule of the knee (i.e., it is intra-articular). The popliteus is located within the deep front line and involved with the superficial back line myofascial meridians.

MISCELLANEOUS 1. The popliteus is located in the deep posterior compartment of the leg. 2. The proximal tendon of the popliteus is located within the knee joint (i.e., it is intra-articular). The only other muscle that has an intra-articular tendon is the (long head of the) biceps brachii at the glenohumeral joint. 3. The popliteus also attaches into the lateral meniscus of the knee joint. This attachment facilitates the posterior movement of the lateral meniscus during knee flexion. This helps to prevent impingement of the lateral meniscus between the femur and tibia during flexion of the knee joint. (Note: The semimembranosus has the same action with regard to the medial meniscus.)

905

REVIEW QUESTIONS 1. What makes reverse actions so common at the knee joint? ____________________________ ____________________________ ____________________________ 2. Please describe the involvement of the quadriceps femoris muscle group at the hip joint. ____________________________ ____________________________ ____________________________ 3. During extension of the leg at the knee joint, the vastus lateralis pulls the patella in what direction at the patellofemoral joint? ____________________________ 4. Pain attributed to the iliotibial band (ITB) is often caused by tightness in what muscle? ____________________________ 5. What is the primary action of the articularis genus? Why is this action important to knee function? ____________________________ ____________________________ ____________________________ ____________________________ 6. Due to the difference in leverage, the hamstrings are more powerful at which one of the two joints that they cross? ____________________________ 7. What is the only muscle that can laterally rotate the leg at the knee joint? ____________________________ 8. Which of the hamstring muscles attaches into the pes anserine tendon? ____________________________ 9. Which of the hamstring muscles attaches into the medial meniscus of the knee? Why is this important? ____________________________ ____________________________ ____________________________ 10. What role does the popliteus play in a fully extended knee joint? ____________________________ ____________________________ ____________________________ ____________________________ For answers to these questions, visit http://evolve.elsevier.com/Muscolino/muscular

906

THINK IT THROUGH The knee joint is acted upon by a number of forces. From what we have learned in this chapter, muscles of the knee joint play a role in the stabilization and functioning of the knee. What potential effects could muscle injury, weakness, or imbalance have on the knee joint? Would this be limited to a local problem, or could there be an impact on overall global functioning? ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________

907

CHAPTER 16

908

Muscles of the Ankle and Subtalar Joints CHAPTER OUTLINE Anterior compartment: Tibialis anterior Fibularis tertius Lateral compartment: Fibularis longus Fibularis brevis Superficial posterior compartment: Gastrocnemius Soleus Plantaris Deep posterior compartment: Tibialis posterior

OBJECTIVES After completing this chapter, the student should be able to perform the following for each of the muscles covered in the chapter: 1. Explain the general structure. 2. Explain the general function 3. State the attachments. 4. State the standard mover actions. 5. State the reverse mover actions. 6. Discuss the line(s) of pull the muscle has and the motion(s) created. 7. State the eccentric antagonist functions. 8. State the isometric stabilization functions. 9. State the nervous innervation.

10. State the arterial supply. 11. Describe the starting position for palpation. 12. Describe the steps for palpation. 13. Discuss the muscle’s relationship to other body structures. 14. Discuss additional information that may help with palpation, assessment, and clinical decision-making. CHAPTER OVERVIEW The muscles addressed in this chapter are the muscles whose principal function is usually considered to be movement of the ankle (talocrural) and subtalar joints. Other muscles in the body can also move the ankle and subtalar joints, but they are placed in different chapters because their primary function is usually considered to be at other joints. These muscles are the extrinsic muscles of the toes covered in Chapter 17; they are the extensor digitorum longus, extensor hallucis longus, flexor digitorum longus, and flexor hallucis longus.

909

Overview of STRUCTURE Fascial compartments are more clearly defined in the leg than anywhere else in the body. Structurally, muscles of the ankle and subtalar joints have their bellies in the leg and are located in one of four distinct compartments. These four compartments of the leg are the anterior, lateral, superficial posterior, and deep posterior compartments and are shown in Figures 16-5 and 16-6 and described in the box below. The location by compartment helps determine the actions of these muscles. For example, all muscles of the anterior compartment do dorsiflexion; all muscles of the lateral and posterior compartments do plantarflexion (except the popliteus, which does not cross into the foot). All muscles of the lateral compartment do eversion. The final determination of exactly what the actions of a muscle of the ankle and subtalar joints will be is where the distal tendon of that muscle crosses these joints (for example, the tibialis anterior is located in the anterolateral leg, but its tendon crosses the subtalar joint medially so it inverts the foot).

Compartments of the Leg: Leg musculature is usually divided into anterior, lateral, superficial posterior, and deep posterior compartments. • The anterior compartment contains the tibialis anterior, extensor digitorum longus, extensor hallucis longus, and fibularis tertius. • The lateral compartment contains the fibularis longus and fibularis brevis. • The superficial posterior compartment contains the gastrocnemius, soleus, and plantaris. • The deep posterior compartment contains the tibialis posterior, flexor digitorum longus, flexor hallucis longus, and popliteus. Overview of FUNCTION The following general rules regarding actions can be stated for the functional groups of muscles of the ankle and subtalar joints: If a muscle crosses the ankle joint anteriorly with a vertical direction to its fibers, it can dorsiflex the foot at the ankle joint by moving the dorsum of the foot toward the anterior (dorsal) surface of the leg. If a muscle crosses the ankle joint posteriorly with a vertical direction to its fibers, it can plantarflex the foot at the ankle joint by moving the plantar surface of the foot toward the posterior (ventral) surface of the leg. If a muscle crosses the subtalar joint laterally, it can evert the foot at the subtalar joint by moving the lateral surface of the foot toward the lateral surface of the leg. Note: Eversion is the principal component of pronation. If a muscle crosses the subtalar joint medially, it can invert the foot at the subtalar joint by moving the medial surface of the foot toward the medial surface of the leg. Note: Inversion is the principal component of supination. Reverse actions occur when the foot is planted on the ground and the leg must move relative to the foot. The same terms can be used to describe these reverse actions. For example, when the anterior (dorsal) surface of the leg moves toward the dorsum of the foot, it is called dorsiflexion of the leg at the ankle joint.

http://evolve.elsevier.com/Muscolino/muscular

910

Anterior View of the Muscles of the Right Ankle and Subtalar Joints

FIGURE 16-1

Anterior view of the muscles of the right ankle and subtalar joints.

911

Posterior View of the Muscles of the Right Ankle and Subtalar Joints—Superficial View

FIGURE 16-2

Posterior views of the muscles of the right ankle and subtalar joints. A, Superficial.

912

Posterior View of the Muscles of the Right Ankle and Subtalar Joints—Intermediate View

FIGURE 16-2

B, Intermediate.

913

Posterior View of the Muscles of the Right Ankle and Subtalar Joints—Deep View

FIGURE 16-2

914

C, Deep.

Lateral View of the Muscles of the Right Ankle and Subtalar Joints

FIGURE 16-3

Lateral view of the muscles of the right ankle and subtalar joints.

915

Medial Views of the Muscles of the Right Ankle and Subtalar Joint

FIGURE 16-4

Medial views of the muscles of the right ankle and subtalar joints. A, Superficial. B, Deep.

916

Transverse Plane Cross Section of the Right Leg— Compartments

FIGURE 16-5

Transverse plane cross section (approximately ⅓ of the way distal to the knee joint), illustrating the four compartments of the leg.

917

Transverse Plane Cross Section of the Right Leg— Muscles

FIGURE 16-6

Transverse plane cross section (approximately ⅓ of the way distal to the knee joint), illustrating the muscles within the compartments of the leg.

918

Tibialis Anterior The name, tibialis anterior, tells us that this muscle attaches to the tibia and is located anteriorly. Derivation tibialis: L. refers to the tibia anterior: L. before, in front of Pronunciation tib-ee-A-lis an-TEE-ri-or

ATTACHMENTS Anterior Tibia the lateral tibial condyle, the proximal ⅔ of the anterior tibia, and the proximal ⅔ of the interosseus membrane to the Medial Foot the first cuneiform and first metatarsal

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Dorsiflexes the foot at the ankle joint 2. Inverts (supinates) the foot at the subtalar joint

Reverse Mover Actions 1. Dorsiflexes the leg at the ankle joint 2. Inverts (supinates) the talus at the subtalar joint

Standard Mover Actions Notes • The tibialis anterior crosses the ankle joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it dorsiflexes the foot at the ankle joint. (action 1) • The tibialis anterior crosses into the foot medial to the axis of motion of the subtalar joint (with its fibers running vertically in the frontal plane); therefore it inverts/supinates the foot (more specifically, it inverts/supinates the calcaneus relative to the talus) at the subtalar joint. Note: Inversion is the major component of supination of the foot; subtalar supination also includes medial rotation and plantarflexion of the foot. (action 2)

Reverse Mover Action Notes • Reverse actions at the ankle and subtalar joints usually occur when the foot is planted on the ground so that the proximal attachment moves toward the distal one. (reverse actions 1, 2) • The tibialis anterior crosses the ankle joint anteriorly (with its fibers running vertically in the sagittal plane). If the distal attachment is fixed, the tibialis anterior pulls the anterior (dorsal) surface of the leg toward the dorsum of the foot; therefore it dorsiflexes the leg at the ankle joint. This action occurs during the gait cycle when our foot is planted on the ground. (reverse action 1)

919

FIGURE 16-7

Anterior view of the right tibialis anterior.

• The reverse action of inversion of the foot at the subtalar joint is inversion of the talus/leg at the subtalar joint. Moving the leg at the subtalar joint involves moving the talus relative to the calcaneus. Inversion is the major component of supination. (reverse action 2) • Another component of supination of the talus at the subtalar joint is lateral rotation of the talus. Because the ankle and (extended) knee joints do not allow rotation, when the talus laterally rotates, the entire lower extremity follows with lateral rotation of the thigh at the hip joint. (reverse action 2)

Motion 1. The tibialis anterior has one line of pull in an oblique plane and therefore creates one motion, which is a combination of dorsiflexion and inversion of the foot.

Eccentric Antagonist Functions 1. Restrains/slows ankle joint plantarflexion 2. Restrains/slows eversion (pronation) at the subtalar joint

Eccentric Antagonist Function Note • The eccentric action of restraining/slowing eversion (pronation) of the foot at the subtalar joint is extremely important during the gait cycle (from heel-strike to foot-flat) so that the arch does not

920

entirely collapse.

Isometric Stabilization Functions 1. Stabilizes the ankle and subtalar joints

Isometric Function Note • As one of the two stirrup muscles, the tibialis anterior plays an important role in supporting and stabilizing the arches (including the subtalar joint) of the foot.

Additional Notes on Actions 1. All four muscles in the anterior compartment of the leg can dorsiflex the foot (and leg) at the ankle joint. 2. The tibialis anterior and the tibialis posterior both invert the foot (at the subtalar joint). However, because the tibialis anterior is anterior, it can also dorsiflex the foot at the ankle joint, whereas the tibialis posterior, being posterior, can plantarflex the foot at the ankle joint.

I N N E RVAT I O N The Deep Fibular Nerve L4, L5

A R T E R I A L S U P P LY The Anterior Tibial Artery (a terminal branch of the Popliteal Artery)

PA L PAT I O N 1. With the client seated or supine, have the client dorsiflex and invert the foot (resistance can be added) and look for and then palpate the distal tendon of the tibialis anterior as it crosses the ankle joint anteromedially. 2. Continue palpating the tibialis anterior proximally on the lateral side of the tibia. 3. Note: So that the extensors digitorum and hallucis longus do not contract, make sure that the client is not extending the toes.

RELATIONSHIP TO OTHER STRUCTURES The tibialis anterior is superficial in the anterolateral leg. The tibialis anterior lies just lateral to the tibia. The extensor digitorum longus is lateral to the tibialis anterior, more distally, the extensor hallucis longus is lateral to the tibialis anterior. Deep to the belly of the tibialis anterior are the extensor digitorum longus and the extensor hallucis longus. The tibialis anterior is located within the superficial front line and spiral line myofascial meridians.

MISCELLANEOUS 1. The tibialis anterior is located in the anterior compartment of the leg. 2. The tibialis anterior has a very prominent distal tendon. 3. The tibialis anterior and the fibularis longus are known as the stirrup muscles. These two muscles both attach at the same location on the medial foot (first cuneiform and first metatarsal) and may be viewed as a stirrup to support the arch (medial longitudinal arch) of the foot. The tibialis anterior is also credited with supporting the transverse arch and the lateral longitudinal arch of the foot. 4. When the tibialis anterior is tight and painful, especially along its tibial attachment, this condition is usually called shin splints or anterior shin splints. (Note: Shin splints is a general term that is applied to most any painful condition that occurs in the leg [i.e., between the knee and the ankle]. Shin splints due to a painful tibialis anterior is probably the most common form of shin splints.)

921

922

Fibularis Tertius The name, fibularis tertius, tells us that this muscle attaches to the fibula and is the third fibularis muscle. The first two fibularis muscles are the fibularis longus and fibularis brevis. Derivation fibularis: L. refers to the fibula tertius: L. third Pronunciation fib-you-LA-ris TER-she-us

ATTACHMENTS Distal Anterior Fibula the distal ⅓ of the anterior fibula and the distal ⅓ of the interosseus membrane to the Fifth Metatarsal the dorsal surface of the base of the fifth metatarsal

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Dorsiflexes the foot at the ankle joint 2. Everts (pronates) the foot at the subtalar joint

Reverse Mover Actions 1. Dorsiflexes the leg at the ankle joint 2. Everts (pronates) the talus at the subtalar joint

Standard Mover Actions Notes • The fibularis tertius crosses the ankle joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it dorsiflexes the foot at the ankle joint. (action 1) • The fibularis tertius crosses into the foot lateral to the axis of motion of the subtalar joint (with its fibers running vertically in the frontal plane); therefore it everts/pronates the foot (more specifically, it everts/pronates the calcaneus relative to the talus) at the subtalar joint. Note: Eversion is the major component of pronation of the foot; subtalar pronation also includes lateral rotation and dorsiflexion of the foot. (action 2)

Reverse Mover Action Notes • Reverse actions at the ankle and subtalar joints usually occur when the foot is planted on the ground so that the proximal attachment moves toward the distal one. (reverse actions 1, 2) • The fibularis tertius crosses the ankle joint anteriorly (with its fibers running vertically in the sagittal plane). If the distal attachment is fixed, the fibularis tertius pulls the anterior (dorsal) surface of the leg toward the dorsum of the foot; therefore it dorsiflexes the leg at the ankle joint. This action occurs during the gait cycle when our foot is planted on the ground. (reverse action 1)

923

FIGURE 16-8

Anterior view of the right fibularis tertius. The extensor digitorum longus has been ghosted in.

• The reverse action of eversion of the foot at the subtalar joint is eversion of the talus/leg at the subtalar joint. Moving the leg at the subtalar joint involves moving the talus relative to the calcaneus. Eversion is the major component of pronation. (reverse action 2) • Another component of pronation of the talus at the subtalar joint is medial rotation of the talus. Because the ankle and (extended) knee joints do not allow rotation, when the talus medially rotates, the entire lower extremity follows with medial rotation of the thigh at the hip joint. (reverse action 2)

Motion 1. The fibularis tertius has one line of pull in an oblique plane and therefore creates one motion, which is a combination of dorsiflexion and eversion of the foot.

Eccentric Antagonist Functions 1. Restrains/slows ankle joint plantarflexion 2. Restrains/slows inversion (supination) at the subtalar joint

Eccentric Antagonist Function Note • The eccentric action of restraining/slowing plantarflexion of the foot is important during the gait cycle (from heel-strike to foot-flat).

924

Isometric Stabilization Functions 1. Stabilizes the ankle and subtalar joints

Additional Notes on Actions 1. All four muscles in the anterior compartment of the leg can dorsiflex the foot (and leg) at the ankle joint. 2. The three fibularis muscles are grouped together, because they all evert the subtalar joint.

I N N E RVAT I O N The Deep Fibular Nerve L5, S1

A R T E R I A L S U P P LY The Anterior Tibial Artery (a terminal branch of the Popliteal Artery)

PA L PAT I O N 1. With the client seated or supine, first locate the tendon of the extensor digitorum longus that goes to the little (fifth) toe. If not visible, it can usually be palpated by strumming perpendicular across it as the client extends the little toe. 2. Once located, look and palpate immediately lateral to it for the tendon of the fibularis tertius running approximately parallel and going to the base of the fifth metatarsal as the client everts and dorsiflexes the foot (resistance can be added). 3. Note: The fibularis tertius is sometimes missing.

RELATIONSHIP TO OTHER STRUCTURES The fibularis tertius is actually part of the extensor digitorum longus. It comprises the most distal part of the belly of the extensor digitorum longus, which becomes the most lateral tendon (and attaches to the fifth metatarsal). The distal tendon of the fibularis tertius is located just lateral to the tendon of the extensor digitorum longus that goes to the little toe. Deep to the fibularis tertius is the fibula. The fibularis tertius is located within the superficial front line myofascial meridian.

MISCELLANEOUS 1. The fibularis tertius is located in the anterior compartment of the leg. 2. The fibularis tertius was formerly named the peroneus tertius. 3. The fibularis tertius is actually the most distal and lateral part of the extensor digitorum longus. Its fibers do not attach onto a digit (a phalanx); for this reason, the fibularis tertius is given a separate name and considered to be a separate muscle from the extensor digitorum longus. 4. The fibularis tertius is homologous to the extensor digiti minimi of the forearm/hand. 5. The fibularis tertius is sometimes missing. 6. The fibularis tertius is pennate.

925

Fibularis Longus The name, fibularis longus, tells us that this muscle attaches to the fibula and is long (longer than the fibularis brevis). Derivation fibularis: L. refers to the fibula longus: L. longer Pronunciation fib-you-LA-ris LONG-us

ATTACHMENTS Proximal Lateral Fibula the head of the fibula and the proximal ½ of the lateral fibula to the Medial Foot the first cuneiform and first metatarsal

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Everts (pronates) the foot at the subtalar joint 2. Plantarflexes the foot at the ankle joint

Reverse Mover Actions 1. Everts (pronates) the talus at the subtalar joint 2. Plantarflexes the leg at the ankle joint

Standard Mover Actions Notes • The fibularis longus crosses onto the foot laterally (with its fibers running vertically in the frontal plane); therefore it everts/pronates the foot (more specifically, it everts/pronates the calcaneus relative to the talus) at the subtalar joint. Note: Eversion is the major component of subtalar pronation; subtalar pronation also includes lateral rotation and dorsiflexion of the foot. (action 1) • The fibularis longus crosses the ankle joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it plantarflexes the foot at the ankle joint. (action 2)

Reverse Mover Action Notes • Reverse actions at the ankle and subtalar joints usually occur when the foot is planted on the ground so that the proximal attachment moves toward the distal one. (reverse actions 1, 2) • The reverse action of eversion of the foot at the subtalar joint is eversion of the talus/leg at the subtalar joint. Moving the leg at the subtalar joint involves moving the talus relative to the calcaneus. Eversion is the major component of pronation. (reverse action 1) • Another component of pronation of the talus at the subtalar joint is medial rotation of the talus. Because the ankle and (extended) knee joints do not allow rotation, when the talus medially rotates, the entire lower extremity follows with medial rotation of the thigh at the hip joint. (reverse action 1)

926

FIGURE 16-9

Lateral view of the right fibularis longus.

• The fibularis longus crosses the ankle joint posteriorly (with its fibers running vertically in the sagittal plane). If the distal attachment is fixed, the fibularis longus pulls the posterior surface of the leg toward the plantar surface of the foot; therefore it plantarflexes the leg at the ankle joint. (reverse action 2)

Motion 1. The fibularis longus has one line of pull in an oblique plane and therefore creates one motion, which is a combination of eversion and plantarflexion of the foot.

Eccentric Antagonist Functions 1. Restrains/slows inversion (supination) at the subtalar joint 2. Restrains/slows ankle joint dorsiflexion

Isometric Stabilization Functions 1. Stabilizes the ankle and subtalar joints

Isometric Function Notes • The action of eversion is important in preventing inversion sprains of the ankle; therefore to help stabilize the ankle joint, it is important to strengthen the fibularis longus in clients who have a

927

history of inversion sprains. • As one of the two stirrup muscles, the fibularis longus plays an important role in supporting and stabilizing the arches (and the subtalar joint) of the foot.

Additional Notes on Actions 1. Both muscles in the lateral compartment of the leg (fibularis longus and brevis) can evert (pronate) the foot (and leg) at the subtalar joint. 2. The three fibularis muscles are grouped together because they all evert the subtalar joint.

I N N E RVAT I O N The Superficial Fibular Nerve L5, S1

A R T E R I A L S U P P LY The Fibular Artery (a branch of the Posterior Tibial Artery)

PA L PAT I O N 1. With the client prone, supine, or side lying, place palpating hand on the proximal lateral leg just distal to the head of the fibula. 2. Ask the client to actively evert the foot and feel for the contraction of the belly of the fibularis longus from the head of the fibula to the point where it becomes tendon halfway down the leg. 3. Continue palpating the distal tendon to the posterior side of the lateral malleolus of the fibula. 4. Distal to the lateral malleolus, the tendon of the fibularis longus is challenging to palpate as it runs toward the cuboid. In the plantar foot, the distal tendon is usually not palpable. 5. Note: The distal tendon of the fibularis brevis is usually prominent distal to the lateral malleolus as it runs to the base of the fifth metatarsal. Do not mistake the fibularis brevis tendon for the fibularis longus tendon.

RELATIONSHIP TO OTHER STRUCTURES Proximally, the fibularis longus is posterior (lateral) to the tibialis anterior and the extensor digitorum longus. Proximally, the fibularis longus is superficial to the extensor digitorum longus. Distally, the fibularis longus is superficial to the fibularis brevis. The fibularis longus is anterior to the soleus. The distal tendon of the fibularis longus is very deep and found in the fourth layer of muscles of the plantar surface of the foot. The fibularis longus is located within the lateral line and spiral line myofascial meridians.

MISCELLANEOUS 1. The fibularis longus is located in the lateral compartment of the leg. 2. The fibularis longus becomes tendon halfway down the leg. 3. The distal tendon of the fibularis longus follows an unusual path; it crosses posterior to the lateral malleolus to enter the lateral side of the foot, where it crosses posterior to the cuboid and then dives deep into the plantar side of the foot. It finally attaches onto the medial side of the foot at the same location as the attachment of the tibialis anterior (first cuneiform and first metatarsal). 4. The three fibularis muscles are grouped together, because they all evert the foot at the subtalar joint. 5. The fibularis longus and the fibularis brevis both cross posterior to the lateral malleolus; therefore they both plantarflex the foot at the ankle joint. The fibularis tertius crosses anterior to the lateral malleolus; therefore it dorsiflexes the foot at the ankle joint. 6. The fibularis longus has a tendon that makes an abrupt turn of approximately 90 degrees. 7. The fibularis longus was formerly named the peroneus longus. 8. The fibularis longus and the tibialis anterior are known as the stirrup muscles. These two muscles both attach at the same location on the medial foot (first cuneiform and first metatarsal) and may be

928

viewed to act as a stirrup to support the arch (medial longitudinal arch) of the foot. The fibularis longus is also credited with supporting the transverse arch and the lateral longitudinal arch of the foot. 9. The fibularis longus and the fibularis brevis should be strengthened in people who have had inversion sprains of the ankle joint.

929

Fibularis Brevis The name, fibularis brevis, tells us that this muscle attaches onto the fibula and is short (shorter than the fibularis longus). Derivation fibularis: L. refers to the fibula brevis: L. shorter Pronunciation fib-you-LA-ris BRE-vis

ATTACHMENTS Distal Lateral Fibula the distal ½ of the lateral fibula to the Fifth Metatarsal the lateral side of the base of the fifth metatarsal

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Everts (pronates) the foot at the subtalar joint 2. Plantarflexes the foot at the ankle joint

Reverse Mover Actions 1. Everts (pronates) the talus at the subtalar joint 2. Plantarflexes the leg at the ankle joint

Standard Mover Actions Notes • The fibularis brevis crosses onto the foot laterally (with its fibers running vertically in the frontal plane); therefore it everts/pronates the foot (more specifically, it everts/pronates the calcaneus relative to the talus) at the subtalar joint. Note: Eversion is the major component of subtalar pronation; subtalar pronation also includes lateral rotation and dorsiflexion of the foot. (action 1) • The fibularis brevis crosses the ankle joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it plantarflexes the foot at the ankle joint. (action 2)

Reverse Mover Action Notes • Reverse actions at the ankle and subtalar joints usually occur when the foot is planted on the ground so that the proximal attachment moves toward the distal one. (reverse actions 1, 2) • The reverse action of eversion of the foot at the subtalar joint is eversion of the talus/leg at the subtalar joint. Moving the leg at the subtalar joint involves moving the talus relative to the calcaneus. Eversion is the major component of pronation. (reverse action 1) • Another component of pronation of the talus at the subtalar joint is medial rotation of the talus. Because the ankle and (extended) knee joints do not allow rotation, when the talus medially rotates, the entire lower extremity follows with medial rotation of the thigh at the hip joint. (reverse action 1)

930

FIGURE 16-10

Lateral view of the right fibularis brevis.

• The fibularis brevis crosses the ankle joint posteriorly (with its fibers running vertically in the sagittal plane). If the distal attachment is fixed, the fibularis brevis pulls the posterior surface of the leg toward the plantar surface of the foot; therefore it plantarflexes the leg at the ankle joint. (reverse action 2)

Motion 1. The fibularis brevis has one line of pull in an oblique plane and therefore creates one motion, which is a combination of eversion and plantarflexion of the foot.

Eccentric Antagonist Functions 1. Restrains/slows inversion (supination) at the subtalar joint 2. Restrains/slows ankle joint dorsiflexion

Isometric Stabilization Functions 1. Stabilizes the ankle and subtalar joints

Isometric Function Note • The action of eversion is important in preventing inversion sprains of the ankle; therefore to help stabilize the ankle joint, it is important to strengthen the fibularis brevis in clients who have a

931

history of inversion sprains.

Additional Notes on Actions 1. Both muscles in the lateral compartment of the leg (fibularis longus and brevis) can evert (pronate) the foot (and leg) at the subtalar joint. 2. The three fibularis muscles are grouped together because they all evert the subtalar joint.

I N N E RVAT I O N The Superficial Fibular Nerve L5, S1

A R T E R I A L S U P P LY The Fibular Artery (a branch of the Posterior Tibial Artery)

PA L PAT I O N 1. With the client prone, supine, or side lying, place palpating hand on the distal lateral leg. 2. Have the client evert the foot (resistance can be added) and feel for the belly of the fibularis brevis on either side (especially the posterior side) of the fibularis longus’ distal tendon. Keep in mind that this will make both the fibularis longus and the fibularis brevis stand out. 3. Distal to the lateral malleolus, the distal tendon of the fibularis brevis is easily palpable and usually visible all the way to its attachment onto the base of the fifth metatarsal.

RELATIONSHIP TO OTHER STRUCTURES The fibularis brevis is deep to the fibularis longus, but it is not entirely covered by the fibularis longus. The fibularis brevis is posterior to the extensor digitorum longus. The fibularis brevis is anterior to the soleus. Deep to the fibularis brevis is the fibula. The fibularis brevis is located within the lateral line myofascial meridian.

MISCELLANEOUS 1. The fibularis brevis is located in the lateral compartment of the leg. 2. The distal tendon of the fibularis brevis travels with the distal tendon of the fibularis longus. Together they both cross posterior to the lateral malleolus. Therefore they both plantarflex the foot at the ankle joint. 3. The fibularis brevis was formerly named the peroneus brevis.

932

Gastrocnemius (Gastrocs) (of Triceps Surae Group) The name, gastrocnemius, tells us that this muscle gives the posterior leg its belly shape. (The contour of the posterior leg is the result of the two bellies of the gastrocnemius.) Derivation gastro: Gr. stomach nemius: Gr. leg Pronunciation GAS-trok-NEE-me-us

ATTACHMENTS Medial and Lateral Femoral Condyles and the distal posteromedial femur and the distal posterolateral femur to the Calcaneus via the Calcaneal (Achilles) Tendon the posterior surface

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Plantarflexes the foot at the ankle joint 2. Flexes the leg at the knee joint 3. Inverts (supinates) the foot at the subtalar joint

Reverse Mover Actions 1. Plantarflexes the leg at the ankle joint 2. Flexes the thigh at the knee joint 2. Inverts (supinates) the talus at the subtalar joint

Standard Mover Actions Notes • The gastrocnemius crosses the ankle joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it plantarflexes the foot at the ankle joint. Plantarflexion of the foot at the ankle joint is an important action during the gait cycle when pushing off the ground (toe-off phase). (action 1) • The gastrocnemius crosses the knee joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the leg at the knee joint. (action 2) • The gastrocnemius crosses into the foot to attach onto the calcaneus medial to the axis of the subtalar joint. Therefore the gastrocnemius inverts/supinates the foot (more specifically, it inverts/supinates the calcaneus relative to the talus) at the subtalar joint. Note: Inversion is the major component of subtalar supination; subtalar supination also includes medial rotation and plantarflexion of the foot. (action 3)

Reverse Mover Action Notes • Reverse actions at the ankle and subtalar joints usually occur when the foot is planted on the ground so that the proximal attachment moves toward the distal one. (reverse actions 1, 2, 3)

933

FIGURE 16-11

Posterior view of the right gastrocnemius.

• The gastrocnemius crosses the ankle joint posteriorly (with its fibers running vertically in the sagittal plane). If the distal attachment is fixed, the gastrocnemius pulls the posterior surface of the leg toward the plantar surface of the foot; therefore it plantarflexes the foot at the ankle joint. (reverse action 1) • The gastrocnemius crosses the knee joint posteriorly (with its fibers running vertically in the sagittal plane). If the distal attachment is fixed, the gastrocnemius pulls the posterior surface of the thigh toward the posterior surface of the leg; therefore it flexes the thigh at the knee joint. (reverse action 2) • The reverse action of inversion of the foot at the subtalar joint is inversion of the talus/leg at the subtalar joint. Moving the leg at the subtalar joint involves moving the talus relative to the calcaneus. Inversion is the major component of supination. (reverse action 3) • Another component of supination of the talus at the subtalar joint is lateral rotation of the talus. Because the ankle and (extended) knee joints do not allow rotation, when the talus laterally rotates, the entire lower extremity follows with lateral rotation of the thigh at the hip joint. (reverse action 3)

Motion 1. The gastrocnemius has one line of pull in an oblique plane and therefore creates one motion,

934

which is a combination of plantarflexion and inversion of the foot, and flexion of the knee joint.

Eccentric Antagonist Functions 1. Restrains/slows ankle joint dorsiflexion 2. Restrains/slows knee joint extension 3. Restrains/slows eversion (pronation) at the subtalar joint

Eccentric Antagonist Function Note • Restraining/slowing dorsiflexion of the leg at the ankle joint is important when standing and bending forward (at the ankle, knee, and hip joints).

Isometric Stabilization Functions 1. Stabilizes the ankle, subtalar, and knee joints

Additional Notes on Actions 1. Even though plantarflexion of the foot at the ankle joint is a very important action during walking, there is very little gastrocnemius activity in walking. The gastrocnemius is not appreciably recruited unless one walks uphill or up stairs, on an unstable surface (such as sand), runs, jumps, or tiptoes. 2. All three muscles in the superficial posterior compartment of the leg (gastrocnemius, soleus, and plantaris) can plantarflex the foot (and leg) at the ankle joint.

I N N E RVAT I O N The Tibial Nerve S1, S2

A R T E R I A L S U P P LY Sural branches of the Popliteal Artery (the continuation of the Femoral Artery)

PA L PAT I O N 1. With the client prone with the leg extended at the knee joint, place palpating hand on the proximal posterior leg. 2. Have the client plantarflex the foot at the ankle joint (resistance can be given) and feel for the contraction of the gastrocnemius. It can be palpated from its proximal attachments to its distal attachment on the calcaneus via the calcaneal (Achilles) tendon.

RELATIONSHIP TO OTHER STRUCTURES The gastrocnemius is superficial in the posterior leg. The soleus is deep to the gastrocnemius and is largely, but not entirely, covered by it. The distal belly and tendon of the biceps femoris is superficial to the proximal attachment of the lateral gastrocnemius. The gastrocnemius is located within the superficial back line myofascial meridian.

MISCELLANEOUS 1. The gastrocnemius is located in the superficial posterior compartment of the leg. 2. The gastrocnemius and the soleus together are sometimes called the triceps surae. Triceps refers to having three heads (medial gastrocnemius, lateral gastrocnemius, and soleus) and surae (SUR-eye) refers to the calf of the leg. They are grouped together as the triceps surae because they all attach to the calcaneus via the calcaneal (Achilles) tendon. 3. Given that the distal tendon of the plantaris is directly next to (and often melds with) the calcaneal (Achilles) tendon, the plantaris is often grouped with the gastrocnemius and the soleus. This group is sometimes called the quadriceps surae. 4. The Achilles tendon derives its name from the Greek myth in which Achilles went into battle to

935

rescue Helen of Troy. When he was young, to make him invulnerable to poison arrows, his mother dipped him into the River Styx. However, she held him by his posterior ankle (i.e., heel). Therefore he was vulnerable in that one spot; hence the expression Achilles’ heel, denoting a person’s weakness. Unfortunately, Paris hit him with a poison arrow in his heel and he died. The relevance to anatomy is that the muscles of the triceps surae are the prime movers of foot plantarflexion, which is needed to push the foot off the ground when walking or running. If the Achilles tendon ruptures, one loses the ability to walk and/or run, which makes one vulnerable and weak. 5. The gastrocnemius becomes tendon approximately halfway down the leg. 6. Excessive use of high-heeled shoes can result in chronic shortened triceps surae muscles. 7. The fact that the gastrocnemius crosses the knee joint and the soleus does not cross the knee joint gives us the ability to preferentially stretch one of these muscles without stretching the other. For either muscle, stretching is accomplished by doing dorsiflexion at the ankle joint, because these muscles are plantarflexors. The key to stretching the gastrocnemius alone is to keep the knee joint straight (i.e., in extension) so that it is stretched across both the knee and ankle joints. Note: This stretch is usually called the runner’s stretch and is done leaning up against a wall. For the gastrocnemius, the heel must be kept down on the ground and the knee joint must be in extension.

936

Soleus (of Triceps Surae Group) The name, soleus, tells us that this muscle attaches onto the sole (calcaneus) of the foot. Derivation soleus: L. sole of the foot Pronunciation SO-lee-us

ATTACHMENTS Posterior Tibia and Fibula the soleal line of the tibia and the head and proximal ⅓ of the fibula to the Calcaneus via the Calcaneal (Achilles) Tendon the posterior surface

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Plantarflexes the foot at the ankle joint 2. Inverts (supinates) the foot at the subtalar joint

Reverse Mover Actions 1. Plantarflexes the leg at the ankle joint 2. Inverts (supinates) the talus at the subtalar joint

Standard Mover Actions Notes • The soleus crosses the ankle joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it plantarflexes the foot at the ankle joint. Plantarflexion of the foot at the ankle joint is an important action during the gait cycle when pushing off the ground (toe-off phase). (action 1) • The soleus crosses into the foot to attach onto the calcaneus medial to the axis of the subtalar joint. Therefore the soleus inverts/supinates the foot (more specifically, it inverts/supinates the calcaneus relative to the talus) at the subtalar joint. Note: Inversion is the major component of subtalar supination; subtalar supination also includes medial rotation and plantarflexion of the foot. (action 2)

Reverse Mover Action Notes • Reverse actions at the ankle and subtalar joints usually occur when the foot is planted on the ground so that the proximal attachment moves toward the distal one. (reverse actions 1, 2) • The soleus crosses the ankle joint posteriorly (with its fibers running vertically in the sagittal plane). If the distal attachment is fixed, the soleus pulls the posterior surface of the leg toward the plantar surface of the foot; therefore it plantarflexes the leg at the ankle joint. (reverse action 1) • The reverse action of inversion of the foot at the subtalar joint is inversion of the talus/leg at the subtalar joint. Moving the leg at the subtalar joint involves moving the talus relative to the calcaneus. Inversion is the major component of supination. (reverse action 2)

937

FIGURE 16-12

Posterior view of the right soleus.

• Another component of supination of the talus at the subtalar joint is lateral rotation of the talus. Because the ankle and (extended) knee joints do not allow rotation, when the talus laterally rotates, the entire lower extremity follows with lateral rotation of the thigh at the hip joint. (reverse action 2)

Motion 1. The soleus has one line of pull in an oblique plane and therefore creates one motion, which is a combination of plantarflexion and inversion of the foot.

Eccentric Antagonist Functions 1. Restrains/slows ankle joint dorsiflexion 2. Restrains/slows eversion (pronation) at the subtalar joint

Eccentric Antagonist Function Note • Restraining/slowing dorsiflexion of the leg at the ankle joint is important when standing and bending forward (bending at the ankle, knee, and hip joints).

938

Isometric Stabilization Functions 1. Stabilizes the ankle and subtalar joints

Additional Note on Actions 1. All three muscles in the superficial posterior compartment of the leg (gastrocnemius, soleus, and plantaris) can plantarflex the foot (and leg) at the ankle joint.

I N N E RVAT I O N The Tibial Nerve S1, S2

A R T E R I A L S U P P LY Sural branches of the Popliteal Artery (the continuation of the Femoral Artery)

PA L PAT I O N 1. With the client prone with the leg flexed to 90 degrees at the knee joint, place palpating hand on the proximal posterior leg. 2. Have the client plantarflex the foot at the ankle joint against mild resistance and feel for the contraction of the soleus through the gastrocnemius. 3. The soleus is superficial and can be palpated on either side of the belly of the gastrocnemius, especially on the lateral side of the leg.

RELATIONSHIP TO OTHER STRUCTURES Posteriorly, the soleus is deep to the gastrocnemius and the plantaris, but medially and laterally the soleus is superficial. Medially, the soleus is located between the gastrocnemius and the tibia. Laterally, the soleus is located between the gastrocnemius and the fibularis longus. The soleus is superficial to the three deep muscles of the posterior leg: the tibialis posterior, the flexor digitorum longus, and the flexor hallucis longus (the Tom, Dick, and Harry muscles). The soleus is located within the superficial back line myofascial meridian.

MISCELLANEOUS 1. The soleus is located in the superficial posterior compartment of the leg. 2. The soleus and the gastrocnemius together are sometimes called the triceps surae. Triceps refers to having three heads (the medial gastrocnemius, the lateral gastrocnemius, and the soleus) and surae (SUR-eye) refers to the calf of the leg. They are grouped together as the triceps surae, because they all attach to the calcaneus via the calcaneal (Achilles) tendon. 3. Given that the distal tendon of the plantaris is directly next to (and often melds with) the calcaneal (Achilles) tendon, the plantaris is often grouped with the gastrocnemius and the soleus. This group is sometimes called the quadriceps surae. 4. The Achilles tendon derives its name from the Greek myth in which Achilles went into battle to rescue Helen of Troy. When he was young, to make him invulnerable to poison arrows, his mother dipped him into the River Styx. However, she held him by his posterior ankle (i.e., heel). Therefore he was vulnerable in that one spot, hence, the expression Achilles’ heel denoting a person’s weakness. Unfortunately, Paris hit him with a poison arrow in his heel and he died. The relevance to anatomy is that the triceps surae are the prime movers of foot plantarflexion, which is needed to push the foot off the ground when walking or running. If the Achilles tendon ruptures, one loses the ability to walk and/or run, which makes one vulnerable and weak. 5. The soleus becomes tendon much farther distally in the leg than the gastrocnemius. 6. The soleus is a thick muscle, largely accounting for the contours of the gastrocnemius being so visible. (“Behind every great gastrocnemius is a great soleus.” J) 7. Excessive use of high-heeled shoes can result in chronic shortened triceps surae muscles. 8. The fact that the soleus does not cross the knee joint and that the gastrocnemius does cross the knee joint gives us the ability to preferentially stretch one of these muscles without stretching the

939

other. For either muscle, stretching is accomplished by doing dorsiflexion at the ankle joint, because these muscles are plantarflexors. The key to stretching the soleus alone is to have the knee joint partially flexed so that the gastrocnemius is slackened across the knee joint. Note: This stretch is usually called the runner’s stretch and is done leaning up against a wall. For the soleus, the heel must be kept down on the ground and the knee joint must be partially flexed.

940

Plantaris The name, plantaris, tells us that this muscle attaches onto the calcaneus, a bone of the plantar surface of the foot. Derivation plantaris: L. refers to the plantar side of the foot Pronunciation plan-TA-ris

ATTACHMENTS Distal Posterolateral Femur the lateral condyle and the distal lateral supracondylar line of the femur to the Calcaneus the posterior surface

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Plantarflexes the foot at the ankle joint 2. Flexes the leg at the knee joint 3. Inverts (supinates) the foot at the subtalar joint

Reverse Mover Actions 1. Plantarflexes the leg at the ankle joint 2. Flexes the thigh at the knee joint 3. Inverts (supinates) the talus at the subtalar joint

Standard Mover Actions Notes • The plantaris crosses the ankle joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it plantarflexes the foot at the ankle joint. Plantarflexion of the foot at the ankle joint is an important action during the gait cycle when pushing off the ground (toe-off phase). (action 1) • The plantaris crosses the knee joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it flexes the leg at the knee joint. (action 2) • The plantaris crosses into the foot to attach onto the calcaneus medial to the axis of the subtalar joint. Therefore the plantaris inverts/supinates the foot (more specifically, it inverts/supinates the calcaneus relative to the talus) at the subtalar joint. Note: Inversion is the major component of subtalar supination; subtalar supination also includes medial rotation and plantarflexion of the foot. (action 3)

Reverse Mover Action Notes • Reverse actions at the ankle and subtalar joints usually occur when the foot is planted on the ground so that the proximal attachment moves toward the distal one. (reverse actions 1, 2, 3) • The plantaris crosses the ankle joint posteriorly (with its fibers running vertically in the sagittal plane). If the distal attachment is fixed, the plantaris pulls the posterior surface of the leg toward the plantar surface of the foot; therefore it plantarflexes the leg at the ankle joint. (reverse action 1)

941

FIGURE 16-13

Posterior view of the right plantaris. The popliteus has been ghosted in.

