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Fundamental Concepts

CONTENTS

Introduction

3

Spinal Nerve and Muscle Charts

26-29

Manual Muscle Testing

4, 5

Treatment Fundamentals

30, 31

Objectivity in Muscle Testing

6-8

Neuromuscular Problems

32, 33

Musculoskeletal System

9

Musculoskeletal Problems

34, 35

Joints: Definitions & Classification, Chart

10

Treatment Procedures

36

Gross Structure of Muscle

11

Treatment Modalities

37

Range of Motion and Muscle Length Testing

12

Polio: Factors Influencing Treatment

38

Classification for Strength Tests

13

Polio and Postpolio Muscle Tests

39A13

Strength Testing Procedures

14-17

Late Complications of Polio

44

Suggested Order of Muscle Tests

18

Polio/Postpolio Suggested Readings

45

Grading Strength and Key to Muscle Grading

19-24

References

46, 47

Nerve Plexuses

25

The underlying philosophy of this book is that there is a continuing need to"get back to basics." This philosophy is especially pertinent in this era of time-limited treatments and advancing technology.

Muscle function, body mechanics, and simple treatment procedures do not change. With respect to muscu-loskeletal problems, the underlying purposes of treatment have been, and continue to be, to restore and maintain appropriate range of motion, good alignment and muscle balance.

It is essential that the practitioner choose and effectively perform tests that aid in solving problems, whether to provide a differential diagnosis, establish or change treatment procedures, improve function, or relieve pain. Of paramount importance, for students and clinicians, is the ability to think critically, to demand objectivity, and to use the caution and care needed for appropriate, accurate and meaningful tests and measurements.

The role of prevention of musculoskeletal problems is destined to become an increasingly important issue in the future. Health practitioners can play an effective role in promoting wellness if they are aware of adverse effects of muscle imbalance, faulty alignment, and improper exercise.

A thorough understanding of muscle problems and painful conditions associated with poor posture will enable practitioners to develop safe and effective home programs for their patients. The costs to society for treatment of common problems, such as low back pain, have reached a critical point. Many cases of low back pain are related to faulty posture and are corrected or alleviated by restoring good alignment.

The timeless importance of effective musculoskele-tal testing is evident in the last segment of Chapter 1. The unique presentation of muscle test results for a post polio patient over a fifty year period demonstrates the durability of testing and grading.

MANUAL MUSCLE TESTING

This book emphasizes muscle balance and the effects of imbalance, weakness, and contracture on alignment and function. It presents the underlying principles involved in preserving muscle testing as an art, and the precision in testing necessary to preserve it as a science.

The art of muscle testing involves the care with which an injured part is handled, the positioning to avoid discomfort or pain, the gentleness required in testing very weak muscles, and the ability to apply pressure or resistance in a manner that permits the subject to exert the optimal response.

Science demands rigorous attention to every detail that might affect the accuracy of muscle testing. Failure to take into account apparently insignificant factors may alter test results. Findings are useful only if they are accurate. Inaccurate test results mislead and confuse and may lead to a misdiagnosis with serious consequences. Muscle testing is a procedure that depends on the knowledge, skill, and experience of the examiner who should not betray, through carelessness or the lack of skill, the confidence that others rightfully place in this procedure.

Muscle testing is an integral part of physical examination. It provides information, not obtained by other procedures, that is useful in differential diagnosis, prognosis and treatment of neuromuscular and muscu-loskeletal disorders.

Many neuromuscular conditions are characterized by muscle weakness. Some show definite patterns of muscle involvement; others show spotty weakness without any apparent pattern. In some cases weakness is symmetrical, in others, asymmetrical. The site or level of peripheral lesion may be determined because the muscles distal to the site of the lesion will show weakness or paralysis. Careful testing and accurate recording of test results will reveal the characteristic findings and aid in diagnosis.

Musculoskeletal conditions frequently show patterns of muscle imbalance. Some patterns are associated with handedness, some with habitually poor posture. Muscle imbalance may also result from occupational or recreational activities in which there is persistent use of certain muscles without adequate exercise of opposing muscles. Imbalance that affects body alignment is an important factor in many painful postural conditions.

The technique of manual muscle testing is basically the same for cases of faulty posture as for neuromuscu-lar conditions, but the range of weakness encountered in faulty posture is less because grades below fair are uncommon. The number of tests used in cases of faulty posture is also less.

Muscle imbalance distorts alignment and sets the stage for undue stress and strain on joints, ligaments, and muscles. Manual muscle testing is the tool of choice to determine the extent of imbalance.

Examination to determine muscle length and strength is essential before prescribing therapeutic exercises because most of these exercises are designed either to stretch short muscles or to strengthen weak muscles.

Muscle length testing is used to determine whether the muscle length is limited or excessive, i.e., whether the muscle is too short to permit normal range of motion, or stretched and allowing too much range of motion. When stretching is indicated, tight muscles should be stretched in a manner that is not injurious to the part or to the body as a whole. Range of motion should be increased to permit normal joint function unless restriction of motion is a desired end result for the sake of stability.

Muscle strength testing is used to determine the capability of muscles or muscle groups to function in movement and their ability to provide stability and support.

Many factors are involved in the problems of weakness and return of strength. Weakness may be due to nerve involvement, disuse atrophy, stretch weakness, pain, or fatigue. Return of muscle strength may be due to recovery following the disease process, return of nerve impulse, after trauma and repair, hypertrophy of unaffected muscle fibers, muscular development resulting from exercises to overcome disuse atrophy, or return of strength after stretch and strain have been relieved.

Muscle weakness should be treated in accordance with the basic cause of weakness. If due to lack of use, then exercise; if due to overwork and fatigue, then rest; if due to stretch and strain, then relief of stretch and strain before the stress of additional exercise is thrust upon the weak muscle.

Every muscle is a prime mover in some specific action. No two muscles in the body have exactly the same function. When any one muscle is paralyzed, stability of the part is impaired or some exact movement is lost. Some of the most dramatic evidence of muscle function comes from observing the effects of loss of the ability to contract as seen in paralyzed muscles, or the effect of excessive shortening as seen in a muscle contracture and the resultant deformity.

