Kinesiology
The Mechanics and Pathomechanics
of Human Movement
Second Edition
Carol A. Oatis, PT, PhD
Professor
Department...
Acquisitions Editor: Emily J. Lupash
Managing Editor: Andrea M. Klingler
Marketing Manager: Missi Carmen
Production Editor...
This book is dedicated to the memories of two people who have graced my life
and whose friendships have sustained me:
Mari...
FEATURES OF THE SECOND EDITION
I Clinical Relevance boxes allow us to emphasize the applicability of the information conta...
v
PAUL F. BEATTIE, PHD, PT, OCS
Clinical Associate Professor
Program in Physical Therapy
Department of Exercise Science
Sc...
ROSCOE C. BOWEN, PHD
Associate Professor
Campbellsville University
Campbellsville, KY
BETH KIPPING DESCHENES, PT, MS, OCS
...
This new edition of Kinesiology: The Mechanics and
Pathomechanics of Human Movement is a very timely arrival!
Hardly a day...
viii
A clinician in rehabilitation treats patients with many and var-
ied disorders, and usually goals of intervention inc...
ixPREFACE FROM THE FIRST EDITION
that focus on the mechanism producing the dysfunction. This
textbook allows the reader to...
x
The purposes of Kinesiology: The Mechanics and Pathome-
chanics of Human Movement were articulated in the
Preface to the...
xiPREFACE TO THE SECOND EDITION
These changes have been made because I firmly believe
that people with musculoskeletal dis...
Completion of this second edition required the work and
commitment of several individuals. Revising chapters is often
less...
xiii
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...
xiv
Unit 5: Spine Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....
Fd
θs
Fs
rs
rd
θd
MAd = rdsin(θd) = (20 cm)sin(5°) ≈ 2 cm
MAs = rssin(θs) = (2 cm)sin(80°) ≈ 2 cm
IBiomechanical Principle...
PART I
T
his part introduces the reader to the basic principles used throughout this book to understand the structure
and ...
Introduction to Biomechanical
Analysis
A N D R E W R . K A R D U N A , P H . D .
1
C H A P T E R
3
MATHEMATICAL OVERVIEW ....
4 Part I | BIOMECHANICAL PRINCIPLES
The units used in biomechanics can be divided into two
categories. First, there are th...
5Chapter 1 | INTRODUCTION TO BIOMECHANICAL ANALYSIS
to use degrees or radians. Additionally, some computer pro-
grams, suc...
6 Part I | BIOMECHANICAL PRINCIPLES
Although graphical representations of vectors are useful for
visualization purposes, a...
7Chapter 1 | INTRODUCTION TO BIOMECHANICAL ANALYSIS
another vector (C ϭ A ϫ B). The orientation of C is such that
it is mu...
8 Part I | BIOMECHANICAL PRINCIPLES
forces and moments applied to, and generated by, the body or
a particular body segment...
9Chapter 1 | INTRODUCTION TO BIOMECHANICAL ANALYSIS
Figure 1.6: Three-dimensional moment analysis. The moment
acting on th...
10 Part I | BIOMECHANICAL PRINCIPLES
Muscle Forces
As mentioned previously, there are three important param-
eters to cons...
11Chapter 1 | INTRODUCTION TO BIOMECHANICAL ANALYSIS
These analyses are useful, since they can be performed even
if the ma...
12 Part I | BIOMECHANICAL PRINCIPLES
around the body of interest. Consider a box that encompasses
both balls and part of t...
13Chapter 1 | INTRODUCTION TO BIOMECHANICAL ANALYSIS
Center of Gravity and Stability
Another example of a parallel force s...
14 Part I | BIOMECHANICAL PRINCIPLES
Advanced Musculoskeletal Problems
One of the most common uses of static equilibrium a...
15Chapter 1 | INTRODUCTION TO BIOMECHANICAL ANALYSIS
the requirements of a task. Options for solving the statically
indete...
16 Part I | BIOMECHANICAL PRINCIPLES
for other problems. Consequently, an alternative approach
is to simply document the j...
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0781774225 kinesiology 2e

  1. 1. Kinesiology The Mechanics and Pathomechanics of Human Movement Second Edition Carol A. Oatis, PT, PhD Professor Department of Physical Therapy Arcadia University Glenside, Pennsylvania With contributors Oatis_FM-i-xiv.qxd 4/18/07 5:46 PM Page i
  2. 2. Acquisitions Editor: Emily J. Lupash Managing Editor: Andrea M. Klingler Marketing Manager: Missi Carmen Production Editor: Sally Anne Glover Designer: Doug Smock Typesetter: International Typesetting and Composition Second Edition Copyright © 2009, 2004 Lippincott Williams & Wilkins, a Wolters Kluwer business. 351 West Camden Street 530 Walnut Street Baltimore, MD 21201 Philadelphia, PA 19106 Printed in India. All rights reserved. This book is protected by copyright. No part of this book may be reproduced or transmitted in any form or by any means, including as photocopies or scanned-in or other electronic copies, or utilized by any information storage and retrieval system without written permission from the copyright owner, except for brief quotations embodied in critical articles and reviews. Materials appearing in this book prepared by individuals as part of their official duties as U.S. government employees are not covered by the above-mentioned copyright. To request permission, please contact Lippincott Williams & Wilkins at 530 Walnut Street, Philadelphia, PA 19106, via email at permissions@lww.com, or via website at lww.com (products and services). 9 8 7 6 5 4 3 2 1 Library of Congress Cataloging-in-Publication Data Oatis, Carol A. Kinesiology : the mechanics and pathomechanics of human movement / Carol A. Oatis, with contributors.—2nd ed. p. ; cm. Includes bibliographical references and index. ISBN-13: 978-0-7817-7422-2 ISBN-10: 0-7817-7422-5 1. Kinesiology. 2. Human mechanics. 3. Movement disorders. I. Title. [DNLM: 1. Biomechanics. 2. Kinesiology, Applied. 3. Movement—physiology. 4. Movement Disorders. WE 103 O11k 2009] QP303.O38 2009 612.7’6—dc22 2007037068 DISCLAIMER Care has been taken to confirm the accuracy of the information present and to describe generally accepted practices. However, the authors, editors, and publisher are not responsible for errors or omissions or for any consequences from application of the information in this book and make no warranty, expressed or implied, with respect to the currency, completeness, or accuracy of the contents of the publication. Application of this information in a particular situation remains the professional responsibility of the practitioner; the clini- cal treatments described and recommended may not be considered absolute and universal recommendations. The authors, editors, and publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accor- dance with the current recommendations and practice at the time of publication. However, in view of ongoing research, changes in govern- ment regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any change in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new or infrequently employed drug. Some drugs and medical devices presented in this publication have Food and Drug Administration (FDA) clearance for limited use in restricted research settings. It is the responsibility of the health care provider to ascertain the FDA status of each drug or device planned for use in their clinical practice. To purchase additional copies of this book, call our customer service department at (800) 638-3030 or fax orders to (301) 223-2320. International customers should call (301) 223-2300. Visit Lippincott Williams & Wilkins on the Internet: http://www.lww.com. Lippincott Williams & Wilkins customer service representa- tives are available from 8:30 am to 6:00 pm, EST. Oatis_FM-i-xiv.qxd 4/18/07 5:46 PM Page ii
  3. 3. This book is dedicated to the memories of two people who have graced my life and whose friendships have sustained me: Marian Magee, PT, MS, a scholar–clinician whose respect for patient, student, and colleague can serve as a model for all practitioners. She demonstrated the value of interprofessional practice and mutual respect in her everyday interactions. She generously shared her wisdom, humor, and friendship with me. Steven S. Goldberg, JD, PhD, educator, author, negotiator, and colleague. He demanded much of his students and of himself. He was a generous colleague and friend who listened carefully, offered wise and thoughtful advice, and never failed to make me laugh. Oatis_FM-i-xiv.qxd 4/18/07 5:46 PM Page iii