• The plantaris crosses the knee joint posteriorly (with its fibers running vertically in the sagittal plane). If the distal attachment is fixed, the plantaris pulls the posterior surface of the thigh toward the posterior surface of the leg; therefore it flexes the thigh at the knee joint. (reverse action 2) • The reverse action of inversion of the foot at the subtalar joint is inversion of the talus/leg at the subtalar joint. Moving the leg at the subtalar joint involves moving the talus relative to the calcaneus. Inversion is the major component of supination. (reverse action 3) • Another component of supination of the talus at the subtalar joint is lateral rotation of the talus. Because the ankle and (extended) knee joints do not allow rotation, when the talus laterally rotates, the entire lower extremity follows with lateral rotation of the thigh at the hip joint. (reverse action 3)

Motion 1. The plantaris has one line of pull in an oblique plane and therefore creates one motion, which is a combination of plantarflexion and inversion of the foot, and flexion of the knee joint.

Eccentric Antagonist Functions 1. Restrains/slows ankle joint dorsiflexion

942

2. Restrains/slows knee joint extension 3. Restrains/slows eversion (pronation) at the subtalar joint

Isometric Stabilization Functions 1. Stabilizes the ankle, subtalar, and knee joints

Additional Notes on Actions 1. All three muscles in the superficial posterior compartment of the leg (gastrocnemius, soleus, and plantaris) can plantarflex the foot (and leg) at the ankle joint. 2. The plantaris muscle is so weak that many sources consider its function to be negligible.

I N N E RVAT I O N The Tibial Nerve S1, S2

A R T E R I A L S U P P LY Sural branches of the Popliteal Artery (the continuation of the Femoral Artery)

PA L PAT I O N 1. With the client prone with the leg extended at the knee joint, place palpating fingers on the proximal posterior leg, at the lateral border of the popliteal fossa (just medial to the proximal attachment of the lateral head of the gastrocnemius). 2. Ask the client to actively flex the leg at the knee joint and plantarflex the foot at the ankle joint and feel for the contraction of the belly of the plantaris. (Distinguishing the plantaris from the lateral head of the gastrocnemius will be difficult given that the gastrocnemius will also contract with these two actions.) 3. The long distal tendon of the plantaris is extremely difficult to palpate and discern.

RELATIONSHIP TO OTHER STRUCTURES The plantaris attaches proximally just medial to the lateral head of the gastrocnemius and the distal tendon of the biceps femoris. Much of the belly of the plantaris is superficial in the posterior knee just medial to the lateral head of the gastrocnemius. Here the plantaris is superficial to the popliteus. The rest of the belly and the proximal ½ of the long distal tendon of the plantaris are sandwiched between the gastrocnemius and the soleus. (The tendon is deep to the gastrocnemius and superficial to the soleus.) The distal ½ of the long distal tendon is superficial just medial to the medial margin of the distal tendon of the gastrocnemius. The plantaris is located within the superficial back line myofascial meridian.

MISCELLANEOUS 1. The plantaris is located in the superficial posterior compartment of the leg. 2. After crossing the knee joint, the plantaris becomes a very long, thin tendon that runs the entire length of the leg and attaches to the calcaneus. 3. The distal tendon of the plantaris often joins with the calcaneal (Achilles) tendon of the gastrocnemius and soleus. 4. Given that the distal tendon of the plantaris is directly next to (and often melds with) the calcaneal (Achilles) tendon, the plantaris is often grouped with the gastrocnemius and the soleus. This group is sometimes called the quadriceps surae. 5. The plantaris of the leg is considered to be homologous to the palmaris longus of the forearm. 6. The name plantaris is misleading, because this muscle does not attach onto the plantar surface of the foot in humans (although it does attach onto the posterior calcaneus, which is near the plantar surface). In other primates, the plantaris curves around the calcaneus to attach into the plantar fascia, thereby actually attaching onto the plantar surface of the foot.

943

944

Tibialis Posterior (Tom of Tom, Dick, and Harry Group) The name, tibialis posterior, tells us that this muscle attaches to the tibia and is located in the posterior leg. Derivation tibialis: L. refers to the tibia posterior: L. behind, toward the back Pronunciation tib-ee-A-lis pos-TEE-ri-or

ATTACHMENTS Posterior Tibia and Fibula the proximal ⅔ of the posterior tibia, fibula, and interosseus membrane to the Navicular Tuberosity and metatarsals two through four and all the tarsal bones except the talus

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Plantarflexes the foot at the ankle joint 2. Inverts (supinates) the foot at the subtalar joint

Reverse Mover Actions 1. Plantarflexes the leg at the ankle joint 2. Inverts (supinates) the talus at the subtalar joint

Standard Mover Actions Notes • The tibialis posterior crosses the ankle joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it plantarflexes the foot at the ankle joint. Plantarflexion of the foot at the ankle joint is an important action during the gait cycle when pushing off the ground (toe-off phase). (action 1) • The tibialis posterior crosses onto the foot on the medial side (with its fibers running vertically in the frontal plane); therefore it inverts/supinates the foot (more specifically, it inverts/supinates the calcaneus relative to the talus) at the subtalar joint. Note: Inversion is the major component of subtalar supination; subtalar supination also includes medial rotation and plantarflexion of the foot. (action 2)

Reverse Mover Action Notes • Reverse actions at the ankle and subtalar joints usually occur when the foot is planted on the ground so that the proximal attachment moves toward the distal one. (reverse actions 1, 2) • The tibialis posterior crosses the ankle joint posteriorly (with its fibers running vertically in the sagittal plane). If the distal attachment is fixed, the tibialis posterior pulls the posterior surface of the leg toward the plantar surface of the foot; therefore it plantarflexes the leg at the ankle joint. (reverse action 1)

945

FIGURE 16-14

Posterior view of the right tibialis posterior.

• The reverse action of inversion of the foot at the subtalar joint is inversion of the talus/leg at the subtalar joint. Moving the leg at the subtalar joint involves moving the talus relative to the calcaneus. Inversion is the major component of supination. (reverse action 2) • Another component of supination of the talus at the subtalar joint is lateral rotation of the talus. Because the ankle and (extended) knee joints do not allow rotation, when the talus laterally rotates, the entire lower extremity follows with lateral rotation of the thigh at the hip joint. (reverse action 2)

Motion 1. The tibialis posterior has one line of pull in an oblique plane and therefore creates one motion, which is a combination of plantarflexion and inversion of the foot.

Eccentric Antagonist Functions 1. Restrains/slows ankle joint dorsiflexion 2. Restrains/slows eversion (pronation) at the subtalar joint

Eccentric Antagonist Function Note

946

• Restraining/slowing dorsiflexion of the leg at the ankle joint is important when standing and bending forward (bending at the ankle, knee, and hip joints).

Isometric Stabilization Functions 1. Stabilizes the ankle and subtalar joints

Isometric Function Note • The tibialis posterior plays an important role in supporting and stabilizing the arches (and the subtalar joint) of the foot.

Additional Note on Actions 1. Because the tendons of the Tom, Dick, and Harry group cross into the foot posterior to the medial malleolus, their line of pull is posteromedial. Therefore all three Tom, Dick, and Harry muscles plantarflex and invert the foot (at the ankle and subtalar joints, respectively).

I N N E RVAT I O N The Tibial Nerve L4, L5

A R T E R I A L S U P P LY The Posterior Tibial Artery (a terminal branch of the Popliteal Artery)

PA L PAT I O N 1. With the client seated or supine, have the client plantarflex and invert the foot (resistance can be given) and look and palpate for the distal tendon of tibialis posterior immediately posterior to the medial malleolus of the tibia. 2. Once located, continue palpating the tibialis posterior distally to the navicular tuberosity and proximally into the posterior leg. 3. Note: Asking the client to extend all five toes will help eliminate contraction of the flexor digitorum longus and the flexor hallucis longus.

RELATIONSHIP TO OTHER STRUCTURES The tibialis posterior, flexor digitorum longus, and flexor hallucis longus are the deepest muscles in the posterior leg. Where these muscles overlap, the tibialis posterior is the deepest of the three. The tibialis posterior is deep to the soleus. Deep to the tibialis posterior are the tibia, the fibula, and the interosseus membrane. Lateral to the belly of the tibialis posterior is the flexor hallucis longus, and medial to the belly of the tibialis posterior is the flexor digitorum longus. The distal tendon of the tibialis posterior crosses posterior to the medial malleolus along with the distal tendons of the flexor digitorum longus and the flexor hallucis longus. Of the three, the tendon of the tibialis posterior is the closest to the medial malleolus. Beyond the navicular tuberosity, the distal tendon of the tibialis posterior is very deep and found in the fourth layer of muscles of the plantar surface of the foot. The tibialis posterior is located within the deep front line myofascial meridian.

MISCELLANEOUS 1. The tibialis posterior is located in the deep posterior compartment of the leg. 2. The Tibialis posterior is Tom of the Tom, Dick, and Harry muscles. The Tom, Dick, and Harry muscles are the tibialis posterior, flexor digitorum longus, and flexor hallucis longus. Tom, Dick, and Harry are grouped together, because they are all deep in the posterior leg and their distal tendons cross posterior to the medial malleolus of the tibia (in order from anterior to posterior, Tom, Dick, and Harry). 3. It is worth noting that the location of the muscle bellies of the Tom, Dick, and Harry muscles in

947

the posterior leg is, from medial to lateral, Dick, Tom, and Harry (i.e., flexor digitorum longus, tibialis posterior, and flexor hallucis longus). 4. The tibialis posterior has a tendon that makes an abrupt turn of approximately 90 degrees. 5. In the ankle region, the distal tendon of the tibialis posterior travels through the tarsal tunnel along with the distal tendon of the flexor digitorum longus. 6. Because the tibialis posterior helps support the arch (medial longitudinal arch) of the foot, some sources consider it to be the medial stirrup muscle, instead of the tibialis anterior. 7. When the tibialis posterior is tight and painful, this condition is often called shin splints or posterior shin splints. 8. The tibialis posterior is pennate.

948

REVIEW QUESTIONS 1. The leg is divided into how many distinct compartments? Name them. ____________________________ 2. What is the principal component of pronation? Of supination? ____________________________ ____________________________ 3. Explain the importance of the tibialis anterior’s eccentric agonist function in the gait cycle. ____________________________ ____________________________ ____________________________ ____________________________ 4. The fibularis tertius is actually part of what other muscle? What is the reason that it is named separately? ____________________________ ____________________________ ____________________________ 5. Clients with a history of what injury would be wise to strengthen the fibularis longus for its stabilizing action at the subtalar joint? ____________________________ 6. The distal tendon of the fibularis brevis crosses to the_______lateral malleolus. 7. In a closed chain scenario, contraction of the gastrocnemius will have what effect on the talus? ____________________________ ____________________________ 8. The triceps surae is composed of what muscle(s)? The quadriceps surae? ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ 9. What is the motion created by contraction of the plantaris? ____________________________ ____________________________ 10. The tibialis posterior attaches onto all of the tarsal bones except for the_______. For answers to these questions, visit http://evolve.elsevier.com/Muscolino/muscular

949

THINK IT THROUGH When stretching the muscles of the posterior leg, it is important to be able to target specific muscles. Given their common actions at the ankle and subtalar joints, how would a therapist specifically target stretches for the gastrocnemius and the soleus? ____________________________ ____________________________ ____________________________ ____________________________ ____________________________

950

CHAPTER 17

951

Extrinsic Muscles of the Toe Joints CHAPTER OUTLINE Anterior compartment: Extensor digitorum longus Extensor hallucis longus Deep posterior compartment: Flexor digitorum longus Flexor hallucis longus

OBJECTIVES After completing this chapter, the student should be able to perform the following for each of the muscles covered in the chapter: 1. Explain the general structure in relation to the joint(s) it crosses. 2. Explain the general rules regarding actions for its functional group. 3. State the attachments. 4. State the standard mover actions. 5. State the reverse mover actions. 6. Discuss the line(s) of pull the muscle has and the motion(s) created. 7. State the eccentric antagonist functions. 8. State the isometric stabilization functions. 9. State the nervous innervation.

10. State the arterial supply. 11. Describe the starting position for palpation. 12. Describe the steps for palpation. 13. Discuss the muscle’s relationship to other body structures. 14. Discuss additional information that may help with palpation, assessment, and clinical decision-making. CHAPTER OVERVIEW The muscles addressed in this chapter are the extrinsic muscles of the foot that move the toes. These muscles attach proximally to the leg and then travel distally to enter and attach to the foot. These extrinsic toe muscles also cross the ankle and subtalar joints; therefore they also move these joints. See Chapter 16 for the muscles of the ankle and subtalar joints. Note: Intrinsic muscles of the foot that also move the toes are addressed in Chapter 18. Overview of STRUCTURE Structurally, extrinsic muscles of the foot that move the toes can be divided into two groups: flexors and extensors. The extensors are the extensor digitorum longus and extensor hallucis longus located in the anterior compartment of the leg. The flexors are the flexor digitorum longus and flexor hallucis longus located in the deep posterior compartment of the leg. Note: Digitorum refers to toes two through five; hallucis means big toe.

952

Compartments of the Leg: Leg musculature is usually divided into anterior, lateral, superficial posterior, and deep posterior compartments. • The anterior compartment contains the tibialis anterior, extensor digitorum longus, extensor hallucis longus, and fibularis tertius. • The lateral compartment contains the fibularis longus and fibularis brevis. • The superficial posterior compartment contains the gastrocnemius, soleus, and plantaris. • The deep posterior compartment contains the tibialis posterior, flexor digitorum longus, flexor hallucis longus, and popliteus. Overview of FUNCTION The following general rules regarding actions can be stated for the functional groups of extrinsic toe muscles: Toes two through five can move at three joints: the metatarsophalangeal (MTP), proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints.

If a muscle crosses only the MTP joint, it can move the toe only at the MTP joint. If the muscle crosses the MTP and PIP joints, it can move the toe at both of these joints. If the muscle crosses the MTP, PIP, and DIP joints, it can move the toe at all three joints. The big toe (toe one) can move at two joints: the metatarsophalangeal (MTP) and interphalangeal (IP) joints. Similarly, a muscle can move the big toe at one or both joints that it crosses. If a muscle crosses the MTP, PIP, DIP, or IP joints of the toes on the plantar side, it can flex the toe at the joint(s) crossed; if a muscle crosses the MTP, PIP, DIP, or IP joints of the toes on the dorsal side, it can extend the toe at the joint(s) crossed. Reverse actions involve the proximal attachment moving toward the distal one. This occurs when the distal end of the foot is fixed, usually when the foot is planted on the ground (for example, when we toe-off during the gait cycle, the metatarsals are mobile and extend toward the toes, which are fixed; therefore the foot extends toward the toes at the MTP joints). Because extrinsic toe muscles attach proximally to the leg, they also cross the ankle and subtalar joints so they can move the foot (or leg) at these joints. If a muscle crosses the ankle joint anteriorly to enter the foot, it can dorsiflex the foot (or leg) at the ankle joint; if it crosses the ankle joint posteriorly to enter the foot, it can plantarflex the foot (or leg) at the ankle joint. If a muscle crosses the subtalar joint on the lateral (fibular) side to enter the foot, it can evert the foot (or leg) at the subtalar joint; if it crosses the subtalar joint on the medial (tibial) side to enter the foot, it can invert the foot (or leg) at the subtalar joint.

http://evolve.elsevier.com/Muscolino/muscular

953

Anterior View of the Extrinsic Muscles of the Toes of the Right Foot—Superficial View

FIGURE 17-1

Anterior views of the extrinsic muscles of the toes of the right foot. A, Superficial.

954

Anterior View of the Extrinsic Muscles of the Toes of the Right Foot—Deep View

FIGURE 17-1

955

B, Deep.

Posterior View of the Extrinsic Muscles of the Toes of the Right Foot—Superficial View

FIGURE 17-2

Posterior views of the extrinsic muscles of the toes of the right foot. A, Superficial.

956

Posterior Views of the Extrinsic Muscles of the Toes of the Right Foot—Intermediate and Deep Views

FIGURE 17-2

B, Intermediate. C, Deep.

957

Medial View of the Extrinsic Muscles of the Toes of the Right Foot—Superficial View

FIGURE 17-3

Medial views of the extrinsic muscles of the toes of the right foot. A, Superficial.

958

Medial View of the Extrinsic Muscles of the Toes of the Right Foot—Deep View

FIGURE 17-3

959

B, Deep.

Transverse Plane Cross Section of the Right Leg

FIGURE 17-4 Transverse plane cross section, approximately ⅓ of the way distal to the knee joint. A, The four compartments of the leg. B, The muscles within the compartments of the leg.

960

Extensor Digitorum Longus The name, extensor digitorum longus, tells us that this muscle extends the digits (i.e., toes two through five) and is long (longer than the extensor digitorum brevis). Derivation extensor: L. a muscle that extends a body part digitorum: L. refers to a digit (toe) longus: L. longer Pronunciation eks-TEN-sor dij-i-TOE-rum LONG-us

ATTACHMENTS Proximal Anterior Fibula the proximal ⅔ of the fibula, the proximal ⅓ of the interosseus membrane, and the lateral tibial condyle to the Dorsal Surface of Toes Two through Five via its dorsal digital expansion onto the dorsal surface of the middle and distal phalanges

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extends toes two through five at the MTP and IP joints

Reverse Mover Actions 1. Extends metatarsals at the MTP joints and extends the more proximal phalanges at the IP joints

2. Dorsiflexes the foot at the ankle joint 3. Everts (pronates) the foot at the subtalar joint

2. Dorsiflexes the leg at the ankle joint 3. Everts (pronates) the talus at the subtalar joint

MTP joints = metatarsophalangeal joints; IP joints = (proximal and distal) interphalangeal joints

Standard Mover Action Notes • The extensor digitorum longus crosses toe joints two through five dorsally (with its fibers running horizontally in the sagittal plane); therefore it extends toes two through five. Given that it attaches all the way onto the distal phalanges, it crosses the MTP joint and the proximal and distal IP joints of toes two through five. Therefore the extensor digitorum longus extends toes two through five at all of these joints. (action 1) • More specifically, extending toes at the MTP and IP joints refers to extending the proximal phalanges of the toes at the MTP joints, extending the middle phalanges at the proximal interphalangeal (PIP) joints, and extending the distal phalanges at the distal interphalangeal (DIP) joints. (action 1) • The extensor digitorum longus crosses the ankle joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it dorsiflexes the foot at the ankle joint. (action 2) • The extensor digitorum longus crosses into the foot lateral to the axis of motion of the subtalar joint (with its fibers running vertically in the frontal plane); therefore it everts the foot (more specifically the calcaneus relative to the talus) at the subtalar joint. Eversion is the major component of subtalar pronation (subtalar pronation also includes lateral rotation and dorsiflexion of the foot). (action 3)

961

FIGURE 17-5

Anterior view of the right extensor digitorum longus. The fibularis tertius has been ghosted in.

Reverse Mover Action Notes • Reverse actions within the lower extremity occur when the distal end is fixed (usually due to the foot being planted on the ground) so that the proximal attachment moves instead. (reverse actions 1, 2, 3) • If the more distal attachment is fixed, the extensor digitorum longus extends the metatarsal relative to the proximal phalanx (at the MTP joint). The reverse action of metatarsal extension at the MTP joint happens during the gait cycle at toe-off. (reverse action 1) • Extending the more proximal phalanges at the IP joints refers to extending the proximal phalanges at the proximal interphalangeal (PIP) joints and extending the middle phalanges at the distal interphalangeal (DIP) joints. (reverse action 1) • The extensor digitorum longus crosses the ankle joint anteriorly with a vertical direction to its fibers (in the sagittal plane). If the foot is fixed by being planted on the ground, the leg is dorsiflexed at the ankle joint by bringing the anterior (dorsal) surface of the leg toward the dorsal surface of the foot. This action occurs during the gait cycle (from foot-flat to toe-off). (reverse action 2) • The reverse action of eversion of the foot at the subtalar joint is eversion of the talus/leg at the subtalar joint. Moving the leg at the subtalar joint involves moving the talus relative to the calcaneus. Eversion is the principal component of pronation. (reverse action 3)

962

• Another component of pronation of the talus at the subtalar joint is medial rotation of the talus. Because the ankle and (extended) knee joints do not allow rotation, when the talus medially rotates, the entire lower extremity follows with medial rotation of the thigh at the hip joint. (reverse action 3)

Motion 1. The extensor digitorum longus has one line of pull in an oblique plane and therefore creates one motion, which is a combination of extension of toes two through five, and dorsiflexion and eversion of the foot.

Eccentric Antagonist Functions 1. Restrains/slows flexion of toes two through five at the MTP and IP joints, and metatarsals two through five at the MTP joints 2. Restrains/slows ankle joint plantarflexion 3. Restrains/slows inversion (supination) at the subtalar joint

Eccentric Antagonist \ Note • The eccentric action of restraining/slowing plantarflexion of the foot is important during the gait cycle (from heel-strike to foot-flat).

Isometric Stabilization Functions 1. Stabilizes the ankle, subtalar, and MTP and IP joints of toes two through five

Additional Note on Actions 1. All four muscles in the anterior compartment of the leg can dorsiflex the foot (and leg) at the ankle joint.

I N N E RVAT I O N The Deep Fibular Nerve L5, S1

A R T E R I A L S U P P LY The Anterior Tibial Artery (a terminal branch of the Popliteal Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating fingers on the dorsum of the foot. 2. Have the client extend toes two through five (resistance can be added) and look and feel for the tensing of the tendons of the extensor digitorum longus. 3. Follow the extensor digitorum longus proximally as far as possible. The belly of the extensor digitorum longus can be palpated between the tibialis anterior and the fibularis longus.

RELATIONSHIP TO OTHER STRUCTURES The tibialis anterior and the extensor hallucis longus are medial to the extensor digitorum longus. The fibularis longus and the fibularis brevis are lateral to the extensor digitorum longus. The extensor digitorum longus is superficial, except proximally, where it is deep to the tibialis anterior and the fibularis longus. Deep to the extensor digitorum longus is the fibula. The fibers of the most distal and lateral part of the extensor digitorum longus (that arise from the distal ⅓ of the fibula) do not attach onto digits (i.e., toes) but rather onto the fifth metatarsal. This portion of the muscle is given a separate name, the fibularis tertius. The extensor digitorum longus is located within the superficial front line myofascial meridian.

MISCELLANEOUS 963

1. The extensor digitorum longus is located in the anterior compartment of the leg. 2. The distal attachment of the extensor digitorum longus spreads out to become a fibrous aponeurotic expansion that covers the dorsal, medial, and lateral sides of the proximal phalanx of toes two through five. It then continues distally to attach onto the dorsal sides of the middle and distal phalanges of these toes. This structure is called the dorsal digital expansion. The dorsal digital expansion also serves as an attachment site for the extensor digitorum brevis, lumbricals pedis, dorsal interossei pedis, and plantar interossei muscles. 3. The most distal and lateral part of the extensor digitorum longus (that arises from the distal ⅓ of the fibula) does not attach onto the digits (toes); therefore it is given a separate name, the fibularis tertius. 4. The extensor digitorum longus is pennate.

964

Extensor Hallucis Longus The name, extensor hallucis longus, tells us that this muscle extends the big toe and is long (longer than the extensor hallucis brevis). Derivation extensor: L. a muscle that extends a body part hallucis: L. refers to the big toe longus: L. longer Pronunciation eks-TEN-sor hal-OO-sis LONG-us

ATTACHMENTS Middle Anterior Fibula the middle ⅓ of the anterior fibula and the middle ⅓ of the interosseus membrane to the Dorsal Surface of the Big Toe (Toe One) the distal phalanx

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extends the big toe (toe one) at the MTP and IP joints

Reverse Mover Actions 1. Extends the metatarsal at the MTP joint and extends the proximal phalanx at the IP joint

2. Dorsiflexes the foot at the ankle joint 3. Inverts (supinates) the foot at the subtalar joint

2. Dorsiflexes the leg at the ankle joint 3. Inverts (supinates) the talus at the subtalar joint

MTP joints = metatarsophalangeal joints; IP joints = (proximal and distal) interphalangeal joints

Standard Mover Action Notes • The extensor hallucis longus crosses the big toe dorsally (with its fibers running horizontally in the sagittal plane); therefore it extends the big toe. Because it attaches onto the distal phalanx, it crosses both the MTP and IP joints of the big toe. Therefore the extensor hallucis longus extends the big toe at both of these joints. (action 1) • More specifically, extending the big toe at the MTP and IP joints refers to extending the proximal phalanx at the MTP joint and extending the distal phalanx at the IP joint. (action 1) • The extensor hallucis longus crosses the ankle joint anteriorly (with its fibers running vertically in the sagittal plane); therefore it dorsiflexes the foot at the ankle joint. (action 2) • The extensor hallucis longus crosses into the foot medial to the axis of motion of the subtalar joint (with its fibers running vertically in the frontal plane); therefore it inverts the foot (more specifically the calcaneus relative to the talus) at the subtalar joint. Inversion is the major component of subtalar supination (subtalar supination also includes medial rotation and plantarflexion of the foot). (action 3)

965

FIGURE 17-6

Anterior view of the right extensor hallucis longus.

Reverse Mover Action Notes • Reverse actions within the lower extremity occur when the distal end is fixed (usually due to the foot being planted on the ground) so that the proximal attachment moves instead. (reverse actions 1, 2, 3) • If the more distal attachment is fixed, the extensor hallucis longus extends the metatarsal of the big toe toward the proximal phalanx (at the MTP joint) and extends the proximal phalanx of the big toe toward the distal phalanx (at the IP joint). (reverse action 1) • The reverse action of metatarsal extension at the MTP joint happens during the gait cycle at toeoff. (reverse action 1) • The extensor hallucis longus crosses the ankle joint anteriorly with a vertical direction to its fibers (in the sagittal plane). If the foot is fixed by being planted on the ground, the leg is dorsiflexed at the ankle joint by bringing the anterior (dorsal) surface of the leg toward the dorsal surface of the foot. This action occurs during the gait cycle (from foot-flat to toe-off). (reverse action 2) • The reverse action of inversion of the foot at the subtalar joint is inversion of the talus/foot at the subtalar joint. Moving the leg at the subtalar joint involves moving the talus relative to the calcaneus. Inversion is the principal component of supination. (reverse action 3) • Another component of supination of the talus at the subtalar joint is lateral rotation of the talus.

966

Because the ankle and (extended) knee joints do not allow rotation, when the talus laterally rotates, the entire lower extremity follows with lateral rotation of the thigh at the hip joint. (reverse action 3)

Motion 1. The extensor hallucis longus has one line of pull in an oblique plane and therefore creates one motion, which is a combination of extension of the big toe, and dorsiflexion and inversion of the foot.

Eccentric Antagonist Functions 1. Restrains/slows flexion of the big toe at the MTP and IP joints, and the metatarsal at the MTP joint 2. Restrains/slows ankle joint plantarflexion 3. Restrains/slows eversion at the subtalar joint

Eccentric Antagonist Function Note • The eccentric action of restraining/slowing plantarflexion of the foot is important during the gait cycle (from heel-strike to foot-flat).

Isometric Stabilization Functions 1. Stabilizes the ankle and subtalar joints, and the MTP and IP joints of the big toe

Additional Note on Actions 1. All four muscles in the anterior compartment of the leg can dorsiflex the foot (and leg) at the ankle joint.

I N N E RVAT I O N The Deep Fibular Nerve L5, S1

A R T E R I A L S U P P LY The Anterior Tibial Artery (a terminal branch of the Popliteal Artery)

PA L PAT I O N 1. With the client either sitting or supine, place palpating fingers on the medial aspect of the dorsum of the foot. 2. Have the client extend the big toe (resistance can be added) and look and feel for the tensing of the tendon of the extensor hallucis longus. 3. Follow the extensor hallucis longus proximally. It may be palpated superficially in the distal leg between the tibialis anterior tendon and the extensor digitorum longus. 4. With careful palpation, the belly of the extensor hallucis longus can be palpated deep to overlying musculature when the client extends the big toe.

RELATIONSHIP TO OTHER STRUCTURES The extensor hallucis longus arises between the tibialis anterior and the extensor digitorum longus and is deep to these muscles proximally. A small portion of the belly of the extensor hallucis longus is superficial in the distal half of the leg between the tendons of the tibialis anterior and the extensor digitorum longus. The distal tendon of the extensor hallucis longus becomes superficial and lies just lateral to the distal tendon of the tibialis anterior in the foot. Deep to the extensor hallucis longus is the fibula. The extensor hallucis longus is located within the superficial front line myofascial meridian.

MISCELLANEOUS 967

1. The extensor hallucis longus is located in the anterior compartment of the leg. 2. The reverse action of extension of the metatarsal at the MTP joint is extremely important to attain the toe-off position during the gait cycle. If this motion is decreased, the length of the stride shortens, likely resulting in decreased hip joint ranges of motion, which then may result in tighter hip joint musculature. 3. The extensor hallucis longus is pennate.

968

Flexor Digitorum Longus (Dick of Tom, Dick, and Harry Group) The name, flexor digitorum longus, tells us that this muscle flexes the digits (i.e., toes) and is long (longer than the flexor digitorum brevis). Derivation flexor: L. a muscle that flexes a body part digitorum: L. refers to a digit (toe) longus: L. longer Pronunciation FLEKS-or dij-i-TOE-rum LONG-us

ATTACHMENTS Middle Posterior Tibia the middle ⅓ of the posterior tibia to the Plantar Surface of Toes Two through Five the distal phalanges

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes toes two through five at the MTP and IP joints

Reverse Mover Actions 1. Flexes metatarsals at the MTP joints and flexes the more proximal phalanges at the IP joints

2. Plantarflexes the foot at the ankle joint

2. Plantarflexes the leg at the ankle joint

3. Inverts (supinates) the foot at the subtalar joint

3. Inverts (supinates) the talus at the subtalar joint

MTP joints = metatarsophalangeal joints; IP joints = (proximal and distal) interphalangeal joints

Standard Mover Action Notes • The flexor digitorum longus crosses the toe joints on the plantar side (with its fibers running horizontally in the sagittal plane); therefore it flexes toes two through five. Given that the flexor digitorum longus attaches onto the distal phalanges, it crosses the MTP joint and the proximal and distal IP joints of toes two through five. Therefore the flexor digitorum longus flexes the toes at all of these joints. (action 1) • More specifically, flexing toes at the MTP and IP joints refers to flexing the proximal phalanges at the MTP joints, flexing the middle phalanges at the proximal interphalangeal (PIP) joints, and flexing the distal phalanges at the distal interphalangeal (DIP) joints. (action 1) • The flexor digitorum longus crosses the ankle joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it plantarflexes the foot at the ankle joint. (action 2) • The flexor digitorum longus enters the foot and crosses the subtalar joint on the medial side (with its fibers running vertically in the frontal plane); therefore it inverts the foot (more specifically, the calcaneus relative to the talus) at the subtalar joint. Inversion is the major component of subtalar supination (subtalar supination also includes medial rotation and plantarflexion of the foot). (action 3)

969

FIGURE 17-7

Posterior view of the right flexor digitorum longus. The flexor hallucis longus has been ghosted in.

Reverse Mover Action Notes • Reverse actions within the lower extremity occur when the distal end is fixed (usually due to the foot being planted on the ground) so that the proximal attachment moves instead. (reverse actions 1, 2, 3) • Reverse actions of the toes involve the metatarsal moving at the MTP joint, the proximal phalanx moving at the proximal interphalangeal (PIP) joint, and middle phalanx moving at the distal interphalangeal (DIP) joint. (reverse action 1) • The flexor digitorum longus crosses the ankle joint posteriorly with a vertical direction to its fibers (in the sagittal plane). If the foot is fixed by being planted on the ground, the leg is plantarflexed at the ankle joint by bringing the posterior surface of the leg toward the plantar surface of the foot. (reverse action 2) • The reverse action of inversion of the foot at the subtalar joint is inversion of the talus/leg at the subtalar joint. Moving the leg at the subtalar joint involves moving the talus relative to the calcaneus. Inversion is the principal component of supination. (reverse action 3) • Another component of supination of the talus at the subtalar joint is lateral rotation of the talus. Because the ankle and (extended) knee joints do not allow rotation, when the talus laterally rotates, the entire lower extremity follows with lateral rotation of the thigh at the hip joint. (reverse action 3)

Motion 1. The flexor digitorum longus has one line of pull in an oblique plane and therefore creates one motion, which is a combination of flexion of toes two through five, and plantarflexion and inversion

970

of the foot.

Eccentric Antagonist Functions 1. Restrains/slows extension of toes two through five at the MTP and IP joints, and metatarsals two through five at the MTP joints. 2. Restrains/slows ankle joint dorsiflexion 3. Restrains/slows eversion of the subtalar joint

Eccentric Antagonist Function Note • Restraining/slowing dorsiflexion of the leg at the ankle joint is important when standing and bending forward (bending at the ankle, knee, and hip joints).

Isometric Stabilization Functions 1. Stabilizes the ankle, subtalar, and MTP and IP joints of toes two through five

Isometric Stabilization Function Note • The flexor digitorum longus helps support and stabilize the arches (and the subtalar joint) of the foot

Additional Note on Actions 1. Because the tendons of the Tom, Dick, and Harry group cross into the foot posterior to the medial malleolus, their line of pull is posteromedial. Therefore all three Tom, Dick, and Harry muscles plantarflex and invert the foot (at the ankle and subtalar joints, respectively).

I N N E RVAT I O N The Tibial Nerve L5, S1, S2

A R T E R I A L S U P P LY The Posterior Tibial Artery (a terminal branch of the Popliteal Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating fingers posterior to the medial malleolus. 2. Have the client flex toes two through five (resistance can be added) and feel for the tensing of the distal tendon of the flexor digitorum longus. 3. Continue palpating the flexor digitorum longus proximally into the posteromedial leg between the soleus and tibia.

RELATIONSHIP TO OTHER STRUCTURES The flexor digitorum longus, tibialis posterior, and flexor hallucis longus are the deepest muscles in the posterior leg. Where these muscles overlap, the tibialis posterior is the deepest of the three. The flexor digitorum longus is deep to the soleus. Deep to the flexor digitorum longus is the tibia. The belly of the flexor digitorum longus is medial to the tibialis posterior and the flexor hallucis longus. The distal tendon of the flexor digitorum longus crosses posterior to the medial malleolus, along with the distal tendons of the tibialis posterior and the flexor hallucis longus. The flexor digitorum longus is located within the deep front line myofascial meridian.

MISCELLANEOUS 1. The flexor digitorum longus is located in the deep posterior compartment of the leg. 2. The flexor Digitorum longus is Dick of the Tom, Dick, and Harry group. The Tom, Dick, and Harry muscles are the tibialis posterior, flexor digitorum longus, and flexor hallucis longus. Tom, Dick,

971

and Harry are grouped together because they are all deep in the posterior leg and all of their distal tendons cross posterior to the medial malleolus of the tibia (in order from anterior to posterior, Tom, Dick, and Harry). 3. It is worth noting that the location of the muscle bellies of the Tom, Dick, and Harry muscles in the posterior leg is, from medial to lateral, Dick, Tom, and Harry (i.e., flexor digitorum longus, tibialis posterior, and flexor hallucis longus). 4. The flexor digitorum longus has a tendon that makes an abrupt turn of approximately 90 degrees. 5. In the ankle region, the distal tendon of the flexor digitorum longus travels through the tarsal tunnel along with the distal tendon of the tibialis posterior. 6. The distal tendons of the flexor digitorum longus reach their attachment site on the distal phalanges in an unusual manner. The tendons of the flexor digitorum brevis (an intrinsic muscle of the foot) lie superficial to the tendons of the flexor digitorum longus. The tendons of the flexor digitorum brevis split, and the tendons of the flexor digitorum longus then pass through these splits to continue on to the distal phalanges. (This is essentially identical to the arrangement of the flexor digitorum superficialis and flexor digitorum profundus of the upper extremity.) 7. Because the four individual distal tendons of the flexor digitorum longus split from one common distal tendon, the flexor digitorum longus does not allow for individual control of toes two through five. 8. The flexor digitorum longus is pennate.

972

Flexor Hallucis Longus (Harry of Tom, Dick, and Harry Group) The name, flexor hallucis longus, tells us that this muscle flexes the big toe and is long (longer than the flexor hallucis brevis). Derivation flexor: L. a muscle that flexes a body part hallucis: L. the big toe longus: L. longer Pronunciation FLEKS-or hal-OO-sis LONG-us

ATTACHMENTS Distal Posterior Fibula the distal ⅔ of the posterior fibula and the distal ⅔ of the interosseus membrane to the Plantar Surface of the Big Toe (Toe One) the distal phalanx

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes the big toe at the MTP and IP joints

Reverse Mover Actions 1. Flexes the metatarsal at the MTP joint and flexes the proximal phalanx at the IP joint

2. Plantarflexes the foot at the ankle joint

2. Plantarflexes the leg at the ankle joint

3. Inverts (supinates) the foot at the subtalar joint

3. Inverts (supinates) the talus at the subtalar joint

MTP joint = metatarsophalangeal joint; IP joint = interphalangeal joint

Standard Mover Action Notes • The flexor hallucis longus crosses the big toe on the plantar side (with its fibers running horizontally in the sagittal plane); therefore it flexes the big toe. Given that the flexor hallucis longus attaches onto the distal phalanx, it crosses both the MTP joint and IP joint of the big toe. Therefore the flexor hallucis longus flexes the big toe at both of these joints. (action 1) • More specifically, flexing the big toe at the MTP and IP joints refers to flexing the proximal phalanx at the MTP joint and flexing the distal phalanx at the IP joint. (action 1) • Flexion of the big toe at the MTP and IP joints contributes to toe-off during the gait cycle. (action 1) • The flexor hallucis longus crosses the ankle joint posteriorly (with its fibers running vertically in the sagittal plane); therefore it plantarflexes the foot at the ankle joint. (action 2) • The flexor hallucis longus enters the foot and crosses the subtalar joint on the medial side (with its fibers running vertically in the frontal plane); therefore it inverts the foot at the subtalar joint. Inversion is the major component of subtalar supination (subtalar supination also includes medial rotation and plantarflexion of the foot). (action 3)

973

FIGURE 17-8

Posterior view of the right flexor hallucis longus. The flexor digitorum longus has been ghosted in.

Reverse Mover Action Notes • Reverse actions within the lower extremity occur when the distal end is fixed (usually due to the foot being planted on the ground) so that the proximal attachment moves instead. (reverse actions 1, 2, 3) • The reverse actions of flexion of the big toe involve the metatarsal moving at the MTP joint and the proximal phalanx moving at the IP joint. (reverse action 1) • The flexor hallucis longus crosses the ankle joint posteriorly with a vertical direction to its fibers (in the sagittal plane). If the foot is fixed by being planted on the ground, the leg is plantarflexed at the ankle joint by bringing the posterior surface of the leg toward the plantar surface of the foot. (reverse action 2) • The reverse action of inversion of the foot at the subtalar joint is inversion of the talus/leg at the subtalar joint. Moving the leg at the subtalar joint involves moving the talus relative to the calcaneus. Inversion is the principal component of supination. (reverse action 3) • Another component of supination of the talus at the subtalar joint is lateral rotation of the talus. Because the ankle and (extended) knee joints do not allow rotation, when the talus laterally rotates, the entire lower extremity follows with lateral rotation of the thigh at the hip joint.

974

(reverse action 3)

Motion 1. The flexor hallucis longus has one line of pull in an oblique plane and therefore creates one motion, which is a combination of flexion of the big toe, and plantarflexion and inversion of the foot.

Eccentric Antagonist Functions 1. Restrains/slows extension of the big toe at the MTP and IP joints, and the metatarsal at the MTP joint 2. Restrains/slows ankle joint dorsiflexion 3. Restrains/slows eversion at the subtalar joint

Eccentric Antagonist Function Note • Restraining/slowing dorsiflexion of the leg at the ankle joint is important when standing and bending forward (bending at the ankle, knee, and hip joints).

Isometric Stabilization Functions 1. Stabilizes the ankle, subtalar, and MTP and IP joints of the big toe

Additional Notes on Actions 1. The flexor hallucis longus is actually quite large and powerful; it is larger and stronger than the flexor digitorum longus. One reason for the size and strength of this muscle is to increase our propulsive force when we push off (toe-off) the ground by flexing the big toe when walking and running. 2. Because the tendons of the Tom, Dick, and Harry group cross into the foot posterior to the medial malleolus, their line of pull is posteromedial. Therefore all three Tom, Dick, and Harry muscles plantarflex and invert the foot (at the ankle and subtalar joints, respectively).

I N N E RVAT I O N The Tibial Nerve L5, S1, S2

A R T E R I A L S U P P LY The Posterior Tibial Artery (a terminal branch of the Popliteal Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating hand immediately posterior to the distal shaft of the tibia in the medial leg. 2. Have the client flex the big toe (resistance can be added) and feel for the tensing of the distal belly of the flexor hallucis longus. 3. Continue palpating the flexor hallucis longus distally into the foot and proximally into the posterior leg.

RELATIONSHIP TO OTHER STRUCTURES The flexor hallucis longus, flexor digitorum longus, and tibialis posterior are the deepest muscles in the posterior leg. Where these muscles overlap, the tibialis posterior is the deepest of the three. The flexor hallucis longus is deep to the soleus. Deep to the flexor hallucis longus are the fibula and the interosseus membrane. Even though the flexor hallucis longus ends up on the big toe in the medial foot, proximally, its belly is lateral in the posterior leg. The belly of the flexor hallucis longus is lateral to the bellies of the tibialis posterior and the flexor digitorum longus. Lateral to the flexor hallucis longus is the fibularis longus. The distal tendon of the flexor hallucis longus crosses posterior to the medial malleolus, along with

975

the distal tendons of the tibialis posterior and the flexor digitorum longus. Of the three tendons, the flexor hallucis longus is the farthest from the medial malleolus (and most difficult to palpate). The flexor hallucis longus is located within the deep front line myofascial meridian.

