Scapula

Current Concepts

The Role of the Scapula in AthleticShoulder Function

W. Ben Kibler,* MD

Lexington Clinic Sports Medicine Center, Lexington, Kentucky

ABSTRACT

The exact role and the function of the scapula aremisunderstood in many clinical situations. This lack ofawareness often translates into incomplete evaluationand diagnosis of shoulder problems. In addition, scap-ular rehabilitation is often ignored. Recent research,however, has demonstrated a pivotal role for the scap-ula in shoulder function, shoulder injury, and shoulderrehabilitation. This knowledge will help the physician toprovide more comprehensive care for the athlete. This“Current Concepts” review will address the anatomy ofthe scapula, the roles that the scapula plays in over-head throwing and serving activities, the normal bio-mechanics of the scapula, abnormal biomechanics andphysiology of the scapula, how the scapula may func-tion in injuries that occur around the shoulder, andtreatment and rehabilitation of scapular problems.

ANATOMY

The scapula is a flat blade lying along the thoracic wall.Its wide, thin configuration allows for smooth gliding ofthe scapula on the thoracic wall and provides a largesurface area for muscle attachments both distally andproximally. Stabilization of the scapula is rather tenuous.It is attached to the axial skeleton by the strut of theclavicle and stabilized onto the chest wall by the muscleattachments to the spinous processes and the ribs. Thestrut configuration allows a degree of stabilization againstmedially directed forces but allows a large amount ofscapular rotation and translation that is then controlledby the dynamic action of the muscles. Three groups of

muscles attach to the scapula (Fig. 1). The first groupincludes the trapezius, rhomboid, levator scapulae, andthe serratus anterior muscles, and is concerned with sta-bilization and rotation of the scapula. The second groupincludes the extrinsic muscles of the shoulder joint—thedeltoid, biceps, and triceps muscles. The final group in-cludes the intrinsic muscles of the rotator cuff—the sub-scapularis, the supraspinatus, infraspinatus, and teresminor muscles. All of the groups have different actions inboth shoulder function and shoulder injury and need to beunderstood in light of these separate actions.

THE ROLES OF THE SCAPULA IN OVERHEADTHROWING AND SERVING ACTIVITIES

The roles of the scapula in throwing and serving areconcerned with achieving appropriate motions and posi-tions to facilitate shoulder function. Optimal function isachieved when normal anatomy interacts with normalphysiology to create normal biomechanics. The scapula’svarious roles are concerned with achieving these motionsand positions to facilitate the efficient physiology andbiomechanics to allow optimum shoulder function. Thefailure of the scapula to perform these roles causes ineffi-cient physiology and biomechanics and, therefore, ineffi-cient shoulder function. This can cause poor performance,and can cause or exacerbate shoulder injury.

The first role of the scapula is to be a stable part of theglenohumeral articulation. The glenoid is the socket of theball-and-socket arrangement of the glenohumeral joint. Tomaintain the ball-and-socket configuration, the scapulamust move in a coordinated relationship with the movinghumerus so that the instant center of rotation—the math-ematical point within the humeral head that defines theaxis of rotation of the glenohumeral joint—is constrainedwithin a physiologic pattern throughout the full range ofshoulder motion in throwing or serving.21

The coordinated movements also keep the angle be-tween the glenoid and the humerus within a physiologi-

* Address correspondence and reprint requests to W. Ben Kibler, MD,Lexington Clinic Sports Medicine Center, 1221 South Broadway, Lexington,KY 40504.

Neither the author nor his related institution received financial benefit fromresearch in this study.