  4. 4. FEATURES OF THE SECOND EDITION I Clinical Relevance boxes allow us to emphasize the applicability of the information contained in this textbook. These were one of the most popular aspects of the first edition and are intended to once again help focus information and enhance understanding. We have added new Clinical Relevance boxes throughout the text to provide additional examples of how a clinician can use the information in this text to understand a dysfunction or choose an intervention strategy. I Muscle Action tables introduce the discussion of muscle actions for each muscle. Actions of each muscle are now intro- duced in table format and include the conclusions drawn from the evidence regarding each action. The evidence is dis- cussed in detail after the table. This format allows the reader to identify at a glance which reported actions are supported by evidence, which are refuted, and which remain controversial. I Examining the Forces boxes and Muscle Attachment boxes explain and highlight more advanced mathematical con- cepts and provide muscle innervation and attachment information, respectively. The Muscle Attachment boxes now also include brief descriptions of palpation strategies. I New and updated artwork, including illustrations and photographs, have been created and revised specifically for this text. I Updated references continue to lend current, evidence-based support to chapter content and direct the student to further research resources ANCILLARIES I Approximately 150 video clips provide dynamic illustrations of concepts discussed in the textbook and demonstrate movement disorders that can occur as a result of impairments. The clips also include demonstrations of palpations of bony landmarks for each anatomical region. A video icon is used throughout the text to identify concepts with related video material. These added elements will help the reader integrate the relationships among structure, force, movement, and function and provide examples for students and teachers to analyze and discuss. I Laboratory Manuals for both students and instructors continue to offer activities for students to enhance learning and applications. The instructors’ laboratory manual includes solutions and brief discussions of most activities. The student manual for Chapter 1 now has 10 additional problems for students to test their analytical skills. The solutions are provided in the Instructors’ Manual. I The Instructors’ Guide is a chapter-by-chapter outline to assist instructors with preparing class lectures. This ancillary has been updated to include the materials added to the revised chapters. Oatis_FM-i-xiv.qxd 4/18/07 5:46 PM Page iv
  5. 5. v PAUL F. BEATTIE, PHD, PT, OCS Clinical Associate Professor Program in Physical Therapy Department of Exercise Science School of Public Health University of South Carolina Columbia, SC EMILY L. CHRISTIAN, PHD, PT Restore Management Co, LLC Pelham, AL JULIE E. DONACHY, PHD, PT Restore Management Co, LLC Pelham, AL Z. ANNETTE IGLARSH, PT, PHD, MBA Chair and Professor Department of Physical Therapy University of the Sciences in Philadelphia Philadelphia, PA ANDREW R. KARDUNA, PHD Assistant Professor Department of Exercise and Movement Science University of Oregon Eugene, OR MARGERY A. LOCKARD, PT, PHD Clinical Associate Professor Pathway to Health Professions Program Drexel University Philadelphia, PA JOSEPH M. MANSOUR, PHD Professor Department of Mechanical and Aerospace Engineering Case Western Reserve University Cleveland, OH THOMAS P. MAYHEW, PT, PHD Associate Professor and Chair Department of Physical Therapy School of Allied Health Professions Virginia Commonwealth University Richmond, VA STUART M. McGILL, PHD Professor Department of Spine Biomechanics University of Waterloo Waterloo, Canada SUSAN R. MERCER, PHD, BPHTY (HON), FNZCP Senior Lecturer Department of Anatomy & Developmental Biology The University of Queensland Brisbane, Australia PETER E. PIDCOE, PT, DPT, PHD Associate Professor Department of Physical Therapy School of Allied Health Professions Virginia Commonwealth University Richmond, VA NEAL PRATT, PHD, PT Emeritus Professor of Rehabilitation Sciences Drexel University Philadelphia, PA L. D. TIMMIE TOPOLESKI, PHD Professor Department of Mechanical Engineering University of Maryland, Baltimore County Baltimore, MD Contributors Oatis_FM-i-xiv.qxd 4/18/07 5:46 PM Page v
  6. 6. ROSCOE C. BOWEN, PHD Associate Professor Campbellsville University Campbellsville, KY BETH KIPPING DESCHENES, PT, MS, OCS Clinical Assistant Professor Department of Physical Therapy UT Southwestern Medical Center at Dallas Dallas, TX JEFF LYNN, PHD Assistant Professor Slippery Rock University Slippery Rock, PA CORRIE A. MANCINELLI, PT, PHD Associate Professor West Virginia University School of Medicine Morgantown, WV ROBIN MARCUS, PT, PHD, OCS Assistant Professor University of Utah Salt Lake City, UT LEE N MARINKO, PT, OCS, FAAOMPT Clinical Assistant Professor Boston University Sargent College of Health and Rehabilitative Sciences Boston, MA PATRICIA ANN McGINN, PHD, ATC, CSCS, LAT Assistant Professor of Athletic Training Nova Southeastern University Ft. Lauderdale, FL MARCIA MILLER SPOTO, PT, DC, OCS Associate Professor Nazareth College of Rochester Rochester, NY KEITH SPENNEWYN, MS Department Head Globe University Minneapolis, MN Reviewers vi Oatis_FM-i-xiv.qxd 4/18/07 5:46 PM Page vi
  7. 7. This new edition of Kinesiology: The Mechanics and Pathomechanics of Human Movement is a very timely arrival! Hardly a day goes by without a newspaper or magazine arti- cle extolling the values of exercise as a regular and enduring part of daily activity. Exercise can only become a sustained part of daily activity if it does not cause injury, but any exer- cise regimen creates the potential for injury to the muscu- loskeletal system. A challenge of exercise is finding the right balance between activity that enhances tissue health versus that which injures tissues. Optimizing the precision of move- ment is the key to achieving this balance. A clear understand- ing of the precision of movement and its contributing factors requires a thorough knowledge of kinesiology. In the field of physical therapy, the focus is on movement and movement- related dysfunctions or impairments; thus kinesiology is the science that provides physical therapy’s major foundation. Since the first kinesiological texts were published, the depth of material has grown immensely. Although knowledge in the fields of kinesiology, pathokinesiology, and kine- siopathology has increased substantially since the first kinesi- ological texts were published, the changes that may come from this new knowledge are not always reflected in clinical practice. All physical therapy students study kinesiology dur- ing their education, but the information is often not retained for application in the clinic, nor is it expanded by additional study. The emphasis on functional performance, prompted in part by reimbursement criteria, has detracted from improv- ing the depth of knowledge of impairments underlying the compromises in performance. Similarly, focus on treatment techniques applied to conditions without attention to the underlying movement dysfunction or the techniques’ effects compromises patient care and the status of the profession. Kinesiology: The Mechanics and Pathomechanics of Human Movement is a wonderful example of both the breadth and depth of the expansion of kinesiological knowledge and the clinical application of that knowledge. How fortunate for rehabilitation specialists that the information they need is readily available in this text. A strong emphasis is currently being placed on evidence- based practice. It may be a long time before even a small percentage of our treatment procedures have met level 3 evi- dence, and all evidence is only the best available at a given time. In the fields of physical therapy, occupational therapy, and athletic training, evidence for the best treatments and the methods used when addressing a person’s movement will change, just as it has for the physicians’ treatments of meta- bolic, cardiopulmonary, or neurological conditions. The improvement in the diagnosis and treatment of any body sys- tem is based on increased understanding of mechanisms and pathophysiology. We therefore have to continue to pursue an understanding of the mechanisms related to any body system that therapists, trainers, and exercise instructors address dur- ing their care, especially the systems involved in movement and its dysfunctions or impairments. Kinesiology: The Mechanics and Pathomechanics of Human Movement is truly unique in its thoroughly researched approach and provides convincing evidence to debunk old and inaccurate theories. This scientific approach to the clinical application of biomechanics means the infor- mation contained in this text is of particular importance to anyone involved in a rehabilitation specialty. I have had many opportunities to interact with therapists and trainers around the world, and I am struck by how few have a thorough understanding of basic kinesiology, such as an understanding of scapulohumeral rhythm, lumbar range of motion, and the determinants of gait. Coupled with this is a deficiency in the ability to observe movement and recognize subtle deviations and variations in normal patterns. I attribute this to an emphasis on both passive techniques and the lack of a strong basic knowledge about exercise program development. Kinesiology: The Mechanics and Pathomechanics of Human Movement is an invaluable resource for people seek- ing to correct this deficiency. Physical therapists must clearly demonstrate themselves to be movement experts and diagnos- ticians of movement dysfunctions. This book is the key to acquiring the knowledge that will enable students and practi- tioners to achieve the required level of expertise. The essentials of kinesiology are all present in this text. The basics of tissue biomechanics are well explained by experts in the field. The specifics of muscle action and the biomechanical basis of those actions, kinetics, and kinematics for each region of the body are analyzed and well described. This text is suited for readers who are interested in acquiring either an introductory and basic knowledge as well as those who want to increase their understanding of the more detailed and biomechanically focused knowledge of kinesiology. In selecting the authors for each chapter, Dr. Oatis has chosen well; each expert has pro- vided an excellent and relevant presentation of normal and abnormal kinesiology. This text is a must-have textbook for every student and reference for every practitioner of physical therapy, as well any other rehabilitation specialist or indi- vidual desiring knowledge of the biomechanical aspects of the human movement system. Shirley Sahrmann, PT, PhD, FAPTA Professor of Physical Therapy Departments of Physical Therapy, Neurology, Cell Biology, and Physiology Washington University School of Medicine—St. Louis St. Louis, Missouri Foreword vii Oatis_FM-i-xiv.qxd 4/18/07 5:46 PM Page vii