The muscle testing described in this book is directed towards examination of individual muscles insofar as is practical. The overlap of muscle actions, as well as the interdependence of muscles in movement, is well recognized by those involved in muscle testing. Because of this close relationship in functions, accurate testing of individual muscles requires strict adherence to the fundamental principles of muscle testing and rules of procedure.

Fundamental components of manual muscle testing are test performance and evaluation of muscle strength and length. To become proficient in these procedures one must possess a comprehensive and detailed knowledge of muscle function. This knowledge must include an understanding of joint motion because length and strength tests are described in terms of joint movements and positions. It must also include knowledge of the agonistic and antagonistic actions of muscles and their role in fixation and in substitution. In addition, it requires the ability to palpate the muscle or its tendon, to distinguish between normal and atrophied contour, and to recognize abnormalities of position or movement.

One who possesses a comprehensive knowledge of the actions of muscles and joints can learn the techniques necessary to perform the tests. Experience is necessary to detect the substitution movements that occur whenever weakness exists; and practice is necessary to acquire skill for performing length and strength tests, and for accurately grading muscle strength.

This book emphasizes the need to "get back to basics" in the study of body structure and function. For musculoskeletal problems, accomplishing this entails a review of the anatomy and function of joints, and of the origins, insertions and actions of muscles. It includes an understanding of the fundamental principles upon which evaluation and treatment procedures are based.

As a textbook, it stresses the importance of muscle tests, postural examinations, assessment of objective findings, musculoskeletal evaluation, and treatment. In a condition that is primarily musculoskeletal, the evaluation may constitute and determine a diagnosis. In a condition not primarily musculoskeletal, the evaluation may contribute to a diagnosis.

OBJECTIVITY A N D RELIABILITY IN MUSCLE TESTING

There is increasing demand for objectivity regarding muscle testing measurements. With the high cost of medical care, the economics of reimbursement requires documentation that improvement has resulted from treatment. There is a demand for numbers as proof. The more gradual the improvement, the more important the numbers become so that even minimal changes can be documented.

Many advocate the use of instrumentation to eliminate the subjective component of manual muscle tests. Several questions, however, have not yet been adequately answered. To what extent can the subjectivity inherent in manual muscle testing be eliminated by the use of instrumentation? How do new problems and variables introduced by instruments affect the accuracy, reliability and validity of muscle tests?

The value of objective measurements obtained through the use of present-day machines must be weighed against their limited usefulness, cost and complexity.

Length tests, if performed with precision, can provide objective data through the use of simple devices such as goniometers to measure angles, and rulers or tape measures to measure distance.

Strength tests cannot rely on such simple devices. The problems are very different when measuring strength. Objectivity is based on the examiner's ability to palpate and observe the tendon or muscle response in very weak muscles, and to observe the capability of a muscle to move a part through partial or full range of motion in the horizontal plane, or to hold the part in an antigravity position.

Visual evidence of objectivity extends to an observer as well as to the examiner. An observer can see a tendon that becomes prominent (i.e., a trace grade), movement of the part in the horizontal plane (i.e., a poor grade), and a part being held in an antigravity position (i.e., a fair grade). Even the fair+ grade, which is based on holding the antigravity position against slight pressure by the examiner, is easy to identify. For these grades of strength, mechanical devices are not applicable or necessary as aids to obtain objectivity.

The grades of strength that remain are the good and normal grades, as identified in manual muscle testing. In addition, a wide range of strength is measured above the grade of normal. To the extent that determining the higher potentials of muscle strength is necessary, useful, and cost-effective, machines may play a role.

Under controlled research conditions, isokinetic machines can help in obtaining valuable information. At present, however, their usefulness in the clinic is limited. Problems occur both in testing muscle strength and in exercising. One problem with machines is providing adequate stabilization to control variables and to ensure the standardization of testing techniques. Tests by ma* chines lack specificity and substitution occurs. In addition to the high cost of the machines, setting up patients is time-consuming; both are important factors when considering cost-effectiveness of the testing procedures.

It is generally agreed that tests done by the same examiner are the most reliable. Interestingly, the same holds true for numerous testing devices that have no "subjective" component. For example, many institutions require that successive bone-density scans always be done on the same machine. Too much variability occurs between similar machines to accurately track an individual's progress. Different machines of the same make and model are unable to produce reliable and comparable results. Even on the same machine an accuracy variant of up to or more than 3% can be found (Dr. David Zackson, personal communication, 2004).

Electromyography (EMG) is another important research tool, but its usefulness in muscle strength testing is questionable. According to Gregory Rash, "EMG data cannot tell us how strong the muscle is, if one muscle is stronger than another muscle, if the contraction is a concentric or eccentric contraction, or if the activity is under voluntary control by the individual" (1).

The search continues for a suitable handheld device that can provide objective data regarding the amount of force that is used during manual muscle strength testing. The problem with a handheld device is that it comes between the examiner and the part being tested. It also interferes with use of the examiner's hand. The examiner's hand must not be encumbered for positioning the part, for controlling the specific direction of pressure, and for applying pressure with the fingers, palm, or whole hand as needed. (Someday, there may be a glove that is sensitive enough to register pressure without interfering with the use of the hand.)

Handheld devices measure the amount of force exerted manually by the examiner. They are not suitable for measuring the higher levels of maximum effort by the subject.

With many different types of dynamometers on the market, it is almost impossible to standardize tests or to establish the reliability of tests. The introduction of new and "better" devices further complicates and compromises all previous testing procedures. The statement by Alvin Toffler that "[ujnder today's competitive conditions, the rate of product innovation is so swift that almost before one product is launched the next generation of better ones appears" may well apply to this as well as other fields (2).

A review of the literature regarding dynamometers reveals some of the problems associated with the use of these devices. A study of intertester reliability concluded that "the handheld dynamometer shows limited reliability when used by two or more testers" (3). Two studies have demonstrated good intratester reliability using handheld dynamometers (4, 5). However, "hand-held dynamometers . . . may underestimate a patient's true maximal isometric strength, due to difficulties in stabilization of the device" (6).