MISCELLANEOUS 1. The flexor hallucis longus is located in the deep posterior compartment of the leg. 2. The flexor Hallucis longus is Harry of the Tom, Dick, and Harry group. The Tom, Dick, and Harry muscles are the tibialis posterior, flexor digitorum longus, and flexor hallucis longus. Tom, Dick, and Harry are grouped together because they are all deep in the posterior leg and all of their distal tendons cross posterior to the medial malleolus of the tibia (in order from anterior to posterior, Tom, Dick, and Harry). 3. It is worth noting that the location of the muscle bellies of the Tom, Dick, and Harry muscles in the posterior leg is, from medial to lateral, Dick, Tom, and Harry (i.e., flexor digitorum longus, tibialis posterior, and flexor hallucis longus). 4. The flexor hallucis longus has a tendon that makes an abrupt turn of approximately 90 degrees.

976

REVIEW QUESTIONS 1. When talking about the extrinsic muscles of the toe joints, digitorum refers to _______ and hallucis means_______. 2. Motion is allowed in toes two, three, four, and five at how many joints? Name those joints. ____________________________ ____________________________ ____________________________ ____________________________ 3. Explain the effect of pronation of the talus at the subtalar joint in a closed chain scenario. ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ 4. The fibers of the most distal and lateral part of the extensor digitorum longus attach onto the_______. This portion of the muscle is given a separate name, the_______. 5. Describe the structure known as the dorsal digital expansion. ____________________________ ____________________________ ____________________________ ____________________________ 6. Describe the motion created by a contraction of the extensor hallucis longus. ____________________________ ____________________________ ____________________________ 7. The distal tendon of the flexor digitorum longus crosses _______ to the medial malleolus. 8. In the ankle region, the distal tendon of the _______ travels through the tarsal tunnel along with the distal tendon of the tibialis posterior. 9. Does the flexor digitorum longus allow for individual control of toes two through five? Explain your answer. ____________________________ ____________________________ ____________________________ 10. What would be the benefit of having a large and powerful flexor hallucis longus? ____________________________ ____________________________ ____________________________ For answers to these questions, visit http://evolve.elsevier.com/Muscolino/muscular

977

THINK IT THROUGH Given the anatomy of the ankle and the foot, what are some activities that would place great stress in these areas? Consider, as an example, the effect that a ballet dancer’s pointe technique would have on muscles like the flexor hallucis longus. What might a therapist expect to see in these clients? ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________

978

CHAPTER 18

979

Intrinsic Muscles of the Toe Joints CHAPTER OUTLINE Dorsal surface: Extensor digitorum brevis Extensor hallucis brevis Plantar surface: Layer I: Abductor hallucis Abductor digiti minimi pedis Flexor digitorum brevis Plantar surface: Layer II: Quadratus plantae Lumbricals pedis Plantar surface: Layer III: Flexor hallucis brevis Flexor digiti minimi pedis Adductor hallucis Plantar surface: Layer IV: Plantar interossei Dorsal interossei pedis

OBJECTIVES After completing this chapter, the student should be able to perform the following for each of the muscles covered in the chapter: 1. Explain the general structure in relation to the joint(s) it crosses. 2. Explain the general rules regarding actions for its functional group. 3. State the attachments. 4. State the standard mover actions. 5. State the reverse mover actions. 6. Discuss the line(s) of pull the muscle has and the motion(s) created. 7. State the eccentric antagonist functions. 8. State the isometric stabilization functions. 9. State the nervous innervation.

10. State the arterial supply. 11. Describe the starting position for palpation. 12. Describe the steps for palpation. 13. Discuss the muscle’s relationship to other body structures. 14. Discuss additional information that may help with palpation, assessment, and clinical decision-making. CHAPTER OVERVIEW

980

The muscles addressed in this chapter are the intrinsic muscles of the foot that move the toes. Intrinsic muscles of the foot are wholly located within the foot; in other words, they begin and end in the foot. Extrinsic muscles of the foot that also move the toes are covered in Chapter 17 (extrinsic muscles of the foot attach proximally to the thigh or leg and then travel distally to enter and attach to the foot). Overview of STRUCTURE Structurally, intrinsic muscles of the foot that move the toes can be divided into two major groups: those on the dorsal side and those on the plantar side. The plantar intrinsic muscles are further subdivided into four groups/layers from superficial to deep, named with Roman numerals I, II, III, and IV, respectively. See the box below for the organization of the intrinsic musculature of the foot. Note that Hallucis means big toe and digiti minimi refers to the little toe. Even though these layers are arranged from superficial to deep, each layer does not entirely cover the layer that is deep to it. So some muscles in the deeper layers may actually be superficial. It is useful to note the symmetry between Layers I and III. Layer I contains two abductors (of big toe and little toe) and a flexor, and Layer III contains two flexors (of big toe and little toe) and an adductor. Layer IV, being the deepest, contains the muscles that, as their names imply, are located between the metatarsal bones, the plantar interossei and dorsal interossei pedis.

Compartments of the Foot: The foot is usually divided into dorsal and plantar compartments. The plantar compartment is then usually divided into four layers. • The dorsal compartment contains the extensor digitorum brevis and extensor hallucis brevis • Plantar Layer I contains the abductor hallucis, abductor digiti minimi pedis, and flexor digitorum brevis • Plantar Layer II contains the quadratus plantae and lumbricals pedis • Plantar Layer III contains the flexor hallucis brevis, flexor digiti minimi pedis, and adductor hallucis • Plantar Layer IV contains the plantar interossei and dorsal interossei pedis Overview of FUNCTION The following general rules regarding actions can be stated for the functional groups of intrinsic toe muscles: Toes two through five can move at three joints: the metatarsophalangeal (MTP), proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints. If a muscle crosses only the MTP joint, it can move the toe only at the MTP joint. If the muscle crosses the MTP and PIP joints, it can move the toe at both of these joints. If the muscle crosses the MTP, PIP, and DIP joints, it can move the toe at all three joints. The big toe (toe number one) can move at two joints: the MTP and interphalangeal (IP) joints. Similarly, a muscle can only move the big toe at a joint or joints that it crosses. If a muscle crosses the MTP, PIP, DIP, or IP joints of a toe on the plantar side, it can flex the toe at the joint(s) crossed; if a muscle crosses the MTP, PIP, DIP, or IP joints of a toe on the dorsal side, it can extend the toe at the joint(s) crossed. If a muscle crosses the MTP joint of toes one, three, four, or five on the side that faces the second toe, it can adduct the toe at the MTP joint; if a muscle crosses the MTP joint of toes one, two, three, four, or five on the side that is away from the (center of the) second-toe side, it can abduct the toe at the MTP joint (the second toe abducts in both directions, tibial and fibular abduction). Note: The axis for abduction/adduction of the toes at the MTP joints is an imaginary line that runs through the center of the second toe when it is in anatomic position. There is a dorsal digital expansion in the foot formed by the distal tendons of the extensor digitorum longus. It is similar to the dorsal digital expansion of the hand; however, it is not as well developed. Similar to the hand, the lumbricals and interossei muscles attach into the dorsal digital expansion and can therefore do flexion of toes at the MTP joints and extension at the IP joints. Regarding motion of the toes, to be more specific, the proximal phalanx of the toe moves at the

981

MTP joint, the middle phalanx moves at the PIP joint, and the distal phalanx moves at the DIP joint. For the big toe, the proximal phalanx moves at the MTP joint and the distal phalanx moves at the IP joint. Reverse actions involve the proximal attachment moving toward the distal one. This usually occurs when the toes are planted on the ground and fixed. Reverse actions of the toes involve the metatarsal moving at the MTP joint (relative to a fixed proximal phalanx), the proximal phalanx moving at the PIP joint (relative to a fixed middle phalanx), and the middle phalanx moving at the DIP joint (relative to a fixed distal phalanx).

http://evolve.elsevier.com/Muscolino/muscular

982

Plantar View of the Right Foot—Superficial Fascial View

FIGURE 18-1

Plantar views of the right foot. A, Superficial view, including the fascia.

983

Plantar View of the Right Foot—Superficial Muscular View

FIGURE 18-1

B, Superficial muscular view.

984

Plantar View of the Right Foot—Intermediate View

FIGURE 18-1

C, Intermediate view.

985

Plantar View of the Right Foot—Deep View

FIGURE 18-1

D, Deep view.

986

Dorsal View of the Muscles of the Right Foot

FIGURE 18-2

Dorsal view of the right foot.

987

Lateral and Medial Views of the Muscles of the Right Foot

FIGURE 18-3

Lateral and medial views of the right foot. A, Lateral view. B, Medial view.

988

Cross Section through the Right Foot

FIGURE 18-4 Cross section through the right foot, looking from distal to proximal. An opponens digiti minimi pedis, an anomalous muscle, is shown. DIP, Dorsal interosseus pedis; EDL, extensor digitorum longus; FDL, flexor digitorum longus; LP, lumbricals pedis; PI, plantar interosseus.

989

DORSAL SURFACE  

990

Extensor Digitorum Brevis The name, extensor digitorum brevis, tells us that this muscle extends the digits (i.e., toes) and is short (shorter than the extensor digitorum longus). Derivation extensor: L. a muscle that extends a body part digitorum: L. refers to a digit (toe) brevis: L. shorter Pronunciation eks-TEN-sor dij-i-TOE-rum BRE-vis

ATTACHMENTS Dorsal Surface of the Calcaneus to the Toes Two through Four

the lateral side of the distal tendons of the extensor digitorum longus muscle of toes two through four (via the dorsal digital expansion into the middle and distal phalanges)

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extends toes two through four at the MTP, PIP, and DIP joints

Reverse Mover Actions 1. Extends metatarsal at the MTP joint and extends the more proximal phalanges at the PIP and DIP joints

MTP joints = metatarsophalangeal joints; PIP joints = proximal interphalangeal joints; DIP joints = distal interphalangeal joints

Standard Mover Action Notes • The extensor digitorum brevis crosses toe joints two through four dorsally (with its fibers running horizontally in the sagittal plane); therefore it extends toes two through four. By attaching onto the distal tendon of the extensor digitorum longus of toes two through four (which attaches onto the distal phalanges of toes two through four), the extensor digitorum brevis pulls these tendons as if the belly of the extensor digitorum longus muscle itself had contracted. Therefore the extensor digitorum brevis has the same actions at toes two through four in the foot as the extensor digitorum longus muscle has, namely, extension of toes two through four at the MTP, PIP, and DIP joints. (action 1) • More specifically, extending toes at the MTP, PIP, and DIP joints refers to extending the proximal phalanges of the toes at the MTP joints, extending the middle phalanges at the PIP joints, and extending the distal phalanges at the DIP joints. (action 1)

991

FIGURE 18-5

Dorsal view of the right extensor digitorum brevis. The extensor hallucis brevis has been ghosted in.

Reverse Mover Action Notes • The reverse actions involve the distal attachment being fixed and the more proximal bone moving instead; in other words, extension of the metatarsal at the MTP joint, extension of the proximal phalanx at the PIP joint, and extension of the middle phalanx at the DIP joint. (reverse action 1) • The reverse action of metatarsal extension happens during the gait cycle as the foot approaches the position of toe-off. (reverse action 1)

Motion 1. The extensor digitorum brevis has one line of pull in the sagittal plane, and therefore its motion for each of toes two through four is its cardinal plane joint action, extension of the toe (at the MTP, PIP, and DIP joints).

Eccentric Antagonist Functions 1. Restrains/slows flexion of toes two through four at the MTP, PIP, and DIP joints, and flexion of metatarsals two through four at the MTP joints

Isometric Stabilization Functions 1. Stabilizes the MTP, PIP, and DIP joints of toes two through four

992

I N N E RVAT I O N The Deep Fibular Nerve L5, S1

A R T E R I A L S U P P LY The Dorsalis Pedis Artery (the continuation of the Anterior Tibial Artery)

PA L PAT I O N 1. With the client seated or supine, place palpating fingers approximately 1 inch (2 to 3 cm) distal to the lateral malleolus on the dorsum of the foot. 2. Have the client extend the toes (two through four) and feel for the contraction of the belly of the extensor digitorum brevis. Resistance can be added.

RELATIONSHIP TO OTHER STRUCTURES The extensor digitorum brevis is superficial except where the distal tendons of the extensor digitorum longus and the fibularis tertius cross superficially to it. Deep to the extensor digitorum brevis are the tarsal and metatarsal bones. The extensor digitorum brevis is lateral to the extensor hallucis brevis. The extensor digitorum brevis is located within the superficial front line myofascial meridian.

MISCELLANEOUS 1. The extensor digitorum brevis and the extensor hallucis brevis are the only intrinsic foot muscles located on the dorsal side. 2. The extensor digitorum brevis and extensor hallucis brevis are actually one muscle. However, the most medial part of the extensor digitorum brevis does not attach onto a digit; therefore it is given a separate name, the extensor hallucis brevis. The term digit in the name of a muscle of the lower extremity is reserved for toes two through five, not toe number one, the big toe. 3. The common belly of the extensors digitorum and hallucis brevis is often visible on the proximal lateral surface of the dorsum of the foot.

993

Extensor Hallucis Brevis The name, extensor hallucis brevis, tells us that this muscle extends the big toe and is short (shorter than the extensor hallucis longus). Derivation extensor: L. a muscle that extends a body part hallucis: L. refers to the big toe brevis: L. shorter Pronunciation eks-TEN-sor hal-OO-sis BRE-vis

ATTACHMENTS Dorsal Surface of the Calcaneus to the Dorsal Surface of the Big Toe (Toe One)

the base of the proximal phalanx of the big toe

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Extends the big toe at the MTP joint

Reverse Mover Actions 1. Extends the metatarsal of the big toe at the MTP joint

MTP joint = metatarsophalangeal joint

Standard Mover Action Notes • The extensor hallucis brevis crosses the MTP joint of the big toe (toe number one) dorsally (with its fibers running horizontally in the sagittal plane) to attach onto the proximal phalanx of the big toe. Therefore it extends the big toe at the MTP joint. (action 1) • More specifically, extending the big toe at the MTP joint refers to extending the proximal phalanx of the big toe at the MTP joint. (action 1)

Reverse Mover Action Notes • The reverse action of metatarsal extension at the MTP joint happens when the distal attachment (the proximal phalanx) is fixed and the proximal attachment (the metatarsal) moves. This occurs during the gait cycle as the foot approaches the position of toe-off. (reverse action 1)

Motion 1. The extensor hallucis brevis has one line of pull in the sagittal plane, and therefore its motion is its cardinal plane joint action, extension of the big toe at the MTP joint.

994

FIGURE 18-6

Dorsal view of the right extensor hallucis brevis. The extensor digitorum brevis has been ghosted in.

Eccentric Antagonist Function 1. Restrains/slows flexion of the MTP joint of the big toe

Isometric Stabilization Function 1. Stabilizes the MTP joint of the big toe

Additional Note on Actions 1. Given that the extensor hallucis brevis crosses the MTP joint of the big toe from lateral on the foot to medial on the big toe, this muscle should have the ability to adduct the big toe at the MTP joint.

I N N E RVAT I O N The Deep Fibular Nerve L5, S1

A R T E R I A L S U P P LY The Dorsalis Pedis Artery (the continuation of the Anterior Tibial Artery)

995

PA L PAT I O N 1. With the client seated or supine, place palpating fingers approximately 1 inch (2 to 3 cm) distal to the lateral malleolus on the dorsum of the foot. 2. Have the client extend the big toe and feel for the contraction of the belly of the extensor hallucis brevis. It will be medial to the extensor digitorum brevis. Resistance can be added.

RELATIONSHIP TO OTHER STRUCTURES The extensor hallucis brevis is superficial, except where the distal tendons of the extensor digitorum longus and the fibularis tertius cross superficially to it. Deep to the extensor hallucis brevis are the tarsal and metatarsal bones. The extensor hallucis brevis is medial to the extensor digitorum brevis. The extensor hallucis brevis is located within the superficial front line myofascial meridian.

MISCELLANEOUS 1. The extensor hallucis brevis and the extensor digitorum brevis are the only intrinsic foot muscles located on the dorsal side. 2. The extensor hallucis brevis is actually the most medial part of the extensor digitorum brevis. The extensor hallucis brevis is differentiated from the rest of the extensor digitorum brevis and given a separate name, because this part of the muscle does not attach onto a digit. Instead it attaches onto the big toe (the hallux). Therefore this portion of the extensor digitorum brevis is called the extensor hallucis brevis. The term digit in the name of a muscle of the lower extremity is reserved for toes two through five, not toe number one, the big toe.

996

PLANTAR SURFACE: LAYER I  

997

Abductor Hallucis The name, abductor hallucis, tells us that this muscle abducts the big toe. Derivation abductor: L. a muscle that abducts a body part hallucis: L. refers to the big toe Pronunciation ab-DUK-tor hal-OO-sis

ATTACHMENTS Tuberosity of the Calcaneus and the flexor retinaculum and plantar fascia to the Big Toe (Toe One) the medial plantar side of the base of the proximal phalanx

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Abducts the big toe at the MTP joint 2. Flexes the big toe at the MTP joint

Reverse Mover Actions 1. Abducts the metatarsal of the big toe at the MTP joint 2. Flexes the metatarsal of the big toe at the MTP joint

MTP joint = metatarsophalangeal joint

Standard Mover Action Notes • The abductor hallucis crosses the MTP joint to attach onto the proximal phalanx of the big toe (toe number one) on the medial side (with its fibers running horizontally). Therefore when the abductor hallucis contracts, it pulls the big toe medially away from the second toe (which is the axis of abduction/adduction of the toes). Therefore the abductor hallucis abducts the big toe at the MTP joint. (action 1) • The abductor hallucis crosses the MTP joint to attach onto the proximal phalanx of the big toe on the plantar side (with its fibers running horizontally in the sagittal plane). Therefore when the abductor hallucis pulls on the big toe, it flexes the big toe at the MTP joint. (action 2) • More specifically, abduction and flexion of the big toe at the MTP joint refers to abduction and flexion of the proximal phalanx of the big toe relative to the first metatarsal at the MTP joint. (actions 1, 2)

Reverse Mover Action Notes • Reverse actions usually occur when the distal attachment is fixed and the proximal attachment moves instead. The reverse actions of the abductor hallucis involve abduction and flexion of the metatarsal of the big toe relative to a fixed proximal phalanx at the MTP joint. These reverse actions are not likely to occur. (reverse actions 1, 2)

998

FIGURE 18-7

Plantar view of the right abductor hallucis.

Motion 1. The abductor hallucis has one line of pull in an oblique plane and therefore creates one motion, which is a combination of abduction and flexion of the big toe at the MTP joint.

Eccentric Antagonist Functions 1. Restrains/slows adduction of the MTP joint of the big toe 2. Restrains/slows extension of the MTP joint of the big toe

Isometric Stabilization Function 1. Stabilizes the MTP joint of the big toe.

I N N E RVAT I O N The Medial Plantar Nerve S1, S2

999

A R T E R I A L S U P P LY The Medial Plantar Artery (a branch of the Posterior Tibial Artery)

PA L PAT I O N 1. With the client prone or supine, place palpating fingers along the proximal half of the plantar foot on the medial side. 2. Have the client abduct the big toe at the metatarsophalangeal joint and feel for the contraction of the abductor hallucis. Resistance can be added. 3. Continue palpating proximally and distally toward its attachments.

RELATIONSHIP TO OTHER STRUCTURES The abductor hallucis is located in the first plantar layer of intrinsic muscles of the foot along with the abductor digiti minimi pedis and the flexor digitorum brevis (and the plantar fascia). The abductor hallucis is medial to the plantar fascia and the flexor digitorum brevis (which is deep to the plantar fascia). The abductor hallucis is located within the superficial back line myofascial meridian.

MISCELLANEOUS 1. All three muscles in the first plantar layer of intrinsic muscles of the foot attach proximally onto the tuberosity of the calcaneus and the plantar fascia, and attach distally onto the toes. 2. Given the attachment of the abductor hallucis into the plantar fascia, strengthening this muscle should help to strengthen the arch structure of the foot, thereby helping to prevent excessive pronation (dropped arch). 3. Given that a bunion (hallux valgus) involves the proximal phalanx of the big toe adducting toward the second toe, strengthening the abductor hallucis should be beneficial for clients with this condition.

1000

Abductor Digiti Minimi Pedis The name, abductor digiti minimi pedis, tells us that this muscle abducts the little toe. Derivation abductor: L. a muscle that abducts a body part digiti: L. refers to a digit (toe) minimi: L. least pedis: L. refers to the foot Pronunciation ab-DUK-tor DIJ-i-tee MIN-i-mee PEED-us

ATTACHMENTS Tuberosity of the Calcaneus and the plantar fascia to the Little Toe (Toe Five) the lateral plantar side of the base of the proximal phalanx

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Abducts the little toe at the MTP joint 2. Flexes the little toe at the MTP joint

Reverse Mover Actions 1. Abducts the metatarsal of the little toe at the MTP joint 2. Flexes the metatarsal of the little toe at the MTP joint

MTP joint = metatarsophalangeal joint

Standard Mover Action Notes • The abductor digiti minimi pedis crosses the MTP joint to attach onto the proximal phalanx of the little toe (toe number five) on the lateral side (with its fibers running horizontally). When the abductor digiti minimi pedis contracts, it pulls the little toe laterally away from the second toe (which is the axis of abduction/adduction of the toes); therefore the abductor digiti minimi pedis abducts the little toe at the MTP joint. (action 1) • The abductor digiti minimi pedis crosses the MTP joint to attach onto the proximal phalanx of the little toe on the plantar side (with its fibers running horizontally in the sagittal plane); therefore when it pulls on the little toe, the abductor digiti minimi pedis flexes the little toe at the MTP joint. (action 2) • More specifically, abduction and flexion of the little toe at the MTP joint refer to abduction and flexion of the proximal phalanx of the little toe relative to the fixed metatarsal at the MTP joint. (actions 1, 2)

1001

FIGURE 18-8

Plantar view of the right abductor digiti minimi pedis.

Reverse Mover Action Notes • Reverse actions usually occur when the distal attachment is fixed and the proximal attachment moves instead. Reverse actions of the abductor digiti minimi pedis involve abduction or flexion of the fifth metatarsal relative to the fixed proximal phalanx of the little toe at the MTP joint. These reverse actions are not very likely to occur. (reverse action 1)

Motion 1. The abductor digiti minimi pedis has one line of pull in an oblique plane and therefore creates one motion, which is a combination of abduction and flexion of the little toe at the MTP joint.

Eccentric Antagonist Functions 1. Restrains/slows adduction of the MTP joint of the little toe 2. Restrains/slows extension of the MTP joint of the little toe

Isometric Stabilization Function 1. Stabilizes the MTP joint of the little toe

1002

I N N E RVAT I O N The Lateral Plantar Nerve S2, S3

A R T E R I A L S U P P LY The Lateral Plantar Artery (a branch of the Posterior Tibial Artery)

PA L PAT I O N 1. With the client prone or supine, place palpating fingers on the lateral side of the plantar surface of the foot. 2. Have the client abduct the little toe and feel for the contraction of the abductor digiti minimi pedis. Resistance can be added. 3. Continue palpating proximally and distally toward its attachments.

RELATIONSHIP TO OTHER STRUCTURES The abductor digiti minimi pedis is located in the first plantar layer of intrinsic muscles of the foot along with the abductor hallucis and the flexor digitorum brevis (and the plantar fascia). The abductor digiti minimi pedis is lateral to the plantar fascia and the flexor digitorum brevis (which is deep to the plantar fascia). The abductor digiti minimi pedis is located within the superficial back line myofascial meridian.

MISCELLANEOUS 1. The abductor digiti minimi pedis is also known as the abductor digiti minimi. However, this allows for confusion with the abductor digiti minimi manus of the hand, which abducts the little finger of the hand. 2. All three muscles in the first plantar layer of intrinsic muscles of the foot attach proximally onto the tuberosity of the calcaneus and the plantar fascia, and attach distally onto the toes. 3. Given the attachment of the abductor digiti minimi pedis into the plantar fascia, strengthening this muscle should help to strengthen the arch structure of the foot, thereby helping to prevent excessive pronation (dropped arch).

1003

Flexor Digitorum Brevis The name, flexor digitorum brevis, tells us that this muscle flexes the digits (i.e., toes) and is short (shorter than the flexor digitorum longus). Derivation flexor: L. a muscle that flexes a body part digitorum: L. refers to a digit (toe) brevis: L. shorter Pronunciation FLEKS-or dij-i-TOE-rum BRE-vis

ATTACHMENTS Tuberosity of the Calcaneus and the plantar fascia to the Toes Two through Five the medial and lateral sides of the middle phalanges

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes toes two through five at the MTP and PIP joints

Reverse Mover Actions 1. Flexes the metatarsals at the MTP joints and flexes the proximal phalanges at the PIP joints

MTP joints = metatarsophalangeal joints; PIP joints = proximal interphalangeal joints

Standard Mover Action Notes • The flexor digitorum brevis crosses both the MTP and PIP joints of toes two through five on the plantar side (with its fibers running horizontally in the sagittal plane) to then attach onto the medial and lateral sides of the middle phalanges of toes two through five. Because the flexor digitorum brevis crosses these joints on the plantar side, it flexes the MTP and the PIP joints of toes two through five. (action 1) • More specifically, flexing toes at the MTP and PIP joints refers to flexing the proximal phalanges at the MTP joints and flexing the middle phalanges at the PIP joints. (action 1)

Reverse Mover Action Notes • The reverse action involves motion of the more proximal bone at each of the joints of the toes. In other words, the reverse action at the MTP joint is flexion of the metatarsal of the toe relative to a fixed proximal phalanx, and the reverse action at the PIP joint is flexion of the proximal phalanx relative to a fixed middle phalanx. These reverse actions are not likely to occur. (reverse action 1)

1004

FIGURE 18-9

Plantar view of the right flexor digitorum brevis.

Motion 1. The flexor digitorum brevis has one line of pull in the sagittal plane, and therefore its motion for each of toes two through five is its cardinal plane joint action, flexion of the toe (at the MTP and PIP joints).

Eccentric Antagonist Functions 1. Restrains/slows extension of toes two through five at the MTP and PIP joints, and extension of metatarsals two through five at the MTP joints

Isometric Stabilization Functions 1. Stabilizes the MTP and PIP joints of toes two through five

I N N E RVAT I O N The Medial Plantar Nerve S1, S2

1005

A R T E R I A L S U P P LY The Medial and Lateral Plantar Arteries (terminal branches of the Posterior Tibial Artery)

PA L PAT I O N 1. With the client prone or supine, place palpating fingers on the midline of the plantar side of the foot. 2. Have the client flex toes two through five and feel for the contraction of the flexor digitorum brevis deep to the plantar fascia. Resistance can be added. 3. Continue palpating proximally and distally toward its attachments.

RELATIONSHIP TO OTHER STRUCTURES The flexor digitorum brevis is located in the first plantar layer of intrinsic muscles of the foot along with the abductor hallucis and the abductor digiti minimi pedis (and the plantar fascia). The flexor digitorum brevis is lateral to the abductor hallucis, medial to the abductor digiti minimi pedis, and deep to the plantar fascia. Deep to the belly of the flexor digitorum brevis is the quadratus plantae. The tendons of the flexor digitorum brevis are superficial to the tendons of the flexor digitorum longus. The flexor digitorum brevis is located within the superficial back line myofascial meridian.

MISCELLANEOUS 1. All three muscles in the first plantar layer of intrinsic muscles of the foot attach proximally onto the tuberosity of the calcaneus and the plantar fascia, and attach distally onto the toes. 2. Given the attachment of the flexor digitorum brevis into the plantar fascia, strengthening this muscle should help to strengthen the arch structure of the foot, thereby helping to prevent excessive pronation (dropped arch). 3. Each distal tendon of the flexor digitorum brevis splits to allow passage for the flexor digitorum longus’ distal tendon to attach onto the distal phalanx (of toes two through five). This arrangement is essentially identical to that of the splitting of each distal tendon of the flexor digitorum superficialis to allow passage for the flexor digitorum profundus’ distal tendon onto the distal phalanx (of fingers two through five in the upper extremity).

1006

PLANTAR SURFACE: LAYER II  

1007

Quadratus Plantae The name, quadratus plantae, tells us that this muscle has a square shape and is located on the plantar side of the foot. Derivation quadratus: L. squared plantae: L. refers to the plantar surface of the foot Pronunciation kwod-RAY-tus PLAN-tee

ATTACHMENTS The Calcaneus the medial and lateral sides to the Distal Tendon of the Flexor Digitorum Longus Muscle the lateral margin

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes toes two through five at the MTP, PIP, and DIP joints

Reverse Mover Actions 1. Flexes metatarsals at the MTP joints and flexes the more proximal phalanges at the PIP and DIP joints

MTP joints = metatarsophalangeal joints; PIP joints = proximal interphalangeal joints; DIP joints = distal interphalangeal joints

Standard Mover Action Notes • The quadratus plantae (with its fibers running horizontally in the sagittal plane) attaches into the distal tendon of the flexor digitorum longus (FDL) muscle. When the quadratus plantae contracts, it pulls on that tendon in the same way as if the belly of the FDL muscle itself had contracted. Therefore the quadratus plantae muscle has the same actions as the FDL muscle (in the foot), namely, flexion of toes two through five. Given that the attachments are onto the distal phalanx of these toes, the MTP, PIP, and DIP joints are all crossed and therefore are all flexed. (action 1) • More specifically, flexing toes at the MTP, PIP, and DIP joints refers to flexing the proximal phalanges of the toes at the MTP joints, flexing the middle phalanges at the PIP joints, and flexing the distal phalanges at the DIP joints. (action 1) • Similar to the FDL, the quadratus plantae has no individual control of flexion of toes two through five because all of its muscle fibers converge into the common distal tendon of the FDL before it splits to go to each of the toes. (action 1)

Reverse Mover Action Notes • Reverse actions usually occur when the distal attachment is fixed and the proximal attachment moves instead. In other words, the reverse action of the quadratus plantae at the MTP joint is flexion of the metatarsal of the toe relative to its fixed proximal phalanx. The reverse action at the PIP joint is flexion of the proximal phalanx relative to the fixed middle phalanx. The reverse action at the DIP joint is flexion of the middle phalanx relative to the fixed distal phalanx. These reverse actions are not likely to occur. (reverse action 1)

1008

FIGURE 18-10

Plantar view of the right quadratus plantae.

Motion 1. The quadratus plantae has one line of pull in the sagittal plane, and therefore its motion for each of toes two through five is its cardinal plane joint action, flexion of the toe (at the MTP, PIP, and DIP joints).

Eccentric Antagonist Functions 1. Restrains/slows extension at the MTP, PIP, and DIP joints of toes two through five

Isometric Stabilization Functions 1. Stabilizes the MTP, PIP, and DIP joints of toes two through five

Additional Note on Actions 1. Given its assistance to the flexor digitorum longus, the quadratus plantae is also known as the flexor accessorius or the flexor digitorum accessorius. The quadratus plantae not only assists by adding further strength but also assists by modifying (straightening out) the line of pull of the flexor digitorum longus muscle. If not for the quadratus plantae’s assistance, the contraction of the flexor

1009

digitorum longus would pull the toes slightly medially as it flexed them.

I N N E RVAT I O N The Lateral Plantar Nerve S2, S3

A R T E R I A L S U P P LY The Medial and Lateral Plantar Arteries (terminal branches of the Posterior Tibial Artery)

PA L PAT I O N 1. With the client prone or supine, place palpating fingers on the midline of the proximal half of the plantar side of the foot and feel for the quadratus plantae deep to the plantar fascia and flexor digitorum brevis. 2. To further bring out the quadratus plantae, resist the client from actively flexing toes two through five. 3. Keep in mind that this will cause the more superficial flexor digitorum brevis to contract as well.

RELATIONSHIP TO OTHER STRUCTURES The quadratus plantae is in the second plantar layer of intrinsic muscles of the foot along with the lumbricals pedis (and the distal tendons of the flexor digitorum longus and the flexor hallucis longus). The quadratus plantae is deep to the flexor digitorum brevis. Deep to the quadratus plantae are the tarsal bones. The quadratus plantae is located within the superficial back line myofascial meridian.

MISCELLANEOUS 1. Proximally, the quadratus plantae has two heads. The medial head attaches onto the medial side of the calcaneus and the lateral head attaches onto the lateral side of the calcaneus.

1010

Lumbricals Pedis (There are four lumbrical pedis muscles, named one, two, three, and four.) The name, lumbricals pedis, tells us that these muscles are shaped like earthworms and located in the foot. Derivation lumbricals: L. earthworms pedis: L. refers to the foot Pronunciation LUM-bri-kuls PEED-us

ATTACHMENTS The Distal Tendons of the Flexor Digitorum Longus Muscle ONE: medial border of the tendon to toe two TWO: adjacent sides of the tendons to toes two and three THREE: adjacent sides of the tendons to toes three and four FOUR: adjacent sides of the tendons to toes four and five to the Dorsal Digital Expansion the medial sides of the extensor digitorum longus tendons merging into the dorsal digital expansion of toes two through five

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flex toes two through five at the MTP joints

Reverse Mover Actions 1. Flex the metatarsals at the MTP joints

2. Extend toes two through five at the PIP and DIP joints

2. Extend the more proximal phalanges at the PIP and DIP joints

MTP joints = metatarsophalangeal joints; PIP joints = proximal interphalangeal joints; DIP joints = distal interphalangeal joints

Standard Mover Action Notes • The lumbricals pedis cross the MTP joint of toes two through five on the plantar side (with their fibers running horizontally in the sagittal plane); therefore they flex toes two through five at the MTP joints. More specifically, flexing toes at the MTP joints refers to flexing the proximal phalanges of the toes at the MTP joints. (action 1) • The lumbricals pedis, by attaching into the dorsal digital expansion of the tendons of the extensor digitorum longus (after the MTP joint but before the interphalangeal [IP] joints of the toes), in effect exert their pull (horizontally in the sagittal plane) at the attachments of the extensor digitorum longus, which are the middle and distal phalanges of toes two through five. The lumbricals pedis, in effect, cross the PIP and DIP joints on the dorsal side and therefore extend these joints of toes two through five. More specifically, extending toes at the IP joints refers to extending the middle phalanges of the toes at the proximal IP joints and extending the distal phalanges at the distal IP joints. (action 2)

1011

FIGURE 18-11

Plantar view of the right lumbricals pedis. The quadratus plantae has been ghosted in.

Reverse Mover Action Notes • Reverse actions usually occur when the distal attachment is fixed and the proximal attachment moves instead. In other words, the reverse action of the lumbricals pedis at the MTP joint is flexion of the metatarsal of the toe relative to its fixed proximal phalanx, the reverse action at the PIP joint is extension of the proximal phalanx relative to the fixed middle phalanx, and the reverse action at the DIP joint is extension of the middle phalanx relative to the fixed distal phalanx. The reverse action of flexion of the metatarsal at the MTP joint is not likely to occur. However, the reverse actions at the IP joints occur during toe-off in the gait cycle. (reverse actions 1, 2)

Motion 1. Each lumbrical pedis has one line of pull in the sagittal plane, and therefore its motion for each of toes two through five is a combination of its cardinal plane joint actions, flexion of the toe at the MTP joint, and extension of the toe at the PIP and DIP joints.

Eccentric Antagonist Functions

1012

1. Restrains/slows flexion of the PIP and DIP joints of toes two through five 2. Restrains/slows extension of the MTP joints of toes two through five

Isometric Stabilization Functions 1. Stabilizes the MTP, PIP, and DIP joints of toes two through five

Additional Notes on Actions 1. The lumbricals pedis flex the MTP joints because they cross these joints on the plantar side. Because they attach into the dorsal digital expansion of the foot, their line of pull is transmitted across the dorsal side of the interphalangeal (IP) joints; therefore they extend the IP joints. All muscles that attach into the dorsal digital expansion of the foot flex the MTP joints and extend the IP joints. 2. The lumbricals manus of the hand have similar actions in that they flex the fingers at the metacarpophalangeal (MCP) joints and extend the fingers at the proximal and distal IP joints.

I N N E RVAT I O N The Medial and Lateral Plantar Nerves S1, S2, S3 medial plantar nerve to lumbrical pedis one lateral plantar nerve to lumbricals pedis two through four

A R T E R I A L S U P P LY The Medial and Lateral Plantar Arteries (terminal branches of the Posterior Tibial Artery) branches of the Plantar Arch (an anastomosis between the Lateral Plantar Artery and the Dorsalis Pedis Artery)

PA L PAT I O N 1. With the client prone or supine, place palpating hand distally on the plantar surface of the foot and feel for the lumbricals pedis between the metatarsal bones. 2. To further bring out the lumbricals pedis, resist the client from actively flexing the metatarsophalangeal joint (with the interphalangeal joints extended) of toes two through five. Note: Many people are unable to isolate these actions.

RELATIONSHIP TO OTHER STRUCTURES The lumbricals pedis are in the second plantar layer of the intrinsic muscles of the foot along with the quadratus plantae (and the distal tendons of the flexor digitorum longus and flexor hallucis longus). The lumbricals pedis are located between the distal tendons of the flexor digitorum longus in the distal foot. The lumbricals pedis are deep to the plantar aponeurosis. No muscles are superficial to the lumbricals pedis except, perhaps, a small part of the flexor digitorum brevis. Deep to the lumbricals pedis are the metatarsals and the plantar interossei and dorsal interossei pedis muscles. The lumbricals pedis may be involved with the superficial back line and deep front line myofascial meridians.

MISCELLANEOUS 1. The lumbricals pedis are actually four small separate muscles named from the medial side: one, two, three, and four. 2. The lumbricals pedis are usually known as the lumbricals. However, this allows for confusion with the lumbricals manus of the hand.

1013

1014

PLANTAR SURFACE: LAYER III  

1015

Flexor Hallucis Brevis The name, flexor hallucis brevis, tells us that this muscle flexes the big toe and is short (shorter than the flexor hallucis longus). Derivation flexor: L. a muscle that flexes a body part hallucis: L. refers to the big toe brevis: L. shorter Pronunciation FLEKS-or hal-OO-sis BRE-vis

ATTACHMENTS Cuboid and the third Cuneiform to the Big Toe (Toe One)

the medial and lateral sides of the plantar surface of the base of the proximal phalanx

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes the big toe at the MTP joint

Reverse Mover Actions 1. Flexes the metatarsal of the big toe at the MTP joint

MTP joint = metatarsophalangeal joint

Standard Mover Action Notes • The flexor hallucis brevis crosses the MTP joint of the big toe (toe number one) on the plantar side (with its fibers running horizontally in the sagittal plane) to attach onto the proximal phalanx of the big toe. Therefore the flexor hallucis brevis flexes the big toe at the MTP joint. (action 1) • More specifically, flexing the big toe at the MTP joint refers to flexing the proximal phalanx of the big toe relative to its fixed metatarsal at the MTP joint. (action 1)

Reverse Mover Action Note • Reverse actions usually occur when the distal attachment is fixed and the proximal attachment moves instead. The reverse action of the flexor hallucis brevis is flexion of the metatarsal of the big toe relative to the fixed proximal phalanx at the MTP joint. This reverse action is not likely to occur. (reverse action 1)

Motion 1. The flexor hallucis brevis has one line of pull in the sagittal plane, and therefore its motion is its cardinal plane joint action, flexion of the big toe at the MTP joint.

1016

FIGURE 18-12

Plantar view of the right flexor hallucis brevis.

Eccentric Antagonist Function 1. Restrains/slows extension of the MTP joint of the big toe

Isometric Stabilization Function 1. Stabilizes the MTP joint of the big toe

Additional Note on Actions 1. The flexor hallucis brevis splits distally to attach onto the medial and lateral sides of the proximal phalanx of the big toe. The medial head of the flexor hallucis brevis crosses the MTP joint medially to attach onto the proximal phalanx of the big toe, so it can pull the big toe medially away from the second toe (abduction). The lateral head of the flexor hallucis brevis crosses the MTP joint laterally to attach onto the proximal phalanx of the big toe, so it can pull the big toe laterally toward the second toe (adduction). Because the second toe is the axis for abduction/adduction of the toes, the flexor hallucis brevis can both abduct and adduct the big toe at the MTP joint.

I N N E RVAT I O N

1017

The Medial Plantar Nerve S1, S2

A R T E R I A L S U P P LY The Medial Plantar Artery (a branch of the Posterior Tibial Artery)

PA L PAT I O N 1. With the client prone or supine, place palpating fingers distally on the medial side of the plantar surface of the foot and feel for the flexor hallucis brevis. 2. To further bring out the flexor hallucis brevis, resist the client from actively flexing the big toe at the metatarsophalangeal joint. 3. Continue palpating proximally and distally toward its attachments.

RELATIONSHIP TO OTHER STRUCTURES The flexor hallucis brevis is located in the third plantar layer of intrinsic muscles of the foot along with the flexor digiti minimi pedis and the adductor hallucis. The flexor hallucis brevis is medial to the oblique head of the adductor hallucis and lateral to the abductor hallucis. Even though the flexor hallucis brevis is in the third plantar layer, it is relatively superficial, because there is no belly of any other muscle directly superficial to it. Only the tendon of the flexor hallucis longus and the plantar fascia are superficial to it. Deep to the flexor hallucis brevis is the first metatarsal and the first dorsal interosseus pedis muscle. The flexor hallucis brevis is located within the superficial back line myofascial meridian.

MISCELLANEOUS 1. The flexor hallucis brevis can be considered to have two heads: a medial head and a lateral head. 2. Distally, there is a sesamoid bone in each of the medial and lateral tendons of the flexor hallucis brevis.