  8. 8. viii A clinician in rehabilitation treats patients with many and var- ied disorders, and usually goals of intervention include improving the individual’s ability to move [1]. Physical thera- pists prevent, identify, assess, and correct or alleviate move- ment dysfunction [3]. Similarly, occupational therapists work to restore or optimize “purposeful actions.” Optimizing movement and purposeful actions and treating movement disorders require a firm foundation in kinesiology, the sci- entific study of movement of the human body or its parts. To evaluate and treat movement disorders effectively, the clinician must address two central questions: What is required to perform the movement, and what effects does the movement produce on the individual? This textbook will help the reader develop knowledge and enhance skills that permit him or her to answer these questions. Two general factors govern the movement of a structure: the composition of the structure and the forces applied to it. A central principle in kinesiology is that the form or shape of a biological structure is directly influenced by its function. In fact, the relationship among movement, structure, and force is multidirectional. It is a complex interdependent relationship in which structure influences a body’s movement, its move- ment affects the forces applied to the structure, and the forces, in turn, influence the structure (see Figure). For example, the unique structure of the tibiofemoral joint produces complex three-dimensional motion of the knee, leading to intricate loading patterns (forces) on the tibia and femur that may con- tribute to structural changes and osteoarthritis later in life. Similarly, the type of movement or function and its intensity influence the forces sustained by a region, which in turn alter the structure. For instance, as muscles hypertrophy with exer- cise and activity, they stimulate bone growth at their attach- ment sites; physically active individuals tend to have more robust skeletons than inactive people. Function is interdependent among structure, force, and movement, so that structure affects both the forces on a struc- ture and the motion of that structure. Similarly, forces on a structure influence its structure and movement. Finally, movement affects both the structure and the forces sustained by the structure. An abnormal structure produces abnormal movement as well as abnormal forces on a structure, contributing to further alterations in structure. Excessive anteversion of the hip, for example, leads to torsional deformities at the knee, which may contribute to abnormal loading patterns at the hip as well as at the knee or foot, ultimately leading to pain and dysfunc- tion. The clinician needs to understand these interrelation- ships to design and direct the interventions used to restore or optimize human movement. An understanding of the relationship among structure, force, and movement requires a detailed image of the struc- ture of a region as well as a grasp of the basic laws of motion and the basic material properties of the tissues comprising the musculoskeletal system. The purposes of this textbook are to: • Provide a detailed analysis of the structures of the muscu- loskeletal system within individual functional regions. • Discuss how the structures affect function within each region. • Analyze the forces sustained at the region during function. This textbook will help the clinician recognize the rela- tionships between form and function, and abnormal structure and dysfunction. This foundation should lead to improved evaluation and intervention approaches to movement dys- function. This book uses terminology that is standard within health care to describe elements of disablement based on a classifi- cation of function developed by the World Health Organization (WHO) and others. In this classification scheme, a disease process, or pathology, alters a tissue, which then changes a structure’s function, producing an impairment. The impairment may cause an individual to have difficulty executing a task or activity, producing an activity limitation or dysfunction. When the dysfunction alters the individual’s ability to participate in life functions, the individual has par- ticipation restriction or a disability [2,4]. Although improving activity and participation are usually the primary objectives in rehabilitation, the WHO model of disease provides a vision of how clinicians can improve function not only by intervening directly at the level of the dysfunction, but also by addressing the underlying impairments. By under- standing the detailed structure and precise movement of an anatomical region, the clinician has tools to identify impair- ments and their influence on function and devise interventions Preface from the First Edition STRUCTURE FORCES MOVEMENT FUNCTION Oatis_FM-i-xiv.qxd 4/18/07 5:46 PM Page viii
  9. 9. ixPREFACE FROM THE FIRST EDITION that focus on the mechanism producing the dysfunction. This textbook allows the reader to examine normal structure and function and then consider the impairments that result from alterations in structure at anatomical regions, thus providing insight into the dysfunctions that may follow. For example, by understanding the normal glenohumeral rhythm of the shoul- der the clinician can appreciate the consequences of an unsta- ble scapula during arm trunk elevation and develop strategies to improve function. The needs of individual readers vary, and I have designed this book to allow readers to use it in ways that best meet their needs. Part I of this textbook introduces the reader to the principles of biomechanics and material properties and then examines the material properties of the major component tis- sues of the musculoskeletal system: bone, muscle, cartilage, and dense connective tissue. These chapters lay out the bio- mechanical foundation for examining human movement. Parts II through IV explore movement by anatomical region, investigating the detailed structure of the bones, joints, and muscles in that region and examining how their structures influence its movement. The ability of the region to sustain the forces generated during movements and function also is explored in Parts II through IV. Finally, Part V considers more global, or whole-body, movements, specifically posture and locomotion. Detailed discussions of forces at joints are presented in separate chapters so that readers may access that information as they need it. Although many readers will be interested in delving into the mathematical analyses used to determine forces on joint structures, others will find little need for such detail. The actual calculations are set apart in boxes that accompany the chapters. Conclusions based on the calcula- tions are contained within the chapters’ text so that readers can read the chapter and glean the essential information and return to the specific analyses as desired. Conclusions regarding structure, function, and dysfunc- tion in this text are based on the best available evidence, and each chapter is extensively referenced using both current and classic resources. I believe that the clinician is best equipped to evaluate current practice and to debunk long-held beliefs by having access to the classic resources that have established a concept and to the most current evidence that confirms or refutes standard impressions. Throughout this book, common clinical beliefs that are unsupported—or actually refuted—by strong evidence are explicitly identified so that the clinician hones the skill of healthy skepticism and develops the practice of demanding the evidence to support a concept. The book also notes where the evidence is meager or inconclusive or the conclusion is the opinion of the author. A strong, evidence-based background in kinesiology also helps develop clinician scholars who can contribute to our understanding of movement and movement dysfunction through the systematic, thoughtful observation and reporting of clinical phenomena. Despite the comment made long ago by a fellow graduate stu- dent that there was “nothing left to learn in gross anatomy,” there is much to be learned yet in functional anatomy and kinesiology. Today one can discover the errors of yesterday, And tomorrow obtain a new light on what seemed certain today. —Prayer of Maimonides References 1. Guide to Physical Therapy Practice, 2nd ed. Phys Ther 2001; 81: 6–746. 2. Nagi SZ: An epidemiology of disability among adults in the United States. Milbank Mem Fund Q Health Soc 1976; 54: 439–467. 3. Sahrmann SA: Moving precisely? Or taking the path of least resistance? Twenty-ninth Mary McMillan Lecture. Phys Ther 1998; 78: 1208–1218. 4. www3.who.int/icf/icftemplate.cfm?myurlintroduction.html% 20&mytitle=Introduction Oatis_FM-i-xiv.qxd 4/18/07 5:46 PM Page ix