Examiner strength presents another variable in handheld dynamometer reliabilities. Work by Marino et al. identified examiner strength as the reason for discrepancy between two examiners testing hip abductor strength (7). The examiner's strength affects the stability of the handheld dynamometer when used with stronger subjects (5). This problem was also related to gender differences by Mulroy et al. The subject's maximal knee extension force, measured by a handheld dynamometer, was accurate only for the male examiner testing female patients (8).

It is evident that the variety of devices used and the many variables involved preclude the establishment of norms for muscle grading. According to Jules Rothstein, "there may be a danger that fascination with new technology will lead to the clouding of sound clinical judgment" (9).

After a decade of scientific review, Newton and Waddell concluded that the "judgment of the clinician appears to be more accurate in determining effort of the patient, than evaluating the results from the machines" (10).

As tools, our hands are the most sensitive, fine-tuned instruments available. One hand of the examiner positions and stabilizes the part adjacent to the part being tested. The other hand determines the pain-free range of motion, guides the tested part into precise test position, and gives the appropriate amount of pressure to determine strength. All the while, this instrument we call the hand is hooked up to the most marvelous computer ever created—the human mind—which can store valuable and useful information on the basis of which judgments about evaluation and treatment can be made. Such information contains objective data that are obtained without sacrificing the art and science of manual muscle testing to the demand for objectivity.

HISTORICAL NOTE

In 1941, while engaged in a research study for the Foundation for Infantile Paralysis, the senior author of this text designed a handheld device to measure the force applied by the examiner during manual muscle testing. The Foundation turned over the design to Dr. W. Beasley in Washington, D.C., who made a prototype. One year later, this device was presented at a symposium on polio. Figure A shows the pressure-sensitive pad in the palm of the hand from which force was transmitted to the gauge on the dorsum of the hand, shown in Figure B. This may have been one of the first handheld dynamometers.

CLASSIC KENDALL

One of the unique features of this text is the preservation of more than half a century of postural analyses and the careful evaluation of muscle balance as it relates to function and pain. Many of the photographs provide outstanding historic examples of postural faults that are genuine rather than posed.

It is essential that every practitioner develop effective problem-solving skills that will result in choosing and performing appropriate and accurate tests to provide meaningful data for the establishment of a successful treatment plan. Anatomy has not changed, but time constraints in some current practice settings have resulted in testing "shortcuts" that can lead to an incorrect diagnosis.

The Kendalls were early pioneers in performing clinical research as part of their continual quest for knowledge regarding how muscle length and weakness relate to painful conditions. A study performed in the early 1950s compared hundreds of "normal" subjects—cadets, physicians, physical therapists and student nurses (age range, 18-40 years)—with patients who had low back pain (LBP). That study led to a better understanding of common muscle imbalances in the general population as compared to those in patients with LBP. In addition, it helped to define the differences in these imbalances between males and females. The data from this clinical study are included in the table below.

Male (% [n])

Female (% [n])

100 LBP Patients

36 Physicians

275 Cadets

Case Findings

307 Student Nurses

50 Physical Therapists

100 LBP Patients

58% (58)

25% (9)

5% (14)

Weakness in "upper" anterior abdominals

44% (135)

52% (26)

8 1 % (81 )

69% (69)

31% (11)

33% (91)

Weakness in "lower" anterior abdominals

79% (243)

72% (36)

96% (96)

71% (71)

45% (16)

10% (28)

Limitation of forward flexion

5% (15)

10% (5)

48% (48)

71% (71)

77% (28)

26% (72)

Right gluteus medius weakness

40% (123)

76% (38)

90% (90)

15% (15)

3% (1)

5% (14)

Left gluteus medius weakness

5.5% (17)

10% (5)

6% (6)

0% (0)

0% (0)

0.3% (1)

Bilateral gluteus medius weakness

5.5% (17)

0% (0)

12% (12)

The musculoskeletal system is composed of striated muscles, various types of connective tissue and the skeleton. This system provides the essential components for strength, flexibility and stability in weight bearing.

The bones of the skeleton are joined together by ligaments, which are strong, fibrous bands or sheets of connective tissue. They are flexible but not extensible. Some ligaments limit motion to such an extent that the joint is immovable; some allow freedom of movement. Ligaments are classified as capsular, extracapsular and intracapsular. They contain nerve endings that are important in reflex mechanisms and in the perception of movement and position. Ligaments may differ from the standpoint of mechanical function. For example, a collateral ligament is an extracapsular type that remains taut throughout the range of joint motion, whereas a cruciate ligament (as in the knee joint) becomes slack during some movements and taut during others.

Skeletal muscle fibers are classified primarily into two types: type I (red slow twitch) and type II (white fast twitch). The two types of fibers are intermingled in most muscles. Usually, however, one type predominates, with the predominant type depending on the contractile properties of the muscle as a whole. Type I fibers seem to predominate in some postural muscles, such as the erector spinae and soleus. Type II fibers often predominate in limb muscles, where rapid, powerful forces are needed. Variability does occur, however, in these ratios in the population, especially as related to development and aging.

Skeletal muscles constitute approximately 40% of body weight and are attached to the skeleton by aponeu-roses, fasciae, or tendons.

Aponeuroses are sheets of dense connective tissue and are glistening white in color. They furnish the broad origins for the latissimus dorsi muscles. The external and internal oblique muscles are attached to the Iinea alba by means of aponeuroses. The palmaris longus inserts into and tenses the palmar aponeurosis.

Fascia is of two types: superficial, which lies beneath the skin and permits free movement of the skin, and deep, which envelopes, invests and separates muscles. Some deep fascia furnish attachments for muscles. For example, the iliotibial tract is a strong band of deep fasciae that provides attachments for the tensor fasciae latae into the tibia and for the gluteus maximus into the femur and tibia. The thoracolumbar fascia furnishes attachment for the transversus abdominis.