0363-5465/98/2626-0325$02.00/0THE AMERICAN JOURNAL OF SPORTS MEDICINE, Vol. 26, No. 2© 1998 American Orthopaedic Society for Sports Medicine

325

cally tolerable range. This “safe zone” of glenohumeralactivity falls roughly within 30° of extension or flexionfrom the neutral position in the scapular plane.24 Thissafe zone and stable constrained center of rotation allow“concavity/compression” of the glenohumeral joint to bemaximal. Concavity/compression is the result of intraar-ticular pressure, positioning of the glenoid in relationshipto the humerus, and muscle activity acting in concert tomaintain the ball-and-socket kinematics.21 Proper align-ment of the glenoid allows the optimum function of thebony constraints to glenohumeral motion and allows themost efficient position of the intrinsic muscles of the rota-tor cuff to allow compression into the glenoid socket,thereby enhancing the muscular constraint systemsaround the shoulder as well.24

The second role of the scapula is retraction and protrac-tion along the thoracic wall. The scapula needs to retractto facilitate the position of cocking for such activities asthe baseball throw, the tennis serve, or the swimmingrecovery. Efficient achievement of this cocking positionallows for retensioning of the anterior muscular struc-tures and efficient change of muscle phase of contractionfrom eccentric to concentric on the anterior muscles andconcentric to eccentric function on the posterior mus-cles.7,24 This position has been called the “full tank ofenergy” position because it allows the explosive phase ofacceleration in throwing or serving. As acceleration pro-ceeds, the scapula must protract in a smooth fashion lat-erally and then anteriorly around the thoracic wall toallow the scapula to maintain a normal position in rela-tionship to the humerus and also to dissipate some of thedeceleration forces that occur in follow-through as the armgoes forward.24

The third role that the scapula plays in the throwingand serving motion is elevation of the acromion. The scap-ula must rotate in the cocking and acceleration phases toclear the acromion from the rotator cuff to decrease im-pingement and coracoacromial arch compression. Almostall throwing and serving activities occur with a humerus-to-spine angle of between 85° and 100° of abduction.7

Therefore, the acromion must be tilted up to avoid imping-ing the rotator cuff in this position.

The fourth role that the scapula plays is as a base formuscle attachment. The scapular stabilizers attach to themedial, superior, and inferior borders of the scapula andcontrol the motion and position of the scapula to allow it toaccomplish all of its roles. The extrinsic muscles—thedeltoid, biceps, and triceps—attach along the lateral as-pect of the scapula, perform gross motor activities of theglenohumeral joint, and form the second cone of Saha.28

The intrinsic muscles of the rotator cuff attach along theentire surface of the scapula and are aligned so that theirmost efficient activity, working concentrically or eccentri-cally in a straight line, occurs with the arm between 70°and 100° of abduction.24 In this fashion, they are biome-chanically considered to be a “compressor cuff” to com-press the humeral head into the socket.

The final role that the scapula plays in shoulder func-tion is that of being a link in the proximal-to-distal se-quencing of velocity, energy, and forces that allows the

most appropriate shoulder function.5,7,12,14 For mostshoulder activities, this sequencing starts at the ground.The individual body segments, or links, are coordinated intheir movements by muscle activity and body positions togenerate, summate, and transfer force through these seg-ments to the terminal link (Fig. 1). This sequencing isusually termed the “kinetic chain.”

The largest proportion of kinetic energy and force in thissequencing is derived from the larger proximal body seg-ments.14 Studies have shown that 51% of the total kineticenergy and 54% of the total force generated in the tennisserve are created by the lower legs, hip, and trunk.14

The scapula is pivotal in transferring the large forcesand high energy from the major source for force and en-ergy—the legs, back, and trunk—to the actual deliverymechanism of the energy and force—the arm and thehand.5,12,14,19 Forces that are generated in the proximalsegments have to be transferred efficiently and must beregulated as they go through the funnel of the shoulder.This can be accomplished most efficiently through thestable and controlled platform of the scapula. The entirearm rotates as a unit around the stable base of the gleno-humeral socket. In many tennis serving motions, the feetand body are actually off the ground when this rotationreaches its maximum peak. The entire stable base of thearm, in this situation, rests on the scapula rather than on

Figure 1. Link sequencing allows efficient generation, sum-mation, and transfer of kinetic energy and force from thebase of support, usually the ground, to the terminal link,usually the hand.