1018

Flexor Digiti Minimi Pedis The name, flexor digiti minimi pedis, tells us that this muscle flexes the little toe. Derivation flexor: L. a muscle that flexes a body part digiti: L. refers to a digit (toe) minimi: L. least pedis: L. refers to the foot Pronunciation FLEKS-or DIJ-i-tee MIN-i-mee PEED-us

ATTACHMENTS Fifth Metatarsal the plantar surface of the base of the fifth metatarsal and the distal tendon of the fibularis longus to the Little Toe (Toe Five) the plantar surface of the proximal phalanx

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Flexes the little toe at the MTP joint

Reverse Mover Actions 1. Flexes the metatarsal of the little toe at the MTP joint

MTP joint = metatarsophalangeal joint

Standard Mover Action Notes • The flexor digiti minimi pedis crosses the MTP joint of the little toe (toe number five) on the plantar side (with its fibers running horizontally in the sagittal plane) to attach onto the proximal phalanx of the little toe. Therefore it flexes the little toe at the MTP joint. (action 1) • More specifically, flexing the little toe at the MTP joint refers to flexing the proximal phalanx of the little toe relative to its fixed metatarsal at the MTP joint. (action 1)

Reverse Mover Action Note • The reverse action involves motion of the fifth metatarsal relative to the proximal phalanx of the little toe at the MTP joint and would occur if the proximal phalanx is fixed and the fifth metatarsal is mobile. This reverse action is not very likely to occur.

Motion 1. The flexor digiti minimi pedis has one line of pull in the sagittal plane, and therefore its motion is its cardinal plane joint action, flexion of the little toe at the MTP joint.

1019

FIGURE 18-13

Plantar view of the right flexor digiti minimi pedis.

Eccentric Antagonist Function 1. Restrains/slows extension of the MTP joint of the little toe

Isometric Stabilization Function 1. Stabilizes the MTP joint of the little toe

I N N E RVAT I O N The Lateral Plantar Nerve S2, S3

A R T E R I A L S U P P LY The Lateral Plantar Artery (a branch of the Posterior Tibial Artery)

PA L PAT I O N 1. With the client prone or supine, place palpating hand distally on the lateral side of the plantar

1020

surface of the foot (just medial to the abductor digiti minimi pedis) and feel for the flexor digiti minimi pedis. 2. To further bring out the flexor digiti minimi pedis, resist the client from actively flexing the little toe at the metatarsophalangeal joint. 3. Continue palpating proximally and distally toward its attachments.

RELATIONSHIP TO OTHER STRUCTURES The flexor digiti minimi pedis is in the third plantar layer of intrinsic muscles of the foot along with the flexor hallucis brevis and the adductor hallucis. The flexor digiti minimi pedis lies directly medial to the abductor digiti minimi pedis and lateral to the fourth lumbrical pedis muscle. Even though the flexor digiti minimi pedis is in the third plantar layer, it is relatively superficial, because there is no belly of any other muscle directly superficial to it. It is deep only to the plantar fascia. Deep to the flexor digiti minimi pedis is the fifth metatarsal (and a small portion of the third plantar interosseus and the fourth dorsal interosseus pedis). The flexor digiti minimi pedis is located within the superficial back line myofascial meridian.

MISCELLANEOUS 1. The flexor digiti minimi pedis is also known as the flexor digiti minimi. However, this allows for confusion with the flexor digiti minimi manus of the hand, which flexes the little finger. 2. The flexor digiti minimi pedis is also known as the flexor digiti minimi brevis, although the addition of the word brevis at the end does not make sense in this case. Usually, the word brevis at the end of a muscle’s name is added to distinguish the muscle from a longer muscle that does the same action. In this case, there is no flexor digiti minimi longus. 3. The flexor digiti minimi pedis occasionally has attachments that range from the tarsals proximally, onto the fifth metatarsal distally. When this occurs, this muscle has the ability to oppose the little toe toward the other toes; therefore it is named the opponens digiti minimi pedis (see Figure 18-4). This muscle is commonly found in apes, who have feet that are more handy than ours!

1021

Adductor Hallucis The name, adductor hallucis, tells us that this muscle adducts the big toe. Derivation adductor: L. a muscle that adducts a body part hallucis: L. refers to the big toe Pronunciation ad-DUK-tor hal-OO-sis

ATTACHMENTS Metatarsals OBLIQUE HEAD: from the base of metatarsals two through four and the distal tendon of the fibularis longus TRANSVERSE HEAD: arises from the plantar metatarsophalangeal ligaments to the Big Toe (Toe One) the lateral side of the base of the proximal phalanx

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Adducts the big toe at the MTP joint 2. Flexes the big toe at the MTP joint

Reverse Mover Actions 1. Adducts the metatarsal of the big toe at the MTP joint 2. Flexes the metatarsal of the big toe at the MTP joint

MTP joint = metatarsophalangeal joint

Standard Mover Action Notes • The adductor hallucis crosses the MTP joint to attach onto the proximal phalanx of the big toe on the lateral side (with its fibers running horizontally in the frontal plane). Therefore when the adductor hallucis contracts, it pulls the big toe laterally toward the second toe (which is the axis of abduction/adduction of the toes). Therefore the adductor hallucis adducts the big toe at the MTP joint. (action 1) • The adductor hallucis crosses the MTP joint to attach onto the proximal phalanx of the big toe on the plantar side (with its fibers running horizontally in the sagittal plane). Therefore when the adductor hallucis pulls on the big toe, it flexes the big toe at the MTP joint. (action 2) • More specifically, adduction and flexion of the big toe at the MTP joint refer to adduction and flexion of the proximal phalanx of the big toe relative to the first metatarsal at the MTP joint. (actions 1, 2)

1022

FIGURE 18-14

Plantar view of the right adductor hallucis.

Reverse Mover Action Note • The reverse actions involve motion (adduction and flexion) of the metatarsal of the big toe relative to a fixed proximal phalanx at the MTP joint. These reverse actions are not likely to occur. (reverse actions 1, 2)

Motion 1. The adductor hallucis has one line of pull in an oblique plane and therefore creates one motion, which is a combination of adduction and flexion of the big toe at the MTP joint.

Eccentric Antagonist Functions 1. Restrains/slows abduction and extension of the MTP joint of the big toe

Isometric Stabilization Function 1. Stabilizes the MTP joint of the big toe

Isometric Stabilization Function Note

1023

• The adductor hallucis (especially the transverse head) also stabilizes the transverse arch of the foot.

I N N E RVAT I O N The Lateral Plantar Nerve S2, S3

A R T E R I A L S U P P LY Branches of the Plantar Arch (an anastomosis between the Lateral Plantar Artery and the Dorsalis Pedis Artery)

PA L PAT I O N 1. With the client prone or supine, place palpating hand on the plantar surface of the foot over the second, third, and fourth metatarsals. 2. Have the client adduct the big toe and feel for the contraction of the adductor hallucis. Resistance can be added.

RELATIONSHIP TO OTHER STRUCTURES The adductor hallucis is located in the third plantar layer of intrinsic muscles of the foot along with the flexor hallucis brevis and the flexor digiti minimi pedis. The oblique head of the adductor hallucis is directly lateral to the flexor hallucis brevis. The oblique head of the adductor hallucis is deep to the lumbricals pedis and the (distal aspect of the) quadratus plantae. The transverse head of the adductor hallucis is deep to the flexors digitorum longus and brevis tendons. Deep to the adductor hallucis are the interossei muscles and the metatarsals. The adductor hallucis is located within the superficial back line myofascial meridian.

MISCELLANEOUS 1. The adductor hallucis has two distinct heads: distally, there is the transverse head, with fibers that run transversely across the foot, and proximally, there is the oblique head, with fibers that run obliquely across the foot. 2. There is an adductor pollicis of the hand that also has two heads: an oblique head and a transverse head. 3. The adductor hallucis occasionally has attachments that attach distally onto the first metatarsal. When this occurs, this muscle has the ability to oppose the big toe toward the other toes and is named the opponens hallucis of the foot. This arrangement is common in apes, who have feet that are more handy than ours! 4. The oblique head of the adductor hallucis often blends with the flexor hallucis brevis. 5. Given that a bunion (hallux valgus) involves the proximal phalanx of the big toe adducting toward the second toe, a tight adductor hallucis could aggravate this condition.

1024

PLANTAR SURFACE: LAYER IV  

1025

Plantar Interossei (There are three plantar interossei, named one, two, and three.) The name, plantar interossei, tells us that these muscles are located between bones (metatarsals) on the plantar side. Derivation plantar: L. refers to the plantar side of the foot interossei: L. between bones Pronunciation PLAN-tar in-ter-OSS-ee-eye

ATTACHMENTS Metatarsals the medial side (second-toe side) of metatarsals three through five: ONE: attaches onto metatarsal three TWO: attaches onto metatarsal four THREE: attaches onto metatarsal five to the Second-Toe Sides of the Proximal Phalanges of Toes Three through Five, and the Dorsal Distal Expansion the bases of the proximal phalanges: ONE: attaches to toe three TWO: attaches to toe four THREE: attaches to toe five

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Adduct toes three through five at the MTP joints 2. Flex toes three through five at the MTP joints

Reverse Mover Actions 1. Adduct the metatarsals of toes three through five at the MTP joints

3. Extend toes three through five at the PIP and DIP joints

2. Flex the metatarsals at the MTP joints 3. Extend the more proximal phalanges at the PIP and DIP joints

MTP joints = metatarsophalangeal joints; PIP joints = proximal interphalangeal joints; DIP joints = distal interphalangeal joints

Standard Mover Action Notes • The plantar interossei cross the MTP joint of toes three through five medially (with their fibers running horizontally) and pull toes three through five medially toward the second toe (which is the axis for abduction/adduction of the toes). Therefore the plantar interossei adduct toes three through five at the MTP joints. (action 1) • The plantar interossei cross the MTP joint of toes three through five on the plantar side (with their fibers running horizontally in the sagittal plane); therefore they flex toes three through five at the MTP joints. (action 2)

1026

FIGURE 18-15

Plantar view of the right plantar interossei.

• More specifically, adducting and flexing toes at the MTP joints refers to adducting and flexing the proximal phalanges of the toes at the MTP joints. (actions 1, 2) • The plantar interossei, by attaching into the dorsal digital expansion, in other words the tendons of the extensor digitorum longus muscle (after the MTP joint but before the interphalangeal [IP] joints of the toes), exert their pull at the attachments of the extensor digitorum longus, the distal phalanx of toes three through five. The plantar interossei, in effect, cross the PIP and DIP joints on the dorsal side (with their fibers running horizontally in the sagittal plane); therefore the plantar interossei extend both the PIP and DIP joints of toes three through five. (action 3) • More specifically, extending toes at the IP joints refers to extending the middle phalanges of the toes at the PIP joints and extending the distal phalanges at the DIP joints. (action 3)

Reverse Mover Action Note • The reverse actions involve motion of the more proximal bone at each of the joints of the toes. In other words, the reverse action at the MTP joint is adduction or flexion of the metatarsal of the toe relative to its fixed proximal phalanx, the reverse action at the PIP joint is extension of the proximal phalanx relative to the fixed middle phalanx, and the reverse action at the DIP joint is extension of the middle phalanx relative to the fixed distal phalanx. The reverse action at the MTP joint is not likely to occur. However, the reverse actions at the PIP and DIP joints occur during

1027

toe-off in the gait cycle. (reverse actions 1, 2, 3)

Motion 1. Each plantar interosseus has one line of pull in an oblique plane, and therefore its motion for each of toes three through five is a combination of adduction of the toe at the MTP joint and flexion of the toe at the MTP joint and extension of the toe at the PIP and DIP joints.

Eccentric Antagonist Functions 1. Restrain/slow abduction of the MTP joints of toes three through five 2. Restrain/slow extension of the MTP joints of toes three through five 3. Restrain/slow flexion of the IP joints of toes three through five

Isometric Stabilization Functions 1. Stabilize toes three through five at the MTP, PIP, and DIP joints

Additional Notes on Actions 1. The plantar interossei flex the MTP joints because they cross these joints on the plantar side. Because they attach into the dorsal digital expansion of the foot, their line of pull is transmitted across the dorsal side of the interphalangeal (IP) joints; therefore they extend the IP joints. All muscles that attach into the dorsal digital expansion of the foot flex the MTP joints and extend the IP joints. 2. The plantar interossei have the same actions as the lumbricals pedis of the foot, namely, flexion of the MTP joints and extension of the IP joints. And the plantar interossei also adduct toes three through five at the MTP joints. 3. There are also palmar interossei manus of the hand that have essentially identical actions (adduction and flexion of the fingers at the metacarpophalangeal [MCP] joints, and extension of the fingers at the PIP and DIP joints) to the plantar interossei of the foot. 4. A mnemonic for remembering the adduction and abduction actions of the plantar interossei and dorsal interossei pedis is DAB PAD: Dorsals ABduct, Plantars ADduct.

I N N E RVAT I O N The Lateral Plantar Nerve S2, S3

A R T E R I A L S U P P LY Branches of the Plantar Arch (an anastomosis between the Lateral Plantar Artery and the Dorsalis Pedis Artery)

PA L PAT I O N Given the thickness of the plantar fascia and the depth of the plantar interossei, it is difficult to distinguish them from other deep muscles of the foot on the plantar side. If attempted, resist the client from adducting toes three through five and feel for the contraction of the plantar interossei between the metatarsals on the plantar side of the foot.

RELATIONSHIP TO OTHER STRUCTURES The plantar interossei are in the fourth plantar layer of intrinsic muscles of the foot along with the dorsal interossei pedis (and the distal tendons of the fibularis longus and tibialis posterior). From the plantar perspective, the plantar interossei are deep to the lumbricals pedis. From the plantar perspective, the plantar interossei are somewhat superficial to (partially overlap) the metatarsals and the dorsal interossei pedis. The plantar interossei are involved with the superficial back line and deep front line myofascial meridians.

1028

MISCELLANEOUS 1. There are three separate plantar interossei muscles. They are named, from the medial side, one, two, and three. 2. The first plantar interosseus attaches to the third digit of the foot and moves the third toe. Similarly, the second plantar interosseus attaches onto and moves the fourth toe, and the third plantar interosseus attaches onto and moves the fifth toe. 3. Knowing the number of plantar interossei muscles and knowing which toes have plantar interossei attached to them can be reasoned out; it does not need to be memorized. The big toe (toe number one) gets its own adductor (the adductor hallucis), and toe number two cannot adduct (its movement is described as being either tibial abduction or fibular abduction). That leaves three toes that can adduct: toes three, four, and five. The result is that there are three plantar interossei muscles attached to toes three, four, and five.

1029

Dorsal Interossei Pedis (There are four dorsal interossei pedis muscles, named one, two, three, and four.) The name, dorsal interossei pedis, tells us that these muscles are located between bones (metatarsals) on the dorsal side and located in the foot. Derivation dorsal: L. refers to the dorsal side interossei: L. between bones pedis: L. refers to the foot Pronunciation DOR-sul in-ter-OSS-ee-eye PEED-us

ATTACHMENTS Metatarsals each one arises from the adjacent sides of two metatarsals: ONE: attaches onto metatarsals one and two TWO: attaches onto metatarsals two and three THREE: attaches onto metatarsals three and four FOUR: attaches onto metatarsals four and five to the Sides of the Phalanges and the Dorsal Digital Expansion the bases of the proximal phalanges (on the sides away from the center of the second toe): ONE: attaches to the medial side of toe number two TWO: attaches to the lateral side of toe number two THREE: attaches to the lateral side of toe number three FOUR: attaches to the lateral side of toe number four

FUNCTIONS Concentric (Shortening) Mover Actions Standard Mover Actions 1. Abduct toes two through four at the MTP joints 2. Flex toes two through four at the MTP joints 3. Extend toes two through four at the PIP and DIP joints

Reverse Mover Actions 1. Abduct the metatarsals of toes two through four at the MTP joints 2. Flex the metatarsals at the MTP joints 3. Extend the more proximal phalanges at the PIP and DIP joints

MTP joints = metatarsophalangeal joints; PIP joints = proximal interphalangeal joints; DIP joints = distal interphalangeal joints

Standard Mover Action Notes

1030

FIGURE 18-16

Dorsal view of the right dorsal interossei pedis. The abductor hallucis and abductor digiti minimi pedis have been ghosted in.

• All the dorsal interossei pedis cross the MTP joint to attach onto the proximal phalanx of toes two through four (with their fibers running horizontally). The first dorsal interosseus pedis attaches onto the medial side of the second toe. When it contracts, it pulls the second toe medially away from the axis of abduction/adduction of the toes (which is an imaginary line drawn through the second toe when it is in anatomic position). Therefore the first dorsal interosseus pedis performs tibial abduction of the second toe at the MTP joint. The second dorsal interosseus pedis attaches onto the lateral side of the second toe. When it contracts, it pulls the second toe laterally away from the axis of abduction/adduction of the toes. Therefore the second dorsal interosseus pedis performs fibular abduction of the second toe at the MTP joint. The third and fourth dorsal interossei pedis attach onto the lateral sides of the third and fourth toes, respectively. When they contract, they pull the third and fourth toes laterally away from the second toe. Therefore the third and fourth dorsal interossei pedis abduct the third and fourth toes at the MTP joints. (action 1) • The dorsal interossei pedis cross the MTP joints of toes two through four on the plantar side (with their fibers running horizontally in the sagittal plane); therefore they flex toes two through four at the MTP joints. (action 2) • More specifically, abduction and flexion of toes at the MTP joints refers to abduction and flexion of the proximal phalanges of the toes at the MTP joints. (actions 1, 2)

1031

• The dorsal interossei pedis, by attaching into the dorsal digital expansion, in other words, tendons of the extensor digitorum longus muscle (after the MTP joint but before the interphalangeal [IP] joints of the toes), exert their pull at the attachment of the extensor digitorum longus (at the distal phalanx of toes two through four). The dorsal interossei pedis, in effect, cross the proximal and distal IP joints on the dorsal side (essentially exerting their pull horizontally in the sagittal plane); therefore the dorsal interossei pedis extend both the PIP and DIP joints of toes two through four. (action 3) • More specifically, extending toes at the IP joints refers to extending the middle phalanges of the toes at the PIP joints and extending the distal phalanges at the DIP joints. (action 3)

Reverse Mover Action Note • The reverse actions involve motion of the more proximal bone at each of the joints of the toes. In other words, the reverse action at the MTP joint is abduction or flexion of the metatarsal of the toe relative to its fixed proximal phalanx, the reverse action at the PIP joint is extension of the proximal phalanx relative to the fixed middle phalanx, and the reverse action at the DIP joint is extension of the middle phalanx relative to the fixed distal phalanx. The reverse action at the MTP joint is not likely to occur. However, the reverse actions at the PIP and DIP joints occur during toe-off in the gait cycle. (reverse actions 1, 2, 3)

Motion 1. Each dorsal interosseus manus has one line of pull in an oblique plane, and therefore its motion for each of toes two through four is a combination of abduction and flexion of the toe at the MTP joint and extension of the toe at the PIP and DIP joints.

Eccentric Antagonist Functions 1. Restrain/slow adduction of the MTP joints of toes two through four 2. Restrain/slow extension of the MTP joints of toes two through four 3. Restrain/slow flexion of the PIP and DIP joints of toes two through four

Isometric Stabilization Functions 1. Stabilize the MTP, PIP, and DIP joints of toes two through four

Additional Notes on Actions 1. The dorsal interossei pedis flex the MTP joints because they cross these joints on the plantar side. Because they attach into the dorsal digital expansion of the foot, their line of pull is transmitted across the dorsal side of the IP joints; therefore they extend the IP joints. All muscles that attach into the dorsal digital expansion of the foot flex the MTP joints and extend the IP joints. 2. The dorsal interossei pedis have the same actions as the lumbricals pedis, namely, flexion of the MTP joints and extension of the IP joints. And the dorsal interossei pedis also abduct toes two through four at the MTP joints. 3. There are four dorsal interossei manus of the hand, which have essentially identical actions (abduction and flexion of the fingers at the metacarpophalangeal [MCP] joints, and extension of the fingers at the PIP and DIP joints) to the dorsal interossei pedis of the foot. 4. A mnemonic for remembering the adduction and abduction actions of the plantar interossei and dorsal interossei pedis is DAB PAD: Dorsals ABduct, Plantars ADduct.

I N N E RVAT I O N The Lateral Plantar Nerve S2, S3

A R T E R I A L S U P P LY Branches of the Plantar Arch (an anastomosis between the Lateral Plantar Artery and the Dorsalis Pedis Artery)

1032

PA L PAT I O N 1. With the client supine, place palpating fingers on the dorsal side of the foot between the first and second metatarsal bones. 2. Have the client abduct the second toe toward the big toe (tibial abduction) and feel for the contraction of the first dorsal interosseus pedis. Resistance can be added. 3. Repeat between the second and third metatarsal bones with fibular abduction of the second toe and feel for the contraction of the second dorsal interosseus pedis. 4. Repeat between metatarsals three-four and four-five with abduction of the third and fourth toes and feel for the contraction of the third and fourth dorsal interossei pedis, respectively.

RELATIONSHIP TO OTHER STRUCTURES The dorsal interossei pedis are in the fourth plantar layer of intrinsic muscles of the foot along with the plantar interossei (and the distal tendons of the fibularis longus and tibialis posterior). The dorsal interossei pedis are located between the metatarsals; hence they are bordered on either side by the metatarsal bones. From the dorsal perspective, the dorsal interossei pedis are deep to the tendons of the extensor digitorum longus and extensor digitorum brevis. From the plantar perspective, the dorsal interossei pedis are adjacent and deep to (partially overlapped by) the plantar interossei. The dorsal interossei pedis are involved with the superficial back line and deep front line myofascial meridians.

MISCELLANEOUS 1. There are four dorsal interossei pedis muscles named, from the medial side, one, two, three, and four. 2. Knowing the number of dorsal interossei pedis muscles and knowing which toes have dorsal interossei pedis attached to them can be reasoned out; this information does not have to be memorized. The big toe and the little toe each get their own abductor muscle (the big toe has the abductor hallucis and the little toe has the abductor digiti minimi pedis). That leaves toes two, three, and four to have dorsal interossei pedis muscles attached. However, toe number two can abduct in the tibial (medial) direction and in the fibular (lateral) direction; therefore it gets two dorsal interossei pedis muscles attached to it (one on each side). The result is that there are four dorsal interossei pedis muscles: one attaching to toe number four, one attaching to toe number three, and two attaching to toe number two.

1033

REVIEW QUESTIONS 1. The plantar intrinsic muscles are divided into how many layers? Name these layers. ____________________________ ____________________________ ____________________________ 2. What is the axis for abduction/adduction of the toes at the metatarsophalangeal joints? ____________________________ ____________________________ 3. What are the only intrinsic muscles located on the dorsal side of the foot? ____________________________ ____________________________ ____________________________ 4. Describe the relationship between the extensor hallucis brevis and the extensor digitorum brevis. ____________________________ ____________________________ ____________________________ 5. What muscles are located in the first plantar layer of intrinsic muscles of the foot? ____________________________ ____________________________ ____________________________ 6. Abduction and flexion of the little toe at the metatarsophalangeal joint refer specifically to what joint actions? ____________________________ ____________________________ 7. What is the motion created by the contraction of the flexor digitorum brevis? ____________________________ ____________________________ 8. What is the role of the quadratus plantae as it relates to the flexor digitorum longus? ____________________________ ____________________________ ____________________________ ____________________________ 9. Describe the distal attachment of the flexor hallucis brevis upon the big toe. What effect, if any, does this have on its joint actions of the big toe? ____________________________ ____________________________ ____________________________ 10. Explain the effect of the first and second dorsal interossei pedis muscles on the second toe. ____________________________ ____________________________ ____________________________ ____________________________ For answers to these questions, visit http://evolve.elsevier.com/Muscolino/muscular

1034

THINK IT THROUGH We have two sets of interossei pedis muscles, but they do not match in number. Can you come up with a simple explanation as to why this is so? ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________

1035

PA R T 5

Functional Mover Groups of Muscles OUTLINE Chapter 19: Functional Groups of Muscles

1036

CHAPTER 19

1037

Functional Groups of Muscles CHAPTER OUTLINE Functional Mover Groups: Upper Extremity Axial Body Lower Extremity Muscles of the Pelvic Floor Myofascial Meridians

OBJECTIVES After completing this chapter, the student should be able to perform the following for each of the functional groups of muscles covered in the chapter: 1. Explain the general relationship of the muscles within a functional group. 2. Explain the general rules regarding actions for functional groups. 3. State the standard joint action of the functional group. 4. List the muscles responsible for the joint action of the functional group. 5. Explain the general structure of the pelvic floor. 6. List the major myofascial meridians. 7. Explain the structure and function of myofascial meridians.

http://evolve.elsevier.com/Muscolino/muscular This chapter contains functional groups of muscles. The first part of the chapter (Figures 19-1 through 19-35) illustrates functional mover groups. All muscles of a functional mover group share the same concentric standard and reverse mover actions. They also share the same eccentric restraining/slowing and isometric stabilization functions as well. This part is divided into three sections: upper extremity, axial body, and lower extremity. The second part of this chapter (Figures 19-36 through 19-38) illustrates muscles of the pelvic floor. The pelvic floor is just that, a floor to the pelvis upon which the contents of the abdominopelvic cavity sit. Medial, superior, and inferior views of the muscles of the pelvic floor are shown. The third part of the chapter (Figures 19-39 through 19-43) illustrates myofascial meridians. A myofascial meridian is a line of myofascial tissues, in other words, muscles embedded within a continuous line of fascial webbing that can serve to transmit tension (pulling) forces across the body. These pulling forces are important for creating mover actions, as well as restraining/slowing and stabilization functions during posture and movement. (For more on myofascial meridians, see Myers T: Anatomy trains: Myofascial meridians for manual and movement therapists, ed 3, Edinburgh, 2014, Churchill Livingstone of Elsevier.)

1038

FUNCTIONAL MOVER GROUPS: UPPER EXTREMITY  

1039

Scapulocostal Joint Elevators

FIGURE 19-1

Scapulocostal joint elevators and depressors. A, Posterior view of the scapulocostal joint elevators. The middle and lower trapezius have been ghosted in on the left.

Scapulocostal Joint Elevators Upper trapezius, levator scapulae, rhomboids, serratus anterior (upper fibers)

1040

Scapulocostal Joint Depressors

FIGURE 19-1 B, Anterior view of the scapulocostal joint depressors. The pectoralis major has been ghosted in. C, Posterior view of the scapulocostal joint depressors. The upper and middle trapezius have been ghosted in on the left.

Scapulocostal Joint Depressors Lower trapezius, pectoralis minor, pectoralis major, serratus anterior (lower fibers), latissimus dorsi

1041

Scapulocostal Joint Protractors and Retractors

FIGURE 19-2 Scapulocostal joint protractors and retractors. A, Anterior view of the scapulocostal joint protractors. The pectoralis major has been ghosted in. B, Posterior view of the scapulocostal joint retractors.

Scapulocostal Joint Protractors Serratus anterior, pectoralis minor, pectoralis major

Scapulocostal Joint Retractors Rhomboids, trapezius, levator scapulae

1042

Scapulocostal Joint Upward and Downward Rotators

FIGURE 19-3 Scapulocostal joint upward rotators and downward rotators. A, Posterior view of the scapulocostal joint upward rotators. The middle trapezius has been ghosted in. B, Posterior view of the scapulocostal joint downward rotators. The pectoralis minor is not pictured.

Scapulocostal Joint Upward Rotators Upper trapezius, lower trapezius, serratus anterior, teres major

Scapulocostal Joint Downward Rotators Rhomboids, levator scapulae, deltoid, pectoralis minor (not seen)

1043

Glenohumeral Joint Flexors and Extensors

FIGURE 19-4 Glenohumeral joint flexors and extensors. A, Anterior view of the glenohumeral joint flexors. The sternocostal head of the pectoralis major and the middle deltoid have been ghosted in. B, Posterior view of the glenohumeral joint extensors. The sternocostal head of the pectoralis major is not pictured. The middle deltoid and the medial and lateral heads of the triceps brachii have been ghosted in.

Glenohumeral Joint Flexors Anterior deltoid, pectoralis major (clavicular head), coracobrachialis, biceps brachii

Glenohumeral Joint Extensors Latissimus dorsi, teres major, posterior deltoid, pectoralis major (sternocostal head; not seen), triceps brachii (long head)

1044

Glenohumeral Joint Abductors

FIGURE 19-5 Glenohumeral joint abductors and adductors. A, Anterior view of the glenohumeral joint abductors. The sternocostal head of the pectoralis major and the short head of the biceps brachii have been ghosted in.

Glenohumeral Joint Abductors Deltoid, supraspinatus, biceps brachii (long head), pectoralis major (clavicular head)

1045

FIGURE 19-5 B, Anterior view of the glenohumeral joint adductors. The long head of the biceps brachii has been ghosted in. C, Posterior view of the glenohumeral joint adductors. The lateral and medial heads of the triceps brachii have been ghosted in.

Glenohumeral Joint Adductors Pectoralis major, latissimus dorsi, teres major, coracobrachialis, biceps brachii (short head), triceps brachii (long head), teres minor

1046

Glenohumeral Joint Lateral and Medial Rotators

FIGURE 19-6 Glenohumeral joint lateral rotators and medial rotators. A, Posterior view of the glenohumeral joint lateral rotators. The middle deltoid has been ghosted in. B, Posterior view of the glenohumeral joint medial rotators. C, Anterior view of the glenohumeral joint medial rotators.

Glenohumeral Joint Lateral Rotators Posterior deltoid, infraspinatus, teres minor

Glenohumeral Joint Medial Rotators Pectoralis major, anterior deltoid, latissimus dorsi, teres major, subscapularis

1047

1048

Elbow Joint Flexors and Extensors

FIGURE 19-7 Elbow joint flexors and extensors. A, Anterior view of the elbow joint flexors. The extensor carpi radialis brevis is not pictured. B, Posterior view of the elbow joint extensors.

Elbow Joint Flexors Brachialis, biceps brachii, brachioradialis, pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris, flexor digitorum superficialis, flexor pollicis longus, extensor carpi radialis longus, extensor carpi radialis brevis (not seen)

Elbow Joint Extensors Triceps brachii, anconeus, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris

1049

1050

Radioulnar Joints Pronators and Supinators

FIGURE 19-8 Radioulnar joints: pronators and supinators. A, Anterior view of the radioulnar joints pronators. The extensor carpi radialis brevis is not pictured. B, Posterior view of the radioulnar joints supinators. The extensors carpi radialis longus and brevis are not pictured.

Radioulnar Joints Pronation Pronator teres, pronator quadratus, brachioradialis, flexor carpi radialis, palmaris longus, extensor carpi radialis longus, extensor carpi radialis brevis (not seen)

Radioulnar Joints Supination Supinator, biceps brachii, brachioradialis, abductor pollicis longus, extensor pollicis longus, extensor indicis, extensor carpi radialis longus (not seen), extensor carpi radialis brevis (not seen)

1051

1052

Wrist Joint Flexors and Extensors

FIGURE 19-9

Wrist joint flexors and extensors. A, Anterior view of the wrist joint flexors. B, Posterior view of the wrist joint extensors.

Wrist Joint Flexors Flexor carpi radialis, palmaris longus, flexor carpi ulnaris, flexor digitorum superficialis, flexor digitorum profundus, flexor pollicis longus, abductor pollicis longus

Wrist Joint Extensors Extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, extensor pollicis longus, extensor indicis

1053

1054

Wrist Joint Radial Deviators

FIGURE 19-10

Wrist joint radial deviators and ulnar deviators. A, Radial (lateral) view of wrist joint radial deviators. B, Anterior view of wrist joint radial deviators.

Wrist Joint Radial Deviators Flexor carpi radialis, extensor carpi radialis longus, extensor carpi radialis brevis, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, flexor pollicis longus

1055

Wrist Joint Ulnar Deviators

FIGURE 19-10

C, Ulnar (medial) view of wrist joint ulnar deviators.

Wrist Joint Ulnar Deviators Flexor carpi ulnaris, extensor carpi ulnaris

1056

Thumb Flexors and Extensors

FIGURE 19-11 Flexors and extensors of the thumb at the carpometacarpal (CMC) (saddle), metacarpophalangeal (MCP), and interphalangeal (IP) joints. A, Anterior view of thumb joint (CMC, MCP, IP) flexors. B, Posterior view of thumb joint (CMC, MCP, IP) extensors.

Thumb Joint (CMC, MCP, IP) Flexors Flexor pollicis longus, flexor pollicis brevis, abductor pollicis brevis, opponens pollicis, adductor pollicis

Thumb Joint (CMC, MCP, IP) Extensors Extensor pollicis longus, extensor pollicis brevis, abductor pollicis longus, abductor pollicis brevis

1057

Thumb Abductors

FIGURE 19-12 Abductors and adductors of the thumb at the carpometacarpal (saddle) joint. The abductor pollicis brevis is not pictured. A, Posterior view of thumb abductors. B, Anterior view of thumb abductors.

Thumb Joint (CMC) Abductors Abductor pollicis longus, abductor pollicis brevis (not seen), extensor pollicis brevis, flexor pollicis brevis, opponens pollicis

1058

FIGURE 19-12

C, Anterior view of thumb adductor.

Thumb Joint (CMC) Adductors Adductor pollicis

1059

Thumb Medial and Lateral Rotators

FIGURE 19-13

Medial rotators and lateral rotators of the thumb at the carpometacarpal (saddle) joint. A, Anterior view of the medial rotators. B, Posterior view of the lateral rotators.

Thumb Joint (CMC) Medial Rotators Opponens pollicis, flexor pollicis brevis, flexor pollicis longus, adductor pollicis

Thumb Joint (CMC) Lateral Rotators Extensor pollicis longus, extensor pollicis brevis, abductor pollicis longus, abductor pollicis brevis

1060

Finger Flexors and Extensors

FIGURE 19-14 Flexors and extensors of fingers two through five at the metacarpophalangeal and proximal and distal interphalangeal joints. A, Anterior view of finger flexors. Dorsal interosseus/interossei manus, DIM. B, Posterior view of finger extensors. The lumbricals manus are not pictured.

Finger Joint (MCP, IP) Flexors (fingers #2-5) Flexor digitorum superficialis, flexor digitorum profundus, flexor digiti minimi manus, opponens digiti minimi, palmar interossei, dorsal interossei manus, lumbricals manus

Finger Joint (MCP, IP) Extensors (fingers #2-5) Extensor digitorum, extensor digiti minimi, extensor indicis, abductor digiti minimi manus, palmar interossei, dorsal interossei manus, lumbricals manus (not seen)

1061

1062

Finger Abductors and Adductors

FIGURE 19-15 Abductors and adductors of fingers two through five at the metacarpophalangeal joint. A, Posterior view of the abductors. B, Anterior view of the adductors. The extensor indicis is not pictured.

Finger Joint (MCP) Abductors (fingers #2-5) Dorsal interossei manus, abductor digiti minimi manus, lumbricals manus (#1 and 2)(not seen)

Finger Joint (MCP) Adductors (fingers #2-5) Palmar interossei, lumbricals manus (#3 and 4), extensor indicis (not seen)

1063

FUNCTIONAL MOVER GROUPS: AXIAL BODY  

1064

Temporomandibular Joint (Mandible): Elevators and Depressors

FIGURE 19-16 Elevators and depressors of the temporomandibular joints. A, Lateral view of temporomandibular joints (mandible) elevators. The medial pterygoid has been ghosted in. The zygomatic arch has been cut away. B, Anterior view of temporomandibular joints (mandible) depressors. The platysma has been ghosted in.

Temporomandibular Joint Elevators Temporalis, masseter, medial pterygoid

Temporomandibular Joint Depressors Digastric, mylohyoid, geniohyoid, platysma

1065

1066

Temporomandibular Joint (Mandible) Protractors, Retractors, and Contralateral Deviators

FIGURE 19-17 Protractors and retractors of the temporomandibular joints. The mandible has been cut. A, Lateral view of temporomandibular joint (mandible) protractors. The masseter has been ghosted in. B, Lateral view of temporomandibular joint (mandible) retractors.

Temporomandibular Joint Protractors Lateral pterygoid, medial pterygoid, masseter

Temporomandibular Joint Retractors Temporalis, masseter, digastric

FIGURE 19-18

Lateral view of temporomandibular joint (mandible) contralateral deviators. The mandible has been cut.

1067

Temporomandibular Joint Contralateral Deviators Lateral pterygoid, medial pterygoid

1068

Hyoid Bone Elevators and Depressors

FIGURE 19-19 Elevators and depressors of the hyoid bone. A, Anterior view of hyoid bone elevators. The mylohyoid has been ghosted in on the left. B, Anterior view of hyoid bone depressors.

Hyoid Bone Elevators Digastric, mylohyoid, geniohyoid, stylohyoid

Hyoid Bone Depressors Sternohyoid, sternothyroid, thyrohyoid, omohyoid

1069

1070

Cervical Spinal Joint (Neck and Head) Flexors

FIGURE 19-20

Flexors and extensors of the cervical spinal joints (neck and head). A, Anterior view of neck and head flexors.

Cervical Spinal (Head and Neck) Joint Flexors Sternocleidomastoid, anterior scalene, middle scalene, longus colli, longus capitis, rectus capitis anterior, sternohyoid, sternothyroid, thyrohyoid, omohyoid, digastric, mylohyoid, geniohyoid, stylohyoid

1071

Cervical Spinal Joint (Neck and Head) Extensors

FIGURE 19-20 B, Posterior view of neck and head extensors (superficial). The middle and lower trapezius have been ghosted in. C, Posterior view of neck and head extensors (deep).

Cervical Spinal (Head and Neck) Joint Extensors Semispinalis, upper trapezius, splenius capitis, splenius cervicis, levator scapulae, iliocostalis, longissimus, spinalis, sternocleidomastoid, multifidus, rotatores, interspinales, rectus capitis posterior major, rectus capitis posterior minor, obliquus capitis superior

1072

Cervical Spinal Joint (Neck and Head) Lateral Flexors

FIGURE 19-21

Lateral flexors of cervical spinal joints (neck and head). A, Anterior view of neck and head lateral flexors.

Cervical Spinal (Head and Neck) Joint Lateral Flexors Upper trapezius, sternocleidomastoid, semispinalis, anterior scalene, middle scalene, posterior scalene, splenius capitis, splenius cervicis, levator scapulae, longus colli, longus capitis, rectus capitis lateralis, iliocostalis, longissimus, spinalis, multifidus, rotatores, intertransversarii

FIGURE 19-21

B, Posterior view of neck and head lateral flexors (superficial). The middle and lower

1073

trapezius have been ghosted in. C, Posterior view of neck and head lateral flexors (deep).

1074

Cervical Spinal Joint (Neck and Head) Contralateral Rotators

FIGURE 19-22 Contralateral rotators and ipsilateral rotators of the cervical spinal joints (neck and head). A, Anterior view of neck and head contralateral rotators. B, Posterior view of neck and head contralateral rotators. The trapezius has been ghosted in.

Cervical Spinal (Head and Neck) Joint Contralateral Rotators Sternocleidomastoid, upper trapezius, rotatores, multifidus, semispinalis, anterior scalene, longus colli

1075

1076

Cervical Spinal Joint (Neck and Head) Ipsilateral Rotators

FIGURE 19-22

C, Posterior view of neck and head ipsilateral rotators.

Cervical Spinal (Head and Neck) Joint Ipsilateral Rotators Splenius capitis, splenius cervicis, obliquus capitis inferior, rectus capitis posterior major, levator scapulae, longissimus, iliocostalis, spinalis

1077

1078

Thoracolumbar Spinal Joint (Trunk) Flexors

FIGURE 19-23

Flexors and extensors of the thoracolumbar spinal joints (trunk). A, Anterior view of trunk flexors.

Thoracolumbar Spinal Joint (Trunk) Flexors Rectus abdominis, external abdominal oblique, internal abdominal oblique, external intercostals, internal intercostals, psoas major, psoas minor

1079

Thoracolumbar Spinal Joint (Trunk) Extensors

FIGURE 19-23

B, Posterior view of trunk extensors. The trapezius has been ghosted in. The latissimus dorsi is not pictured.

Thoracolumbar Spinal Joint (Trunk) Extensors Iliocostalis, longissimus, spinalis, semispinalis, multifidus, rotatores, external intercostals, internal intercostals, quadratus lumborum, middle and lower trapezius, latissimus dorsi (not seen), interspinales, levatores costarum

1080

1081

Thoracolumbar Spinal Joint (Trunk) Lateral Flexors

FIGURE 19-24

Lateral view of the thoracolumbar spinal flexors (trunk). A, Anterior view of trunk lateral flexors.

Thoracolumbar Spinal Joint (Trunk) Lateral Flexors Iliocostalis, longissimus, spinalis, external abdominal oblique, internal abdominal oblique, rectus abdominis, external intercostals, internal intercostals, psoas major, psoas minor, quadratus lumborum, semispinalis, multifidus, rotatores, intertransversarii, levatores costarum

1082

FIGURE 19-24

B, Posterior view of trunk lateral flexors.

1083

Thoracolumbar Spinal Joint (Trunk) Contralateral Rotators

FIGURE 19-25

Contralateral rotators and ipsilateral rotators of the thoracolumbar spinal joints (trunk). A, Anterior view of trunk contralateral rotators.

Thoracolumbar Spinal Joint (Trunk) Contralateral Rotators External abdominal oblique, external intercostals, rotatores, multifidus, semispinalis, psoas major, levatores costarum, rhomboids, serratus posterior superior, serratus posterior inferior

1084

FIGURE 19-25

B, Posterior view of trunk contralateral rotators.

1085

Thoracolumbar Spinal Joint (Trunk) Ipsilateral Rotators

FIGURE 19-25

C, Anterior view of trunk ipsilateral rotators. D, Posterior view of trunk ipsilateral rotators.

Thoracolumbar Spinal Joint (Trunk) Ipsilateral Rotators Internal abdominal oblique, internal intercostals, iliocostalis, longissimus, spinalis

1086

FUNCTIONAL MOVER GROUPS: LOWER EXTREMITY  

1087

Hip Joint Flexors and Extensors

FIGURE 19-26 Hip joint flexors and extensors. Flexion of the hip joint is flexion of the thigh and/or anterior tilt of the pelvis at the hip joint. Extension of the hip joint is extension of the thigh and/or posterior tilt of the pelvis at the hip joint. A, Anterior view of the hip joint flexors (thigh flexors and pelvic anterior tilters). The adductor brevis and gluteus minimus are not pictured. B, Posterior view of the hip joint extensors (thigh extensors and pelvic posterior tilters). The gluteus maximus has been ghosted in. The gluteus minimus is not pictured.