Tendons are white, fibrous bands that attach muscles to bones. They have great tensile strength but are practically inelastic and resistant to stretch. Tendons have few blood vessels but are supplied with sensory nerve fibers that terminate in organs of Golgi near the musculotendinous junction. In injuries that involve a severe stretch, the muscle most likely is affected, and sometimes the tendinous attachment to the bone is affected. For example, the peroneus brevis attachment at the base of the fifth metatarsal may be disrupted in an inversion injury of the foot. Tendons can also rupture. When the Achilles tendon ruptures, there is retraction of the gastrocnemius and soleus muscles with spasm and acute pain.

JOINTS: DEFINITIONS AND CLASSIFICATION

JOINTS

Stedman's Concise Dictionary defines a joint as follows:

Joint in anatomy, the place of union, usually more or less movable, between two or more bones and classified into three general morphologic types: fibrous joints, cartilaginous joints, and synovial joints (11).

In this edition, the following definition adheres to the meaning as stated above with the addition of how the joints are named:

Joint is defined as a skeletal, bone to bone connection, held together by fibrous, cartilaginous or synovial tissue. Joints are named according to the bones mat are held together.

For some joints, the bones are held so close together that no appreciable motion occurs. They provide great stability. Some joints provide stability in one direction and freedom of motion in the opposite direction, and some provide freedom of motion in all directions.

Joints that provide little or no movement are those that hold the two sides of the body together. The sagittal suture of the skull is considered to be an immovable joint, held together by a strong fibrous membrane. The sacroiliac joint and the symphysis pubis are considered to be slightly movable and are held together by strong fibrocartilaginous membranes.

Most joints fall into the category of freely movable joints held together by synovial membranes. The elbow and knee joints are essentially hinge joints. The structure of the joint surfaces and the strong lateral and medial ligaments limit sideways movements, and posterior ligaments and muscles limit extension. Hence, there is stability and strength in the extended position. In contrast, the shoulder joints are movable in all directions and have less stability.

CLASSIFICATION OF JOINTS

According to Type of

Tissue

Joint

Movement

Example

Fibrous

Synarthrosis

Syndesmosis

Immovable

Tibiofibular (distal)

Sutura

Immovable

Suture of skull

Gomphosis

Immovable

Tooth in bony socket

Cartilaginous

Amphiarthrosis

Synchondrosis

Slightly movable

First sternocostal

Symphysis

Slightly movable

Symphysis pubis

Synovial

Diarthrosis

Spheroid or ball-and-socket

All joint movements

Shoulder and hip

Ginglymus

Flexion and extension

Elbow

Modified ginglymus

Flexion, extension, and slight rotation

Knee and ankle

Ellipsoid or condyloid

All except rotation and opposition

Metacarpopha-langeal and metatar-sophalangeal

Trochoid or pivot

Supination, pronation, and rotation

Atlantoaxial and radioulnar

Reciprocal-reception or saddle

AH except rotation

Calcaneocuboid and carpometacarpal

Plane or gliding

Gliding

Head of fibula with lateral condyle of tibia

Combined ginglymus and gliding

Flexion, extension, and gliding

Temporomandibular

TYPES OF STRUCTURE

The gross structure of muscle helps to determine muscle action and affects the way that a muscle responds to stretching. Muscle fibers are arranged in bundles called fasciculi. The arrangement of fasciculi and their attachments to tendons varies anatomically. Two main divisions are found in gross structure: fusiform (or spindle) and pennate. A third arrangement, fan-shaped, is probably a modification of the other two but has a distinct significance clinically.

In fusiform structure, fibers are arranged essentially parallel to the line from origin to insertions, and the fasciculi terminate at both ends of the muscle in flat tendons. In pennate structure, fibers are inserted obliquely into the tendon or tendons that extend the length of the muscle on one side (i.e., unipennate) or through the belly of the muscle (i.e., bipennate).

In all probability, the long fusiform muscle is the most vulnerable to stretch. The joint motion is in the same direction as the length of the fiber, and each lon gitudinal component is dependent on every other one.

The pennate muscles are probably the least vulnerable to stretch, both because the muscle fiber is oblique to the direction of joint motion and because the fibers and fasciculi are short and parallel and, thereby, are not dependent on other segments for continuity in action.

The fan-shaped muscle has advantages and disadvantages of both of the above. It might be thought of as a group of muscles arranged side by side to form a fan-shaped unit. Each segment is independent in that it has its own origin with a common insertion. For example, in the fan-shaped pectoralis major, the clavicular part may be unaffected but the sternal part paralyzed in a spinal cord lesion.

According to Gray's Anatomy, the "arrangement of fasciculi is correlated with the power of the muscles. Those with comparatively few fasciculi, extending the length of the muscle, have a greater range of motion but not as much power. Penniform muscles, with a large number of fasciculi distributed along their tendons, have greater power but smaller range of motion" (14).

FUSIFORM

FAN-SHAPED

PENNATE

Tibialis anterior

Tibialis anterior

Metatarsal I Medial cuneiform

Gluteus minimus

Gluteus minimus

Metatarsal I Medial cuneiform

[j ¿^Flexor hallucis longus

RANGE OF MOTION AND MUSCLE LENGTH TESTING

RANGE OF JOINT MOTION AND RANGE OF MUSCLE LENGTH

The phrases "range of joint motion" and "range of muscle length" have specific meanings. Range of joint motion refers to the number of degrees of motion that are present in a joint. Descriptions of joints and the joint measurement charts include references to normal ranges of joint motion. Range of muscle length, also expressed in terms of degrees of joint motion, refers to the length of the muscle.

For muscles that pass over one joint only, the range of joint motion and range of muscle length will measure the same. Both may be normal, limited, or excessive.

In some instances, when measuring range of joint motion, it is necessary to allow the muscle to be slack over one joint to determine the full range of joint motion in the other. For example, when measuring the range of knee joint flexion, the hip is flexed to allow the rectus femoris to be slack over the hip joint and permit full range of joint motion at the knee. When measuring range of hip joint flexion, the knee is flexed to allow the hamstrings to be slack over the knee joint and permit full range of joint motion at the hip.