  10. 10. x The purposes of Kinesiology: The Mechanics and Pathome- chanics of Human Movement were articulated in the Preface to the first edition and are unchanged in this new edition. They are to: • Provide a detailed analysis of the structures of the muscu- loskeletal system within individual functional regions • Discuss how the structures affect function within each region • Analyze the forces sustained at the region during function If the purposes of this textbook remain the same what is the point of a second edition? Is there a compelling reason to undertake a second edition? As I considered these questions, I recalled the conclusion of the Preface to the first edition, the Prayer of Maimonides. That prayer provides the impetus for a second edition: Today one can discover the errors of yesterday, And tomorrow obtain a new light on what seemed certain today. —Prayer of Maimonides A new edition provides the opportunity to correct “the errors of yesterday” and offer suggestions on where to look for “new light” tomorrow. The primary goal of this second edition of Kinesiology: The Mechanics and Pathomechanics of Human Movement is to ensure that it reflects the most current under- standing of kinesiology and biomechanics science. Chapter contributors reviewed the literature and updated chapters wherever necessary. We have also explicitly identified new knowledge and emerging areas of study or controversy. These additions will aid the reader in the quest for principles that underlie and drive best practice in the fields of rehabilitation and exercise. The second purpose of the revision has been to build on the strong clinical links available from the first edition. We provide additional examples of the interrelationships among structure, force, and movement and their effects on function (as described in the Preface from the First Edition). A strong and clear understanding of the interdependency of these fac- tors allows practitioners to recognize abnormal movement and systematically search for and identify the underlying pathome- chanics. By recognizing underlying mechanisms, practitioners will be able to intervene at the level of the mechanism to nor- malize or remediate dysfunction. One means to demonstrate these relationships and enhance the applicability of the infor- mation contained in this textbook is through the use of the Clinical Relevance boxes. We have added more of these boxes throughout the text to provide more direct examples of how structure, function, and forces affect movement, demonstrating ways a clinician can use the information in this text to understand a dysfunction or choose an interven- tion strategy. Updating the content to reflect new information and current research and practice also has helped us build on those clinical links. Although little has changed in the bio- mechanical principles outlined in Chapter 1, Dr. Karduna has clarified certain aspects of analysis. He has also provided additional “practice problems” for students to access on the associated website. Drs. Topoleski and Mansour have reor- ganized their chapters on basic material properties (Chapters 2) and on the properties of bone and cartilage (Chapters 3 and 5) and added clinical examples to help readers see the connections between engineering princi- ples and the clinical issues important to practitioners. Dr. Lockard has included emerging evidence regarding tissue response to activity gleaned from new research technolo- gies (Chapter 6). Drs. Pidcoe and McGill reorganized their chapters to help the readers utilize the information and understand the evidence (Chapters 27, 33, and 34). Dr. McGill also updated evidence and addressed some con- temporary issues. Drs. Beattie and Christian reviewed the literature to ensure that their chapters reflected an under- standing based on the most current scientific evidence (Chapters 32, 35, and 36). The final purpose of producing a second edition was to provide dynamic illustrations of the principles and con- cepts presented in this text. We all know that a “picture is worth a thousand words,” but kinesiology is the study of movement, and video provides benefits not found in still images. Recognizing that movement is the central theme of kinesiology and biomechanics, we have produced a DVD with approximately 150 video clips to provide action videos of concepts discussed in the textbook and demon- strate movement disorders that can occur as the result of impairments. These will help the reader integrate the rela- tionships among structure, force, movement, and function and provide examples for students and teachers to analyze and discuss. In the second edition we have also slightly modified the format of the chapters that address muscles of specific regions. The format change will help the reader quickly rec- ognize the strength of the evidence supporting the identified muscle actions. Actions of each muscle are now presented in table format, which includes the conclusions drawn from the evidence regarding each action. Preface to the Second Edition Oatis_FM-i-xiv.qxd 4/18/07 5:46 PM Page x
  11. 11. xiPREFACE TO THE SECOND EDITION These changes have been made because I firmly believe that people with musculoskeletal disorders or those who want to optimize their already normal function require the wisdom and guidance of individuals who have a clear, evidence-based understanding of musculoskeletal structure and function, a firm grasp of biomechanical principles, and the ability to observe and document movement. This sec- ond edition is meant to help further advance the ability of exercise and rehabilitation specialists to serve this role. — Carol A. Oatis Oatis_FM-i-xiv.qxd 4/18/07 5:46 PM Page xi
  12. 12. Completion of this second edition required the work and commitment of several individuals. Revising chapters is often less “fun” than writing the original piece. I want to thank the contributing authors for undertaking the project willingly and enthusiastically. Their efforts to identify changes in knowl- edge or perspective help ensure that this textbook remains at the forefront of kinesiologic science. I am also grateful to the contributors to the functional region chapters who also reviewed and revised their chapters as necessary. An extensive team at Lippincott Williams & Wilkins has provided invaluable developmental, managerial, and techni- cal support throughout the project. Peter Sabatini, Acquisitions Editor, helped me articulate my goals for the project and provided me the freedom and support to under- take new approaches. Andrea Klingler, Managing Editor, has been patient, persistent, and enthusiastic—frequently at the same time! She has held me to deadlines while simultaneously acknowledging the exciting challenges we were facing. She also brought together an exceptional team of talented indi- viduals to produce the accompanying DVD. This team included Freddie Patane, Art Director (video); Ben Kitchens, Director of Photography (video); and his wonderful crew: Andrew Wheeler, Gaffer, David Mattson, Grip, and Kevin Gallagher, Grip. These people made the production of the DVD not only exciting and successful but wonderfully fun. They provided extraordinary artistic insight and technical skill, but always remained focused on the learning objectives for each clip, wanting to ensure that each clip met the needs of the student and teacher. Brett McNaughton, the Art Director of Photography/Illustration, coordinated the models for video and photography and coordinated the photography shoot. His wisdom and experience helped make the whole process of producing videos and photography smooth and successful. I also want to thank all of the people who were filmed or photographed, including students and people with disabilities, who willingly participated so others could learn. I am indebted to three people who provided clinical insight, technical and organizational assistance, and moral support during the production of the DVD. Amy Miller, DPT, assisted with setting up the EMGs and monitored those activities. Her understanding of EMG and kinesiology was invaluable for the production of these clips. Additionally her enthusiasm for the entire project was a constant support. Marianne Adler, PT, worked with me to write the scripts for the video clips. Her understanding of the subject matter and her logical thinking yielded clear, concise scripts to describe the action and articulate the principles to be learned. Michele Stake, MS, DPT, coordinated the overall video and photography