326 Kibler American Journal of Sports Medicine

the feet or the ground. Therefore, stability of the scapulain relationship to the entire moving arm is the key point atthis important time in the throwing sequence.

In summary, it may be seen that there are many diverseroles that the scapula must play to achieve appropriateshoulder function. These roles are interrelated and aredirected toward maintaining the glenohumeral instantcenter of rotation in the normal path and providing astable base for muscular function.

NORMAL BIOMECHANICS AND PHYSIOLOGY OFTHE SCAPULA

Descriptive biomechanics of the scapula reveal that largerotations and large motions occur in athletic shoulderfunction. In the normal abduction mechanism, the scapulamoves laterally in the first 30° to 50° of glenohumeralabduction. As further abduction occurs, the scapula thenrotates about a fixed axis through an arc of approximately65° as the shoulder reaches full elevation.26 This motionaccounts for the 2:1 ratio between glenohumeral abduc-tion and scapulothoracic rotation that is observed in mostthrowing athletes. Other studies have shown that thisratio varies between 1:1 and 4:1 depending on the phasesof abduction; however, for the entire abduction motion, theapproximate 2:1 ratio holds true.12

Translation of the scapula in retraction and protractionoccurs around the curvature of the thoracic wall. Depend-ing on the size of the person and the vigorousness of thethrowing activity, this translation may occur over dis-tances of 15 to 18 cm.15 Retraction is mainly in a curvi-linear fashion around the wall, but protraction may pro-ceed in a slightly upward or downward motion dependingon the position of the arm in the throwing or servingactivity. The motion is a bit more in a superior direction inthe tennis serve, in which a lot of the acceleration is in asuperior direction, compared with the baseball throw, inwhich most of the acceleration is in an anteriordirection.7,17

Descriptive physiology shows that these motions andtranslations occur as a result of active muscle firing, inaddition to passive motion due to the angular accelera-tions of the trunk and arm. There is a large amount ofmuscle activity around the scapula in the scapular stabi-lizers.1,4,22 These muscles act mainly as force couples,which are muscles that are paired to control the move-ment or position of a joint or a body part. The appropriateforce couples for scapular stabilization include the upperand lower portions of the trapezius muscle working to-gether with the rhomboid muscles, paired with the serra-tus anterior muscle. The appropriate force couples foracromial elevation are the lower trapezius and the serra-tus muscles working together paired with the upper tra-pezius and rhomboid muscles. Muscles are noted to act indifferent parts of the force couples depending on the ac-tivity requirements. Each of these specific actions andforce couples must be evaluated and rehabilitated withthese different functions in mind.24,29

ABNORMAL BIOMECHANICS AND PHYSIOLOGY

The scapular roles can be altered by many anatomic fac-tors to create abnormal biomechanics and physiology, bothlocally and in the kinetic chain. The bony anatomy can bealtered by either body posture or by bony injury. Thoracickyphosis or neck lordosis can result in excessive protrac-tion of the scapula so that impingement occurs with ele-vation, and excessive muscular energy will be required toachieve the proper position of retraction on the thoracicwall (Fig. 2). Excessive drooping of the shoulder, termed“tennis shoulder,” can affect the positioning of the scapula,once again leading to impingement or problems with mus-cle function. Injuries of the clavicle or scapula can alterthe orientation of the scapula, or the length of the clavic-ular strut of the scapula, or cause painful clinical situa-tions that would inhibit muscle function. Acromioclavicu-lar joint arthrosis or separation can also lead toabnormalities with the strut function of the clavicle andalter normal kinematics of the scapula.

Most of the abnormal biomechanics and physiology thatoccur in injuries seen in a sports medicine setting can betraced to alterations in the function of the muscles thatcontrol the scapula.20,22 Nerve injury either to the longthoracic nerve or the spinal accessory nerve can altermuscular function of the serratus anterior or the trapeziusmuscle, respectively, to give abnormal stabilization andcontrol. This type of nerve injury occurs in less than 5% ofthe muscle function abnormalities.