MEASURING JOINT MOTION AND MUSCLE LENGTH

It is easier and more accurate to use a measuring device that permits the stationary arm of the caliper to rest on the table and the examiner to place the movable arm in line with or parallel to the axis of the humerus or femur, as the case may be. The fulcrum will be shifted to permit this change, but the angle will remain the same—as if the stationary arm were held parallel to the table along the trunk in line with the shoulder joint or hip joint.

CORRELATION BETWEEN JOINT RANGE AND MUSCLE LENGTH

An interesting correlation exists between the total range of joint motion and the range of muscle length chosen as a standard for hamstring and hip flexor length tests. In each case, the muscle length adopted as a standard is approximately 80% of the total range of joint motion of the two joints over which the muscles pass.

The following are the joint ranges considered to be normal:

Hip—10° extension, 125° flexion, for a total of 135°

Knee—0° extension, 140° flexion, for a total of 140°

Total of both joints—275°

Hip Flexor Length Test Used as a Standard: Supine, with the low back and sacrum flat on the table, hip joint extended, and hip flexors elongated 135° over the hip joint. With the knee flexed over the end of the table at an angle of 80°, the two-joint hip flexors are elongated 80° over the knee joint, for a total of 215°. Thus, 215° divided by the 275° is 78.18%, and range of muscle length is 78% of total joint range.

Hamstring Length Test Used as a Standard: Supine, with the low back and sacrum flat on the table and straight-leg raising to an 80° angle with table. Hamstrings are elongated 140° over the knee by full extension and 80° over the hip joint by the straight-leg raising, for a total of 220°. Thus, 220° divided by 275° is 80%, and range of muscle length is 80% of total joint range.

MUSCLE LENGTH TESTS

Muscle length tests are performed to determine whether the range of muscle length is normal, limited, or excessive. Muscles that are excessive in length are usually weak and allow adaptive shortening of opposing muscles; muscles that are too short are usually strong and maintain opposing muscles in a lengthened position.

Muscle length testing consists of movements that increase the distance between origin and insertion, thereby elongating muscles in directions opposite those of the muscle actions.

Accurate muscle length testing usually requires that the bone of origin be in a fixed position while the bone of insertion moves in the direction of lengthening the muscle. Length tests use passive or active-assisted movements to determine the extent to which a muscle can be elongated.

PASSIVE INSUFFICIENCY I

As defined by O'Connell and Gardner:

Passive insufficiency of a muscle is indicated whenever a full range of motion of any joint or joints that the muscle crosses is limited by that muscle's length, rather than by the arrangement of ligaments or structures of the joint itself (12).

As defined by Kendall et al.

Passive insufficiency. Shortness of a two-joint (or multi-joint) muscle; the length of the muscle is not sufficient to permit normal elongation over both joints simultaneously, e.g., short hamstrings (13).

Note: By both definitions, the term passive insufficiency refers to lack of muscle length. In contrast, the term active insufficiency refers to lack of muscle strength.

ACTIVE INSUFFICIENCY

As defined by O'Connell and Gardner:

If a muscle which crosses two or more joints produces simultaneous movement at all of the joints that it crosses, it soon reaches a length at which it can no longer generate a useful amount of force. Under these conditions, the muscle is said to be actively insufficient. An example of such insufficiency occurs when one tries to achieve full hip extension with maximal knee flexion. The two-joint hamstrings are incapable of shortening sufficiently to produce a complete range of motion of both joints simultaneously (12).

As defined by Kendall et al.:

Active insufficiency. The inability of a Class III or IV two-joint (or multijoint) muscle to generate an effective force when placed in a fully shortened position. The same meaning is implied by the expression "the muscle has been put on a slack" (13).

The two definitions above only apply to two-joint or multijoint muscles. However, the statement that one-joint muscles exhibit their greatest strength at completion of range of motion has appeared in all four editions of Kendall's Muscles: Testing and Function. Knowing where the muscle exhibits its greatest strength in relation to the range of motion is of utmost importance for determining test position. After careful analysis, it is evident that there are four classifications.

TEST FOR STREN AT END RANGE WITH MAXIM

Class I

One-joint muscles that actively shorten (i.e., concentric contraction) through range to completion of joint motion and exhibit maximal strength at completion of range (i.e., short and strong).

Examples: Triceps, medial and lateral heads; deltoid; pectoralis major; three one-joint thumb muscles; gluteus maximus; iliopsoas; and soleus.

iTH—CLASS I & II: AL SHORTENING OF MUSCLE

Class II

Two-joint and multijoint muscles that act like one-joint muscles by actively shortening over both or all joints simultaneously and exhibiting maximal strength at completion of range (i.e., short and strong).

Examples: Sartorius, tibialis anterior and posterior, and peroneus longus, brevis, and tertius.

TEST FOR STRENGTH—CLASS III & IV: AT MIDRANGE OF OVERALL LENGTH OF MUSCLE

Class III

Two-joint muscles that shorten over one-joint and lengthen over the other to provide midrange of the overall muscle length for maximal contraction and strength (as represented by the length-tension curve).

Examples: Rectus femoris, hamstrings, and gastrocne-mius.

Class IV

Two-joint or multijoint muscles that physiologically act in one direction but are prevented from overshortening by the coordinated action of synergic muscles.

Example of Two-Joint Muscle: The biceps act to flex the shoulder joint and the elbow joint. If acting to flex both joints simultaneously, the muscle would become overshortened. To prevent this, the shoulder extensors, as synergists, extend the shoulder joint, thereby lengthening the biceps over the shoulder joint when the elbow is maximally flexed by the biceps.

Example of Multijoint Muscle: If acting in one direction by flexing the wrists and fingers simultaneously, the finger flexors and extensors would overshorten and become actively insufficient. Nature, however, prevents this from happening. In forceful flexion of fingers, such as when making a fist, the flexors shorten over the finger joints but are prevented from shortening over their entire length by the synergic action of wrist extensors that hold the wrist in moderate extension, thereby lengthening the flexors over wrist joint for them to forcefully shorten over the finger joints.