Hip Joint Flexors (Thigh Flexors/Pelvis Anterior Tilters) Psoas major, iliacus, tensor fasciae latae, rectus femoris, sartorius, pectineus, adductor longus, adductor brevis (not seen), gracilis, gluteus medius (anterior fibers), gluteus minimus (anterior fibers) (not seen)

Hip Joint Extensors (Thigh Extensors/Pelvis Posterior Tilters) Gluteus maximus, semitendinosus, semimembranosus, biceps femoris (long head), adductor magnus, gluteus medius (posterior fibers), gluteus minimus (posterior fibers) (not seen)

1088

1089

Hip Joint Abductors (Pelvic Depressors)

FIGURE 19-27 Hip joint abductors and adductors. Abduction of the hip joint is abduction of the thigh and/or depression of the same-side pelvis. Adduction of the hip joint is adduction of the thigh and/or elevation of the same-side pelvis. A, Posterior view of the hip joint abductors (thigh abductors and sameside pelvic depressors). The lower gluteus maximus has been ghosted in. Note: Horizontal abductors (horizontal extensors) included in this figure.

Hip Joint Abductors (Thigh Abductors/Ipsilateral Pelvic Depressors) Gluteus medius, gluteus minimus, gluteus maximus (upper 1/3), tensor fasciae latae, sartorius. Note: Horizontal abductors: piriformis, superior gemellus, obturator internus, inferior gemellus

1090

Hip Joint Adductors (Pelvic Elevators)

FIGURE 19-27 B and C: Views of the hip joint adductors (thigh adductors and same-side pelvic elevators). B, Anterior view. C, Posterior view. The upper gluteus maximus has been ghosted in.

Hip Joint Adductors (Thigh Adductors/Ipsilateral Pelvic Elevators) Adductor magnus, adductor longus, adductor brevis, pectineus, gracilis, gluteus maximus (lower 2/3), quadratus femoris, biceps femoris (long head)

1091

Hip Joint Lateral Rotators (Pelvic Contralateral Rotators)

FIGURE 19-28 Hip joint lateral and medial rotators. Lateral rotation of the hip joint is lateral rotation of the thigh and/or contralateral rotation of the pelvis at the hip joint. Medial rotation of the hip joint is medial rotation of the thigh and/or ipsilateral rotation of the pelvis at the hip joint. A and B: Views of the hip joint lateral rotators (thigh lateral rotators and pelvic contralateral rotators). A, Posterior view. B, Anterior view.

Hip Joint Lateral Rotators (Thigh Lateral Rotators/Pelvic Contralateral Rotators) Gluteus maximus, gluteus medius (posterior fibers), gluteus minimus (posterior fibers), piriformis, quadratus femoris, superior gemellus, obturator internus, inferior gemellus, obturator externus, sartorius, psoas major, iliacus, biceps femoris (long head)

1092

Hip Joint Medial Rotators (Pelvic Ipsilateral Rotators)

FIGURE 19-28

C and D: Views of the hip joint medial rotators (thigh medial rotators and pelvic ipsilateral rotators). C, Anterior view. D, Posterior view.

Hip Joint Medial Rotators (Thigh Medial Rotators/Pelvic Ipsilateral Rotators) Gluteus medius (anterior fibers), gluteus minimus (anterior fibers), tensor fasciae latae, piriformis, semitendinosus, semimembranosus

1093

Knee Joint Flexors

FIGURE 19-29

Flexors and extensors of the knee joint. A, Posterior view of the knee joint flexors.

Knee Joint Flexors Semitendinosus, semimembranosus, biceps femoris, sartorius, gracilis, popliteus, gastrocnemius, plantaris

1094

Knee Joint Extensors

FIGURE 19-29

B, Anterior view of the knee joint extensors. The vastus intermedius is not pictured.

Knee Joint Extensors Rectus femoris, vastus lateralis, vastus medialis, vastus intermedius (not seen), tensor fasciae latae, gluteus maximus

1095

Knee Joint Medial and Lateral Rotators

FIGURE 19-30 Rotators of the knee joint. Medial rotation of the leg at the knee joint and lateral rotation of the thigh at the knee joint are reverse actions of each other. Similarly, lateral rotation of the leg at the knee joint and medial rotation of the thigh at the knee joint are reverse actions of each other. A, Posterior view of the knee joint medial rotators of the leg (lateral rotators of the thigh). B, Posterior view of the knee joint lateral rotators of the leg (medial rotators of the thigh).

Knee Joint Medial Rotators (Tibial Medial Rotators; Femoral Lateral Rotators) Popliteus, semitendinosus, gracilis, sartorius, semimembranosus

Knee Joint Lateral Rotators (Tibial Lateral Rotators; Femoral Medial Rotators) Biceps femoris

1096

Ankle Joint Dorsiflexors and Plantarflexors

FIGURE 19-31 Dorsiflexors and plantarflexors of the ankle joint. A, Anterior view of the ankle joint dorsiflexors. B, Posterior view of the ankle joint plantarflexors. The gastrocnemius has been ghosted in.

Ankle Joint Dorsiflexors Tibialis anterior, extensor digitorum longus, fibularis tertius, extensor hallucis longus

Ankle Joint Plantarflexors Gastrocnemius, soleus, plantaris, tibialis posterior, flexor digitorum longus, flexor hallucis longus, fibularis longus, fibularis brevis

1097

Subtalar Joint Pronators (Everters)

FIGURE 19-32 Pronators and supinators of the subtalar joint. Note: Eversion is the principle component of pronation; inversion is the principle component of supination. A, Lateral view of the subtalar joint pronators (everters).

Subtalar Joint Pronators (Everters) Fibularis longus, fibularis brevis, fibularis tertius, extensor digitorum longus

1098

Subtalar Joint Supinators (Inverters)

FIGURE 19-32

B, Posterior view of the subtalar joint supinators (inverters). The gastrocnemius has been ghosted in. C, Anterior view of the subtalar joint supinators (inverters)

Subtalar Joint Supinators (Inverters) Tibialis anterior, tibialis posterior, extensor hallucis longus, flexor digitorum longus, flexor hallucis longus, gastrocnemius, soleus, plantaris

1099

Toe Flexors

FIGURE 19-33 Flexors of the five toes at the metatarsophalangeal and interphalangeal joints. A, Plantar view of the flexors of the big toe. B, Plantar view of the flexors of toes two through five.

Toe Joint (MTP, IP) Flexors (big toe: toe #1) Flexor hallucis longus, flexor hallucis brevis, adductor hallucis, abductor hallucis

Toe Joint (MTP, IP) Flexors (toes #2-5) Flexor digitorum longus, flexor digitorum brevis, quadratus plantae, flexor digiti minimi pedis, abductor digiti minimi pedis, lumbricals pedis, plantar interossei, dorsal interossei pedis

1100

Toe Extensors

FIGURE 19-34 Extensors of the five toes at the metatarsophalangeal and interphalangeal joints. A, Dorsal view of the extensors of the big toe. The extensor digitorum brevis has been ghosted in. B, Dorsal view of the extensors of toes two through five. The extensor hallucis brevis has been ghosted in. The lumbricals pedis and plantar interossei are not pictured.

Toe Joint (MTP, IP) Extensors (big toe: toe #1) Extensor hallucis longus, extensor hallucis brevis

Toe Joint (MTP, IP) Extensors (toes #2-5) Extensor digitorum longus, extensor digitorum brevis, dorsal interossei pedis, lumbricals pedis (not seen), plantar interossei (not seen)

1101

Toe Abductors and Adductors

FIGURE 19-35

Abductors and adductors of the five toes at the metatarsophalangeal joints. A, Dorsal view of the toe abductors. B, Plantar view of the toe adductors.

Toe Joint (MTP) Abductors (toes #1-5) Dorsal interossei pedis, abductor hallucis, abductor digiti minimi pedis

Toe Joint (MTP) Adductors (toes #1-5) Plantar interossei, adductor hallucis

1102

MUSCLES OF THE PELVIC FLOOR  

1103

Medial Views of the Pelvic Floor

FIGURE 19-36

Medial views of the muscles of the right side of the pelvis. A, Superficial view. B, Deep view.

1104

Superior Views of the Pelvic Floor

FIGURE 19-37

Superior views of the muscles of the female pelvic floor. A, Superficial view. B, Deep view.

1105

Inferior Views of the Pelvic Floor

FIGURE 19-38 Inferior views of the muscles of the female pelvic floor. A, Superficial view. The gluteus maximus has been ghosted in on the right. B, Intermediate view. C, Deep view.

1106

MYOFASCIAL MERIDIANS  

1107

Superficial Back and Front Lines

FIGURE 19-39 Superficial back line and superficial front line myofascial meridians. A, Posterior view of the superficial back line. B, Anterior view of the superficial front line. (Modeled from Myers TW: Anatomy trains: myofascial meridians for manual & movement therapists, ed 3, Edinburgh, 2014, Churchill Livingstone, Elsevier.)

1108

Lateral and Deep Front Lines

FIGURE 19-40 Lateral line and deep front line myofascial meridians. A, Lateral view of the lateral line. B, Anterior view of the deep front line. (Modeled from Myers TW: Anatomy trains: myofascial meridians for manual & movement therapists, ed 3, Edinburgh, 2014, Churchill Livingstone, Elsevier.)

1109

Spiral Lines

FIGURE 19-41 Anterior, posterior, and lateral views of the spiral line myofascial meridian, respectively. (Modeled from Myers TW: Anatomy trains: myofascial meridians for manual & movement therapists, ed 3, Edinburgh, 2014, Churchill Livingstone, Elsevier.)

1110

Arm Lines

FIGURE 19-42 Arm line myofascial meridians. A, Anterior view of the superficial and deep front arm lines. B, Posterior view of the superficial and deep back arm lines. (Modeled from Myers TW: Anatomy trains: myofascial meridians for manual & movement therapists, ed 3, Edinburgh, 2014, Churchill Livingstone, Elsevier.)

1111

Functional Lines

FIGURE 19-43 Functional line myofascial meridians. A, posterolateral view of the back functional line. B, Anterior view of the front functional line. C, Lateral view of the ipsilateral functional line. (Modeled from Myers TW: Anatomy trains: myofascial meridians for manual & movement therapists, ed 3, Edinburgh, 2014, Churchill Livingstone, Elsevier.)

1112

REVIEW QUESTIONS 1. What functions do muscles of a mover group share? ____________________________ ____________________________ 2. A line of tissue that is composed of multiple muscles and their fascial attachments and can serve to transmit tension (pulling) forces across the body is known as a_______. 3. What muscles comprise the functional group of downward rotators of the scapula at the scapulocostal joint? ____________________________ ____________________________ ____________________________ 4. What muscles comprise the functional group of extensors of the elbow joint? ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ 5. What muscles comprise the functional group of lateral rotators of the thumb at the carpometacarpal joint? ____________________________ ____________________________ ____________________________ 6. What muscles comprise the functional group of flexors of the cervical spine (head and neck) at the spinal joints? ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ 7. What muscles comprise the functional group of ipsilateral rotators of the thoracolumbar spine (trunk) at the spinal joints? ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ 8. What muscles comprise the functional group of adductors of the thigh (and ipsilateral elevators of the pelvis) at the hip joint? ____________________________ ____________________________ ____________________________ ____________________________ 9. What muscles comprise the functional group of medial rotators of the leg at the knee joint? ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ 10. What muscles comprise the functional group of plantarflexors of the ankle joint? ____________________________ ____________________________ ____________________________ ____________________________ For answers to these questions, visit

1113

http://evolve.elsevier.com/Muscolino/muscular

1114

THINK IT THROUGH When thinking about the body in terms of myofascial meridians, we must move toward considering things from a more global perspective. Could a local phenomenon have a distant cause? How would this work? Pick any of the myofascial meridians and trace the line of pull of that band of tissue. What body structures are affected along the way? How might they be affected? What possible signs or symptoms could manifest as a result? ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________

1115

REFERENCES   1.Standring S., ed. Gray’s anatomy, 40th ed., London: Churchill Livingstone, Elsevier, 2008. 2.Neumann, D.A. Kinesiology of the musculoskeletal system: Foundations for rehabilitation, 2nd ed. St. Louis, MO: Mosby Elsevier, 2010. 3.Hamilton, N., Weimar, W., Luttgens, K. Kinesiology: Scientific basis of human motion, 12th ed. New York, NY: McGraw-Hill, 2012. 4.Oatis, C.A.Kinesiology: The mechanics & pathomechanics of human movement. Philadelphia, PA: Lippincott Williams & Wilkins, 2004. 5.Levangie, P.K., Norton, C.C. Joint structure and function: A comprehensive analysis, 5th ed. Philadelphia, PA: F.A. Davis, 2011. 6.Simons, D.G., Travell, J.G., Simons, L.S. Travell & Simons’ myofascial pain and dysfunction: The trigger point manual; Volume 1: Upper half of body, 2nd ed. Baltimore, MD: Williams & Wilkins, 1999. 7.Travell, J.G., Simons, D.G. Myofascial pain and dysfunction: The trigger point manual; Volume 2: The lower extremities. Baltimore, MD: Williams & Wilkins, 1992. 8.Kendall, F.P., McCreary, E.K., Provance, P.G., Rodgers, M.M., Romani, W.A. Muscles: Testing and function with posture and pain, 5th ed. Baltimore, MD: Lippincott Williams & Wilkins, 2005. 9.Smith, L.K., Weiss, E.L., Lehmkuhl, L.D. Brunnstrom’s clinical kinesiology, 5th ed. Philadelphia, PA: F.A. Davis, 1996. 10.Hamill, J., Knutzen, K.M. Biomechanical basis of human movement, 2nd ed. Baltimore, MD: Lippincott Williams & Wilkins, 2000. 11.Kapandji, I.A. The physiology of the joints; Volume 1: Upper limb, 5th ed. Edinburg: Churchill Livingstone, 1983. 12.Sahrmann, S.A. Diagnosis and treatment of movement impairment syndromes. St. Louis, MO: Mosby, Inc, 2002. 13.Chaitow, L., Delany, J.W. Clinical applications of neuromuscular techniques; Volume 1: The upper body. Edinburg: Churchill Livingstone, 2000. 14.Chaitow, L., Delany, J.W. Clinical applications of neuromuscular techniques; Volume 2: The lower body. Edinburg: Churchill Livingstone, 2000. 15.Adams, J. B. Kinesiology [PowerPoint slides]. Retrieved from http://www.kean.edu/~jeadams/docs/Kinesiology/Kines_Power_Points/, 2008. 16.Feltner, M., Gidley, L. Lecture notes [multiple formats]. Retrieved from http://faculty.pepperdine.edu/mfeltner/classes/spme330/, 2012. 17.Fritz, S. Mosby’s essential sciences for therapeutic massage: Anatomy, physiology, biomechanics, and pathology, 4th ed. St. Louis, MO: Elsevier, 2013. 18.Dauzvardis, M. F., McNulty, J. A., Espiritu, B., Lee, D., Sadowski, S., Klitz, G., Yuan, M. Loyola university medical education network master muscle list. Retrieved from http://www.meddean.luc.edu/lumen/meded/grossanatomy/dissector/mml/, 1998. 19.Son, E., Watts, T., Quinn, F. B., Jr., Quinn, M. S. Superficial facial musculature [PDF document]. Retrieved from http://www.utmb.edu/otoref/Grnds/facial-plastic-2012-0329/facial-musc-2012-0329-B.pdf, 2012. 20.Milner, C.Functional anatomy for sport and exercise: Quick reference. New York, NY: Routledge, 2008. 21.Brown, E. Principles of coaching 1 [HTML document]. Retrieved from Department of Kinesiology. website https://www.msu.edu/course/kin/400/shoulder.htm, 2000. 22.Comeford, M., Mottram, S.Kinetic control: The management of uncontrolled movement. Australia: Churchill Livingstone, 2012. 23.Muscolino, J. Psoas major function: A biomechanical examination of the psoas major. Massage

1116

Therapy Journal. 2012; 52(1):17–31. 24.Walsh, F. The anatomy and function of the muscles of the hand and of the extensor tendons of the thumb—Primary source edition. Charleston, SC: Nabu Press, 2014. [(Original work published 1897).]. 25.Myers, T.W. Anatomy trains: Myofascial meridians for manual and movement therapists, 2nd ed. Oxford: Churchill Livingstone, 2009. 26. Anatomy Expert Online Database. www.anatomyexpert.com. 27.Wilson, P. D. Functional anatomy laboratory review [HTML document]. Retrieved from http://www.vetmed.wsu.edu/van308/thoraxm.htm, 2011. 28.Weinberg, D. A. Lower eyelid malposition: Evaluation and treatment. Review of Ophthalmology. 2013; 20(1):46–50. 29.Arnold, A. S., Anderson, F. C., Pandy, M. G., Delp, S. L. Muscular contributions to hip and knee extension during the single limb stance phase of normal gait: A framework for investigating the causes of crouch gait. Journal of Biomechanics. 2005; 38(11):2181–2189. 30.Bid, B. Biomechanics of the knee complex: 7 [PowerPoint slides]. Retrieved from http://www.slideshare.net/dnbid71/biomechanics-of-knee-complex-7-muscles, 2012. 31.Grunning, T.B.Treatment of fracture of the jaw. Charleston, SC: Nabu Press, 2010. [(Original work published 1881).]. 32.Patel, K.Corrective exercise: A practical approach. New York, NY: Routledge, 2014.

1117

1118

1119

1120

1121

1122

1123

1124

1125

1126

1127

1128

1129

1130

1131

INDEX A Abdominal breathing, 399 Abduction, definition of, 9 Abduction/adduction, terms (pairs), 9 Abductor digiti minimi, 261, 647 Abductor digiti minimi manus, 260–261 actions, notes, 261 anterior view of, 260f arterial supply to, 261b attachments of, 260 CMC/MCP joints, crossing, 260 concentric (shortening) mover actions, 260t derivation of, 260b eccentric antagonist functions, 261 functions of, 260 innervation of, 261b isometric stabilization functions, 261 miscellaneous information, 261 motion of, 261 palpation of, 261b pronunciation of, 260b reverse mover action, notes, 260–261 standard mover action, notes, 260 structures, relationship, 261 Abductor digiti minimi pedis, 646–647 arterial supply to, 647b attachments of, 646 concentric (shortening) mover actions, 646t derivation of, 646b eccentric antagonist functions, 646 functions of, 646 innervation of, 647b isometric stabilization function, 646 miscellaneous information, 647 motion of, 646 MTP joint, crossing, 646 palpation of, 647b plantar view of, 646f pronunciation of, 646b reverse mover action, notes, 646 standard mover action, notes, 646 structures, relationship, 647 Abductor hallucis, 644–645 arterial supply to, 645b attachments of, 644

1132

concentric (shortening) mover actions, 644t derivation of, 644b eccentric antagonist functions, 644 functions of, 644 innervation of, 645b isometric stabilization function, 644 miscellaneous information, 645 motion of, 644 palpation of, 645b plantar view of, 644f pronunciation of, 644b reverse mover action, notes, 644 standard mover action, notes, 644 structures, relationship, 645 Abductor pollicis brevis, 252–253 anterior view of, 252f arterial supply to, 253b attachments of, 252 concentric (shortening) mover actions of, 252t derivation of, 252b eccentric antagonist functions, 253 functions of, 252 innervation of, 253b isometric stabilization functions, 253 miscellaneous information, 253 palpation of, 253b pronunciation of, 252b reverse mover actions, notes, 253 standard mover actions, notes, 252–253 structures, relationship, 253 thumb, first CMC joint crossing, 252 Abductor pollicis longus (deep distal four group), 225–227 actions of, notes, 226 arterial supply to, 227b attachments of, 225 concentric (shortening) mover actions, 225t derivation of, 225b eccentric antagonist functions, 226 first CMC joint, crossing, 225 functions of, 225 innervation of, 227b isometric stabilization functions, 226 miscellaneous information, 227 motions of, 226 palpation of, 227b posterior view of, 225f pronunciation of, 225b reverse mover action, notes, 226 standard mover action, notes, 225 structures, relationship, 227 Achilles tendon (calcaneal tendon), 604, 605, 607, 609 Acromion process, upper trapezius, pulling, 96–97 Actin filament, 86 illustration of, 86f

1133

pulling of, 86 Adduction, definition of, 9 Adductor brevis (adductor group), 522–523 anterior view of, 522f arterial supply to, 523b attachments of, 522 concentric (shortening) mover actions, 522t derivation of, 522b eccentric antagonist functions, 523 functions of, 522–523 hip joint, crossing, 522 innervation of, 523b isometric stabilization functions, 523 miscellaneous information, 523 palpation of, 523b pronunciation of, 522b reverse mover action, notes, 522 standard mover action, notes, 522 structures, relationship, 523 Adductor gracilis, 521 Adductor group, 512. See also Adductor brevis (adductor group) Adductor longus (adductor group) Adductor magnus (adductor group) Gracilis (adductor group) Pectineus (adductor group) arterial supply to, 512b attachments of, 512 derivation of, 512b functions of, 512 innervation of, 512b miscellaneous information, 512 pronunciation of, 512b Adductor hallucis, 658–659 arterial supply to, 659b attachments of, 658 concentric (shortening) mover actions, 658t derivation of, 658b eccentric antagonist functions, 658 functions of, 658–659 innervation of, 659b isometric stabilization function, 659 note, 659 miscellaneous information, 659 motion of, 658 MTP joint, crossing, 658 palpation of, 659b plantar view of, 658f pronunciation of, 658b reverse mover action, note, 658 standard mover action, notes, 658 structures, relationship, 659 Adductor hiatus, 526 Adductor longus (adductor group), 518–519 anterior view of, 518f arterial supply to, 519b attachments of, 518 concentric (shortening) mover actions, 518t

1134

derivation of, 518b eccentric antagonist functions, 518 functions of, 518–519 hip joint, crossing, 518 innervation of, 519b isometric stabilization functions, 518 miscellaneous information, 519 palpation of, 519b pronunciation of, 518b reverse mover action, notes, 518 standard mover action, notes, 518 structures, relationship, 519 Adductor magnus (adductor group), 524–526 arterial supply to, 525b attachments of, 524 concentric (shortening) mover actions, 524t derivation of, 524b eccentric antagonist functions, 525 functions, 524–525 hip joint, crossing, 524 innervation of, 525b isometric stabilization functions, 525 miscellaneous information, 526 palpation of, 525b posterior view of, 524f pronunciation of, 524f reverse mover action, notes, 524 standard mover action, notes, 524 structures, relationship, 525 Adductor minimus, 526 Adductor pollicis, 268–270 actions, notes, 269 anterior view of, 268f arterial supply to, 269b attachments of, 268 CMC joint, crossing, 268–269 concentric (shortening) mover actions, 268t derivation of, 268b eccentric antagonist functions, 269 functions of, 268 innervation of, 269b isometric stabilization functions, 269 miscellaneous information, 270 motions of, 269 oblique head, 270 palpation of, 269b pronunciation of, 268b reverse mover action, notes, 269 standard mover action, notes, 268–269 structures, relationship, 269–270 transverse head, 270 Agonist, 81 Anatomic position, 2 location terms relative to, 5f

1135

as reference position, 4f usage of, 7–9 Anconeus, 163–164 actions of, note, 163 arterial supply to, 164b attachments of, 163 concentric (shortening) mover actions, 163t derivation of, 163b eccentric antagonist function, 163 elbow joint, crossing, 163 functions of, 163 innervation of, 164b isometric stabilization function, 163 miscellaneous information, 164 motion of, 163 palpation of, 164b posterior view of, 163f pronunciation of, 163b reverse mover action, note, 163 standard mover action, note, 163 structures, relationship, 164 Angularis (head), 466 Ankle joint dorsiflexors, anterior view of, 710f plantarflexors, posterior view of, 710f Ankle joint, foot, 29 dorsiflexion and plantarflexion of, lateral views of, 29f eversion/inversion of, frontal plane components of, 30f lateral/medial rotation of, transverse plane components of, 30f motion of, cardinal plane components of, 30f Ankle joint, muscles anterior view of, 588, 588f function of, overview, 587 lateral view of, 592, 592f medial views of, 593, 593f overview of, 586 posterior view of deep view of, 591 intermediate view of, 590 superficial view of, 589 structure of, overview, 586–587 Antagonist, 83 Anterior, definition of, 2 Anterior abdominal wall. See also External abdominal oblique (anterior abdominal wall) Internal abdominal oblique (anterior abdominal wall) Rectus abdominis (anterior abdominal wall) Transversus abdominis (anterior abdominal wall) muscles, 363–364 anterior views of, 364f arterial supply to, 363b attachments of, 363 deep view of, 365f functions of, 363 innervation of, 363b miscellaneous information, 363 Anterior axillary fold, pectoralis major proportion, 127

1136

Anterior belly, 426 Anterior deltoid, GH joint (crossing), 120 Anterior distal radius, 167 Anterior distal ulna, 167 Anterior ear, 452 Anterior hand radial side, 185 ulnar side, 190 Anterior head, 525 Anterior inferior iliac spine (AIIS), 564, 565 Anterior/posterior, terms (pairs), 2 Anterior scalene (scalene group), 330–331 arterial supply to, 331b attachments of, 330 cervical attachment, fixation, 330 cervical spinal joint, crossing, 330 concentric (shortening) mover actions, 330t derivation of, 330b eccentric antagonist functions, 331 functions of, 330 innervation of, 331b isometric stabilization functions, 331 miscellaneous information, 331 motion of, 330 palpation of, 331b pronunciation of, 330b reverse mover action, notes, 330 standard mover action, notes, 330 structures, relationship, 331 syndrome, 331, 333 Anterior shin splints, 597 Anterior superior iliac spine (ASIS), 507 Anterior tibia, 596 Anterior ulna, 213 Anterolateral lumbar spine, 501 Anterolateral views, 8f AOJ. See Atlanto-occipital joint (AOJ) Aponeurosis, 86 Appendicular body, divisions of, 2f–3f Arm abduction, 120, 121 illustration of, 118f fixation, 120 flexion, reverse action of, 186 at glenohumeral joint, 14 abduction of, 99 frontal plane actions of, 14f sagittal plane actions of, 14f transverse plane actions of, 14f trunk relative to, reverse actions in, 15f lateral rotators of, in humerus (wrapping), 113 medial rotators of, in humerus (wrapping), 113 motions of, 121 brachialis in, 81

1137

frontal plane, 7f oblique plane, 7f 90 degree abduction, 120 scapula, movement, 120 Arm line myofascial meridians, 722f Articularis genus, 571, 572 anterior view of, 572f arterial supply to, 572b attachments of, 572 concentric (shortening) mover actions, 572t derivation of, 572b distal attachment, pulling, 572 eccentric antagonist function, 572 functions of, 572 innervation of, 572b isometric stabilization function, 572 miscellaneous information, 572 motion of, 572 palpation of, 572b pronunciation of, 572b standard mover action, notes, 572 structures, relationship, 572 ASIS. See Anterior superior iliac spine (ASIS) Atlantoaxial joint, of spine, 37f Atlanto-occipital joint (AOJ) lateral flexion motions at, posterior views of, 20f longus capitis, crossing, 340 rectus capitis lateralis, crossing, 344 rotation motions at, posterior views of, 20f sagittal plane motions at, lateral views of, 20f splenius capitis, crossing, 346 Atlas, transverse process, 103, 356, 358 Attachments., 83–84 Muscle attachment origin and insertion vs. Auricularis group, 452–453 arterial supply to, 453b attachments of, 452 concentric (shortening) mover actions, 452t derivation of, 452b functions of, 452–453 innervation of, 453b lateral view of, 452f miscellaneous information, 453 motions of, 452 mover action notes, 452 palpation of, 453b pronunciation of, 452b structures, relationship, 453 Auricularis muscles, lateral view of, 452f Axial body, 2f–3f, 686–701 Axis (axes), 7 imaginary line, 5 spinous process, 352, 356 B

1138

Back, trapezius (superficiality), 98 Back functional line, posterolateral view of, 723f Ball-and-socket joint, 37 Belly breathing, 399 Biaxial condyloid joint, example of, 37f Biaxial joints, 36–37 Biaxial saddle joint, example of, 38f Biceps brachii, 152–154 actions, note, 153 anterior view of, 152f arterial supply to, 154b attachments of, 152 concentric (shortening) mover actions, 152t derivation of, 152b eccentric antagonist functions, 153 notes, 153 elbow joint, crossing, 89, 152 functions of, 152 innervation of, 154b isometric stabilization functions, 153 miscellaneous information, 154 motions of, 153 palpation of, 154b pronunciation of, 152b reverse mover action, notes, 153 standard mover action, notes, 152 structures, relationship, 154 Biceps femoris (hamstring group), 575–577 actions, note, 576 arterial supply to, 576b attachments of, 575 concentric (shortening) mover actions, 575t derivation of, 575b eccentric antagonist functions, 576 functions of, 575–576 innervation of, 576b isometric stabilization functions, 576 knee joint, crossing, 575 miscellaneous information, 577 motions of, 576 palpation of, 576b posterior views of, 575f pronunciation of, 575b reverse mover action, notes, 576 standard mover action, notes, 575–576 structures, relationship, 576–577 Bicipital aponeurosis, 154 Bicipital groove, 154 Big toe dorsal surface of, 624, 642 plantar surface of, 628 Bipennate muscle, rectus femoris as, 87f Biventer cervicis, 309, 315 Body

1139

anatomic position of, 4f anterior view of, 2f anterolateral views of, 6f divisions of, 2f–3f lateral view of, 3f motions of body parts in, 1 within planes, 4–5 parts, 1 motion examples of, 7f posterior view of, 3f Bones anterior view of, 40f, 44f, 52f, 56f, 60f, 66f, 70f bony landmarks on, atlas of, 40–77 dorsal view of, 50f, 74f inferior view of, 64f landmarks of, atlas of, 40–77 lateral view of, 62f movement of, 81f muscle attachment on, atlas of, 40–77 palmar view of, 48f plantar view of, 76f posterior view of, 42f, 46f, 54f, 58f, 68f, 72f Bony landmarks anterior view of, 40f, 44f, 52f, 56f, 60f, 66f, 70f atlas, 40–77 dorsal view of, 50f, 74f inferior view of, 64f lateral view of, 62f palmar view of, 48f plantar view of, 76f posterior view of, 42f, 46f, 54f, 58f, 68f, 72f posterolateral view of, 52f Bony peripheral attachments, fixation of, 399 Brachialis, 155–156 anterior view of, 155f arterial supply to, 156b attachments of, 155 pulling force, exertion, 80 concentric (shortening) mover actions, 155t contraction and shortening of, 80 arm movement, 80 movement, 81 requirements of, 80f derivation of, 155b eccentric antagonist function, 155 note, 155 elbow joint, crossing, 155 functions of, 155 fusiform-shaped muscle, demonstration of, 87f humerus attachment of, 80f innervation of, 156b isometric stabilization function, 155 miscellaneous information, 156

1140

motion of, 155 mover action of, 82f palpation of, 156b pronunciation of, 155b reverse mover action of, notes, 155 standard mover action of, notes, 155 structures, relationship, 156 Brachioradialis, 157–159 actions, note, 158 anterior view of, 157f arterial supply to, 158b attachments of, 157 concentric (shortening) mover actions, 157t derivation of, 157b eccentric antagonist functions, 158 notes, 158 elbow joint, crossing, 157 functions of, 157 innervation of, 158b isometric stabilization functions, 158 miscellaneous information, 159 motions of, 158 palpation of, 158b pronunciation of, 157b reverse mover action, notes, 158 standard mover action, notes, 157 structures, relationship, 158 Brevis, term, 657 Buccinator, 483–484 anterior view of, 483f arterial supply to, 483b attachments of, 483 concentric (shortening) mover actions, 483t derivation of, 483b functions of, 483 innervation of, 483b miscellaneous information, 484 motions of, 483 mover action notes, 483 palpation of, 483b pronunciation of, 483b structures, relationship, 483–484 Bucket handle motion, 400 C C1-C4, transverse processes, 102 C2-C6 anterior bodies/transverse processes, 338 C2-T3 transverse process/anterior bodies, 338 C3-C6, nuchal ligament, 346 C7-T4, spinous processes, 346 C7-T5, spinous processes, 100 C7-T12, spinous processes, 96 Calcaneal tendon (Achilles tendon), 604, 605, 607, 609 Calcaneus

1141

dorsal surface of, 640, 642 tuberosity of, 644, 646, 648 Cardinal planes action, opposition, 256 components of, 30f corresponding axes for, 8f motions, 8b Carpal tunnel syndrome, 212, 214, 217 Carpometacarpal (CMC) joint abductor pollicis brevis, crossing, 252–253 abductor pollicis longus, crossing, 225 adductor pollicis, crossing, 268–269 extensor pollicis brevis, crossing, 228 extensor pollicis longus, crossing, 231 flexor pollicis longus, crossing, 215 little finger movement at, 201 muscles, crossing, 201–202 opponens pollicis, crossing, 256 thumb, 19, 37b as biaxial saddle joint example, 38f Cartilaginous joints, 36f Caudal, definition of, 4 Central compartment group, 266–267 anterior view of, 266f arterial supply to, 267b attachments, 266 deep view of, 267f functions of, 267 innervation of, 267b Cervical spinal joint contralateral rotators of, 693f extensors, posterior view of, 690f flexors, anterior view of, 689f ipsilateral rotators of, 694f lateral flexors of, 691f–692f neck, 21 splenius cervicis, crossing, 348 Cervical spine fixation of, 102 levator scapulae crossing, 102 transverse process, 330, 332 Chin, fascia and skin of, 481 Christmas tree muscles, 101 Circumduction, 10 Clavicle at sternoclavicular joint, 13 trapezius attachment to, 98 Closed-chain, 82–83 CMC joint. See Carpometacarpal (CMC) joint Coccyx, 528 Common extensor tendon, 173 Common flexor tendon, 173 Concentric, definition of, 80 Concentric contraction, 80–81

1142

exploring, 81 of muscle, 81f occurrence of, 80–81, 82–83 Condyloid joint, 36 example. See Biaxial condyloid joint Contract, definition of, 79 Contractions. See also Concentric contraction Eccentric contractions Isometric contractions lengthening, 83 resistance force compared with, 79–80 Contralateral rotation, term (usage), 9 Coracobrachialis, 123–124 actions, notes, 124 anterior view of, 123f arterial supply to, 124b attachments of, 87, 123 concentric (shortening) mover actions, 123t derivation of, 123b eccentric antagonist functions, 123 functions of, 123 GH joint, crossing, 123 innervation of, 124b isometric stabilization functions, 123 miscellaneous information, 124 motion of, 123 palpation of, 124b pronunciation of, 123b reverse mover actions, notes, 123 standard mover actions, notes, 123 structures, relationship, 124 Core stabilization, 84 Coronal plane, 5b Coronoid process, 416 Corrugator supercilii, 457–458 anterior view of, 457f arterial supply to, 457b attachments of, 457 concentric (shortening) mover actions, 457t derivation of, 457b functions of, 457 innervation of, 457b miscellaneous information, 458 motions of, 457 mover action notes, 457 palpation of, 457b pronunciation of, 457b structures, relationship, 457–458 Costal cartilages, internal surface of, 396 Costoclavicular syndrome, 108, 328, 331, 333 Cranial, definition of, 4 Cranial/caudal, terms (pairs), 4 Cross-bridges, creation of, 86 Cubital tunnel syndrome, 191 D

1143

DAB PAD. See Dorsals ABduct, Palmars ADduct (DAB PAD) Deep, definition of, 4 Deep back arm lines, 722f Deep distal four group, 224–236. See also Abductor pollicis longus (deep distal four group) Extensor indicis (deep distal four group) Extensor pollicis brevis (deep distal four group) Extensor pollicis longus (deep distal four group) posterior views of, 224f Deep head, 161, 162 Deep lateral rotator group, 537. See also Inferior gemellus (deep lateral rotator group) Obturator externus (deep lateral rotator group) Obturator internus (deep lateral rotator group) Piriformis (deep lateral rotator group) Quadratus femoris (deep lateral rotator group) Superior gemellus (deep lateral rotator group) arterial supply to, 537b attachments of, 537 functions of, 537 innervation of, 537b miscellaneous information, 537 posterior views of, 538, 538f Deep six, 537 Deltoid, 119–122. See also Right deltoid actions, notes, 121 arterial supply to, 121b attachments of, 119 concentric (shortening) mover actions, 119t derivation of, 119b eccentric antagonist functions, 121 note, 121 functions of, 119 GH joint, crossing, 120 innervation of, 121b isometric contraction of, example of, 84f isometric stabilization functions, 121 miscellaneous information, 122 motions of, 121 as multipennate muscle, 87f palpation of, 121b pronunciation of, 119b reverse mover actions, 119 notes, 120 standard mover actions, 119 notes, 120 structures, relationship, 121 Depression, definition of, 9 Depressor anguli oris, 477–478 anterior view of, 47f arterial supply to, 478b attachments of, 477 concentric (shortening) mover actions, 477t derivation of, 477b functions of, 477–478 innervation of, 478b miscellaneous information, 478 motions of, 477 mover action notes, 477 palpation of, 478b pronunciation of, 477b structures, relationship, 478

1144

Depressor labii inferioris, 479–480 anterior view of, 479f arterial supply to, 480b attachments of, 479 concentric (shortening) mover actions, 479t derivation of, 479b functions of, 479–480 innervation of, 480b miscellaneous information, 480 motions of, 479 mover action notes, 479 palpation of, 480b pronunciation of, 479b structures, relationship, 480 Depressor septi nasi, 463–464 anterior view of, 463f arterial supply to, 463b attachments of, 463 concentric (shortening) mover actions, 463t derivation of, 463b functions of, 463–464 innervation of, 463b miscellaneous information, 464 motions of, 463 mover action notes, 463 palpation of, 463b pronunciation of, 463b structures, relationship, 464 Depressor supercilii muscle, 455 de Quervain’s disease, 227 De-rotation, 9b Diaphragm, 398–401 anterior view of, 398f arterial supply to, 400b attachments of, 398 central tendon (dome) of, 398 concentric (shortening) mover actions, 399t contraction of, 399 derivation of, 398b eccentric antagonist function, 399 functions of, 399–400 notes, 399–400 inferior view of, 398f innervation of, 400b isometric stabilization function, 399 note, 399 miscellaneous information, 400 motions of, 399 palpation of, 400b pronunciation of, 398b reverse mover action, notes, 399 standard mover action, notes, 399 structures, relationship, 400 term, meaning, 400

1145

Diarthrotic synovial joints, subdivision of, 33 Digastric (hyoid group), 426–427 anterior view of, 426f arterial supply to, 427b attachments of, 426 concentric (shortening) mover actions, 426t derivation of, 426b eccentric antagonist functions, 427 functions of, 426–427 innervation of, 427b isometric stabilization functions, 427 miscellaneous information, 427 palpation of, 427b pronunciation of, 426b reverse mover action notes, 427 standard mover action notes, 426 structures, relationship, 427 Digit, term (usage), 641, 643 Dilatator nasi, 462 DIM. See Dorsal interossei manus (DIM) DIP joints. See Distal interphalangeal (DIP) joints Distal, definition of, 4 Distal attachment, movement of, 81 Distal forearm movement of, 82f proximal arm movement toward, 82f Distal interphalangeal (DIP) joints extensor digitorum, crossing, 218 FDP, crossing, 213 finger movement at, 201 reverse actions at, 219, 222 Distal phalanx, base of, anterior aspect of, 215 Distal posterior fibula, 628 Distal posterior forearm, deep muscles in extensor indicis, 235 extensor pollicis longus, 233 Distal posterolateral femur, 583, 608 Dorsal, term (usage), 2 Dorsal digital expansion, 220, 233, 249, 270, 623 attachment site, 249 lateral view, 249f sides, 662 views, 249f Dorsal hood, 220, 233 Dorsal interossei manus (DIM), 276–278 actions, notes, 277–278 arterial supply to, 278b attachments of, 276 concentric (shortening) mover actions, 276t derivation of, 276b eccentric antagonist functions, 277 functions of, 276 innervation of, 278b isometric stabilization functions, 277

1146

miscellaneous information, 278 palpation of, 278b posterior view of, 276f pronunciation of, 276b reverse mover action, notes, 277 standard mover action, notes, 277 structures, relationship, 278 Dorsal interossei pedis, 662–664 actions, notes, 663 arterial supply to, 663b attachments of, 662 concentric (shortening) mover actions, 662t derivation of, 662b dorsal view of, 662f eccentric antagonist functions, 663 functions of, 662–663 innervation of, 663b isometric stabilization functions, 663 miscellaneous information, 664 motion of, 663 MTP joint, crossing, 662 palpation of, 663b pronunciation of, 662b reverse mover action, notes, 663 standard mover action, notes, 662–663 structures, relationship, 663–664 Dorsals ABduct, Palmars ADduct (DAB PAD), 267, 274, 277 Dorsiflexion, as cardinal plane component, 30f Dorsiflexion/plantarflexion, terms (pairs), 10 Dracula expression, 474 E Ear, fascia superior to, 451 Eccentric contractions, 83, 83f Eight-pack (8-pack) muscle, 368 Elbow, humeroulnar joint of, 36f Elbow joint anconeus crossing, 163 biceps brachii, crossing, 89, 152 brachialis, engagement, 155 brachioradialis, crossing, 157 extensors, posterior view of, 675f flexion at, 16f flexors, anterior view of, 675f forearm at, 16 motions at, 16f muscles of. See also Right elbow joint function, overview of, 145 overview of, 144 structure, overview of, 144 triceps brachii, crossing, 161 Elevation, definition of, 9 Elevation/depression, terms (pairs), 9 Endomysium (endomysia), 85–86