program, from finding and scheduling patients to helping to direct each shoot and ensuring that the video or photograph told the story we intended. Without these women’s commitment to the project and their friendship, I could not have completed the job. I had the wonderful good fortune of working again with Kim Battista, the talented artist who created the artwork in the original textbook. She contributed new art with the same skill and artistry as in the first edition. Similarly, Gene Smith, the photographer for the first edition, returned to work with me again and has provided new photographs that, like the ones in the first text, “tell the story.” These two artists together have created images that bring kinesiology and biomechanics alive. Jennifer Clements, Art Director, oversaw the entire art pro- gram and coordinated the production of new and revised art. She was wonderfully patient and receptive to the little “tweaks” we requested to optimize the art program. I am grateful to Jon McCaffrey, DPT, who provided essen- tial help in tracking down references as well as proofreading and offering helpful editorial suggestions, and to Luis Lopez, SPT, who played a pivotal role in final manuscript production. Again I wish to thank the Department of Physical Therapy and Arcadia University for their support during this process. I am particularly grateful for the support provided by Margaret M. Fenerty, Esq., who listened to my fears, tolerated my stress, and encouraged my efforts. Finally, I wish to thank all the students and colleagues who have used the first edition and provided insightful feedback and valuable suggestions that have informed this new edition. They helped identify errors, offered new ideas, and graciously told me what worked. I look forward to hearing new ideas and suggestions for this second edition. Acknowledgments xii Oatis_FM-i-xiv.qxd 4/18/07 5:47 PM Page xii
  13. 13. xiii Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .v Reviewers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .vi Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .vii Preface from the First Edition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .viii Preface to the Second Edition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .x Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xii PART I: BIOMECHANICAL PRINCIPLES 1 1 Introduction to Biomechanical Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3 2 Mechanical Properties of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 3 Biomechanics of Bone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36 4 Biomechanics of Skeletal Muscle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45 5 Biomechanics of Cartilage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69 6 Biomechanics of Tendons and Ligaments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .84 7 Biomechanics of Joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103 PART II: KINESIOLOGY OF THE UPPER EXTREMITY 117 Unit 1: Shoulder Unit: The Shoulder Complex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 8 Structure and Function of the Bones and Joints of the Shoulder Complex . . . . . . . . . . . . . . . . . . . . . . . . . .120 9 Mechanics and Pathomechanics of Muscle Activity at the Shoulder Complex . . . . . . . . . . . . . . . . . . . . . . .150 10 Analysis of the Forces on the Shoulder Complex during Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .188 Unit 2: Elbow Unit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 11 Structure and Function of the Bones and Noncontractile Elements of the Elbow . . . . . . . . . . . . . . . . . . . . .198 12 Mechanics and Pathomechanics of Muscle Activity at the Elbow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .219 13 Analysis of the Forces at the Elbow during Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .243 Unit 3: Wrist and Hand Unit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 14 Structure and Function of the Bones and Joints of the Wrist and Hand . . . . . . . . . . . . . . . . . . . . . . . . . . . .255 15 Mechanics and Pathomechanics of the Muscles of the Forearm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .294 16 Analysis of the Forces at the Wrist during Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .331 17 Mechanics and Pathomechanics of the Special Connective Tissues in the Hand . . . . . . . . . . . . . . . . . . . . . .339 18 Mechanics and Pathomechanics of the Intrinsic Muscles of the Hand . . . . . . . . . . . . . . . . . . . . . . . . . . . . .351 19 Mechanics and Pathomechanics of Pinch and Grasp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .370 PART III: KINESIOLOGY OF THE HEAD AND SPINE 389 Unit 4: Musculoskeletal Functions within the Head . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 390 20 Mechanics and Pathomechanics of the Muscles of the Face and Eyes . . . . . . . . . . . . . . . . . . . . . . . . . . . . .391 21 Mechanics and Pathomechanics of Vocalization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .412 22 Mechanics and Pathomechanics of Swallowing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .423 23 Structure and Function of the Articular Structures of the TMJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .438 24 Mechanics and Pathomechanics of the Muscles of the TMJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .452 25 Analysis of the Forces on the TMJ during Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .466 Contents Oatis_FM-i-xiv.qxd 4/18/07 5:47 PM Page xiii
  14. 14. xiv Unit 5: Spine Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 472 26 Structure and Function of the Bones and Joints of the Cervical Spine . . . . . . . . . . . . . . . . . . . . . . . . . . . . .473 27 Mechanics and Pathomechanics of the Cervical Musculature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .492 28 Analysis of the Forces on the Cervical Spine during Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .511 29 Structure and Function of the Bones and Joints of the Thoracic Spine . . . . . . . . . . . . . . . . . . . . . . . . . . . . .520 30 Mechanics and Pathomechanics of the Muscles of the Thoracic Spine . . . . . . . . . . . . . . . . . . . . . . . . . . . . .538 31 Loads Sustained by the Thoracic Spine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .556 32 Structure and Function of the Bones and Joints of the Lumbar Spine . . . . . . . . . . . . . . . . . . . . . . . . . . . . .563 33 Mechanics and Pathomechanics of Muscles Acting on the Lumbar Spine . . . . . . . . . . . . . . . . . . . . . . . . . .587 34 Analysis of the Forces on the Lumbar Spine during Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .601 35 Structure and Function of the Bones and Joints of the Pelvis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .620 36 Mechanics and Pathomechanics of Muscle Activity in the Pelvis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .654 37 Analysis of the Forces on the Pelvis during Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .676 PART IV: KINESIOLOGY OF THE LOWER EXTREMITY 685 Unit 6: Hip Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 686 38 Structure and Function of the Bones and Noncontractile Elements of the Hip . . . . . . . . . . . . . . . . . . . . . . .687 39 Mechanics and Pathomechanics of Muscle Activity at the Hip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .705 40 Analysis of the Forces on the Hip during Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .727 Unit 7: Knee Unit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 737 41 Structure and Function of the Bones and Noncontractile Elements of the Knee . . . . . . . . . . . . . . . . . . . . . .738 42 Mechanics and Pathomechanics of Muscle Activity at the Knee . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .767 43 Analysis of the Forces on the Knee during Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .791 Unit 8: Ankle and Foot Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 806 44 Structure and Function of the Bones and Noncontractile Elements of the Ankle and Foot Complex . . . . . .807 45 Mechanics and Pathomechanics of Muscle Activity at the Ankle and Foot . . . . . . . . . . . . . . . . . . . . . . . . . .838 46 Analysis of the Forces on the Ankle and Foot during Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .865 PART V: POSTURE AND GAIT 873 47 Characteristics of Normal Posture and Common Postural Abnormalities . . . . . . . . . . . . . . . . . . . . . . . . . . .875 48 Characteristics of Normal Gait and Factors Influencing It . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .892 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .919 CONTENTS Oatis_FM-i-xiv.qxd 4/18/07 5:47 PM Page xiv
  15. 15. Fd θs Fs rs rd θd MAd = rdsin(θd) = (20 cm)sin(5°) ≈ 2 cm MAs = rssin(θs) = (2 cm)sin(80°) ≈ 2 cm IBiomechanical Principles 1 Chapter 1: Introduction to Biomechanical Analysis Chapter 2: Mechanical Properties of Materials Chapter 3: Biomechanics of Bone Chapter 4: Biomechanics of Skeletal Muscle Chapter 5: Biomechanics of Cartilage Chapter 6: Biomechanics of Tendons and Ligaments Chapter 7: Biomechanics of Joints P A R T Oatis_Ch01_001-020.qxd 4/18/07 2:14 PM Page 1