BASIC RULES OF PROCEDURE THAT APPLY TO MUSCLE STRENGTH TESTING

Place the subject in a position that offers the best fixation of the body as a whole (usually supine, prone, or side-lying).

Stabilize the part proximal to the tested part or, as in the case of the hand, adjacent to the tested part. Stabilization is necessary for specificity in testing.

Place the part to be tested in precise antigravity test position, whenever appropriate, to help elicit the desired muscle action and aid in grading.

Use test movements in the horizontal plane when testing muscles that are too weak to function against gravity. Use test movements in antigravity positions for most trunk muscle tests in which body weight offers sufficient resistance.

Apply pressure directly opposite the line of pull of the muscle or the muscle segment being tested. Like the antigravity position, the direction of pressure helps to elicit the desired muscle action.

Apply pressure gradually but not too slowly, allowing the subject to "get set and hold." Apply uniform pressure; avoid localized pressure that can cause discomfort.

Use a long lever whenever possible, unless contraindicated. The length of the lever is determined by the location of the pressure along the lever arm. Better discrimination of strength for purposes of grading is obtained through use of a long lever.

Use a short lever if the intervening muscles do not provide sufficient fixation for use of a long lever.

The order in which muscles are tested is largely a matter of choice, but it generally is arranged to avoid frequent and unnecessary changes of position for the subject. Muscles that are closely related in position or action tend to appear in a testing order in sequence in order to distinguish test differences. As a general rule, length testing precedes strength testing. When the specific order of tests is important, it is so indicated in the text. (See suggested order of muscle tests, p. 18.)

In all muscle testing, the comfort of the patient and the intelligent handling of affected muscles are important factors. In some instances, the comfort of the patient or the condition of the affected muscles will necessitate some modification of the test position. For example, insisting on an antigravity position may result in absurd positioning of a patient. Side-lying, which offers the best test position for several muscles, may be uncomfortable and result in strain of other muscles.

TERMS USED IN DESCRIPTION OF MUSCLE STRENGTH TESTS

Descriptions of the muscle tests in Chapters 4 through 7 are presented under the headings of Patient, Fixation, Test, and Pressure. This chapter discusses each of these topics in detail to point out its particular significance in relation to accurate muscle testing.

Patient

In the description of each muscle test, this heading is followed by the position in which the patient is placed to accomplish the desired test. The position is important in relation to the test in two respects. First, insofar as practical, the position of the body should permit function against gravity for all muscles in which gravity is a factor in grading. Second, the body should be placed in such a position that the parts not being tested will remain as stable as possible. (This point is discussed further under Fixation.)

Fixation

This heading refers to the firmness or stability of the body or body part, which is necessary to insure an accurate test of a muscle or muscle group. Stabilization (i.e., holding steady or holding down), support (i.e., holding up), and counterpressure (i.e., equal and opposite pressure) are all included under fixation, which implies holding firm. Fixation will be influenced by the firmness of the table, body weight, and in some tests, the muscles that furnish fixation.

Adequate fixation depends, to a great extent, on the firmness of the examining table, which offers much of the necessary support. Testing and grading of strength will not be accurate if the table on which the patient lies has a thick, soft pad or soft mattress that "gives" as the examiner applies pressure.

Body weight may furnish the necessary fixation. Because the weight of the body is an important factor in offering stability, the horizontal position, whether supine, prone, or side-lying, offers the best fixation for most tests. In the extremities, the body part that is proximal to the tested part must be stable.

The examiner may stabilize the proximal part in tests of finger, wrist, toe and foot muscles, but in other tests, the body weight should help to stabilize the proximal part. In some instances, the examiner may offer fixation in addition to the weight of the proximal part. There may be a need to hold a part firmly down on the table so that the pressure applied on the distal part (plus the weight of that part) does not displace the weight of the proximal part. In rotation tests, it is necessary for the examiner to apply counterpressure to ensure exact test performance. (See pp. 321,322, 429, 431.)

In some tests, muscles furnish fixation. The muscles that furnish fixation do not cross the same joint or joints as the muscle being tested. The muscles that stabilize the scapula during arm movements and the pelvis during leg movements are referred to as fixation muscles. They do not enter directly into the test movement, but they do stabilize the movable scapula to the trunk or the pelvis to the thorax and, thereby, make it possible for the tested muscle to have a firm origin from which to pull. In the same way, anterior abdominal muscles fix the thorax to the pelvis as anterior neck flexors act to lift the head forward in flexion from a supine position. (See p. 180 regarding action of opposite hip flexors in stabilizing the pelvis during hip extension.)

Muscles that have an antagonistic action give fixation by preventing excessive joint movement. This principle is illustrated by the fixation that the lumbricales and interossei provide in restricting hyperextension at the metacarpophalangeal joint during finger extension. In the presence of weak lumbricales and interossei, the pull of a strong extensor digitorum results in hyperextension of these joints and passive flexion of the inter-phalangeal joints. This hyperextension does not occur, however, and the fingers can be extended normally if the examiner prevents hyperextension of the metacarpopha-langeal joints by fixation equivalent to that of the lum-bricales and interossei. (See bottom, p. 274.)

When the fixation muscles are either too weak or too strong, the examiner can simulate the normal stabilization by assisting or restricting movement of the part in question. The examiner must be able to differentiate between the normal action of these muscles in fixation and the abnormal actions that occur when substitution or muscle imbalance is present.

Strength Testing

In muscle testing, weakness must be distinguished from restriction of range of motion. Frequently, a muscle cannot complete the normal range of joint motion. It may be that the muscle is too weak to complete the movement, or it may be that the range of motion is restricted because of shortness of the muscles, capsule, or liga-

mentous structures. The examiner should passively carry the part through the range of motion to determine whether any restriction exists. If no restriction is present, then failure by the subject to hold the test position may be interpreted as weakness unless joint or tendon laxity is present.

When testing one-joint muscles in which the ability to hold the part at completion of range of motion is expected, the examiner must distinguish between muscle weakness and tendon insufficiency. For example, the quadriceps may be strong but unable to fully extend the knee because the patellar tendon or quadriceps tendon has been stretched.