1147

as fibrous fascial sheaths, 85f Epicranial aponeurosis, 450 Epicranius, 451 components of. See Occipitofrontalis (epicranius component) Temporoparietalis (epicranius component) Epimysium, 85–86 as fibrous fascial sheaths, 85f Erector spinae group, 299–301. See also Iliocostalis (erector spinae group) Longissimus (erector spinae group) Spinalis (erector spinae group) actions, additional notes on, 300 arterial supply to, 300b attachments of, 299 concentric (shortening) mover actions, 299t derivation of, 299b eccentric antagonist functions, 300 notes on, 300 functions of, 299 innervation of, 300b isometric stabilization functions, 300 notes on, 300 miscellaneous information, 301 motion of, 300 palpation of, 300b posterior view of, 299f pronunciation of, 299b reverse mover action, notes on, 299–300 standard mover action, notes on, 299 structures, relationship, 301 Eversion as cardinal plane component, 30f definition of, 10 Everters, 711f Extended knee joint, unlocking, 584 Extension, definition of, 9 Extensor carpi radialis brevis (wrist extensor and radial group), 194–196 arterial supply to, 195b attachments of, 194 concentric (shortening) mover actions, 194t derivation of, 194b eccentric antagonist functions, 195 note, 195 functions of, 194 innervation of, 195b isometric stabilization functions, 195 note, 195 miscellaneous information, 196 motions of, 195 palpation of, 195b posterior view of, 194f pronunciation of, 194b reverse mover action, notes, 195 standard mover action, notes, 194 structures, relationship, 195 Extensor carpi radialis longus (wrist extensor and radial group), 192–193 arterial supply to, 193b

1148

attachments of, 192 concentric (shortening) mover actions, 192t derivation of, 192b eccentric antagonist functions, 193 note, 193 functions of, 192 innervation of, 193b isometric stabilization functions, 193 note, 193 miscellaneous information, 193 motions of, 193 palpation of, 193b posterior view of, 192f pronunciation of, 192b reverse mover action, notes, 193 standard mover action, notes, 192 structures, relationship, 193 Extensor carpi ulnaris (wrist extensor group), 197–198 arterial supply to, 198b attachments of, 197 concentric (shortening) mover actions, 197t derivation of, 197b eccentric antagonist functions, 198 note, 195 functions of, 197 innervation of, 198b isometric stabilization functions, 198 note, 198 miscellaneous information, 198 motion of, 198 palpation of, 198b posterior view of, 197f pronunciation of, 197b reverse mover action, notes, 197 standard mover action, notes, 197 structures, relationship, 198 Extensor digiti minimi, 221–223 actions, notes, 222 arterial supply to, 222b attachments of, 221 concentric (shortening) mover actions, 221t derivation of, 221b eccentric antagonist functions, 222 note, 222 fifth MCP joint, crossing, 221 functions of, 221 innervation of, 222b isometric stabilization functions, 222 miscellaneous information, 223 motions of, 222 palpation of, 222b posterior view of, 221f pronunciation of, 221b reverse mover action, notes, 222

1149

standard mover action, notes, 221 structures, relationship, 223 Extensor digitorum, 218–220 actions, notes, 219 arterial supply to, 219b attachments of, 218 communis, 220 concentric (shortening) mover actions, 218t derivation of, 218b distal tendons, 271 eccentric antagonist functions, 219 note, 219 functions of, 218 innervation of, 219b isometric stabilization functions, 219 MCP/PIP/DIP joints, crossing, 218 miscellaneous information, 220 motions of, 219 palpation of, 219b posterior view of, 218f pronunciation of, 218b reverse mover action, notes, 219 standard mover action, notes, 218 structures, relationship, 219 Extensor digitorum brevis, 640–641 arterial supply to, 641b attachments of, 640 concentric (shortening) mover actions, 640t derivation of, 640b dorsal view of, 640f eccentric antagonist functions, 641 functions of, 640–641 innervation of, 641b isometric stabilization functions, 641 miscellaneous information, 641 motion of, 640 palpation of, 641b pronunciation of, 640b reverse mover action, notes, 640 standard mover action, notes, 640 structures, relationship, 641 toe joints, crossing, 640 Extensor digitorum longus, 622–623 actions, note, 623 anterior view of, 622f arterial supply to, 623b attachments of, 622 concentric (shortening) mover actions, 622t derivation of, 622b eccentric antagonist functions, 623 note, 623 functions of, 622–623 innervation of, 623b isometric stabilization functions, 623

1150

miscellaneous information, 623 motion of, 623 palpation of, 623b pronunciation of, 622b reverse mover action, notes, 622–623 standard mover action, notes, 622 structures, relationship, 623 toe joints, crossing, 622 Extensor expansion, 220, 233 Extensor hallucis brevis, 642–643 actions, note, 642 arterial supply to, 642b attachments of, 642 concentric (shortening) mover actions, 642t derivation of, 642b dorsal view of, 642f eccentric antagonist function, 642 functions of, 642 innervation of, 642b isometric stabilization function, 642 miscellaneous information, 643 motion of, 642 palpation of, 643b pronunciation of, 642b reverse mover action, notes, 642 standard mover action, notes, 642 structures, relationship, 643 Extensor hallucis longus, 624–625 actions, note, 625 anterior view of, 624f arterial supply to, 625b attachments of, 624 big toe, crossing, 624 concentric (shortening) mover actions, 624t derivation of, 624b eccentric antagonist functions, 625 note, 625 functions of, 624–625 innervation of, 625b isometric stabilization functions, 625 miscellaneous information, 625 motion of, 625 palpation of, 625b pronunciation of, 624b reverse mover action, notes, 624–625 standard mover action, notes, 624 structures, relationship, 625 Extensor indicis (deep distal four group), 234–236 actions, notes, 235 arterial supply to, 235b attachments of, 234 concentric (shortening) mover actions, 234t derivation of, 234b eccentric antagonist functions, 235

1151

functions of, 234 innervation of, 235b isometric stabilization functions, 235 miscellaneous information, 236 motion of, 235 palpation of, 235b posterior view of, 234f pronunciation of, 234b reverse mover action, notes, 235 second MCP joint, crossing, 234 standard mover action, notes, 234 structures, relationship, 235 Extensor pollicis brevis (deep distal four group), 228–230 actions, notes, 229 arterial supply to, 230b attachments of, 228 concentric (shortening) mover actions, 228t derivation of, 228b eccentric antagonist functions, 229 in first CMC joint, crossing, 228 functions of, 228 innervation of, 230b isometric stabilization functions, 229 miscellaneous information, 230 motions of, 229 palpation of, 230b posterior view of, 228f pronunciation of, 228b reverse mover action, notes, 229 standard mover action, notes, 228 structures, relationship, 230 Extensor pollicis longus (deep distal four group), 231–233 actions, notes, 232 arterial supply to, 233b attachments of, 231 CMC joint, crossing, 231 concentric (shortening) mover actions, 231t derivation of, 231b eccentric antagonist functions, 232 functions of, 231 innervation of, 233b isometric stabilization functions, 232 miscellaneous information, 233 motion of, 232 palpation of, 233b posterior view of, 231f pronunciation of, 231b reverse mover action, notes, 232 standard mover action, notes, 231 structures, relationship, 233 External abdominal oblique (anterior abdominal wall), 369–372 actions, notes, 371 anterior view of, 369f arterial supply to, 371b

1152

attachments of, 369 concentric (shortening) mover actions, 370t derivation of, 369b eccentric antagonist functions, 371 notes on, 371 functions of, 370 innervation of, 371b isometric stabilization functions, 371 notes on, 371 lateral view of, 369f miscellaneous information, 372 motions in, 371 palpation of, 371b pronunciation of, 369b reverse mover action, notes on, 370–371 standard mover action, notes on, 370 structures, relationship, 372 External ilium, 531, 534 External intercostals, 390–392 actions, note, 391 anterior view of, 390f arterial supply to, 391b attachments of, 390 concentric (shortening) mover actions, 390t derivation of, 390b eccentric antagonist functions, 391 functions of, 390–391 innervation of, 391b isometric stabilization functions, 391 note, 391 location of, 390 miscellaneous information, 392 motions of, 391 palpation of, 392b posterior view of, 390f pronunciation of, 390b reverse mover action, notes, 391 standard mover action, notes, 391 structures, relationship, 392 External occipital protuberance, 96 External pterygoid, 421 Extrinsic finger, muscles of anterior view of deep view of, 205, 205f intermediate view of, 204, 204f superficial view of, 203, 203f lateral view of, 208, 208f medial view of, 209, 209f posterior view of intermediate/deep views of, 207f superficial view of, 206, 206f Eye, 454–458 medial side of, 454 Eyebrow

1153

fascia and skin medial to, 459 fascia and skin superior to, 457 Eyelid, upper, 456 F Face, anterior view, 448f Facial expression muscles arterial supply to, 444b innervation of, 444b overview, 443–488 Facial landmarks, 448 Fan-shaped muscle, demonstration of, 87f Fascicles, 85 as fiber bundles, 85f FDP. See Flexor digitorum profundus (FDP) FDS. See Flexor digitorum superficialis (FDS) Female pelvic floor muscles, 717f, 718f Femur gluteal tuberosity of, 528 greater trochanter of, 531, 534, 539, 542, 544, 546 head of, hip joint and, 39f intertrochanteric crest of, 550 lesser trochanter of, 501, 505 linea aspera of, 518, 522, 524, 566, 568, 570 proximal posterior shaft of, 516 trochanteric fossa of, 548 Fibrous fascia muscle envelopment of, 86b sheaths, 85f Fibrous joints, 36f Fibular, definition of, 4 Fibular abduction, 662 Fibularis brevis, 602–603 actions, notes, 603 arterial supply to, 603b attachments of, 602 concentric (shortening) mover actions, 602t derivation of, 602b eccentric antagonist functions, 602 foot, crossing, 602 functions of, 602–603 innervation of, 603b isometric function, note, 603 isometric stabilization functions, 602 lateral view of, 602f miscellaneous information, 603 motion of, 602 palpation of, 603b pronunciation of, 602b reverse mover actions, notes, 602 standard mover actions, notes, 602 structures, relationship, 603 Fibularis longus, 600–601 actions, notes, 601

1154

arterial supply to, 601b attachments of, 600 concentric (shortening) mover actions, 600t derivation of, 600b eccentric antagonist functions, 600 functions of, 600–601 innervation of, 601b isometric function, notes, 601 isometric stabilization functions, 600 lateral view of, 600f miscellaneous information, 601 motion of, 600 palpation of, 601b pronunciation of, 600b reverse mover actions, notes, 600 standard mover actions, notes, 600 structures, relationship, 601 Fibularis tertius, 598–599, 623 actions, notes, 599 ankle joint, crossing, 598 anterior view of, 598f arterial supply to, 599b attachments of, 598 concentric (shortening) mover actions, 598t derivation of, 598b eccentric antagonist functions, 599 note, 599 functions of, 598–599 innervation of, 599b isometric stabilization functions, 599 miscellaneous information, 599 motion of, 598 palpation of, 599b pronunciation of, 598b reverse mover actions, notes, 598 standard mover actions, notes, 598 structures, relationship, 599 Finger abduction, restraint, 274 anterior surfaces of, 210, 213 extension, restraint, 274 flexion, restraint, 274 flexors, location of, 201 MCP joints actions, 18f reverse actions, 27 metacarpals, 273, 276 phalanges of, 218 proximal phalanges, 273, 276 Finger joints extrinsic muscles of, 200–236 function of, overview in, 201–202 overview, 200–202 structure of, overview in, 200–201

1155

intrinsic muscles of, 238–280 function, overview, 239–240 overview, 238–240 structure, overview, 238–239 First CMC joint, motion (reverse action), 254–255 Fixed attachment, 81 Flexion, definition of, 9 Flexion/extension, terms (pairs), 9 Flexor accessorius, 651 Flexor carpi radialis (wrist flexor group), 185–186 anterior view of, 185f arterial supply to, 186b attachments of, 185 concentric (shortening) mover actions, 185t derivation of, 185b eccentric antagonist functions, 186 note, 186 functions of, 185 innervation of, 186b isometric stabilization functions, 186 miscellaneous information, 186 motion of, 186 palpation of, 186b pronunciation of, 185b reverse mover action, notes, 185 standard mover action, notes, 185 structures, relationship, 186 Flexor carpi ulnaris (wrist flexor group), 190–191 anterior view of, 190f arterial supply to, 191b attachments of, 190 concentric (shortening) mover actions, 190t derivation of, 190b eccentric antagonist functions, 191 note, 191 functions of, 190 innervation of, 191b isometric stabilization functions, 191 note, 191 miscellaneous information, 191 motion of, 191 palpation of, 191b pronunciation of, 190b reverse mover action, notes, 190 standard mover action, notes, 190 structures, relationship, 191 Flexor digiti minimi, 263 Flexor digiti minimi brevis, 263 Flexor digiti minimi manus, 262–263 actions, notes, 263 anterior view of, 262f arterial supply to, 263b attachments of, 262 concentric (shortening) mover actions, 262t

1156

derivation, 262b eccentric antagonist functions, 262 functions of, 262 innervation of, 263b isometric stabilization functions, 262 little finger, MCP joint (crossing), 262 miscellaneous information, 263 motion of, 262 palpation of, 263b pronunciation of, 262b reverse mover action, notes, 262 standard mover action, notes, 262 structures, relationships, 263 Flexor digiti minimi pedis, 656–657 arterial supply to, 656b attachments of, 656 concentric (shortening) mover actions, 656t derivation of, 656b eccentric antagonist function, 656 functions of, 656 innervation of, 656b isometric stabilization function, 656 miscellaneous information, 657 motion of, 656 MTP joint, crossing, 656 palpation of, 657b plantar view of, 656f pronunciation of, 656b reverse mover action, notes, 656 standard mover action, notes, 656 structures, relationship, 657 Flexor digitorum accessorius, 651 Flexor digitorum brevis, 648–649 arterial supply to, 649b attachments of, 648 concentric (shortening) mover actions, 648t derivation of, 648b eccentric antagonist functions, 648 functions of, 648 innervation of, 649b isometric stabilization functions, 648 miscellaneous information, 649 motion of, 648 MTP and PIP joints, crossing, 648 palpation of, 649b plantar view of, 648f pronunciation of, 648b reverse mover action, notes, 648 standard mover action, notes, 648 structures, relationship, 649 Flexor digitorum longus (Dick of Tom, Dick, and Harry group), 626–627 actions, note, 627 arterial supply to, 627b attachments of, 626

1157

concentric (shortening) mover actions, 626t derivation of, 626b eccentric antagonist functions, 627 note, 627 functions of, 626–627 innervation of, 627b isometric stabilization functions, 627 note, 627 miscellaneous information, 627 motion of, 627 muscle, distal tendon, 650, 652 palpation of, 627b posterior view of, 626f pronunciation of, 626b quadratus plantae, attachment, 650 reverse mover action, notes, 626–627 standard mover action, notes, 626 structures, relationship, 627 toe joints, crossing, 626 Flexor digitorum profundus (FDP), 213–214 actions, notes, 214 anterior view of, 213f arterial supply to, 214b attachments of, 213 concentric (shortening) mover actions, 213t derivation of, 213b distal tendons, 271 eccentric antagonist functions, 214 functions of, 213 innervation of, 214b isometric stabilization functions of, 214 MCP/PIP/DIP joints, crossing, 213 miscellaneous information, 214 motions of, 214 palpation of, 214b pronunciation of, 213b reverse mover action, notes, 213 standard mover action, notes, 213 structures, relationship, 214 Flexor digitorum sublimis, 211 Flexor digitorum superficialis (FDS), 210–212 actions, notes, 211 anterior view of, 210f arterial supply to, 211b attachments of, 210 concentric (shortening) mover actions, 210t derivation of, 210b eccentric antagonist functions, 211 note, 211 functions of, 210 innervation of, 211b isometric stabilization functions, 211 note, 211 MCP/PIP joints, crossing, 210

1158

miscellaneous information, 211–212 motions of, 211 palpation of, 211b pronunciation of, 210b reverse mover action, notes, 210 standard mover action, notes, 210 structures, relationship, 211 Flexor hallucis brevis, 654–655 actions, note, 654–655 arterial supply to, 655b attachments of, 654 concentric (shortening) mover actions, 654t derivation of, 654b eccentric antagonist function, 654 functions of, 654–655 innervation of, 655b isometric stabilization function, 654 miscellaneous information, 655 motion of, 654 MTP joint, crossing, 654 palpation of, 655b plantar view of, 654f pronunciation of, 654b reverse mover action, notes, 654 standard mover action, notes, 654 structures, relationship, 655 Flexor hallucis longus (Harry of Tom, Dick, and Harry group), 628–629 actions, notes, 629 arterial supply to, 629b attachments of, 628 big toe, crossing, 628 concentric (shortening) mover actions, 628t derivation of, 628b eccentric antagonist functions, 629 note, 629 functions of, 628–629 innervation of, 629b isometric stabilization functions, 629 miscellaneous information, 629 motion of, 629 palpation of, 629b posterior view of, 628f pronunciation of, 628b reverse mover action, notes, 628–629 standard mover action, notes, 628 structures, relationship, 629 Flexor pollicis brevis, 254–255 actions, notes, 255 anterior view of, 254f arterial supply to, 255b attachments of, 254 concentric (shortening) mover actions, 254t deep head, 255, 270 derivation of, 254b

1159

eccentric antagonist functions, 255 functions of, 254 innervation of, 255b isometric stabilization functions, 255 medial portion, superficial, 255 miscellaneous information, 255 motion of, 255 palpation of, 255b pronunciation of, 254b reverse mover action, notes, 254–255 standard mover action, notes, 254 structures, relationship, 255 superficial head, 255 thumb, CMC joint (crossing), 254 Flexor pollicis longus, 215–217 actions, notes, 216 anterior view of, 215f arterial supply to, 216b attachments of, 215 CMC joint, crossing, 215 concentric (shortening) mover actions, 215t derivation of, 215b eccentric antagonist functions, 216 note, 216 functions of, 215 innervation of, 216b isometric stabilization functions, 216 note, 216 miscellaneous information, 217 motion of, 216 palpation of, 216b pronunciation of, 215b reverse mover action, notes, 216 standard mover action, notes, 215 structures, relationship, 216–217 Flexor retinaculum, 252, 256, 262, 279 Foot (feet). See Right foot ankle joint, 29 dorsiflexion and plantarflexion of, lateral views of, 29f eversion/inversion of, frontal plane components of, 30f lateral/medial rotation of, transverse plane components of, 30f motion of, cardinal plane components of, 30f cross section of, 639, 639f fibularis brevis, crossing, 602 fixation of, 81–82 lateral rotation (abduction) of, 30f lumbrical pedis of, 272 muscles dorsal view of, 637, 637f lateral view of, 638, 638f medial view of, 638, 638f opponens hallucis of, 659 plantar view deep view of, 636

1160

intermediate view of, 635 superficial fascial view of, 633, 633f–636f superficial muscular view of, 634 pronation of, 10 in oblique plane, 30f subtalar joint, 30 motions of, 30f supination of, in oblique plane, 30f talocrural joint, 29f toes, extrinsic muscles anterior view of, 615–616, 615f–616f medial view of, 619–620, 619f–620f posterior view of, 617–618, 617f–618f Forearm. See Right forearm compartments of, 173b, 201b at elbow joint, 16, 16f flexor, effectiveness, 157 flexor pollicis longus in, 216 motions, in sagittal plane, 7f movement of., 80f See also Distal forearm requirement for, muscles, radial group, 159, 193, 196 pronation of, 10, 193, 195 proximal/middle/distal, 184f radioulnar joint, 16 supination of, 193, 195 transverse plane cross sections of, 184 wrist extensor group of, 193, 196, 198 wrist flexor group of, 191 Fourth hamstring, 525 Front functional line, anterior view of, 723f Frontal plane, 4, 5b examples of, 6f head/neck/arm motions in, 7f motion occurring in, 8f Frontalis, 450 Full skeleton anterior view of, 34f posterior view of, 35f Full spine, 299–301 Functional line myofascial meridians, 723f Functional mover groups, 667–715 Functional short leg, 508, 533 Fusiform-shaped muscle, demonstration of, 87f

1161

G Galea aponeurotica, 449, 452 lateral border of, 451 Gastrocnemius (Gastrocs) (triceps surae group), 604–605 actions, notes, 605 arterial supply to, 605b attachments of, 604 concentric (shortening) mover action, 604t derivation of, 604b eccentric antagonist functions, 605 note, 605 functions of, 604–605 innervation of, 605b isometric stabilization functions, 605 miscellaneous information, 605 motion of, 605 palpation of, 605b posterior view of, 604f pronunciation of, 604b reverse mover actions, notes, 604 standard mover actions, notes, 604 structures, relationship, 605 Geniohyoid (hyoid group), 430–431 anterior view of, 430f arterial supply to, 431b attachments of, 430 concentric mover actions, 430t derivation of, 430b eccentric antagonist functions, 430 functions of, 430–431 innervation of, 431b isometric stabilization functions, 431 miscellaneous information, 431 palpation of, 431b pronunciation of, 430b reverse mover action notes, 430 standard mover action notes, 430 structures, relationship, 431 views of, 430f

1162

Girdle. See Shoulder girdle Glenohumeral (GH) joint abductors, anterior view of, 672f–673f adductors, anterior view of, 672f–673f anterior deltoid, crossing, 120 arm at, 14 frontal plane actions of, 14f sagittal plane actions of, 14f transverse plane actions of, 14f trunk relative to, reverse actions in, 15f coracobrachialis, crossing, 123 deltoid, crossing, 120 extensors, posterior view of, 671f flexors, anterior view of, 671f functional group approach to, application of, 89 infraspinatus, crossing, 137 lateral rotators, posterior view of, 674f latissimus dorsi, crossing, 128 medial rotators, posterior view of, 674f muscles of, 112 anterior view of, 115f, 116f, 117f function, overview of, 113 left side, superficial, 114f posterior view of, 114f, 116f right lateral views of, 118f right side, superficial, 115f rules, 113 structure, overview of, 112 pectoralis major clavicular head, crossing, 125 sternocostal head, crossing, 125–126 scapula and trunk at, reverse action of, 15, 15f subscapularis, crossing, 141 supraspinatus, crossing, 135 teres major, crossing, 131 teres minor, crossing, 139 Gluteal aponeurosis, 533 Gluteal fascia, 533 Gluteal group, 526–527 Gluteal muscles, right lateral views, 526f Gluteus maximus, 528–530

1163

arterial supply to, 529b attachments of, 528 concentric mover actions, 528t derivation of, 528b eccentric antagonist functions, 529 functions of, 528–530 innervation of, 529b isometric stabilization functions, 529 note, 529 miscellaneous information, 530 palpation of, 530b posterior view of, 528f pronunciation of, 528b reverse mover action, notes, 529 standard mover action, notes, 528 structures, relationship, 530 Gluteus medius, 531–533 arterial supply to, 533b attachments of, 531 concentric mover actions, 531t derivation of, 531b eccentric antagonist functions, 532 functions of, 531–533 hip joint, crossing, 531 innervation of, 533b isometric stabilization functions, 532 note, 532 lateral view of, 531f miscellaneous information, 533 palpation of, 533b pronunciation of, 531b reverse mover action, notes, 531 standard mover action, notes, 531 structures, relationship, 533 Gluteus minimus, 534–536 arterial supply to, 536b attachments of, 534 concentric mover actions, 534t derivation of, 534b eccentric antagonist functions, 535 functions of, 534–535

1164

innervation of, 536b isometric stabilization functions, 535 note, 535 lateral view of, 534f miscellaneous information, 536 palpation of, 536b pronunciation of, 534b reverse mover action, notes, 534–535 standard mover action, notes, 534 structures, relationship, 536 Golfer’s elbow, 166, 186, 191, 212 Golf tee muscle, 347 Gracilis (adductor group), 520 anterior view of, 520f arterial supply to, 521b attachments of, 520 concentric mover actions, 520t derivation of, 520b eccentric antagonist functions, 521 functions of, 520–521 hip joint, crossing, 520 innervation of, 521b isometric stabilization functions, 521 note, 521 miscellaneous information, 521 palpation of, 521b pronunciation of, 520b reverse mover action, notes, 520 standard mover action, notes, 520 structures, relationship, 521 Gravity, force of, 83, 83f Greater occipital nerve, 99 Greater occipital neuralgia, 99 H Hallux, 643 Hamate, 262 Hamstring group, 573–582. See also Biceps femoris (hamstring group) Semimembranosus (hamstring group) Semitendinosus (hamstring group) arterial supply to, 573b attachments of, 573

1165

functions of, 573 innervation of, 573b miscellaneous information, 573 posterior views of, 574f views of, 574 Hand. See Right hand abduction and adduction of, in frontal plane, 37f compartments of, 239 fixation of, 82f flexion and extension of lateral views of, 17f in sagittal joint, around mediolateral axis, 37f heavy weight in, holding of, 99 metacarpal bones, cross-section of, 248, 248f metacarpophalangeal joint of, 37f midcarpal joints, motions of, 17f palm of, 187 radial deviation (abduction) of, 17f at radiocarpal joints, motions of, 17f superficial view, palmar aponeurosis, 241f–245f ulnar deviation (adduction) of, 17f wrist joint, motions of, 17f Hand musculature anterior/palmar view deep muscular view, 244f deepest muscular view, 245f intermediate muscular view, 243f superficial muscular view, 242f superficial view, palmar aponeurosis, 241f posterior/dorsal view, 246f Head at atlanto-occipital joint lateral flexion motions of, posterior views of, 20f rotation motions of, posterior views of, 20f sagittal plane motions of, lateral views of, 20f bones of anterior view of, 60f inferior view of, 64f lateral view of, 62f bony landmarks of anterior view of, 60f

1166

inferior view of, 64f lateral view of, 62f joint of contralateral rotators of, 693f extensors, posterior view of, 690f flexors, anterior view of, 689f ipsilateral rotators of, 694f lateral flexors of, 691f–692f left lateral flexion of, 20f motions of, 7f muscle attachment sites on anterior view of, 61f inferior view of, 65f lateral view of, 63f muscles anterior views of, 446, 446f posterior view of, 447, 447f superficial lateral view of, 445, 445f superficial right lateral view, 413, 413f superficial views of, 446f right lateral flexion of, 20f Hiking up the hip, term (usage), 362 Hinge joints, 33 example. See Uniaxial hinge joint Hip joint abductors, posterior view of, 703f adductor brevis, crossing, 521 adductor longus, crossing, 517 adductor magnus, crossing, 523 adductors, posterior view of, 704f extensors, posterior view of, 702f flexion and extension of, in sagittal plane, around mediolateral axis, 39f flexors, anterior view of, 702f gluteus medius, crossing, 531 gracilis, crossing, 519 lateral rotators of, 705f medial and lateral rotation of, in transverse plane, 39f medial rotators of, 706f muscles, 490–551 function, overview, 491–492 overview, 490–551

1167

structure, overview, 490–491 pectineus, crossing, 515 pelvis at, 27–28 depression and elevation of, anterior views of, 28f motion of, 27f–28f posterior and anterior tilt of, lateral views of, 27f rotation of, anterior and superior views of, 28f sartorius, crossing, 509 TFL, crossing, 507 thigh at, 26 abduction and adduction of, anterior views of, 26f flexion and extension of, lateral views of, 26f lateral and medial rotation of, anterior views of, 26f motions of, 26f as triaxial ball-and-socket joint example, 39f Hitchhiker muscle, 159 Horizontal extension, definition of, 10 Horizontal fibers, 525 Horizontal flexion, definition of, 10 Horizontal flexion/horizontal extension, terms (pairs), 10 Horizontal plane, 5b Humeral head, 165 Humeroulnar head, 210 Humeroulnar joint, of elbow, 36f Humerus anterior shaft of, 155 bicipital groove of lateral lip and, 125 medial lip of, 128, 131 deltoid tuberosity of, 119 greater tubercle of, 135, 137, 139 lateral epicondyle of, 163, 194, 197, 218, 221 lateral rotators of, wrapping, 113 lateral supracondylar ridge of, 157, 192 lesser tubercle of, 141 medial epicondyle of, 165, 185, 187, 190, 210 medial rotators of, wrapping, 113 medial shaft of, 123 posterior shaft of, 160 Hyoid bone depressors, anterior view of, 688f

1168

digastric, attachment, 426 elevators, anterior view of, 688f geniohyoid, attachment, 430 mylohyoid, attachment, 428 omohyoid, attachment, 440 sternohyoid, attachment, 434 stylohyoid, attachment, 432 Hyoid group, 424. See also Digastric (hyoid group) Geniohyoid (hyoid group) Mylohyoid (hyoid group) Omohyoid (hyoid group) Sternohyoid (hyoid group) Sternothyroid (hyoid group) Stylohyoid (hyoid group) Thyrohyoid (hyoid group) actions, 424 anterior belly, 426 arterial supply to, 424b attachments of, 424 innervation of, 424b miscellaneous information, 424 omohyoid, attachment, 440 posterior belly, 426 thyrohyoid, attachment, 438 Hyoid muscle group, anterior view, 425f Hyperextension, 10 Hyperlordosis, 506 Hypothenar eminence group, 258 arterial supply to, 258b attachments of, 258 functions of, 258 innervation of, 258b Hypothenar group, 238–239 muscles of. See also Right hypothenar group anterior views of, 258f I Iliacus (iliopsoas), 506–507 anterior view of, 506f arterial supply to, 507b attachments of, 506 concentric mover actions, 506t derivation of, 506b eccentric antagonist functions, 506 functions, 506–507 innervation of, 507b

1169

isometric stabilization functions, 506 note, 507 miscellaneous information, 507 palpation of, 507b pronunciation of, 506b reverse mover action, notes, 506 standard mover action, notes, 506 structures, relationship, 507 Iliocostalis (erector spinae group), 302–304 actions, notes, 303 arterial supply to, 303b attachments of, 302 concentric (shortening) mover actions, 302t derivation of, 302b eccentric antagonist functions, 303 notes, 303 functions of, 302 innervation of, 303b isometric stabilization functions, 303 notes, 303 miscellaneous information, 304 motion of, 303 palpation of, 303b posterior view of, 302f pronunciation of, 302b reverse mover action, notes, 303 spinal joints, crossing, 302 standard mover action, notes, 302–303 structures, relationship, 304 Iliopsoas. See Iliacus (iliopsoas) Psoas major (iliopsoas) Iliotibial band (ITB), 508, 528 friction syndrome, 509 Index finger, 234 dorsal digital expansion, 249 Indicis, 236 Inferior, definition of, 4 Inferior frontal bone, 457 Inferior gemellus (deep lateral rotator group), 546–547 arterial supply to, 547b attachments of, 546 concentric (shortening) mover actions, 546t

1170

derivation of, 546b eccentric antagonist functions, 546 functions of, 546 innervation of, 547b isometric stabilization functions, 546 note, 546 miscellaneous information, 547 palpation of, 547b posterior view of, 546f pronunciation of, 546b reverse mover action, notes, 546 standard mover action, notes, 546 structures, relationship, 547 Infrahyoids, 434–441 Infraorbitalis (head), 466 Infraspinatus (rotator cuff group), 133, 133f, 137–138 actions, note, 138 arterial supply to, 138b attachments of, 137 concentric (shortening) mover actions, 137t derivation of, 137b eccentric antagonist functions, 137 note, 137 functions of, 137 GH joint crossing, 137 innervation of, 138b isometric stabilization functions, 138 note, 138 miscellaneous information, 138 motion of, 137 palpation of, 138b posterior view of, 134f, 137f pronunciation of, 137b reverse mover action, notes, 137 standard mover action, notes, 137 structures, relationship, 138 Innermost intercostals, 395 Insertion attachments vs., 83–84 definition of, 83 term, usage, 83

1171

Intercostals intimi, 395 Intermuscular septa, 86b Internal abdominal oblique (anterior abdominal wall), 373–376 actions, notes, 375 anterior view of, 373f arterial supply to, 375b attachments of, 373 concentric (shortening) mover actions, 374t derivation of, 373b eccentric antagonist functions, 375 notes, 375 functions of, 374 innervation of, 375b isometric stabilization functions, 375 notes, 375 lateral view of, 373f miscellaneous information, 376 motions of, 375 palpation of, 375b pronunciation of, 373b reverse mover action, notes, 374–375 spinal joints crossing, 374 standard mover action, notes, 374 structures, relationship, 376 Internal ilium, 505 Internal intercostals, 393–395 actions, notes, 394 anterior view of, 393f arterial supply to, 394b attachments of, 393 concentric (shortening) mover actions, 393t derivation of, 393b eccentric antagonist functions, 394 functions of, 393–394 innervation of, 394b isometric stabilization functions, 394 function, 394 location of, 394 miscellaneous information, 395 motions of, 394 palpation of, 395b

1172

posterior view of, 393f pronunciation of, 393b reverse mover action, notes, 394 standard mover action, notes, 394 structures, relationship, 395 Internal pterygoid, 423 Interphalangeal (IP) joint extensors, posterior view of, 684f flexors, anterior view of, 684f muscles, crossing, 201–202 thumb, flexion of, 19f toes, 31 extensors, dorsal view of, 714f flexion and extension, lateral views, 31f flexors, plantar view of, 713f Interspinales, 321–322 actions, notes, 322 arterial supply to, 322b concentric (shortening) mover actions, 321t derivation of, 321b eccentric antagonist function, 321 functions of, 321 innervation of, 322b isometric stabilization function, 321 note on, 322 miscellaneous information, 322 motion, 321 palpation of, 322b posterior view of, 321 pronunciation of, 321b reverse mover action, notes, 321 standard mover action, notes, 321 structures, relationship, 322 Intertarsal joint, of ankle region, 39f Intertransversarii, 323–324 actions, notes, 324 arterial supply to, 324b attachments of, 323 concentric (shortening) mover actions, 323t derivation of, 323b eccentric antagonist functions, 323

1173

functions of, 323 innervation of, 324b isometric stabilization functions, 323 notes on, 324 miscellaneous information, 324 motion of, 323 palpation of, 324b posterior view of, 323f pronunciation of, 323b reverse mover action, notes, 323 standard mover action, notes, 323 structures, relationship, 324 transverse process, attachment, 323 Intertubercular groove, 154 Inversion, definition of, 10 Inversion/eversion, terms (pairs), 10 Inverters, 712f IP joint. See Interphalangeal (IP) joint Ipsilateral functional line, lateral view of, 723f Ipsilateral lateral flexion, cause of, 98 Ipsilateral rotation, term (usage), 9 Ischial spine, 542 Ischial tuberosity, 546, 550 Ischiocondylar section, 525 Ischium, 523 Isometric contractions, 84, 84f ITB. See Iliotibial band (ITB) J Joint action atlas, 11–31 mover of, occurrence, 81 terms, 8b Joints, 33–39 definition of, 33 functional classification of, 33 muscles, crossing determination of, 88 function of, 88 location of, 88 structural classification of, 33

1174

types of, structural illustration of, 36f upper trapezius, crossing, 97 K Kinesiology terminology, basic, 1–31 Knee joint extensors, anterior view of, 708f flexors, posterior view of, 707f lateral rotators, posterior view of, 709f leg flexion and extension of, lateral views of, 29f lateral and medial rotation of, anterior views of, 29f medial rotators, posterior view of, 709f muscles, 553–584. See also Right knee joint anterior views of, 555–556, 555f–556f function of, 554 overview of, 553 posterior views of, 557–558, 557f–558f structure of, 553–554 L L1-L4 transverse process, 360 L5-C4 vertebrae, 316 Lacertus fibrosis, 154 Lamina, 319 Lateral definition of, 2–4 term (usage), 421 Lateral deviation, definition of, 10 Lateral epicondylitis, 164, 170, 196, 198, 220, 223 Lateral epicondylosis, 164, 170, 196, 198, 220, 223 Lateral femoral condyles, 604 Lateral hamstrings, 573 Lateral pterygoid, 420–421 arterial supply to, 421b attachments of, 420 concentric (shortening) mover actions, 420t derivation of, 420b eccentric antagonist functions, 421 functions of, 420–421 innervation of, 421b

1175

isometric stabilization functions, 421 lateral view of, 420f miscellaneous information, 421 palpation of, 421b pronunciation of, 420b reverse mover action, notes, 420 standard mover action, notes, 420 structures, relationship, 421 Lateral radius, 165 Lateral rotation, definition of, 9 Lateral rotation/medial rotation, terms (pairs), 9 Lateral rotators, in humerus, wrapping, 113 Lateral tilt/medial tilt, terms (pairs), 10 Latissimus dorsi, 128–130 actions, notes, 129 arterial supply in, 130b attachments of, 128 concentric (shortening) mover actions, 128t derivation of, 128b distal tendon of, attachment of, 130 eccentric antagonist functions, 129 fibers, twist, 130 functions of, 128 GH joint, crossing, 128 innervation of, 130b isometric stabilization functions, 129 miscellaneous information, 130 motion of, 129 palpation of, 130b pelvic attachments of, 130 posterior view of, 128f pronunciation of, 128b reverse mover actions of, 128 notes, 129 spinal attachments of, 130 standard mover actions of, notes, 128 structures, relationship, 130 Left clavicle, 13f Left interspinales, posterior view of, 321f Left lateral flexion, definition of, 9 Left pelvis, elevation of, 24f

1176

Left rotation, definition of, 9 Left scapula, in anatomic position, 12f Leg. See Right leg knee joint flexion and extension of, lateral views of, 29f lateral and medial rotation of, anterior views of, 29f Lengthening contraction, 83 Levator anguli oris, 473–474 anterior view of, 473f arterial supply to, 473b attachments of, 473 concentric (shortening) mover actions, 473t derivation of, 473b functions of, 473 innervation of, 473b miscellaneous information, 474 motions of, 473 mover action notes, 473 palpation of, 473b pronunciation of, 473b structures, relationship, 473–474 Levatores costarum, 406–407 actions, note, 407 arterial supply to, 407b attachments of, 406 concentric (shortening) mover actions, 406t derivation of, 406b eccentric antagonist functions, 406 functions of, 406–407 innervation of, 407b isometric stabilization functions, 407 note, 407 miscellaneous information, 407 motion of, 406 palpation of, 407b posterior view of, 406f pronunciation of, 406b reverse mover action, notes, 406 standard mover action, notes, 406 structures, relationship, 407 Levatores costarum breves, 407

1177

Levatores costarum longi, 407 Levator labii superioris alaeque nasi (LLSAN), 465–466 anterior view of, 465f arterial supply to, 466b attachments of, 465 concentric (shortening) mover actions, 465t derivation of, 465b functions of, 465–466 innervation of, 466b lateral slip, 466 miscellaneous information, 466 motions of, 466 mover action notes, 465 palpation of, 466b pronunciation of, 465b structures, relationship, 466 Levator labii superioris (LLS), 467–468 anterior view of, 467f arterial supply to, 468b attachments of, 467 concentric (shortening) mover actions, 467t derivation of, 467b functions of, 467–468 innervation of, 468b miscellaneous information, 468 motions of, 467 mover action notes, 467 palpation of, 468b pronunciation of, 467b structures, relationship, 468 Levator palpebrae superioris, 456 anterolateral view of, 456f arterial supply to, 456b attachments of, 456 concentric mover action, 456 derivation of, 456b functions of, 456 innervation of, 456b lateral view of, 456f motions of, 456 mover action notes, 456

1178

palpation of, 456b pronunciation of, 456b structures, relationship, 456 Levator scapulae, 102–103 actions, notes, 103 arterial supply to, 103b atlas and, transverse process of, 103 attachments of, 102 C1-C4, transverse processes of, 102 cervical spine, crossing, 102 concentric (shortening) mover actions, 102t derivation of, 102b eccentric antagonist functions, 103 fibers, in cervical spine, wrapping, 102–103 functions of, 102–103 innervation of, 103b isometric stabilization functions, 103 medial border and, 102 motions of, 103 palpation of, 103b posterior view of, 102f pronunciation of, 102b reverse mover action, notes, 102–103 scapular attachment of, 102 superior position of, 103 spine attachment of, 102 standard mover action, notes, 102 structures, relationship, 103 Lips buccinator, attachment, 483 protraction/protrusion, 485 Lister’s tubercle, 233 Little brother (little helper), 132 Little finger CMC/MCP joints, abductor digiti minimi manus (crossing), 260 fifth metacarpal, 264 phalanges of, 221, 223 proximal phalanx, 260, 262 LLS. See Levator labii superioris (LLS) LLSAN. See Levator labii superioris alaeque nasi (LLSAN) Location terminology, 2–4

1179

Location, terms of, combining, 4 Longissimus (erector spinae group), 305–307 actions, notes, 306 arterial supply to, 307b attachments of, 305 concentric (shortening) mover actions, 305t derivation of, 305b eccentric antagonist functions, 306 notes, 306 functions of, 305 innervation of, 307b isometric stabilization functions, 306 notes, 306 miscellaneous information, 307 motion of, 306 palpation of, 307b posterior view of, 305f pronunciation of, 305b reverse mover action, notes, 306 spinal joints, crossing, 305–306 standard mover action, notes, 305–306 structures, relationship, 307 Longitudinal muscles, architectural types of, 87f Longus capitis (prevertebral group), 340–341 actions, notes, 340 anterior view of, 340f arterial supply to, 341b atlanto-occipital joint, crossing, 340 attachments of, 340 concentric (shortening) mover actions, 340t derivation of, 340b eccentric antagonist functions, 340 innervation of, 341b isometric stabilization function, 340 notes, 340 miscellaneous information, 341 motion in, 340 palpation of, 341b pronunciation of, 340b reverse mover action, notes, 340 standard mover action, notes, 340

1180

structures, relationship, 341 upper neck joints, crossing, 340 Longus colli (prevertebral group), 338–339 actions, note, 339 anterior view of, 338f arterial supply to, 339b attachments of, 338 concentric (shortening) mover actions, 338t derivation of, 338b eccentric antagonist function, 339 functions of, 338 innervation of, 339b isometric stabilization functions, 339 notes, 339 miscellaneous information, 339 motion in, 338–339 neck joints, crossing, 338 palpation of, 339b parts of, 339 pronunciation of, 338b reverse mover action, notes, 338 standard mover action, notes, 338 structures, relationship, 339 superior oblique part, 339 vertical part, 339 Low back, 360–361 Lower extremities, 702–715 bony landmarks, atlas, 66–77 illustration of, 2f–3f joint action in, 26–31 muscle attachment, atlas, 66–77 reverse actions in, commonness of, 81–82 Lower lip, 479 eversion, 481 Lower trapezius, eccentric antagonist functions of, 97 Lumbosacral joint, pelvis at motion of, 23f–24f posterior and anterior tilt of, lateral views of, 23f–24f rotation of, 24f Lumbricals manus, 271–272 actions, notes, 272