  16. 16. PART I T his part introduces the reader to the basic principles used throughout this book to understand the structure and function of the musculoskeletal system. Biomechanics is the study of biological systems by the applica- tion of the laws of physics. The purposes of this part are to review the principles and tools of mechanical analysis and to describe the mechanical behavior of the tissues and structural units that compose the musculoskeletal system. The specific aims of this part are to I Review the principles that form the foundation of biomechanical analysis of rigid bodies I Review the mathematical approaches used to perform biomechanical analysis of rigid bodies I Examine the concepts used to evaluate the material properties of deformable bodies I Describe the material properties of the primary biological tissues constituting the musculoskeletal system: bone, muscle, cartilage, and dense connective tissue I Review the components and behavior of joint complexes By having an understanding of the principles of analysis in biomechanics and the biomechanical properties of the pri- mary tissues of the musculoskeletal system, the reader will be prepared to apply these principles to each region of the body to understand the mechanics of normal movement at each region and to appreciate the effects of impairments on the pathomechanics of movement. Oatis_Ch01_001-020.qxd 4/18/07 2:14 PM Page 2
  17. 17. Introduction to Biomechanical Analysis A N D R E W R . K A R D U N A , P H . D . 1 C H A P T E R 3 MATHEMATICAL OVERVIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 Units of Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 Trigonometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 Vector Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5 Coordinate Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7 FORCES AND MOMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7 Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 Moments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 Muscle Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 STATICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11 Newton’s Laws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11 Solving Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11 Simple Musculoskeletal Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 Advanced Musculoskeletal Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 KINEMATICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17 Rotational and Translational Motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17 Displacement, Velocity, and Acceleration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17 KINETICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 Inertial Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 Work, Energy, and Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 Friction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 A lthough the human body is an incredibly complex biological system composed of trillions of cells, it is subject to the same fundamental laws of mechanics that govern simple metal or plastic structures. The study of the response of biological systems to mechanical forces is referred to as biomechanics. Although it wasn’t rec- ognized as a formal discipline until the 20th century, biomechanics has been studied by the likes of Leonardo da Vinci, Galileo Galilei, and Aristotle. The application of biomechanics to the musculoskeletal system has led to a better under- standing of both joint function and dysfunction, resulting in design improvements in devices such as joint arthroplasty systems and orthotic devices. Additionally, basic musculoskeletal biomechanics concepts are important for clinicians such as orthopaedic surgeons and physical and occupational therapists. CHAPTER CONTENTS Oatis_Ch01_001-020.qxd 4/18/07 2:14 PM Page 3
  18. 18. 4 Part I | BIOMECHANICAL PRINCIPLES The units used in biomechanics can be divided into two categories. First, there are the four fundamental units of length, mass, time, and temperature, which are defined on the basis of universally accepted standards. Every other unit is considered a derived unit and can be defined in terms of these fundamental units. For example, velocity is equal to length divided by time and force is equal to mass multiplied by length divided by time squared. A list of the units needed for biomechanics is found in Table 1.1. Trigonometry Since angles are so important in the analysis of the muscu- loskeletal system, trigonometry is a very useful biomechanics tool. The accepted unit for measuring angles in the clinic is the degree. There are 360° in a circle. If only a portion of a circle is considered, then the angle formed is some fraction of 360°. For example, a quarter of a circle subtends an angle of 90°. Although in general, the unit degree is adopted for this text, angles also can be described in terms of radians. Since there are 2π radians in a circle, there are 57.3° per radian. When using a calculator, it is important to determine if it is set MATHEMATICAL OVERVIEW This section is intended as a review of some of the basic math- ematical concepts used in biomechanics. Although it can be skipped if the reader is familiar with this material, it would be helpful to at least review this section. Units of Measurement The importance of including units with measurements cannot be emphasized enough. Measurements must be accompanied by a unit for them to have any physical meaning. Sometimes, there are situations when certain units are assumed. If a cli- nician asks for a patient’s height and the reply is “5-6,” it can reasonably be assumed that the patient is 5 feet, 6 inches tall. However, that interpretation would be inaccurate if the patient was in Europe, where the metric system is used. There are also situations where the lack of a unit makes a number completely useless. If a patient was told to perform a series of exercises for two, the patient would have no idea if that meant two days, weeks, months, or even years. Biomechanics is often referred to as the link between structure and function. While a therapist typically evaluates a patient from a kinesiologic perspective, it is often not practical or necessary to perform a complete biomechanical analysis. However, a comprehensive knowledge of both biomechanics and anatomy is needed to understand how the musculoskeletal system functions. Biomechanics can also be useful in a critical evaluation of current or newly proposed patient evaluations and treatments. Finally, a fundamental understanding of biomechanics is necessary to understand some of the terminology associated with kinesiology (e.g., torque, moment, moment arms). The purposes of this chapter are to I Review some of the basic mathematical principles used in biomechanics I Describe forces and moments I Discuss principles of static analysis I Present the basic concepts in kinematics and kinetics The analysis is restricted to the study of rigid bodies. Deformable bodies are discussed in Chapters 2–6. The material in this chapter is an important reference for the force analysis chapters throughout the text. TABLE 1.1: Units Used in Biomechanics Quantity Metric British Conversion Length meter (m) foot (ft) 1 ft ϭ 0.3048 m Mass kilogram (kg) slug 1 slug ϭ 14.59 kg Time second (s) second (s) 1 s ϭ 1 s Temperature Celsius (ЊC) Fahrenheit (°F) °F ϭ (9/5) ϫ ЊC ϩ 32° Force newton (N ϭ kg ϫ m/s2 ) pound (lb ϭ slug ϫ ft/s2 ) 1 lb ϭ 4.448 N Pressure pascal (Pa ϭ N/m2 ) pounds per square inch (psi ϭ lb/in2 ) 1 psi ϭ 6895 Pa Energy joule (J ϭ N ϫ m) foot pounds (ft-lb) 1 ft-lb ϭ 1.356 J Power watt (W ϭ J/s) horsepower (hp) 1 hp ϭ 7457 W Oatis_Ch01_001-020.qxd 4/18/07 2:14 PM Page 4