Muscle examinations should take into account such superimposed factors as relaxed, unstable joints. The degree of actual muscle weakness is difficult to judge in such cases. From the standpoint of function, the muscle is weak and should be so graded. When the muscle exhibits a strong contraction, however, it is important to recognize this as the potential for improvement. In a muscle that fails to function because of joint instability rather than because of weakness of the muscle itself, treatment should be directed at correcting the joint problem and relieving strain on the muscle. Instances are not uncommon in which the deltoid muscle shows a "fullness" of contraction throughout the muscle belly yet cannot begin to lift the weight of the arm. Such a muscle should be protected from strain by application of an adequate support for the express purpose of allowing the joint structures to shorten to their normal position. Failure to distinguish between real and apparent muscle weakness resulting from joint instability may deprive a patient of adequate follow-up treatment.

Test Position

Test position is the position in which the part is placed by the examiner and held (if possible) by the patient. It is the position used for the purpose of evaluating strength for most muscles.

The optimal test position is at the completion of range for one-joint muscles and for two or multijoint muscles that act like one-joint muscles. The optimal test position for other two or multijoint muscles is at midrange of overall length, in accordance with the length-tension principle. (See classifications, p. 13.)

Test position (as opposed to test movement) offers the advantages of precision in positioning and accuracy in testing. In addition, the examiner can determine immediately whether any limitation of motion exists by moving the part through the existing range of motion to the test position.

Use of the test position also enables the examiner to detect substitution movements. When muscle weakness exists, other muscles immediately substitute in an attempt to hold a position resembling the test position.

The visible shift from the test position indicates a substitution movement.

Placing the part in the test position expedites grading the muscle strength. As the effort is made to hold the test position, the ability or inability to hold the position against gravity is at once established. If it fails to hold, the examiner tests for strength below the fair grade: If the position is held, the examiner then applies pressure to grade above fair. (See Key to Muscle Grading, p. 23.)

Test Movement

Test movement is a movement of the part in a specified direction and through a specific arc of motion. For strength tests of extremity muscles that are too weak to act against gravity (i.e., muscles that grade in the range of poor), tests are done in the horizontal plane. Test movement is also used when testing the trunk lateral flexors, upper abdominal flexors, back extensors, quadratus lumborum, serratus anterior (in standing), and gastrocnemius.

Test movement may be used for certain muscles, such as those that cross hinge joints, but it is not practical when a test requires a combination of two or more joint positions or movements. It is difficult for a patient to assume the exact position through verbal instruction or imitating a movement demonstrated by the examiner. For accurate testing, the examiner should place the part in precisely the desired test position.

Pressure and Resistance

The term pressure* is used throughout this text to refer to the external force that is applied by the examiner to determine the strength of the muscle holding in the test position (i.e., for grades of F+ or better).

The term resistance refers to the external force that opposes the test movement. The resistance may be the force of gravity or a force that is supplied by the examiner. Resistance may vary according to body weight (i.e., back extensor test), arm position (i.e., upper abdominal test), or leg positions (i.e., lower abdominal test). Occasionally, the examiner may offer resistance. An example of this is the traction the examiner provides in the quad-ratus lumborum test.

The placement, direction, and amount of pressure are important factors when testing for strength above the grade of fair.

In the descriptions of muscle tests, pressure is specified as against or in the direction of. Against refers to

*Use of the term pressure in this text is not the physics definition (i.e.. force per unit area;.

the position of the examiner's hand in relation to the patient; in the direction of describes the direction of the force that is applied directly opposite the line of pull of the muscle or its tendon.

In some of the illustrations of muscle tests, the examiner's hand has been held extended for the purpose of indicating, photographically, that the direction of pressure is perpendicular to the palmar surface of the hand. Pressure should be applied only in the direction indicated. (It is not necessary that the extended hand position be imitated during routine muscle testing.) An extended hand is not appropriate when applying pressure in a test that includes a rotation component.

Just as the direction of the pressure is an important part of accurate test performance, the amount of pressure is the determining factor in grading strength above fair. (See Grading, p. 20, for further discussion related to amount of pressure.)

The place at which the pressure is applied depends on muscle insertions, strength of intervening muscles, and leverage. As a general rule, pressure is applied near the distal end of the part on which the muscle is inserted. For example, pressure is applied near the distal end of the forearm during the biceps test. Exceptions to this rule occur when pressure on the bone of insertion does not provide adequate leverage to obtain discrimination for grading.

Both the length of the lever and the amount of pressure are closely related with respect to grading above fair. Using a long lever gives the examiner a mechanical advantage and allows more sensitive grading of muscle strength.

Test results might be more indicative of the lack of strength of the examiner than of the subject if the examiner did not have the advantage of leverage.

When testing strong muscles like hip abductors, it is necessary to use a long lever (i.e., placing pressure just proximal to the ankle). When testing hip adductors, however, it is necessary to use a shorter lever, with pressure just above the knee joint, to avoid strain on the an-teromedial area of that joint.

Pressure must be applied gradually to determine the degree of strength above fair in muscles. The patient must be allowed to get set and hold the test position against the examiner's pressure. The examiner cannot gauge the degree of strength unless pressure is applied gradually, because slight pressure that is applied suddenly can "break" the pull of a strong muscle. Grading strength involves a subjective evaluation based on the amount of pressure applied. Differences in strength are so apparent, however, that an observer who understands grading can estimate the strength with a high degree of accuracy while watching the examiner apply pressure.

Substitution

Substitution results from one or more muscles attempting to compensate for the lack of strength in another muscle or group of muscles. Substitution is a good indication that the tested muscle is weak, that adequate fixation has not been applied, or that the subject has not been given adequate instruction concerning how to perform the test. Muscles that normally act together in movements may act in substitution. These include fixation muscles, agonists and antagonists.