1181

anterior view of, 271f arterial supply to, 272b attachments of, 271 concentric (shortening) mover actions, 271t derivation of, 271b eccentric antagonist functions, 272 extensor digitorum, distal tendons, attachment to, 271 functions of, 271 innervation of, 272b isometric stabilization functions, 272 miscellaneous information, 272 motion of, 272 palpation of, 272b pronunciation of, 271b reverse mover action, notes, 272 standard mover action, notes, 271–272 structures, relationship, 272 Lumbricals pedis, 652–653 actions, notes, 653 arterial supply to, 653b attachments of, 652 concentric (shortening) mover actions, 652t derivation of, 652b eccentric antagonist functions, 653 functions of, 652–653 innervation of, 653b isometric stabilization functions, 653 miscellaneous information, 653 motion of, 653 MTP joint, crossing, 652 palpation of, 653b plantar view of, 652f pronunciation of, 652b reverse mover action, notes, 652–653 standard mover action, notes, 652 structures, relationship, 653 M Major body parts, 1 Mandible, 477, 479, 483. See also Temporomandibular joint (TMJ), mandible bony landmarks of, posterolateral view of, 52f

1182

coronoid process of, 418 depression and elevation of, lateral views of, 25f depressor labii inferioris, attachment, 479 inner surface of, 428, 430 internal surface of, 422 mentalis, attachment, 481 muscle attachment sites on, posterolateral view of, 52f protraction and retraction of, lateral views of, 25f ramus of, 416 right and left lateral deviation of, anterior views of, 25f at temporomandibular joints, 25 Masseter, 418–419 arterial supply to, 419b attachments of, 418 concentric (shortening) mover actions, 418t deep layer, 419 derivation of, 418b eccentric antagonist functions, 419 fascia and skin superficial to, 475 functions of, 418–419 innervation of, 419b isometric stabilization functions, 419 lateral view of, 418f layers, division, 419 middle layer, 419 miscellaneous information, 419 palpation of, 419b pronunciation of, 418b reverse mover action notes, 419 right lateral view, 414f standard mover action notes, 418 structures, relationship, 419 superficial layer, 419 Mastication, major muscles (views), 414 Maxilla, 461, 463, 465, 467, 473, 483 MCP joints. See Metacarpophalangeal (MCP) joints Medial, definition of, 2 Medial epicondylitis, 166, 186, 191, 212 Medial epicondylosis, 166, 186, 191, 212 Medial femoral condyles, 604 Medial foot, 596

1183

Medial hamstrings, 573 Medial/lateral, terms (pairs), 2–4 Medial pterygoid, 422–423 arterial supply to, 423b attachments of, 422 concentric (shortening) mover actions, 422t derivation of, 422b eccentric antagonist functions, 423 functions of, 422–423 innervation of, 423b isometric stabilization functions, 423 lateral view of, 422f miscellaneous information, 423 palpation of, 423b pronunciation of, 422b reverse mover action notes, 423 right lateral view, 422f standard mover action notes, 422 structures, relationship, 423 Medial rotation, definition of, 9 Medial rotators, in humerus, wrapping, 113 Medial ulna, 213 Mentalis, 481–482 anterior view of, 481f arterial supply to, 482b attachments of, 481 concentric (shortening) mover actions, 481t derivation of, 481b functions of, 481–482 innervation of, 482b miscellaneous information, 482 motions of, 481 mover action, notes, 481 palpation of, 482b pronunciation of, 481b structures, relationship, 482 Metacarpal bones, cross-section of, 248, 248f Metacarpophalangeal (MCP) joints abductors, posterior view of, 685f adductors, anterior view of, 685f extensor digiti minimi, crossing, 221

1184

extensor digitorum, crossing, 218 extensor indicis, crossing, 234 extensors, posterior view of, 684f FDP, crossing, 213 FDS, crossing, 210 fingers actions, 18f movement, 201 flexors, anterior view of, 684f muscles, crossing, 201–202 reverse actions at, 210, 213, 219, 222 Metatarsophalangeal (MTP) joints abductors, dorsal view of, 715f adductors, plantar view of, 715f extensors, dorsal view of, 714f flexors, plantar view of, 713f second toes fibular abduction of, 31f tibial abduction of, 31f toes, 31 motion of, 31f Middle anterior fibula, 624 Middle deltoid, 120, 121 Middle posterior tibia, 626 Middle scalene (scalene group), 332–333 actions, note, 332 anterior view of, 332 arterial supply to, 332b attachments of, 332 concentric (shortening) mover actions, 332t derivation of, 332b eccentric antagonist functions, 332 functions of, 332 innervation of, 332b isometric stabilization functions, 332 miscellaneous information, 333 motion of, 332 palpation of, 333b pronunciation of, 332b reverse mover action, notes, 332 standard mover action, notes, 332

1185

structures, relationship, 333 Middle trapezius, eccentric antagonist functions of, 97 Mobile attachment, 81 Mouth, angle of, 471, 473, 475, 477 Movement terminology, 7–10 Mover, 81 Mover actions, 82f. See also Reverse mover action Standard mover actions Mover muscle, contraction and shortening of, definition of, 84b MTP joints. See Metatarsophalangeal (MTP) joints Multifidus (of transversospinalis group), 316–318 actions, notes, 317 arterial supply to, 317b attachments of, 316 concentric (shortening) mover actions, 316t derivation of, 316b functions of, 316 innervation of, 317b isometric stabilization functions, 317 notes on, 317 miscellaneous information, 318 motion of, 317 palpation of, 317b posterior view of, 316f pronunciation of, 316b reverse mover action, notes on, 317 spinal joints, crossing, 316 standard mover action, notes on, 316–317 structures, relationship, 317 Multipennate muscle, deltoid as, 87f Muscle action determination of, 88 learning of, visual and kinesthetic exercise, 89 Muscle attachment to bones and joint, 80b illustration of, 80f joint in, crossing, 80–81, 80f memorization of, 87 naming of, 83–84 Muscle attachment sites anterior view of, 41f, 45f, 53f, 57f, 61f, 67f, 71f atlas, 40–77

1186

dorsal view of, 51f, 75f inferior view of, 65f lateral view of, 63f palmar view of, 49f plantar view of, 77f posterior view of, 43f, 47f, 55f, 59f, 69f, 73f posterolateral view of, 52f Muscles cells, 85–86 components of, 85f concentric contraction of, 81f contraction of, 83 defining, 79–83 pulling force in, 86 co-ordering of, 80b cross sections of, 85f fibers, 85–86 architecture of, 86 arrangement of, 86 function of essence of, 79 view of, 84–85 functional groups of, 666–723 joint, crossing determination of, 88 function of, 88 location of, 88 learning of, 87–89 five-step approach to, 87–88 functional group approach to, 89 visual and kinesthetic exercise for, 89 motion in, cause of, 81f movement of, complex, 80b palpation guidelines for, 89–90 pulling forces and, 79 roles of, 84–85 standard mover actions of, 81 system function of, studying of, 82–83 Musculus quadratus labii superioris (head), 466, 468, 470 Mylohyoid (hyoid group), 428–429 anterior view of, 428f

1187

arterial supply to, 429b attachments of, 428 concentric (shortening) mover actions, 428t derivation of, 428b eccentric antagonist functions, 428 functions of, 428–429 innervation of, 429b isometric stabilization functions, 428–429 miscellaneous information, 429 palpation of, 429b pronunciation of, 428b reverse mover action notes, 428 standard mover action notes, 428 structures, relationship, 429 views of, 428f Myofascial meridian, 666, 719–723 arm lines of, 722f functional lines of, 723f lateral and deep front lines of, 720f spiral lines of, 721f superficial back and front lines of, 719f Myofibrils, 86 filament composition of, 85f Myosin filament, 86, 86f heads, 86f N Nasal bone, fascia and skin over, 459 Nasalis, 461–462 anterior view of, 461f arterial supply to, 462b attachments of, 461 concentric (shortening) mover actions, 461t derivation of, 461b functions of, 461–462 innervation of, 462b miscellaneous information, 462 motions of, 461 mover action notes, 461 palpation of, 462b

1188

pronunciation of, 461b structures, relationship, 462 Neck anterior view intermediate/deep views, 296, 296f superficial view, 295, 295f anterior views of, 415 bones of anterior view of, 52f posterior view of, 54f bony landmarks of anterior view of, 52f posterior view of, 54f C5 vertebral level, cross-section of, 298f at cervical spinal joints, 21 cross-sectional view of, 298 flexion and extension of, sagittal plane, 21f joints contralateral rotators of, 693f extensors, posterior view of, 690f flexors, anterior view of, 689f ipsilateral rotators of, 694f lateral flexors of, 691f–692f longus colli, crossing, 338 left and right lateral flexion, frontal plane, 21f motions of, 7f muscle attachment sites on anterior view of, 53f posterior view of, 55f muscles, right lateral views of, 118f, 297, 297f posterior triangle, 98, 327, 347 levator scapulae and, relationship of, 103 posterior view deep view, 294, 294f intermediate view, 293, 293f superficial view, 292, 292f region, muscles of, right lateral view of, 95 sternocleidomastoid (SCM), 325–327 suboccipital triangle of, 357, 359 superficial views, 415f trapezius in, superficiality of, 98

1189

Nonaxial joints, 37 example of, 39f Nose, 459–464 anterolateral view, 448f cartilage of, 463 upper lip and, 465 Nostril, constricts, 463 Nuchal ligament, 96 O Oblique fibers, 526 Oblique head adductor hallucis, 659 adductor pollicis, 270 Oblique plane, 4 examples of, 6f head/neck/arm motions in, 7f motion occurring in, 8f Obliquus, term (meaning), 350 Obliquus capitis inferior (suboccipital group), 356–357 actions, notes, 357 arterial supply to, 357b attachments of, 356 concentric (shortening) mover actions, 356t derivation of, 356b eccentric antagonist functions, 357 functions of, 356 innervation of, 357b isometric stabilization function, 357 notes, 357 lateral view of, 356f miscellaneous information, 357 misnomer, 357 motion of, 356 palpation of, 357b posterior view, 356f pronunciation of, 356b reverse mover action, notes, 356 standard mover action, notes, 356 structures, relationship, 357 Obliquus capitis superior (suboccipital group), 358–359

1190

actions, notes, 359 arterial supply to, 359b atlas, horizontal movement, 358 attachments of, 358 concentric (shortening) mover actions, 358t derivation of, 358b eccentric antagonist functions, 359 innervation of, 359b isometric stabilization function, 359 notes, 359 lateral view of, 358f miscellaneous information, 359 motion of, 359 palpation of, 359b posterior view of, 358f pronunciation of, 358b reverse mover actions, notes, 358–359 standard mover actions, notes, 358 structures, relationship, 359 Obturator, meaning, 545 Obturator externus (deep lateral rotator group), 548–549 arterial supply to, 549b attachments of, 548 concentric (shortening) mover actions, 548t derivation of, 548b eccentric antagonist functions, 548 functions of, 548–549 innervation of, 549b isometric stabilization functions, 549 miscellaneous information, 549 palpation of, 549b posterior view of, 548f pronunciation of, 548b reverse mover action, notes, 548 standard mover action, notes, 548 structures, relationship, 549 Obturator foramen, 544, 548 Obturator internus (deep lateral rotator group), 544–545 arterial supply to, 545b attachments of, 544 concentric (shortening) mover actions, 544t

1191

derivation of, 544b eccentric antagonist functions, 544 functions of, 544–545 innervation of, 545b isometric stabilization functions, 544 miscellaneous information, 545 palpation of, 545b posterior view of, 544f pronunciation of, 544b reverse mover action, notes, 544 standard mover action, notes, 544 structures, relationship, 545 Occipital bone, 449 mastoid process, 346 Occipital nerve, greater, 99 Occipitalis, 450 Occipitofrontalis (epicranius component), 449, 449f anterior view of, 522f arterial supply to, 450b attachments of, 449 concentric (shortening) mover actions, 449t derivation of, 449b functions of, 449–450 miscellaneous information, 450 mover action notes, 449 palpation of, 450b pronunciation of, 449b standard mover action notes, 522 structures, relationship, 450 Omohyoid (hyoid group), 440–441 anterior view of, 440f arterial supply to, 441b attachments of, 440 concentric (shortening) mover actions, 440t derivation of, 440b eccentric antagonist functions, 440 functions of, 440–441 innervation of, 441b isometric stabilization functions, 440 miscellaneous information, 441 palpation of, 441b

1192

pronunciation of, 440b reverse mover action notes, 440 standard mover action notes, 440 structures, relationship, 441 Open-chain, 82–83 Opponens digiti minimi, 264–265 action, notes, 265 anterior view of, 264 arterial supply to, 265b attachments of, 264 CMC joint, crossing, 264 concentric (shortening) mover actions of, 264t derivation of, 264b eccentric antagonist functions of, 265 functions of, 264 innervation of, 265b isometric stabilization function, 265 medial portion, 265 miscellaneous information, 265 motion of, 265 palpation of, 265b pronunciation of, 264b reverse mover action, notes, 265 standard mover actions, notes, 264 structures, relationship, 265 Opponens digiti minimi pedis, 657 Opponens hallucis, 659 Opponens pollicis, 256–257 actions, notes, 257 anterior view of, 256f arterial supply to, 257b attachments, 256 CMC joint, crossing, 256 concentric (shortening) mover actions, 256t derivation of, 256b eccentric antagonist functions, 257 functions of, 256 innervation of, 257b isometric stabilization function, 257 miscellaneous information, 257 motion of, 257

1193

palpation of, 257b pronunciation of, 256b reverse mover action, notes, 257 standard mover action, notes, 256–257 structures, relationship, 257 Opposite-side nasalis muscle, 461 Opposition/reposition, terms (pairs), 10 Orbicularis oculi, 454–455 anterior view of, 454f anterolateral view of, 454f arterial supply to, 455b attachments of, 454 concentric (shortening) mover actions, 454t derivation of, 454b functions of, 454–455 innervation of, 455b miscellaneous information, 455 motions of, 455 mover action notes, 454 palpation of, 455b pronunciation of, 454b structures, relationship, 455 Orbicularis oris, 485–486 anterior view of, 485f arterial supply to, 486b attachments of, 485 concentric (shortening) mover actions, 485t derivation of, 485b functions of, 485–486 innervation of, 486b miscellaneous information, 486 motions of, 485 mover action notes, 485 palpation of, 486b pronunciation of, 485b structures, relationship, 486 Origin attachments vs., 83–84 definition of, 83 term, usage of, 83

1194

1195

P Palmar, definition of, 4 Palmar aponeurosis, 241f–245f, 279 Palmar/dorsal, terms (pairs), 4 Palmar interossei, 273–275 actions, notes, 274 anterior view of, 273f arterial supply to, 274b attachments of, 273 concentric (shortening) mover actions, 273t derivation of, 273b eccentric antagonist functions, 274 functions of, 273 innervation of, 274b isometric stabilization functions, 274 miscellaneous information, 275 motion of, 274 notes, 240b palpation of, 274b pronunciation of, 273b reverse mover action, notes, 274 structures, relationship, 274–275 Palmaris brevis, 279–280 anterior view of, 279f arterial supply to, 280b attachments of, 279 concentric (shortening) mover actions, 279t derivation of, 279b eccentric antagonist function, 279 note, 279 innervation of, 279b isometric stabilization function, 279 note, 279 miscellaneous information, 280 motion of, 279 palpation of, 280b pronunciation of, 279b reverse mover action, note, 279 standard mover action, note, 279

1196

structures, relationship, 280 Palmaris longus (wrist flexor group), 187–189 anterior view of, 187f arterial supply to, 188b attachments of, 187 concentric (shortening) mover actions, 187t derivation of, 187b, 188b eccentric antagonist functions, 188 note, 188 functions of, 187 innervation of, 188b isometric stabilization functions, 188 miscellaneous information, 189 motion of, 188 palpation of, 188b pronunciation of, 187b reverse mover action, notes, 188 standard mover action, notes, 187 structures, relationship, 188 Palpation guidelines, 89–90 Paraspinal muscles, 284 Paraspinal musculature, 301 Pars marginalis, 486 Pars peripheralis, 486 Pectineus (adductor group), 516–517 actions, notes, 516 anterior view of, 516f arterial supply to, 517b attachments of, 516 concentric (shortening) mover actions, 516t derivation of, 516b eccentric antagonist functions, 516 functions of, 516 hip joint, crossing, 516 innervation of, 517b isometric stabilization functions, 516 miscellaneous information, 517 motions of, 516 palpation of, 517b pronunciation of, 516b reverse mover action, notes, 516

1197

standard mover action, notes, 516 structures, relationship, 517 Pectoral is major, 125–127 actions of, notes on, 126 anterior view of, 125f arterial supply in, 127b attachments of, 125 clavicular head, GH joint (crossing), 125 concentric (shortening) mover actions, 125t derivation of, 125b eccentric antagonist functions, 126 examination of, 88 functions of, 125 innervation of, 127b isometric stabilization functions, 126 miscellaneous information, 127 motions of, 126 palpation of, 127b pronunciation of, 125b reverse mover actions of, 125 notes, 126 standard mover actions, notes, 125 sternocostal head, GH joint (crossing), 125–126 structures, relationship, 127 triangular-shaped muscle, demonstration of, 87f Pectoralis minor, 107–108 actions of, note on, 108 anterior view of, 107f arterial supply to, 108b attachments of, 107 brachial plexus of nerves and, 108 concentric (shortening) mover actions, 107t contraction of, 107 derivation of, 107b eccentric antagonist functions, 108 functions of, 107–108 innervation of, 108b isometric stabilization functions, 108 motion of, 108 palpation of, 108b pronunciation of, 107b

1198

reverse mover action, notes, 108 scapular attachment of, 107 standard mover action, notes, 107 structures, relationship, 108 subclavian artery and vein in, 108 syndrome, 108 tight, 108 Pelvic bone, acetabulum of, 39f Pelvic elevators, 704f Pelvic floor, 666 inferior views of, 718f medial views of, 716f muscles of, 716–718 superior views of, 717f Pelvis contralateral rotators of, 705f depressors of, 703f elevation of, 129 at hip joint, 27–28 depression and elevation of, anterior views of, 28f motion of, 27f–28f posterior and anterior tilt of, lateral views of, 27f rotation of, anterior and superior views of, 28f ipsilateral rotators of, 706f at lumbosacral joint motion of, 23f–24f posterior and anterior tilt of, lateral views of, 23f–24f rotation of, anterior and superior views of, 23f–24f orientation of, 27f–28f Pennate muscles, architectural types of, 87f Perimysium (perimysia), 85–86 as fibrous fascial sheaths, 85f Pes anserine, meaning, 510, 579 Pes anserine tendon, muscles (attachment), 519 Phalanges, sides of, 662 PIP joints. See Proximal interphalangeal (PIP) joints Piriformis (deep lateral rotator group), 539–541 arterial supply to, 540b attachments of, 539 concentric (shortening) mover actions, 539t derivation of, 539b

1199

eccentric antagonist functions, 540 functions of, 539–540 innervation of, 540b isometric stabilization functions, 540 note, 540 miscellaneous information, 541 palpation of, 540b pronunciation of, 539b reverse mover action, notes, 540 standard mover action, notes, 539 structures, relationship, 540 syndrome, 541 view of, 528f Pisiform, 260 Pivot joint, 33 example. See Uniaxial pivot joint Planes, 4–5, 5b body parts within, motion of, 7f Plantar, definition of, 4 Plantar/dorsal, terms (pairs), 4 Plantar interossei, 660–661 actions, notes, 661 arterial supply to, 661b attachments of, 660 concentric (shortening) mover actions, 660t derivation of, 660b eccentric antagonist functions, 661 functions of, 660–661 innervation of, 661b isometric stabilization functions, 661 miscellaneous information, 661 motion of, 661 MTP joint, crossing, 660 palpation of, 661b plantar view of, 660f pronunciation of, 660b reverse mover action, notes, 661 standard mover action, notes, 660–661 structures, relationship, 661 Plantarflexion, definition of, 10 Plantaris, 608–609

1200

actions, notes, 609 ankle joint, crossing, 608 arterial supply to, 609b attachments of, 608 concentric (shortening) mover actions, 608t derivation of, 608b eccentric antagonist functions, 609 functions of, 608–609 innervation of, 609b isometric stabilization functions, 609 miscellaneous information, 609 motion of, 609 palpation of, 609b posterior view of, 608f pronunciation of, 608b reverse mover actions, notes, 608 standard mover actions, notes, 608 structures, relationship, 609 Planting and cutting, 537 Platysma, 487–488 anterior view of, 487f arterial supply to, 488b attachments of, 487 concentric (shortening) mover actions, 487t derivation of, 487b functions of, 487–488 innervation of, 488b miscellaneous information, 488 motions of, 487 mover action notes, 487 palpation of, 488b pronunciation of, 487b structures, relationship, 488 Pocket muscle, 372 Pollicis, term (usage), 200 Popliteus, 583–584 arterial supply to, 584b attachments of, 583 concentric (shortening) mover actions, 583t derivation of, 583b eccentric antagonist functions, 583

1201

functions of, 583–584 note, 584 innervation of, 584b isometric stabilization function, 583 knee joint, wrapping, 583 miscellaneous information, 584 motions of, 583 palpation of, 584b posterior view of, 583f pronunciation of, 583b reverse mover actions, notes, 583 standard mover actions, notes, 583 structures, relationship, 584 Posterior, definition, 2 Posterior axillary fold, teres major in, 132 Posterior deltoid, GH joint and, 120 Posterior hand on radial side, 192, 194 on ulnar side, 197 Posterior head, 525 Posterior iliac crest, 360, 528 spinous processes of, 128 Posterior proximal ulna, 163 Posterior radius, 225, 228 Posterior sacroiliac ligament, 316 Posterior sacrum, spinous processes of, 128 Posterior scalene (scalene group), 334–335 anterior view of, 334f arterial supply to, 334b attachments of, 334 concentric (shortening) mover actions, 334t derivation of, 334b eccentric antagonist function, 334 functions of, 334 innervation of, 334b isometric stabilization functions, 334 miscellaneous information, 335 motion in, 334 palpation of, 334b pronunciation of, 334b reverse mover action, notes, 334

1202

standard mover action, notes, 334 structures, relationship, 334–335 Posterior superior iliac spine (PSIS), 316 Posterior triangle, 98, 327 Posterior ulna, 231, 234 Posterolateral sacrum, 528 Prevertebral group, 336. See also Longus capitis (prevertebral group) Longus colli (prevertebral group) Rectus capitis anterior (prevertebral group) Rectus capitis lateralis (prevertebral group) anterior view of, 336f–337f clinical importance of, 336 Prevertebral muscle, 339, 341, 343, 345 Procerus, 459–460 anterior view of, 459f arterial supply to, 459b attachments of, 459 concentric (shortening) mover actions, 459t derivation of, 459b functions of, 459–460 innervation of, 459b miscellaneous information, 460 motions of, 459 mover action notes, 459 palpation of, 460b pronunciation of, 459b structures, relationship, 460 Pronation in cardinal plane components, 30f definition of, 10 mobile radius, 153, 158, 165 movement, 165, 167 Pronation/supination, terms (pairs), 10 Pronator quadratus, 167–168 anterior view of, 167f arterial supply to, 168b attachments of, 167 concentric (shortening) mover actions, 167t derivation of, 167b eccentric antagonist function, 168 functions of, 167 innervation of, 168b isometric stabilization function, 168

1203

note, 168 miscellaneous information, 168 motion of, 167 palpation of, 168b pronunciation of, 167b rectangular-shaped muscle, demonstration of, 87f reverse mover action of, notes, 167 standard mover action of, notes, 167 structures, relationship, 168 Pronator teres, 165–166 anterior view of, 165f arterial supply to, 166b attachments of, 165 concentric (shortening) mover actions, 165t derivation of, 165b eccentric antagonist functions, 166 note, 166 functions of, 165 innervation of, 166b isometric stabilization functions, 166 miscellaneous information, 166 motion of, 166 palpation of, 166b pronunciation of, 165b reverse mover action, notes, 165 standard mover action, notes, 165 structures, relationship, 166 Protraction definition of, 9 of head, 9b Protraction/retraction, terms (pairs), 9 Proximal, definition of, 4 Proximal anterior fibula, 622 Proximal arm, distal forearm movement toward, 82f Proximal attachment, distal attachment approach to, 81 Proximal/distal, terms (pairs), 4 Proximal interphalangeal (PIP) joints extensor digitorum, crossing, 218 FDP, crossing, 213 FDS, crossing, 210 finger movement at, 201

1204

little finger extension, reverse action, 261 muscles, crossing, 201 reverse actions at, 210, 219, 222 Proximal posteromedial tibia, 583 PSIS. See Posterior superior iliac spine (PSIS) Psoas major (iliopsoas), 502–505 additional notes on actions, 503 anterior view of, 502f arterial supply to, 504b attachments of, 502 concentric (shortening) mover actions, 502t controversy, 502 derivation of, 502b eccentric antagonist functions, 503 note, 503 functions of, 502–505 hip joint, crossing, 502 innervation of, 504b isometric stabilization functions, 503 note, 503 miscellaneous information, 505 motions of, 503 palpation of, 504b pronunciation of, 502b reverse mover action, notes, 502–503 standard mover action, notes, 502 structures, relationship, 505 Psoas minor, 379–380 actions, note, 380 anterior view of, 379f arterial supply to, 380b attachments of, 379 concentric (shortening) mover actions, 379t derivation of, 379b eccentric antagonist functions, 380 functions of, 379 innervation of, 380b isometric stabilization function, 380 miscellaneous information, 380 motions of, 380 palpation of, 380b

1205

pronunciation of, 379b reverse mover action, notes, 379–380 standard mover action, notes, 379 structures, relationship, 380 Pubis, 515, 517, 519, 521, 523 Pull-up bar, 81 Pulling forces, 79, 86 exertion of, 80 strength of, 86f Pump handle motion, 400 Q QL. See Quadratus lumborum (QL) Quadratus femoris (deep lateral rotator group), 550–551 arterial supply to, 551b attachments of, 550 concentric (shortening) mover actions, 550t derivation of, 550b eccentric antagonist functions, 550–551 functions of, 550–551 innervation of, 551b isometric stabilization functions, 551 note, 551 miscellaneous information, 551 palpation of, 551b posterior view of, 550f pronunciation of, 550b reverse mover action, notes, 550 standard mover action, notes, 550 structures, relationship, 551 Quadratus lumborum (QL), 360–362 actions, notes, 361 arterial supply to, 361b attachments of, 360 concentric (shortening) mover actions, 360t derivations of, 360b eccentric antagonist functions, 361 functions of, 360 innervation of, 361b isometric stabilization functions, 361 notes, 361

1206

miscellaneous information, 362 motions of, 361 palpation of, 361b posterior view of, 360f pronunciation of, 360b reverse mover action, notes, 360–361 same-side pelvis elevation, 360 standard mover action, notes, 360 structures, relationship, 361 Quadratus plantae, 650–651 actions, note, 651 arterial supply to, 651b attachments of, 650 concentric (shortening) mover actions, 650t derivation of, 650b eccentric antagonist function, 650 flexor digitorum longus muscle, distal tendon of (attachment), 650 functions of, 650–651 innervation of, 651b isometric stabilization functions, 651 miscellaneous information, 651 motion of, 650 palpation of, 651b plantar view of, 650f pronunciation of, 650b reverse mover action, notes, 650 standard mover action, notes, 650 structures, relationship, 651 Quadriceps femoris group (quads), 562–571. See also Rectus femoris (quadriceps femoris group) Vastus intermedius (quadriceps femoris group) Vastus lateralis (quadriceps femoris group) Vastus medialis (quadriceps femoris group) arterial supply to, 562b attachments of, 562 functions of, 562 innervation of, 562b miscellaneous information, 562 patella, group, 562 views of, 563, 563f Quadriceps femoris musculature, reverse mover action of, 82f Quadriceps surae, 605, 609

1207

R Radial, definition of, 4 Radial group. See also Extensor carpi radialis brevis (wrist extensor and radial group) Extensor carpi radialis longus (wrist extensor and radial group) brachioradialis of, 157–159 Radial head, 210 Radial tuberosity, 152 Radial/ulnar, terms (pairs), 4 Radioulnar (RU) joints forearm at, 16 involvement, 153, 158, 169 muscles of. See also Right radioulnar joints function, overview of, 145 overview of, 144 right, views of, 150f structure, overview of, 144 pronators, anterior view of, 676f right forearm at, pronation/supination of, 16f supinators, posterior view of, 676f Radius anterior surface, 215 dorsal tubercle of, 233 styloid process of, 157 supination of, 226, 232 Rectangular-shaped muscle, demonstration of, 87f Rectus, term (meaning), 350 Rectus abdominis (anterior abdominal wall), 366–368 actions, notes, 367 anterior view of, 366f arterial supply to, 367b attachments, 366 concentric (shortening) mover actions, 366t derivation of, 366b eccentric antagonist function, 367 notes, 367 functions of, 366 innervation of, 367b isometric stabilization functions, 367 notes, 367 miscellaneous information, 368 motions of, 367

1208

palpation of, 368b pronunciation, 366b standard mover action, notes, 366–367 structures, relationship, 368 Rectus capitis anterior (prevertebral group), 342–343 actions, notes, 342 anterior view of, 342f arterial supply to, 342b attachments of, 342 concentric (shortening) mover actions, 342t derivation of, 342b eccentric antagonist function, 342 functions of, 342 innervation of, 342b isometric stabilization function, 342 notes, 342 miscellaneous information, 343 motion of, 342 palpation of, 342b pronunciation of, 342b reverse mover action, notes, 342 standard mover action, notes, 342 structures, relationship, 343 Rectus capitis lateralis (prevertebral group), 344–345 anterior view of, 344f AOJ, crossing, 344 arterial supply to, 344b attachments to, 344 concentric (shortening) mover actions, 344t derivation of, 344b eccentric antagonist function of, 344 functions of, 344 innervation of, 344b isometric stabilization function, 344 miscellaneous information, 345 motion of, 344 palpation of, 345b pronunciation of, 344b reverse mover action, notes, 344 standard mover action, notes, 344 structures, relationship, 345

1209

Rectus capitis posterior major (suboccipital group), 352–353 actions, notes, 353 AOJ, crossing, 352 arterial supply to, 353b attachments of, 352 concentric (shortening) mover actions, 352t derivation of, 352b eccentric antagonist functions, 353 functions of, 352 innervation of, 353b isometric stabilization functions, 353 notes, 353 lateral view of, 352f miscellaneous information, 353 motion of, 353 palpation of, 353b posterior view of, 352f pronunciation of, 352b reverse mover action, notes, 352–353 standard mover action, notes, 352 structures, relationship, 353 Rectus capitis posterior minor (suboccipital group), 354–355 actions, notes, 355 arterial supply to, 355b atlas, horizontal movement, 354 concentric (shortening) mover actions, 354t derivation of, 354b eccentric antagonist functions, 355 functions of, 354 innervation of, 355b isometric stabilization function, 355 notes, 355 miscellaneous information, 355 motion of, 354–355 palpation of, 355b pronunciation of, 354b reverse mover action, notes, 354 standard mover action, notes, 354 structures, relationship, 355 Rectus femoris (quadriceps femoris group), 564–565 actions, notes, 565

1210

anterior views of, 564f arterial supply to, 565b attachments of, 564 as bipennate muscle, 87f concentric (shortening) mover actions, 564t derivation of, 564b eccentric antagonist functions, 564 functions of, 564–565 innervation of, 565b isometric function, note, 565 knee joint, crossing, 564 major isometric stabilization functions, 565 miscellaneous information, 565 motions of, 564 palpation of, 565b pronunciation of, 564b reverse mover actions, notes, 564 standard mover actions, notes, 564 structures, relationship, 565 Reflected tendon, 565 Reposition, definition of, 10 Resistance force, contraction compared with, 79–80 Retraction, definition of, 9 Reverse actions, 81–82 commonness. See Lower extremities Reverse mover action, 81, 82f. See also Quadriceps femoris musculature Rhomboidal-shaped muscles, demonstration of, 87f Rhomboids arterial supply to, 101b attachments of, 100 concentric (shortening) mover actions, 100t derivation of, 100b eccentric antagonist functions, 101 functions of, 100–101 innervation of, 101b isometric stabilization functions, 101 major, 100–101 spinous processes, 100 minor, 100–101 scapula attachment of, 101 spinous processes, 100

1211

motion of, 101 palpation of, 101b posterior view of, 100f pronunciation of, 100b reverse mover action, notes, 101 rhomboidal-shaped muscles, demonstration of, 87f serratus anterior, blending to, 101, 106 standard mover action, notes, 100–101 structures, relationship, 101 Rhomboserratus muscle, 106 Rib cage, internal surfaces of, 398 Rib cage joints, muscles of, 382–409 function of, 382–383 overview of, 382 structure of, 382 Ribs cartilage, 366 costal cartilages of, 125 elevation of, 109 intercostal spaces of, 390, 393 serratus posterior inferior, attachment of, 404 serratus posterior superior, attachment of, 402 subclavius to, attachment of, 109 Right abductor digiti minimi manus, anterior view of, 260f Right abductor digiti minimi pedis, plantar view of, 646f Right abductor hallucis, plantar view of, 644f Right abductor pollicis brevis, anterior view, 252f Right abductor pollicis longus, posterior view of, 225f Right adductor brevis, anterior view, 522f Right adductor hallucis, plantar view of, 658f Right adductor longus, anterior view, 518f Right adductor magnus, posterior view, 524f Right adductor pollicis, anterior view of, 268f Right anconeus, posterior view of, 163f Right ankle joint, muscles anterior view of, 588, 588f lateral view of, 592, 592f medial views of, 593, 593f posterior view of deep view of, 591 intermediate view of, 590

1212

superficial view of, 589, 589f–591f Right arm bones of anterior view of, 40f posterior view of, 42f bony landmarks of anterior view of, 40f posterior view of, 42f muscle attachment sites on anterior view of, 41f posterior view of, 43f transverse plane cross sections of, 151f Right articularis genus, anterior view of, 572f Right auricularis muscles, lateral view, 452f Right biceps brachii, anterior view of, 152f Right biceps femoris, posterior views of, 575f Right brachialis, anterior view of, 155f Right brachioradialis, anterior view of, 157f Right buccinator, views, 483f Right central compartment group muscles, anterior view of, 266f Right clavicle depression of, 13f elevation of, at sternoclavicular (SC) joint, 13f protraction of, at sternoclavicular (SC) joint, 13f retraction of, 13f upward rotation of, at sternoclavicular (SC) joint, 13f Right coracobrachialis, anterior view of, 123f Right corrugator supercilii, anterior view, 457f Right deep distal four group, posterior views of, 224f Right deltoid, 119f Right depressor anguli oris, anterior view, 477f Right depressor labii inferioris, anterior view, 479f Right depressor septi nasi, anterior views, 463f Right digastric, views, 426 Right dorsal interossei manus, posterior view of, 276f Right dorsal interossei pedis, dorsal view of, 662f Right ear, lateral view, 448f Right elbow joint, muscles of anterior views of, 146f deep view of, 146f, 147f lateral view of, 148f

1213

medial view of, 149f posterior views of, 147f superficial view of, 146f, 147f Right erector spinae group, posterior view of, 299f Right extensor carpi radialis brevis, posterior view of, 194f Right extensor carpi radialis longus, posterior view of, 192f Right extensor carpi ulnaris, posterior view of, 197f Right extensor digiti minimi, posterior view of, 221f Right extensor digitorum, posterior view of, 218f Right extensor digitorum brevis, dorsal view of, 640f Right extensor digitorum longus, anterior view of, 622f Right extensor hallucis brevis, dorsal view of, 642f Right extensor hallucis longus, anterior view of, 624f Right external abdominal oblique, views of, 369f Right external intercostals, views of, 390f Right fibularis brevis, lateral view of, 602f Right fibularis longus, lateral view of, 600f Right fibularis tertius, anterior view of, 598f Right flexor carpi radialis, anterior view of, 185f Right flexor carpi ulnaris, anterior view of, 190f Right flexor digiti minimi, anterior view of, 262f Right flexor digiti minimi pedis, plantar view of, 656f Right flexor digitorum brevis, plantar view of, 648f Right flexor digitorum longus, posterior view of, 626f Right flexor digitorum profundus, anterior view of, 213f Right flexor digitorum superficialis, anterior view of, 210f Right flexor hallucis brevis, plantar view of, 654f Right flexor hallucis longus, posterior view of, 628f Right flexor pollicis brevis, anterior view, 254f Right flexor pollicis longus, anterior view of, 215f Right foot bones of dorsal view of, 74f plantar view of, 76f bony landmarks of dorsal view of, 74f plantar view of, 76f cross section of, 639, 639f muscle attachment sites on dorsal view of, 75f plantar view of, 77f

1214

muscles dorsal view of, 637, 637f lateral view of, 638, 638f medial view of, 638, 638f plantar view deep view of, 636 intermediate view of, 635 superficial fascial view of, 633, 633f–636f superficial muscular view of, 634 toes, extrinsic muscles anterior views of, 615–616, 615f–616f medial view of, 619–620, 619f–620f posterior view of, 617–618, 617f–618f Right forearm bones of anterior view of, 44f posterior view of, 46f bony landmarks of anterior view of, 44f posterior view of, 46f muscle attachment sites on anterior view of, 45f posterior view of, 47f pronation/supination of, at radioulnar joints, 16f proximal/middle/distal, 184f transverse plane cross sections of, 184 Right gastrocnemius, posterior view of, 604f Right geniohyoid, views, 430 Right glenohumeral joint, frontal plane section through, anterior view of, 117f Right gluteus maximus lateral view of, 531f posterior view of, 528f Right gracilis, anterior view, 520 Right hamstring group, posterior views of, 574f Right hand bones of dorsal view of, 50f palmar view of, 48f bony landmarks of dorsal view of, 50f palmar view of, 48f

1215

index finger, dorsal digital expansion lateral view, 249f views, 249f metacarpal bones, cross-section of, 248, 248f muscle attachment sites on dorsal view of, 51f palmar view of, 49f Right hip joint deep views, 497, 497f elevation of, anterior views of, 28f muscles, lateral view, 498, 498f deep view, 499, 499f muscles, medial views of superficial/deep views, 497, 497f muscles, medial views (superficial/deep views), 497, 497f muscles, posterior views deep views, 496, 496f superficial view, 498, 498f Right hypothenar group, muscles anterior view of, 258f deep view of, 259f Right infraspinatus, posterior view of, 137f Right internal intercostals, views of, 393f Right internal oblique, views of, 373f Right interspinales, posterior view of, 321f Right knee joint, muscles lateral views of, 559, 559f medial views of, 560, 560f Right lateral deviation/left lateral deviation, terms (pairs), 10 Right lateral flexion, definition of, 9 Right lateral flexion/left lateral flexion, terms (pairs), 9 Right lateral pterygoids, views of, 414f, 420f Right latissimus dorsi, posterior view of, 128f Right leg bones of anterior view of, 70f posterior view of, 72f bony landmarks of anterior view of, 70f posterior view of, 72f compartments, transverse plane cross section of, 594, 594f, 621, 621f

1216

muscle attachment sites on anterior view of, 71f posterior view of, 73f muscles, transverse plane cross section of, 595, 595f, 621, 621f Right levator anguli oris, anterior view, 473f Right levator palpebrae superioris, views of, 456f Right levatores costarum, posterior view of, 406f Right longus capitis, anterior view of, 340f Right longus colli, anterior view of, 338f Right lumbricals manus, anterior view of, 271f Right lumbricals pedis, plantar view of, 652f Right masseter, lateral views of, 418f Right medial pterygoids, views, 414f Right mentalis, views, 481f Right multifidus, posterior view of, 316f Right nasalis, anterior views, 461f Right obliquus capitis superior, views of, 358f Right occipitofrontalis, lateral view of, 449f Right opponens pollicis, anterior view of, 256f Right orbicularis oculi, views, 454f Right orbicularis oris, anterior view, 485f Right palmar interossei, anterior view of, 274f Right palmaris longus, anterior view of, 187f Right pectoralis major, anterior view of, 125f Right pectoralis minor, anterior view of, 107f Right pelvis bones of anterior view of, 66f posterior view of, 68f bony landmarks of anterior view of, 66f posterior view of, 68f elevation of, 24f, 28f muscle attachment sites on anterior view of, 67f posterior view of, 69f Right plantar interossei, plantar view of, 660f Right plantaris, posterior view of, 608f Right popliteus, posterior view of, 583f Right procerus, anterior view, 459f Right pronator quadratus, anterior view of, 167f

1217

Right pronator teres, anterior view of, 165f Right quadratus lumborum, posterior view of, 360f Right quadratus plantae, plantar view of, 650f Right radioulnar joints, muscles of, views of, 150f Right rectus capitis posterior minor, views, 354f Right rhomboids, major and minor, posterior view of, 100f Right risorius, anterior view, 475f Right rotation, definition of, 9 Right rotation/left rotation, terms (pairs), 9 Right rotatores, posterior view of, 319f Right scapula bones of anterior view of, 40f posterior view of, 42f bony landmarks of anterior view of, 40f posterior view of, 42f depression of, 11f elevation of, 11f lateral tilt of, 12f muscle attachment sites on anterior view of, 41f posterior view of, 43f protraction of, 11f retraction of, 11f superior view of, 133f, 134f upward rotation of, at scapulocostal (ScC) joint, 12f upward tilt of, 12f Right semimembranosus, posterior view of, 580f Right semitendinosus, posterior view of, 578f Right serratus anterior, lateral view of, 104f Right serratus posterior superior, posterior view of, 402f Right soleus, posterior view of, 606f Right splenius capitis, posterior view of, 346f Right splenius cervicis, posterior view of, 348f Right sternocleidomastoid, lateral view of, 325f Right subclavius, anterior view of, 109f Right suboccipital group, posterior/lateral views, 351f Right subscapularis, anterior view of, 141f Right subtalar joints, muscles lateral view of, 592, 592f