  19. 19. 5Chapter 1 | INTRODUCTION TO BIOMECHANICAL ANALYSIS to use degrees or radians. Additionally, some computer pro- grams, such as Microsoft Excel, use radians to perform trigonometric calculations. Trigonometric functions are very useful in biomechanics for resolving forces into their components by relating angles to distances in a right triangle (a triangle containing a 90° angle). The most basic of these relationships (sine, cosine, and tan- gent) are illustrated in Figure 1.1A. A simple mnemonic to help remember these equations is sohcahtoa—sine is the opposite side divided by the hypotenuse, cosine is the adja- cent side divided by the hypotenuse, and tangent is the opposite side divided by the adjacent side. Although most cal- culators can be used to evaluate these functions, some impor- tant values worth remembering are sin (0°) ϭ 0, sin (90°) ϭ 1 (Equation 1.1) cos (0°) ϭ 1, cos (90°) ϭ 0 (Equation 1.2) tan (45°) ϭ 1 (Equation 1.3) Additionally, the Pythagorean theorem states that for a right triangle, the sum of the squares of the sides forming the right angle equals the square of the hypotenuse (Fig. 1.1A). Although less commonly used, there are also equations that relate angles and side lengths for triangles that do not contain a right angle (Fig. 1.1B). Vector Analysis Biomechanical parameters can be represented as either scalar or vector quantities. A scalar is simply represented by its magnitude. Mass, time, and length are examples of scalar quantities. A vector is generally described as having both magnitude and orientation. Additionally, a complete description of a vector also includes its direction (or sense) and point of application. Forces and moments are examples of vector quantities. Consider the situation of a 160-lb man sitting in a chair for 10 seconds. The force that his weight is exerting on the chair is represented by a vector with magni- tude (160 lb), orientation (vertical), direction (downward), and point of application (the chair seat). However, the time spent in the chair is a scalar quantity and can be represented by its magnitude (10 seconds). To avoid confusion, throughout this text, bolded notation is used to distinguish vectors (A) from scalars (B). Alternative notations for vectors found in the literature (and in class- rooms, where it is difficult to bold letters) include putting a line under the letter (A), a line over the letter – A, or an arrow over the letter S A. The magnitude of a given vector (A) is represented by the same letter, but not bolded (A). By far, the most common use of vectors in biomechanics is to represent forces, such as muscle, joint reaction and resist- ance forces. These vectors can be represented graphically with the use of a line with an arrow at one end (Fig. 1.2A). The length of the line represents its magnitude, the angular posi- tion of the line represents its orientation, the location of the arrowhead represents its direction, and the location of the line in space represents its point of application. Alternatively, this same vector can be represented mathematically with the use of either polar coordinates or component resolution. Polar coordinates represent the magnitude and orientation of the vector directly. In polar coordinates, the same vector would be 5 N at 37° from horizontal (Fig. 1.2B). With compo- nents, the vector is resolved into its relative contributions from both axes. In this example, vector A is resolved into its components: AX ϭ 4 N and AY ϭ 3 N (Fig. 1.2C). It is often useful to break down vectors into components that are aligned with anatomical directions. For instance, the x and y axes may correspond to superior and anterior directions, respectively. b a c θ b a c θψ φ A B Trigonometric functions: Pythagorean theorem: a2 + b2 = c2 Law of cosines: a2 + b2 – 2abcos(θ) = c2 Law of cosines: sin (θ) = b c cos (θ) = a c atan (θ) = b b = a = c sin(ψ) sin(φ) sin(θ) Figure 1.1: Basic trigonometric relationships. These are some of the basic trigonometric relationships that are useful for biome- chanics. A. A right triangle. B. A general triangle. θ Direction Magnitude Orientation Point of application A A = 5 N θ = 37° Ax = 4 N Ay = 3 N Ax Ay A. Graphical B. Polar coordinates C. Components Figure 1.2: Vectors. A. In general, a vector has a magnitude, orientation, point of application, and direction. Sometimes the point of application is not specifically indicated in the figure. B. A polar coordinate representation. C. A component representation. Oatis_Ch01_001-020.qxd 4/18/07 2:14 PM Page 5
  20. 20. 6 Part I | BIOMECHANICAL PRINCIPLES Although graphical representations of vectors are useful for visualization purposes, analytical representations are more convenient when adding and multiplying vectors. Note that the directional information (up and to the right) of the vector is also embedded in this information. A vector with the same magnitude and orientation as the vector repre- sented in Figure 1.2C, but with the opposite direction (down and to the left) is represented by AX ϭ Ϫ4 N and AY ϭ Ϫ3 N, or 5 N at 217°. The description of the point-of-application information is discussed later in this chapter. VECTOR ADDITION When studying musculoskeletal biomechanics, it is common to have more than one force to consider. Therefore, it is important to understand how to work with more than one vector. When adding or subtracting two vectors, there are some important properties to consider. Vector addition is commutative: A ϩ B ϭ B ϩ A (Equation 1.4) A Ϫ B ϭ A ϩ (ϪB) (Equation 1.5) Vector addition is associative: A ϩ (B ϩ C) ϭ (A ϩ B) ϩ C (Equation 1.6) Unlike scalars, which can just be added together, both the magnitude and orientation of a vector must be taken into account. The detailed procedure for adding two vectors (A ϩ B ϭ C) is shown in Box 1.1 for the graphical, polar coor- dinate, and component representation of vectors. The graphi- cal representation uses the “tip to tail” method. The first step is to draw the first vector, A. Then the second vector, B, is drawn so that its tail sits on the tip of the first vector. The vec- tor representing the sum of these two vectors (C) is obtained by connecting the tail of vector A and the tip of vector B. Since vector addition is commutative, the same solution would have been obtained if vector B were the first vector. When using polar coordinates, the vectors are drawn as in the graphical method, and then the law of cosines is used to determine the magnitude of C and the law of sines is used to determine the direction of C (see Fig 1.1 for definitions of these laws). For the component resolution method, each vector is bro- ken down into its respective x and y components. The compo- nents represent the magnitude of the vector in that direction. The x and y components are summed: CX ϭ AX ϩ BX (Equation 1.7) CY ϭ AY ϩ BY (Equation 1.8) The vector C can either be left in terms of its components, CX and CY , or be converted into a magnitude, C, using the Pythagorean theorem, and orientation, ␪, using trigonometry. This method is the most efficient of the three presented and is used throughout the text. VECTOR MULTIPLICATION Multiplication of a vector by a scalar is relatively straightfor- ward. Essentially, each component of the vector is individually multiplied by the scalar, resulting in another vector. For example, if the vector in Figure 1.2 is multiplied by 5, the result is AX ϭ 5 ϫ 4 N ϭ 20 N and AY ϭ 5 ϫ 3 N ϭ 15 N. Another form of vector multiplication is the cross product, in which two vectors are multiplied together, resulting in ADDITION OF TWO VECTORS EXAMINING THE FORCES BOX 1.1 B A C A2 + B2 – 2ABcos(θ + φ) = C2 C = 5.4N θφ φ θ θ B A C B A A θ ψ φ C BBy Ay Ax Cx Bx Cy Law of cosines: sin ψ = sin (θ + φ) ψ = 31° Ax = Acos(θ) = 4N Ay = Asin(θ) = 3N Bx = -Bcos(φ) = -2N By = Bsin(φ) = 2N Cx = Ax + Bx = 2N Cy = Ay + By = 5N A = 5N B = 2.8N θ = 37° φ = 45° Law of sines: Therefore, the angle that C makes with a horizontal axis is 68° (= ψ + θ) CB Addition of 2 vectors: A + B Case A: Graphical Case B: Polar Case C: Components y x Oatis_Ch01_001-020.qxd 4/18/07 2:14 PM Page 6
  21. 21. 7Chapter 1 | INTRODUCTION TO BIOMECHANICAL ANALYSIS another vector (C ϭ A ϫ B). The orientation of C is such that it is mutually perpendicular to A and B. The magnitude of C is calculated as C ϭ A ϫ B ϫ sin (␪), where ␪ represents the angle between A and B, and ϫ denotes scalar multiplication. These relationships are illustrated in Figure 1.3. The cross product is used for calculating joint torques later in this chapter. Coordinate Systems A three-dimensional analysis is necessary for a complete rep- resentation of human motion. Such analyses require a coordi- nate system, which is typically composed of anatomically aligned axes: medial/lateral (ML), anterior/posterior (AP), and superior/inferior (SI). It is often convenient to consider only a two-dimensional, or planar, analysis, in which only two of the three axes are considered. In the human body, there are three perpendicular anatomical planes, which are referred to as the cardinal planes. The sagittal plane is formed by the SI and AP axes, the frontal (or coronal) plane is formed by the SI and ML axes, and the transverse plane is formed by the AP and ML axes (Fig. 1.4). The motion of any bone can be referenced with respect to either a local or global coordinate system. For example, the motion of the tibia can be described by how it moves with respect to the femur (local coordinate system) or how it moves with respect to the room (global coordinate system). Local coordinate systems are useful for understanding joint function and assessing range of motion, while global coordinate systems are useful when functional activities are considered. Most of this text focuses on two-dimensional analyses, for several reasons. First, it is difficult to display three- dimensional information on the two-dimensional pages of a book. Additionally, the mathematical analysis for a three- dimensional problem is very complex. Perhaps the most important reason is that the fundamental biomechanical prin- ciples in a two-dimensional analysis are the same as those in a three-dimensional analysis. It is therefore possible to use a simplified two-dimensional representation of a three- dimensional problem to help explain a concept with minimal mathematical complexity (or at least less complexity). FORCES AND MOMENTS The musculoskeletal system is responsible for generating forces that move the human body in space as well as prevent unwanted motion. Understanding the mechanics and patho- mechanics of human motion requires an ability to study the B A C Magnitude of C: C = ABsin(θ) Orientation of C: perpendicular to both A and B θ Figure 1.3: Vector cross product. C is shown as the cross product of A and B. Note that A and B could be any two vectors in the indicated plane and C would still have the same orientation. Figure 1.4: Cardinal planes. The cardinal planes, sagittal, frontal, and transverse, are useful reference frames in a three- dimensional representation of the body. In two-dimensional analyses, the sagittal plane is the common reference frame. Superior Inferior Posterior AnteriorTransverse Frontal Sagittal Lateral Medial Oatis_Ch01_001-020.qxd 4/18/07 2:14 PM Page 7