Substitution by fixation muscles occurs specifically in relation to movements of the shoulder joint and the hip joint. Muscles that move the scapula may produce a secondary movement of the arm; muscles that move the pelvis may produce a secondary movement of the thigh. These substitution movements appear similar to—but are not—movements of the shoulder or hip joint.

The close relationship of muscles determines their action in substitution, assistance, and stabilization during tests of individual muscles. The grouping of muscles according to joint action, as seen in the charts on pages 254 and 255 and 366 and 367, has been done to aid the examiner in understanding the allied action of muscles.

True abduction of the hip joint is accomplished by hip abductors with normal fixation by the lateral trunk muscles. When the hip abductors are weak, apparent abduction may occur by the substitution action of lateral trunk muscles. The pelvis is hiked up laterally, the leg is raised from the table, but no true hip joint abduction occurs. (See pp. 184 and 434.)

Antagonists may produce movements similar to test movements. If finger flexors are weak, action of the wrist extensors may produce passive finger flexion by the tension placed on flexor tendons.

Substitution by other agonists results in either a movement of the part in the direction of the stronger agonist or a shift of the body in a way that favors the pull of that agonist. For example, during the gluteus medius test in side-lying, the thigh will tend to flex if the tensor fasciae latae is attempting to substitute for the gluteus medius, or the trunk may rotate back so that the tensor fasciae latae can hold a position that appears to be the desired test position.

For accurate muscle examinations, no substitutions should be permitted. The position or movement described as the test should be done without shifting the body or turning the part. Such secondary movements allow other muscles to substitute for the weak or paralyzed muscle.

An experienced examiner who is aware of the ease with which normal muscles perform the tests will readily detect substitutions. When test position is employed instead of test movement, even an inexperienced examiner can detect the sudden shift of the body or the part that results from an effort to compensate for the muscle weakness.

Weakness, Shortness, and Contracture

Included with the descriptions of the muscles in this text is a discussion of the loss of movement or the position of deformity that results from muscle weakness or muscle shortness.

Weakness is used as an overall term that covers a range of strength from zero to fair in non weight-bearing muscles but also includes fair+ in weight-bearing muscles. Weakness will result in loss of movement if the muscle cannot contract sufficiently to move the part through partial or complete range of motion.

A contracture or shortness will result in loss of motion if the muscle cannot be elongated through its full range of motion. Contracture refers to a degree of shortness that results in a marked loss of range of motion. Shortness refers to a degree of shortness that results in slight to moderate loss of range of motion.

A fixed deformity usually does not exist as a result of weakness unless contractures develop in the stronger opponents. In the wrist, for example, a fixed deformity will not develop as a result of wrist extensor weakness unless the opposing flexors maintain the position of wrist flexion.

A state of muscle unbalance exists when a muscle is weak and its antagonist is strong. The stronger of the two opponents tends to shorten, and the weaker of the two tends to elongate. Either weakness or shortness can cause faulty alignment. Weakness permits a position of deformity, but shortness creates a position of deformity.

In some parts of the body, positions of deformity may develop as a result of weakness even though the opposing muscles do not become contracted. Gravity and body weight exert opposing forces. A kyphotic position of the upper back may result from weakness of the upper back muscles regardless of whether the anterior trunk muscles become contracted. A position of pronation of the foot may exist if the inverters are weak because the body weight in standing will distort the bony alignment. If opposing peroneal muscles become contracted, a fixed deformity will result.

The word tight has two meanings. It may be used interchangeably with the term short, or it may be used to mean taut, in which case it may be applied to either a short or a stretched muscle. On palpation, hamstrings that are short and drawn taut will feel tight. Hamstrings that are stretched and drawn taut will also feel tight. From the standpoint of prescribing treatment, it is very important to recognize the difference between stretched muscles and shortened muscles. In addition, some muscles are short and remain in what appears to be a state of semicontrac-tion. On palpation, they feel firm or even rigid without being drawn taut. For example, posterior neck and upper trapezius muscles often are tight in people with bad posture of the upper back, head and shoulders.

The order in which muscles are tested is largely a matter of choice but generally arranged to avoid any unnecessary changes of position for the subject. Muscles that are closely related in position or action tend to appear in sequence in order to distinguish test differences. When a specific order of tests is important, it is so indicated in the text. As a general rule, length testing precedes strength testing.

SUGGESTED ORDER OF MUSCLE TESTS

1. Supine

Toe extensors Toe flexors Tibialis anterior Tibialis posterior Peroneals

Tensor fasciae latae Sartorius Iliopsoas Abdominals Neck flexors Finger flexors Finger extensors Thumb muscles Wrist extensors Wrist flexors Supinators Pronators Biceps

Brachioradialis Triceps (supine test) Pectoralis major, upper part Pectoralis major, lower part Pectoralis minor

Medial rotators of shoulder (supine test) Teres minor and infraspinatus Lateral rotators of shoulder (supine test) Serratus anterior Anterior deltoid (supine test)

Hip adductors Lateral abdominals

3. Prone

Gastrocnemius and plantaris Soleus

Hamstrings, medial and lateral

Gluteus maximus

Neck extensors

Back extensors

Quadratus lumborum

Latissimus dorsi

Lower trapezius

Middle trapezius

Rhomboids

Posterior deltoid (prone test) Triceps (prone test) Teres major

Medial rotators of shoulder (prone test) Lateral rotators of shoulder (prone test)

4. Sitting

Quadriceps

Medial rotators of hip

Lateral rotators of hip

Hip flexors (group test)

Deltoid, anterior, middle, and posterior

Coracobrachialis

Upper trapezius

Serratus anterior (preferred test)

2. Side-Lying 5. Standing

Gluteus medius Serratus anterior

Gluteus minimus Ankle plantar flexors

GRADING

Grades represent an examiner's assessment of the strength or weakness of a muscle or a muscle group. In manual muscle testing, grading is based on a system in which the ability to hold the tested part in a given position against gravity establishes a grade referred to as fair or the numerical equivalent (depending on the grading symbols being used). The grade of fair is the most objective grade because the pull of gravity is a constant factor.

For grades above fair, pressure is applied in addition to the resistance offered by gravity. A break

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