1218

medial views of, 593, 593f posterior view of deep view of, 591 intermediate view of, 590 superficial view of, 589, 589f–591f Right supinator, posterior view of, 169f Right supraspinatus, posterior view of, 135f Right temporalis, lateral view of, 416f Right temporoparietalis, lateral view, 451f Right tensor fasciae latae, lateral view, 507 Right teres major, views of, 131f Right teres minor, posterior view of, 139f Right thenar group, muscles (anterior views), 250f Right thigh bones of anterior view of, 66f posterior view of, 68f bony landmarks of anterior view of, 66f posterior view of, 68f distal view, 501f middle view, 501f muscle attachment sites on anterior view of, 67f posterior view of, 69f proximal view, 500f transverse plane cross-sections, 501, 561, 561f Right tibialis anterior, anterior view of, 596f Right tibialis posterior, posterior view of, 610f Right transversus abdominis, views of, 377f Right transversus thoracis, anterior view of, 396f Right trapezius, posterior view of, 96f Right triceps brachii, posterior views of, 160f Right wrist cross section of, 247, 247f muscles of extensor group, (posterior view), 180f flexor group of (posterior view), 177f Right wrist joint, muscles of anterior views of deep view of, 176f, 205, 205f

1219

intermediate view of, 175f, 204, 204f superficial view of, 174f, 203, 203f lateral views of, 181f–183f, 182–183, 208, 208f medial view of, 181, 181f, 209, 209f posterior views of, 178f–179f deep views of, 179f intermediate/deep views of, 207f superficial view of, 178f, 206, 206f Right zygomaticus major, anterior view, 471f Right zygomaticus minor, anterior view, 469f Risorius, 475–476 anterior view of, 475f arterial supply to, 475b attachments of, 475 concentric (shortening) mover actions, 475t derivation of, 475b functions of, 475 innervation of, 475b miscellaneous information, 476 motions of, 475 mover action notes, 475 palpation of, 475b pronunciation of, 475b structures, relationship, 475 Rotator cuff group, 133–134. See also Infraspinatus (rotator cuff group) Subscapularis (rotator cuff group) Supraspinatus (rotator cuff group) Teres minor (rotator cuff group) arterial supply to, 133b attachments of, 133 functions of, 133 innervation of, 133b miscellaneous information, 133 supraspinatus of, 135 views of, 133f, 134f Rotatores (transversospinalis group), 319–320 arterial supply to, 320b attachments of, 319 concentric (shortening) mover actions, 319t derivation of, 319b eccentric antagonist functions, 320 functions of, 319 innervation of, 320b

1220

isometric stabilization function, 320 notes, 320 miscellaneous information, 320 motion of, 320 palpation of, 320b posterior view of, 319f pronunciation of, 319b reverse mover action, notes, 319–320 standard mover action, notes, 319 structures, relationship, 320 Rounded shoulders, 99, 101 pectoralis minor and, 108 RU joints. See Radioulnar (RU) joints Rubber band exercise, 89 importance of, 89b S Sacrospinalis group, 301 Sacrum, piriformis (attachment), 539 Saddle joint, 36–37 biaxial consideration of, 38f example. See Biaxial saddle joint of thumb, 19f, 37b Sagittal plane, 4 examples of, 6f head/neck/arm motions in, 7f motion occurring in, 8f Same-side lateral flexion, cause of, 98 Same-side pelvis elevation, QL (impact), 360 Sarcomere, 86 composition of, 86f Sartorius, 510–511 actions, notes, 511 anterior view of, 510f arterial supply to, 511b attachments of, 510 concentric (shortening) mover actions, 510t derivation of, 510b eccentric antagonist functions, 511 functions of, 510–511 hip joint, crossing, 510

1221

innervation of, 511b isometric stabilization functions, 511 notes, 511 miscellaneous information, 511 motions of, 511 palpation of, 511b pronunciation of, 510b reverse mover action, notes, 510–511 strap muscle, 87f structures, relationship, 511 Sartorius, Gracilis, Semitendinosus (SGS), 511, 579 SC joint. See Sternoclavicular (SC) joint Scalene group, 328 anterior view of, 329f arterial supply to, 328b attachments of, 328 clinical applications, 328 functions of, 328 injury of, 328 innervation, 328b miscellaneous information, 328 Scalp, 449–453 Scapula acromion process of, 119 coracoid process of, 107, 123, 152 downward rotation of, 100 reverse action of, 120 at scapulocostal joint, 107 downward tilt of, 105 elevation/depression of, nonaxial actions of, 11f inferior angle and inferior lateral border of, 131 infraglenoid tubercle of, 160 infraspinous fossa of, 137 lateral clavicle of, 119 levator scapulae, attachment on, 102 medial border of, 100, 102 anterior surface of, 104 medial tilt of, 100–101 medial border and, 104–105 movement of, humerus and, 113 protraction/retraction of, nonaxial actions of, 11f

1222

reverse action of, 15 rhomboid minor, attachment to, 101 at scapulocostal joint, 11–12 spine of, 96, 119 subscapular fossa of, 141 superior lateral border of, 139 superior view of, 133f supraglenoid tubercle of, 152 supraspinous fossa of, 135 tilt, 97–98 tilt actions of, at scapulocostal (ScC) joint, 12f trapezius attachment to, 96 upward rotation of, 104 Scapular protraction, importance of, 104 Scapulocostal (ScC) joint depressors of, 668f downward rotators of, 670f elevators of, 667f protractors of, 669f retractors of, 669f tilt actions at, 12f upward rotation at, 12f upward rotators of, 670f Sciatica, symptoms, 541 Second toe, at MTP joint, 31f Semimembranosus (hamstring group), 580–582 arterial supply to, 581b attachments of, 580 concentric (shortening) mover actions, 580t derivation of, 580b eccentric antagonist functions, 581 functions of, 580–581 note, 581 innervation of, 581b isometric stabilization functions, 581 knee joint, crossing, 580 miscellaneous information, 582 motions of, 581 palpation of, 581b posterior view of, 580f pronunciation of, 580b

1223

reverse mover actions, notes, 580–581 standard mover actions, notes, 580 structures, relationship, 581 Semispinalis (transversospinalis group), 313–314 actions, notes, 314 arterial supply to, 314b attachments of, 313 concentric (shortening) mover actions, 313t derivation of, 313b eccentric antagonist functions, 314 functions of, 313 innervation of, 314b isometric stabilization functions, 314 miscellaneous information, 314 motion of, 314 palpation of, 314b posterior view of, 313f pronunciation of, 313b reverse mover action, notes, 314 spinal joints, crossing, 313 standard mover action, notes, 313–314 structure, relationship, 314 Semitendinosus (hamstring group), 578–579 actions, notes, 579 arterial supply to, 579b attachments of, 578 concentric (shortening) mover actions, 578t derivation of, 578b eccentric antagonist functions, 579 functions of, 578–579 innervation of, 579b isometric function, note, 579 isometric stabilization functions, 579 knee joint, crossing, 578 miscellaneous information, 579 motions of, 579 palpation of, 579b posterior view of, 578f pronunciation of, 578b reverse mover actions, notes, 578–579 standard mover actions, notes, 578

1224

structures, relationship, 579 Serratus anterior, 104–106 actions, notes, 105 arterial supply to, 105b attachments of, 104 concentric (shortening) mover actions, 104t costal attachment of anterior position of, 104 slips of, 105 derivation of, 104b eccentric antagonist functions, 105 functions of, 104–105 innervation of, 105b isometric stabilization functions, 105 lateral view of, 104f motion of, 105 palpation of, 105b parts of, 106 pronunciation of, 104b reverse mover action, notes, 105 rhomboid muscles with, blending of, 101, 106 scapula, relationship to, 105 as scapular protraction mover, 104 serrated appearance of, 106 standard mover action, notes, 104–105 structures, relationship, 105 Serratus posterior inferior, 404–405 actions, notes, 405 arterial supply to, 405b attachments of, 404 concentric (shortening) mover actions, 404t derivation of, 404b eccentric antagonist functions, 405 functions of, 404–405 innervation of, 405b isometric stabilization functions, 405 note, 405 miscellaneous information, 405 motion of, 405 palpation of, 405b posterior view of, 404f

1225

pronunciation of, 404b reverse mover action, notes, 404–405 ribs, attachment, 404 standard mover action, notes, 404 structures, relationship, 405 Serratus posterior superior, 402–403 arterial supply to, 403b attachments of, 402 concentric (shortening) mover actions, 402t derivation of, 402b eccentric antagonist functions, 402 functions of, 402–403 innervation of, 403b isometric stabilization functions, 402 miscellaneous information, 403 motion of, 402 palpation of, 403b posterior view of, 402f pronunciation of, 402b reverse mover action, notes, 402 ribs, attachment, 402 standard mover action, notes, 402 structures, relationship, 403 SGS. See Sartorius, Gracilis, Semitendinosus (SGS) Shin splints, 597 Short leg, 508 Shoulder girdle joints, muscles of, 91–110 function, overview, 92 structure, overview, 92 left side of depth of, 94f superficiality of, 93f muscles of, right lateral views of, 118f region, muscles of anterior view of, 94, 115f posterior view of, 93, 114f right lateral view of, 95 right side of depth of, 93f superficiality of, 94f

1226

SITS muscle. See Supraspinatus, infraspinatus, teres minor, and subscapularis (SITS muscles) Skeletal system, 33–77 Skeleton, 33 anterior view of, 34f posterior view of, 35f Sliding filament mechanism, 85–86 Soleus (triceps surae group), 606–607 actions, note, 607 ankle joint, crossing, 606 arterial supply to, 607b attachments of, 606 concentric (shortening) mover actions, 606t derivation of, 606b eccentric antagonist functions, 606 note, 607 functions of, 606–607 innervation of, 607b isometric stabilization functions of, 607 miscellaneous information, 607 motion of, 606 palpation of, 607b posterior view of, 606f pronunciation of, 606b reverse mover actions, notes, 606 standard mover actions, notes, 606 structures, relationship, 607 Sphenoid bone, 420, 456 Spinal extension, latissimus dorsi extension, 129 Spinal joints external abdominal oblique, crossing, 370 internal oblique, crossing, 374 longissimus, crossing, 305–306 multifidus, crossing, 316 muscles of, 283–380 crossing, 284 function, overview of, 284 overview of, 283–284 structure, overview of, 283–284 rectus abdominis, crossing, 366 thoracolumbar spine at, motions of, 22f Spinalis capitis, 308

1227

Spinalis cervicis, 308 Spinalis (erector spinae group), 308–309 actions, notes, 309 arterial supply to, 309b attachments of, 308 concentric (shortening) mover actions, 308t derivation of, 308b eccentric antagonist functions of, 309 notes, 309 innervation of, 309b isometric stabilization function, 309 miscellaneous information, 309 motion of, 309 palpation of, 309b posterior view of, 308f pronunciation of, 308b reverse mover action, notes, 308 standard mover action, notes, 308 structures, relationship, 309 Spinalis thoracis, 308 Spindle-shaped muscle, demonstration of, 87f Spine atlantoaxial joint of, 37f levator scapulae, attachment on, 102 motions, consideration for, 306, 311, 319–320 Spinous process, obliquus capitis inferior (attachment), 356 Splenius capitis, 346–347 AOJ, crossing, 346 arterial supply to, 347b attachments of, 346 concentric (shortening) mover actions, 346t derivation of, 346b eccentric antagonist functions, 347 functions of, 346 innervation of, 347b isometric stabilization functions, 347 miscellaneous information, 347 motion of, 346 palpation of, 347b posterior view of, 346f pronunciation of, 346b

1228

reverse mover action, notes, 346 standard mover action, notes, 346 structures, relationship, 347 Splenius cervicis, 348–349 actions, notes, 349 arterial supply to, 349b attachments of, 348 cervical neck joints, crossing, 348 concentric (shortening) mover actions, 348t derivation of, 348b eccentric antagonist functions, 348 functions of, 348 innervation of, 348b–349b isometric stabilization functions, 348 miscellaneous information, 349 motion of, 348 palpation of, 349b posterior view of, 348f pronunciation of, 348b reverse mover action, notes, 348 standard mover action, notes, 348 structures, relationship, 349 Stabilizers, in isometric contraction, 84 Standard mover actions, 81 Standing, quadriceps femoris musculature in, 82f Sternal head, 325 Sternoclavicular (SC) joint, clavicle at, 13 right, 13f Sternocleidomastoid (SCM), 325–327. See also Head Neck actions, notes, 326 arterial supply to, 326b attachments of, 325 concentric (shortening) mover actions, 325t cutting, 94f derivation of, 325b eccentric antagonist functions, 326 functions of, 325 innervation of, 326b isometric stabilization functions, 326 notes, 326 joints, crossing, 325

1229

lateral view of, 325f miscellaneous information, 326–327 motion of, 326 palpation of, 326b pronunciation of, 325b reverse mover action, notes, 326 standard mover action, notes, 325 structures, relationship, 326 Sternocostalis, 397 Sternohyoid (hyoid group), 434–435 anterior view of, 434f arterial supply to, 435b attachments of, 434 concentric (shortening) mover actions, 434t derivation of, 434b eccentric antagonist functions, 434 functions of, 434–435 innervation of, 434b isometric stabilization functions, 434 miscellaneous information, 435 palpation of, 435b pronunciation of, 434b reverse mover action, notes, 434 standard mover action, notes, 434 structures, relationship, 435 Sternothyroid (hyoid group), 436–437 anterior view of, 436f arterial supply to, 437b attachments of, 436 concentric (shortening) mover actions, 436t derivation of, 436b eccentric antagonist functions, 436 functions of, 436–437 innervation of, 437b isometric stabilization functions, 436 notes, 436 miscellaneous information, 437 palpation of, 437b pronunciation of, 436b reverse mover action, notes, 436 standard mover action, notes, 436

1230

structures, relationship, 437 Sternum internal surface of, 396 manubrium, 325 Stirrup muscles, 597 Straight tendon, 565 Strap muscle, 87f Structural short leg, 508, 533 Stylohyoid (hyoid group), 432–433 anterior view of, 432f arterial supply to, 433b attachments of, 432 concentric (shortening) mover actions, 432t derivation of, 432b eccentric antagonist functions, 432 functions of, 432–433 innervation of, 433b isometric stabilization functions, 432 miscellaneous information, 433f palpation of, 433b pronunciation of, 432b reverse mover action, notes, 432 standard mover action, notes, 432 structures, relationship, 433 views, 432f Subacromial bursa, 133 Subclavius, 109–110 actions, notes on, 110 anterior view of, 109f arterial supply to, 110b attachments of, 109 brachial plexus of nerves and, 110 concentric (shortening) mover actions, 109t contraction of, 109 to coracoid process, attachment of, 110 derivation of, 109b eccentric antagonist functions, 109 functions of, 109–110 innervation of, 110b isometric stabilization functions, 109 motion of, 109

1231

palpation of, 110b pronunciation of, 109b reverse mover action, notes, 109 rib attachment of, 109 standard mover action, notes, 109 structures, relationship, 110 subclavian artery and vein in, 110 Subcostales, 408–409 arterial supply to, 408b attachments of, 408 concentric (shortening) mover actions, 408t derivation of, 408b eccentric antagonist function, 408 functions of, 408 innervation of, 408b isometric stabilization function, 408 note, 408 miscellaneous information, 409 motions of, 408 palpation of, 409b posterior view of, 408f pronunciation of, 408b reverse mover action, note, 408 standard mover action, note, 408 structures, relationship, 409 Subdeltoid bursa, 133 Suboccipital group, 350. See also Obliquus capitis inferior (suboccipital group) Obliquus capitis superior (suboccipital group) Rectus capitis posterior major (suboccipital group) Rectus capitis posterior minor (suboccipital group) arterial supply to, 350b attachments of, 350 functions of, 350 innervation of, 350b lateral view of, 351f miscellaneous information, 350 posterior view of, 351f views of, 351f Suboccipital muscles, 355, 357, 359 Subscapularis (rotator cuff group), 133, 133f, 141–142 actions of, notes on, 141 anterior view of, 141f

1232

arterial supply in, 142b attachment of, 141 concentric (shortening) mover actions of, 141t derivation of, 141b functions of, 141 eccentric antagonist, 141 isometric stabilization, 141 GH joint crossing, 141 innervation of, 142b miscellaneous information, 142 motion of, 141 palpation of, 142b posterior view of, 134f pronunciation of, 141b reverse mover action of, note, 141 standard mover action of, note, 141 structures, relationship, 142 Subtalar joint foot at, 30 dorsiflexion/plantarflexion of, sagittal plane of, 30f lateral/medial rotation of, transverse plane of, 30f motions of, 30f pronators (everters), lateral view of, 711f supinators (inverters), posterior view of, 712f Subtalar joint, muscles, 586–611. See also Right subtalar joints anterior view of, 588, 588f function of, 587 lateral view of, 592, 592f medial views of, 593, 593f overview of, 586 posterior view of deep view of, 591 intermediate view of, 590 superficial view of, 589–591f structure of, 586–587 Superficial, definition of, 4 Superficial back line, 719f Superficial/deep, terms (pairs), 4 Superficial front line, of myofascial meridians, 719f Superior, definition of, 4 Superior chest, subcutaneous fascia of, 487

1233

Superior gemellus (deep lateral rotator group), 542–543 arterial supply to, 543b attachments of, 542 concentric (shortening) mover actions, 542t derivation of, 542b eccentric antagonist functions, 542 functions, 542–543 innervation of, 543b isometric stabilization functions, 542 note, 542 miscellaneous information, 543 palpation of, 543b posterior view of, 542f pronunciation of, 542b reverse mover action, notes, 542 standard mover action, notes, 542 structures, relationship, 543 Superior/inferior, terms (pairs), 4 Supination, 152 definition of, 10 mobile radius, 153 movement, 169 Supinator, 169–170 arterial supply to, 170b attachments of, 169 concentric (shortening) mover actions, 169t derivation of, 169b eccentric antagonist functions, 170 functions of, 169 innervation of, 170b isometric stabilization functions, 170 miscellaneous information, 170 motions of, 170 palpation of, 170b posterior view of, 169f pronunciation of, 169b reverse mover action, notes, 169 standard mover action, notes, 169 structures, relationship, 170 Suprahyoids, 426–433 Supraspinatus, infraspinatus, teres minor, and subscapularis (SITS muscles), 136, 138, 140, 142

1234

Supraspinatus (rotator cuff group), 133, 133f, 135–136 actions, notes, 136 arterial supply to, 136b attachments of, 135 concentric (shortening) mover actions, 135t derivation of, 135b eccentric antagonist functions, 135 functions of, 135 GH joint crossing, 135 innervation of, 136b isometric stabilization function, 135 note, 135 miscellaneous information, 136 motion of, 135 palpation of, 136b posterior view of, 134f, 135f pronunciation of, 135b reverse mover action, notes, 135 standard mover action, notes, 135 structures, relationship, 136 Surae, 605, 607 Swayback, 506 Synovial biaxial joints, types of, 36–37 Synovial joints, 36f types of, 33–39 Synovial nonaxial joints example of, 39f motion of, 37 Synovial triaxial joint, 37 Synovial uniaxial joints, types of, 33

1235

T T7-L5, spinous processes of, 128 Talocrural joint, foot at, dorsiflexion and plantarflexion of, lateral views of, 29f Tarsal joint, foot at, 30 motions of, 30f Temporal bone, 449 mastoid process, 305, 325, 346 styloid process of, 433 zygomatic arch/bone, inferior margins, 418 Temporal fossa, 416 Temporalis, 416–417 arterial supply to, 416b attachments of, 416 concentric (shortening) mover actions, 416t derivation of, 416b eccentric antagonist functions, 416 functions of, 416–417 innervation of, 416b isometric stabilization functions, 416 lateral view of, 416f miscellaneous information, 417 palpation of, 417b pronunciation of, 416b reverse mover action notes, 416 right lateral view, 414f standard mover action notes, 416 structures, relationship, 417 Temporalis fascia, 417 Temporomandibular joint (TMJ) mandible, 25f contralateral deviators, lateral view of, 687f depression of, lateral views of, 25f depressors, anterior view of, 686f elevation of, lateral views of, 25f elevators, lateral view of, 686f protraction of, lateral views of, 25f protractors, lateral view of, 687f retraction of, lateral views of, 25f retractors, lateral view of, 687f

1236

right and left lateral deviation of, anterior views of, 25f muscles, 411–441 arterial supply to, 412b function, overview, 412 innervation of, 412b overview, 411–441 structure, overview, 411 syndrome, 417 Temporoparietalis (epicranius component), 451 arterial supply to, 451b attachments of, 451 concentric (shortening) mover actions, 451t derivation of, 451b functions of, 451 innervation of, 451b miscellaneous information, 451 motion of, 451 mover action notes, 451 palpation of, 451b pronunciation of, 451b structures, relationships, 451 Tendon, 86 Tennis elbow, 164, 170, 196, 198, 220, 223 Tenosynovitis, de Quervain’s stenosing, 227, 230 Tension headache, 99 Tensor fasciae latae (TFL), 508–509 actions, notes, 509 attachments of, 508 concentric (shortening) mover actions, 508t derivation of, 508b eccentric antagonist functions, 509 functions of, 508–509 hip joint, crossing, 508–509 isometric stabilization functions, 509 notes, 509 lateral view of, 508f miscellaneous information, 509 motions of, 509 palpation of, 509b pronunciation of, 508b reverse mover action, notes, 508

1237

standard mover action, notes, 508 structures, relationship, 509 Teres major, 131–132 actions, note, 132 arterial supply to, 132b attachments of, 131 concentric (shortening) mover actions, 131t derivation of, 131b eccentric antagonist functions, 132 note, 132 functions of, 131 GH joint, crossing, 131 innervation of, 132b isometric stabilization functions, 132 miscellaneous information, 132 motion of, 132 palpation of, 132b pronunciation of, 131b reverse mover action, notes, 131 standard mover action, notes, 131 structures, relationship, 132 views of, 131f Teres minor (rotator cuff group), 139–140 actions, note, 140 arterial supply to, 140b attachments of, 139 concentric (shortening) mover actions, 139t derivation of, 139b eccentric antagonist functions, 140 note, 140 functions of, 139 GH joint crossing, 139 innervation of, 140b isometric stabilization functions, 140 miscellaneous information, 140 motion of, 139 palpation of, 140b posterior view of, 134f, 139f pronunciation of, 139b reverse mover action, notes, 139 standard mover action, notes, 139

1238

structures, relationship, 140 Terms, pairs of, 2–4, 9–10 TFL. See Tensor fasciae latae (TFL) Thenar eminence group, 250 arterial supply, 250b attachments, 250 deep view, 251f functions of, 250 innervation of, 250b Thenar group, 238 muscles anterior views of, 250f layering, 250 organization, 250 Thigh. See Right thigh hip joint, 26 abduction and adduction of, anterior views of, 26f abductors, posterior view of, 703f adductors, posterior view of, 704f extensors, posterior view of, 702f flexion and extension of, lateral views of, 26f flexors, anterior view of, 702f lateral and medial rotation of, anterior views of, 26f lateral rotators of, 705f medial rotators of, 706f motions of, 26f Thigh adductors anterior views of, 513, 513f medial views of, 514, 514f posterior views of, 515, 515f Third metacarpal, 268 Thoracic outlet syndrome, 108, 328, 331, 333 Thoracolumbar spinal joint (trunk), 22 contralateral rotators of, 699f–700f extensors, posterior view of, 696f flexors, anterior view of, 695f ipsilateral rotators of, 699f–701f lateral flexors of, 697f–698f Thumb, 215, 225, 228, 231 abduction of, 38f, 225, 254 adduction of, 38f

1239

anterior views of, 19f carpometacarpal joint, 19, 37b as biaxial saddle joint example, 38f CMC joint, flexor pollicis brevis (crossing), 254 extension of, 225–226, 231 at first carpometacarpal joint, actions of, 19f first metacarpal, 256 flexion, 268 at interphalangeal joint, flexion of, 19f joint abductors, posterior and anterior views of, 681f adductors, anterior view of, 682f extensors, posterior view of, 680f flexors, anterior view of, 680f lateral rotators, posterior view of, 683f medial rotators, anterior view of, 683f lateral views of, 19f metacarpal of, reverse action of, 226, 229 proximal phalanx, 252, 268 saddle joint of, 19f, 37b Thyrohyoid (hyoid group), 438–439 anterior view of, 438f arterial supply to, 439b attachments of, 438 concentric (shortening) mover actions, 438t derivation of, 438b eccentric antagonist functions, 438 functions of, 438–439 innervation of, 439b isometric stabilization functions, 438 note, 438 miscellaneous information, 439 palpation of, 439b pronunciation of, 438b reverse mover action notes, 438 standard mover action notes, 438 structures, relationship, 439 Thyroid cartilage sternothyroid, attachment, 436 thyrohyoid, attachment, 438 Tibia

1240

knee joint medial and lateral rotators, 709f medial condyle of, posterior surface of, 580 Tibial, definition of, 4 Tibial abduction, 662 Tibial/fibular, terms (pairs), 4 Tibial tuberosity, 564, 566, 568, 570 Tibialis anterior, 596–597 actions, notes, 597 ankle joint, crossing, 596 anterior view of, 596f arterial supply to, 597b attachments of, 596 concentric (shortening) mover actions, 596t derivation of, 596b eccentric antagonist functions, 596 note, 597 functions of, 596–597 innervation of, 597b isometric function, note, 597 isometric stabilization functions, 597 miscellaneous information, 597 motion of, 596 palpation of, 597b pronunciation of, 596b reverse mover action, notes, 596 standard mover action, notes, 596 structures, relationship, 597 Tibialis posterior (Tom of Tom, Dick, and Harry group), 610–611 actions, note, 611 ankle joint, crossing, 610 arterial supply to, 611b attachments of, 610 concentric (shortening) mover actions, 610t derivation of, 610b eccentric antagonist functions, 611 note, 611 functions of, 610–611 innervation of, 611b isometric function, note, 611 isometric stabilization functions, 611 miscellaneous information, 611

1241

motion of, 611 palpation of, 611b posterior view of, 610f pronunciation of, 610b reverse mover actions, notes, 610 standard mover actions, notes, 610 structures, relationship, 611 Tibiofemoral joint, motions at, 29f TMJ. See Temporomandibular joint (TMJ) Toe joint extrinsic muscles, 613–629 function of, 614 overview of, 613 structure of, 613–614 intrinsic muscles, 631–664 function of, 632 overview of, 631 structure of, 631–632 MTP abductors, dorsal view of, 715f adductors, plantar view of, 715f Toe-off, 629 Toes dorsal surface of, 622 extrinsic muscles anterior views of, 615–616, 615f–616f medial view of, 619–620, 619f–620f posterior view of, 617–618, 617f–618f metatarsophalangeal and interphalangeal joints, 31 abduction and adduction of, dorsal views of, 31f fibular abduction of, 31f flexion and extension of, lateral views of, 31f motion of, 31f tibial abduction of, 31f plantar surface of, 626 Tom, Dick, and Harry group. See Flexor digitorum longus (Dick of Tom, Dick, and Harry group) Flexor hallucis longus (Harry of Tom, Dick, and Harry group) Tibialis posterior (Tom of Tom, Dick, and Harry group) Tom, Dick, and Harry muscles, 607 Transverse head adductor hallucis, 659

1242

adductor pollicis, 270 Transverse plane, 4, 5b examples of, 6f head/neck/arm motions in, 7f motion occurring in, 8f Transverse process, 319 Transversospinalis group, 310–312. See also Multifidus (of transversospinalis group) Rotatores (transversospinalis group) Semispinalis (transversospinalis group) actions, notes, 311–312 arterial supply to, 312b attachments of, 310 concentric (shortening) mover actions, 310t derivation of, 310b eccentric antagonist functions, 311 functions of, 310 innervation of, 312b isometric stabilization functions, 311 notes, 311 miscellaneous information, 312 motion of, 311 name, indication of, 312 palpation of, 312b posterior view of, 310f pronunciation of, 310b reverse mover action, notes, 311 spinal joints, crossing, 310–311 standard mover action, notes, 310–311 structures, relationship, 312 Transversus abdominis (anterior abdominal wall), 377–378 actions, notes, 378 anterior view of, 377f arterial supply to, 378b attachments of, 377 concentric (shortening) mover actions, 377t derivation of, 377b eccentric antagonist function, 378 functions of, 377 innervation of, 378b isometric stabilization functions, 378 notes, 378 lateral view of, 377f

1243

miscellaneous information, 378 motion of, 378 palpation of, 378b pronunciation of, 377b reverse mover action, notes, 378 standard mover action, notes, 377–378 structures, relationship, 378 Transversus thoracis, 396–397 anterior view of, 396f arterial supply to, 396b attachments of, 396 concentric (shortening) mover actions, 396t derivation of, 396b eccentric antagonist functions, 396 functions of, 396 innervation of, 396b isometric stabilization functions, 396 miscellaneous information, 397 motion of, 396 palpation of, 397b pronunciation of, 396b reverse mover action, notes, 396 standard mover action, notes, 396 structures, relationship, 397 Trapezius, 96–99 actions, notes, 97–98 arterial supply to, 98b attachments of, 96 concentric (shortening) mover actions, 96t derivation of, 96b eccentric antagonist functions, 97. See also Lower trapezius Middle trapezius Upper trapezius entire muscle of, 96 functions of, 96–98 innervation of, 98b isometric stabilization functions, 97 miscellaneous information, 98–99 motions of, 97 palpation of, 98b posterior view of, 96f pronunciation of, 96b reverse mover action, notes, 97

1244

standard mover actions, notes, 96–97 structures, relationship, 98 Triangular-shaped muscle, demonstration of, 87f Triangularis sternae, 397 Triaxial ball-and-socket joint, example of, 39f Triaxial joints, 37 Triceps, 605, 607 Triceps brachii, 160–162 arterial supply to, 161b attachments of, 160 concentric (shortening) mover actions, 160t derivation of, 160b eccentric antagonist functions, 161 note, 161 elbow joint, crossing, 161 functions of, 160 innervation of, 161b isometric stabilization functions, 161 miscellaneous information, 162 motions of, 161 palpation of, 161b posterior views of, 160f pronunciation of, 160b reverse mover action, notes, 161 standard mover action, notes, 161 structures, relationship, 161 Triceps surae, 605, 607 Triceps surae group. See Gastrocnemius (Gastrocs) (triceps surae group) Soleus (triceps surae group) Trunk bones of anterior view of, 56f posterior view of, 58f bony landmarks of anterior view of, 56f posterior view of, 58f cross-sections of, 290, 290f–291f depression of, reverse action of, 105 elevation of, reverse action of, 105 flexion and extension of, lateral views of, 22f at glenohumeral joint

1245

neutral position of, 15f reverse action of, 15, 15f joint contralateral rotators of, 699f–700f extensors, posterior view of, 696f flexors, anterior view of, 695f ipsilateral rotators of, 699f–701f lateral flexors of, 697f–698f muscle attachment sites on anterior view of, 57f posterior view of, 59f regions, muscles of, right lateral views of, 118f retraction of, reverse action of, 105 reverse actions of, 126 right and left lateral flexion of, frontal plane, 22f right and left rotation of, transverse plane, 22f thoracolumbar spinal joints, 22 Trunk, muscles anterior views of deep views, 288f, 386f–387f, 387 superficial and intermediate views, 287f, 386, 386f–387f deeper muscles of, 385f lateral view of, 289, 289f posterior views of deeper views, 286f, 385 superficial and intermediate views, 285f, 384 right lateral view of deep view, 388f–389f, 389 superficial views, 388, 388f–389 superficial views of, 285f–286f, 384f–385f U Ulna anterior distal, 167 coronoid process of, 165 olecranon process of, 160 posterior proximal, 163 Ulnar, definition of, 4 Ulnar head, 165 Ulnar tuberosity, 155 Uniaxial hinge joint, example of, 36f

1246

Uniaxial joints, 33 Uniaxial pivot joint, example of, 37f Unipennate muscle, vastus lateralis as, 87f Upper back, posterior view deep view, 294, 294f intermediate view, 293, 293f superficial view, 292, 292f Upper body, orientation of, 27f–28f Upper chest, anterior view, 415 intermediate/deep views, 296, 296f superficial view, 295, 295f Upper extremities, 2f–3f, 667–685 bony landmarks on, atlas of, 40–51 joint action in, 11–19 muscle attachment on, atlas of, 40–51 reverse actions in, occurrence of, 81 Upper neck joints, longus capitis (crossing), 340 Upper spine contralateral rotation, reverse action, 284 flexion/extension, reverse action, 284 lower spine, relationship, 299–300 motions, consideration for, 323 Upper trapezius, 98 acromion process pulling, 96–97 eccentric antagonist functions of, 97 joints, crossing, 97 scapula attachment of, 96 Upward rotation/downward rotation, terms (pairs), 10 Upward tilt/downward tilt, terms (pairs), 10 V Vastus intermedius (quadriceps femoris group), 570–571 anterior views of, 570f arterial supply to, 570b attachments of, 570 concentric (shortening) mover actions, 570t derivation of, 570b eccentric antagonist function, 570 functions of, 570 notes, 570 innervation of, 570b

1247

isometric function, note, 570 isometric stabilization function, 570 miscellaneous information, 571 motion of, 570 palpation of, 571b pronunciation of, 570b reverse mover actions, notes, 570 standard mover actions, notes, 570 structures, relationship, 571 Vastus lateralis (quadriceps femoris group), 566–567 anterior views of, 566f arterial supply to, 567b attachments of, 566 concentric (shortening) mover actions, 566t derivation of, 566b eccentric antagonist function, 566 functions of, 566–567 notes, 567 innervation of, 567b isometric function, note, 567 isometric stabilization function, 567 miscellaneous information, 567 motion of, 566 palpation of, 567b pronunciation of, 566b reverse mover actions, notes, 566 standard mover actions, notes, 566 structures, relationship, 567 unipennate muscle, 87f Vastus medialis longus (VML), 569 Vastus medialis oblique (VMO), 569 Vastus medialis (quadriceps femoris group), 568–569 actions, notes, 568–569 anterior views of, 568f arterial supply to, 569b attachments of, 568 concentric (shortening) mover actions, 568t derivation of, 568b eccentric antagonist function, 568 functions of, 568 innervation of, 569b

1248

isometric function, note, 568 isometric stabilization function, 568 knee joint, crossing, 568 miscellaneous information, 569 motion of, 568 palpation of, 569b pronunciation of, 568b reverse mover actions, notes, 568 standard mover actions, note, 568 structures, relationship, 569 Vastus quadriceps femoris muscles, linea aspera (attachment), 562 Ventral, term, 2 Vertebrae three-four-segmental levels, spinous process, 316 Vertical fiber direction, 89 VML. See Vastus medialis longus (VML) VMO. See Vastus medialis oblique (VMO) W Wad of three, 193, 196 Whiplash, 327, 328, 331, 333, 335 Winged scapula, 107 Wrist extensor group extensor carpi radialis brevis. See Extensor carpi radialis brevis extensor carpi radialis longus. See Extensor carpi radialis longus extensor carpi ulnaris. See also Extensor carpi ulnaris right, muscles of, 180f Wrist flexor group flexor carpi radialis. See Flexor carpi radialis (wrist flexor group) flexor carpi ulnaris. See Flexor carpi ulnaris (wrist flexor group) palmaris longus. See Palmaris longus (wrist flexor group) right, muscles of, posterior view of, 177f Wrist joint extensors, posterior view of, 677f flexors, anterior view of, 677f hand at, 17, 17f radial deviators of, 678f ulnar deviators of, 679f Wrist joint, muscles of, 172–198 anterior views of deep view of, 176f intermediate view of, 175f

1249

superficial view of, 174f function, overview of, 173 lateral views of, 181f–183f medial view of, 181, 181f overview, 172–173 posterior views of deep views of, 179f superficial view of, 178f structure, overview of, 172–173 X Xiphoid process, 366, 396 Z Z-lines, 86 illustration of, 86f Zygomatic bone, 469 Zygomaticus (head), 466 Zygomaticus major, 471–472 anterior view of, 471f arterial supply to, 472b attachments of, 87, 471 concentric (shortening) mover actions, 471t derivation of, 471b functions of, 471–472 innervation of, 472b miscellaneous information, 472 motions of, 471 mover action notes, 471 palpation of, 472b pronunciation of, 471b structures, relationship, 472 zygomatic bone, attachment, 471 Zygomaticus minor, 469–470 anterior view of, 469f arterial supply to, 469b attachments of, 469 concentric (shortening) mover actions, 469t derivation of, 469b functions of, 469–470 innervation of, 469b

1250

miscellaneous information, 470 motions of, 469 mover action notes, 469 palpation of, 470b pronunciation of, 469b structures, relationship, 470

1251

Skeletal Muscles of the Body—Alphabetically Abductor Digiti Minimi Manus, 260 Abductor Digiti Minimi Pedis, 646 Abductor Hallucis, 644 Abductor Pollicis Brevis, 252 Abductor Pollicis Longus, 225 Adductor Brevis, 522 Adductor Group, 512 Adductor Hallucis, 658 Adductor Longus, 518 Adductor Magnus, 524 Adductor Pollicis, 268 Anconeus, 163 Anterior Abdominal Wall Muscles, 363 Anterior Scalene, 330 Articularis Genus, 572 Auricularis Group, 452 Biceps Brachii, 152 Biceps Femoris, 575 Brachialis, 155 Brachioradialis, 157 Buccinator, 483 Central Compartment Group, 266 Coracobrachialis, 123 Corrugator Supercilii, 457 Deep Distal Four Group, 224 Deep Lateral Rotator Group, 537 Deltoid, 119 Depressor Anguli Oris, 477 Depressor Labii Inferioris, 479 Depressor Septi Nasi, 463 Diaphragm, 398 Digastric, 426 Dorsal Interossei Manus, 276 Dorsal Interossei Pedis, 662 Erector Spinae Group, 299 Extensor Carpi Radialis Brevis, 194 Extensor Carpi Radialis Longus, 192 Extensor Carpi Ulnaris, 197 Extensor Digiti Minimi, 221 Extensor Digitorum, 218 Extensor Digitorum Brevis, 640 Extensor Digitorum Longus, 622 Extensor Hallucis Brevis, 642 Extensor Hallucis Longus, 624 Extensor Indicis, 234 Extensor Pollicis Brevis, 228 Extensor Pollicis Longus, 231 External Abdominal Oblique, 369 External Intercostals, 390 Fibularis Brevis, 602 Fibularis Longus, 600 Fibularis Tertius, 598

1252

Flexor Carpi Radialis, 185 Flexor Carpi Ulnaris, 190 Flexor Digiti Minimi Manus, 262 Flexor Digiti Minimi Pedis, 656 Flexor Digitorum Brevis, 648 Flexor Digitorum Longus, 626 Flexor Digitorum Profundus, 213 Flexor Digitorum Superficialis, 210 Flexor Hallucis Brevis, 654 Flexor Hallucis Longus, 628 Flexor Pollicis Brevis, 254 Flexor Pollicis Longus, 215 Gastrocnemius, 604 Geniohyoid, 430 Gluteal Group, 527 Gluteus Maximus, 528 Gluteus Medius, 531 Gluteus Minimus, 534 Gracilis, 520 Hamstring Group, 573 Hyoid Group, 424 Hypothenar Eminence Group, 258 Iliacus, 506 Iliocostalis, 302 Inferior Gemellus, 546 Infraspinatus, 137 Internal Abdominal Oblique, 373 Internal Intercostals, 393 Interspinales, 321 Intertransversarii, 323 Lateral Pterygoid, 420 Latissimus Dorsi, 128 Levator Anguli Oris, 473 Levatores Costarum, 406 Levator Labii Superioris, 467 Levator Labii Superioris Alaeque Nasi, 465 Levator Palpebrae Superioris, 456 Levator Scapulae, 102 Longissimus, 305 Longus Capitis, 340 Longus Colli, 338 Lumbricals Manus, 271 Lumbricals Pedis, 652 Masseter, 418 Medial Pterygoid, 422 Mentalis, 481 Middle Scalene, 332 Multifidus, 316 Mylohyoid, 428 Nasalis, 461 Obliquus Capitis Inferior, 356 Obliquus Capitis Superior, 358 Obturator Externus, 548 Obturator Internus, 544 Occipitofrontalis, 449 Omohyoid, 440 Opponens Digiti Minimi, 264 Opponens Pollicis, 256

1253

Orbicularis Oculi, 454 Orbicularis Oris, 485 Palmar Interossei, 273 Palmaris Brevis, 279 Palmaris Longus, 187 Pectineus, 516 Pectoralis Major, 125 Pectoralis Minor, 107 Piriformis, 539 Plantar Interossei, 660 Plantaris, 608 Platysma, 487 Popliteus, 583 Posterior Scalene, 334 Prevertebral Group, 336 Procerus, 459 Pronator Quadratus, 167 Pronator Teres, 165 Psoas Major, 502 Psoas Minor, 379 Quadratus Femoris, 550 Quadratus Lumborum, 360 Quadratus Plantae, 650 Quadriceps Femoris Group, 562 Rectus Abdominis, 366 Rectus Capitis Anterior, 342 Rectus Capitis Lateralis, 344 Rectus Capitis Posterior Major, 352 Rectus Capitis Posterior Minor, 354 Rectus Femoris, 564 Rhomboids Major and Minor, 100 Risorius, 475 Rotator Cuff Group, 133 Rotatores, 319 Sartorius, 510 Scalene Group, 328 Semimembranosus, 580 Semispinalis, 313 Semitendinosus, 578 Serratus Anterior, 104 Serratus Posterior Inferior, 404 Serratus Posterior Superior, 402 Soleus, 606 Spinalis, 308 Splenius Capitis, 346 Splenius Cervicis, 348 Sternocleidomastoid, 325 Sternohyoid, 434 Sternothyroid, 436 Stylohyoid, 432 Subclavius, 109 Subcostales, 408 Suboccipital Group, 350 Subscapularis, 141 Superior Gemellus, 542 Supinator, 169 Supraspinatus, 135 Temporalis, 416

1254

Temporoparietalis, 451 Tensor Fasciae Latae, 508 Teres Major, 131 Teres Minor, 139 Thenar Eminence Group, 250 Thyrohyoid, 438 Tibialis Anterior, 596 Tibialis Posterior, 610 Transversospinalis Group, 310 Transversus Abdominis, 377 Transversus Thoracis, 396 Trapezius, 96 Triceps Brachii, 160 Vastus Intermedius, 570 Vastus Lateralis, 566 Vastus Medialis, 568 Zygomaticus Major, 471 Zygomaticus Minor, 469

1255