  22. 22. 8 Part I | BIOMECHANICAL PRINCIPLES forces and moments applied to, and generated by, the body or a particular body segment. Forces The reader may have a conceptual idea about what a force is but find it difficult to come up with a formal definition. For the pur- poses of this text, a force is defined as a “push or pull” that results from physical contact between two objects. The only exception to this rule that is considered in this text is the force due to gravity, in which there is no direct physical contact between two objects. Some of the more common force genera- tors with respect to the musculoskeletal system include muscles/ tendons, ligaments, friction, ground reaction, and weight. A distinction must be made between the mass and the weight of a body. The mass of an object is defined as the amount of matter composing that object. The weight of an object is the force acting on that object due to gravity and is the product of its mass and the acceleration due to gravity (g ϭ 9.8 m/s2 ). So while an object’s mass is the same on Earth as it is on the moon, its weight on the moon is less, since the acceleration due to gravity is lower on the moon. This dis- tinction is important in biomechanics, not to help plan a trip to the moon, but for ensuring that a unit of mass is not treated as a unit of force. As mentioned previously, force is a vector quantity with magnitude, orientation, direction, and a point of application. Figure 1.5 depicts several forces acting on the leg in the frontal plane during stance. The forces from the abductor and adduc- tor muscles act through their tendinous insertions, while the hip joint reaction force acts through its respective joint center of rotation. In general, the point of application of a force (e.g., tendon insertion) is located with respect to a fixed point on a body, usually the joint center of rotation. This information is used to calculate the moment due to that force. Moments In kinesiology, a moment (M) is typically caused by a force (F) acting at a distance (r) from the center of rotation of a seg- ment. A moment tends to cause a rotation and is defined by the cross product function: M ϭ r ϫ F. Therefore, a moment is represented by a vector that passes through the point of interest (e.g., the center of rotation) and is perpendicular to both the force and distance vectors (Fig. 1.6). For a two- dimensional analysis, both the force and distance vectors are in the plane of the paper, so the moment vector is always directed perpendicular to the page, with a line of action through the point of interest. Since it has only this one orien- tation and line of action, a moment is often treated as a scalar quantity in a two-dimensional analysis, with only magnitude and direction. Torque is another term that is synonymous with a scalar moment. From the definition of a cross product, the magnitude of a moment (or torque) is calculated as M ϭ r ϫ F ϫ sin (␪). Its direction is referred to as the direction in which it would tend to cause an object to rotate (Fig. 1.7A). Although there are several different distances that can be used to connect a vector and a point, the same moment is calculated no matter which distance is selected (Fig. 1.7B). The distance that is perpendicular to the force vector is referred to as the moment arm (MA) of that force (r2 in Fig. 1.7B). Since the sine of 90° is equal to 1, the use of a moment arm simplifies the calculation of moment to FAB FJR FAD FGR FAB - Abductor muscle force FAD - Adductor muscle force FJR - Joint reaction force FGR - Ground reaction force Figure 1.5: Vectors in anatomy. Example of how vectors can be combined with anatomical detail to represent the action of forces. Some of the forces acting on the leg are shown here. Oatis_Ch01_001-020.qxd 4/18/07 2:14 PM Page 8
  23. 23. 9Chapter 1 | INTRODUCTION TO BIOMECHANICAL ANALYSIS Figure 1.6: Three-dimensional moment analysis. The moment acting on the elbow from the force of the biceps is shown as a vector aligned with the axis of rotation. F, force vector; r, distance from force vector to joint COR; M, moment vector. Figure 1.7: Continued F M r F r Rotation θ M = Frsin(θ) r1 r2 r3 r4 r1 θ1 M = Fr1sin(θ1) M = Fr2sin(θ2) = F*MA M = Fr3sin(θ3) M = Fr4sin(θ4) θ2 θ3 θ4 F A B M ϭ MA ϫ F. The moment arm can also be calculated from any distance as MA ϭ r ϫ sin (␪). Additionally, although there are four separate angles between the force and distance vec- tors, all four angles result in the same moment calculation (Fig. 1.7C). The examples in Figures 1.6 and 1.7 have both force and moment components. However, consider the situation in Figure 1.8A. Although the two applied forces create a moment, they have the same magnitude and orientation but opposite directions. Therefore, their vector sum is zero. This is an example of a force couple. A pure force couple results in rotational motion only, since there are no unbalanced forces. In the musculoskeletal system, all of these conditions are seldom met, so pure force couples are rare. In general, muscles are responsible for producing both forces and moments, thus resulting in both translational and rotational motion. However, there are examples in the human body in which two or more muscles work in concert to produce a moment, such as the upper trapezius and serratus anterior (Fig. 1.8B). Although these muscles do not have identical magnitudes or orientations, this situation is frequently referred to as a force couple. Oatis_Ch01_001-020.qxd 4/18/07 2:14 PM Page 9
  24. 24. 10 Part I | BIOMECHANICAL PRINCIPLES Muscle Forces As mentioned previously, there are three important param- eters to consider with respect to the force of a muscle: ori- entation, magnitude, and point of application. With some care, it is possible to measure orientation and line of action from cadavers or imaging techniques such as magnetic res- onance imaging (MRI) and computed tomography (CT) [1,3]. This information is helpful in determining the func- tion and efficiency of a muscle in producing a moment. As an example, two muscles that span the glenohumeral joint, the supraspinatus and middle deltoid, are shown in Box 1.2. From the information provided for muscle orientation and point of application in this position, the moment arm of the deltoid is approximately equal to that of the supraspinatus, even though the deltoid insertion on the humerus is much farther away from the center of rotation than the supraspinatus insertion. MOMENT ARMS OF THE DELTOID (MAd ) AND THE SUPRASPINATUS (MAs ) EXAMINING THE FORCES BOX 1.2 Figure 1.7: Two-dimensional moment analysis. A. Plantar flexion moment created by force at the Achilles tendon. B. Note that no matter which distance vector is chosen, the value for the moment is the same. C. Also, no matter which angle is chosen, the value for the sine of the angle is the same, so the moment is the same. r1 θ2 θ4 F θ1 θ3 sin(θ1) = sin(θ3) = sin(180º – θ1) = sin(θ2) = sin(180º – θ1) = sin(θ4) r C Figure 1.8: Force couples. Distinction between an idealized force couple (A) and a more realistic one (B). Even though the scapular example given is not a true force couple, it is typically referred to as one. COR, center of rotation. ⎯F1 ⎯F1 ⎯F2 ⎯F2 Serratus anterior Upper trapezius COR COR d d A. Idealized B. Actual ⎯F1 = ⎯F2- ⎯F1 ϶ ⎯F2- Fd θs Fs rs rd θd MAd = rdsin(θd) = (20 cm)sin(5°) ≈ 2 cm MAs = rssin(θs) = (2 cm)sin(80°) ≈ 2 cm y x MUSCLE FORCES: In addition to generating moments that are responsible for angular motion (rotation), muscles also produce forces that can cause linear motion (translation). Clinical Relevance (continued) Oatis_Ch01_001-020.qxd 4/18/07 2:15 PM Page 10
  25. 25. 11Chapter 1 | INTRODUCTION TO BIOMECHANICAL ANALYSIS These analyses are useful, since they can be performed even if the magnitude of a muscle’s force is unknown. However, to understand a muscle’s function completely, its force magni- tude must be known. Although forces can be measured with invasive force transducers [13], instrumented arthroplasty systems [6], or simulations in cadaver models [9], there are currently no noninvasive experimental methods that can be used to measure the in vivo force of intact muscles. Consequently, basic concepts borrowed from freshman physics can be used to predict muscle forces. Although they often involve many simplifying assumptions, such methods can be very useful in understandin