More commonly, muscles are either directly injuredfrom direct blow trauma, have microtrauma-inducedstrain in the muscles leading to muscle weakness andforce couple imbalance, or are inhibited by painful condi-tions around the shoulder. Muscle inhibition or weaknessis common in glenohumeral abnormalities, whether frominstability, labral lesions, or arthrosis.1,20,22,29 It appearsthat the serratus anterior and the lower trapezius musclesare the most susceptible to the effect of the inhibition, andthey are involved in early phases of shoulder abnormali-ties.8,24 Muscle inhibition, and resulting scapular insta-bility, appears to be a nonspecific response to a painfulcondition in the shoulder rather than a specific responseto a certain glenohumeral pathologic situation. This isverified by the finding of scapular instability in as manyas 68% of rotator cuff problems and 100% of glenohumeralinstability problems.20,30 Inhibition is seen both as a de-creased ability for the muscles to exert torque and stabi-lize the scapula and also as a disorganization of the nor-mal muscle firing patterns of the muscles around theshoulder.8,20,30

Glenohumeral inflexibility also can create abnormalbiomechanics of the scapula. Posterior shoulder inflexibil-ity, whether due to capsular or muscular tightness, affectsthe smooth motion of the glenohumeral joint and creates awind-up effect so that the glenoid and scapula actually getpulled in a forward and inferior direction by the movingarm.7 This may create an excessive amount of protractionof the scapula on the thorax due to the obligatory nature ofbringing the throwing arm into the horizontally adductedposition in follow-through. Because of the geometry of the

Vol. 26, No. 2, 1998 The Scapula in Athletic Shoulder Function 327

Figure 2. Scapular protraction affects arm elevation before impingement. Normal scapular position (A) and motion (B);abnormal shoulder drooping and scapular protraction (C), and resulting early impingement (D).


upper aspect of the thorax, the more the scapula is pro-tracted in follow-through, the farther it and its acromionmove anteriorly and inferiorly around the thorax. Themore inferiorly the scapula moves, the less it is able toelevate and avoid impingement. Therefore, in the positionof acceleration and follow-through, the excessive protrac-tion may cause decreased clearance and increased risk ofrotator cuff impingement because of the abnormalbiomechanics.

THE ROLE OF THE SCAPULA INSHOULDER INJURIES

The abnormal biomechanics and physiology that can occuraround the shoulder create abnormal scapular positionsand motions that decrease normal shoulder function. Thisset of abnormal motions and positions has been termed“scapulothoracic dyskinesis,”30 “floating scapula” (F. W.Jobe, personal communication, 1990), or “lateral scapularslide”16 by different authors, but basically it denotes thesame phenomenon: the roles of the scapula are not beingfulfilled in their normal fashion (Fig. 3).

Alterations in retraction and protraction will change thenormal parameters for scapular motion. Lack of full re-

traction of the scapula on the thorax would cause loss of astable cocking point and lack of ability to explode duringacceleration out of the full tank of energy position of fullcocking. Lack of full scapular protraction around the tho-racic wall increases the deceleration forces on the shoul-der and causes alteration in the normal safe zone relation-ship between the glenoid and the humerus as the armmoves through the acceleration phase.4,7,24 Too much pro-traction because of tightness in the glenohumeral capsulewill cause abnormalities of impingement as the scapularotates down and forward. These cumulatively lead toabnormalities in concavity/compression due to thechanges in the safe zone of the glenohumeral angle.

Loss of coordinated retraction/protraction in the throw-ing motion also creates a relative glenoid antetilting orfunctional anteversion, whereby the anterior aspect of theglenohumeral joint is more open and the normal anteriorbony buttress to anterior translation is deficient (Fig. 4).This opening up and lack of bony buttress causes in-creased shear stresses on the rest of the anterior stabiliz-ing structures, the labrum and glenohumeral ligaments,which further causes increased risk of shear injury orstrain.10,16 This decreases the ability of the glenoid to bea stable socket for the rotating humerus as the instantcenter of rotation changes.

Lack of appropriate acromial elevation leads to impinge-ment problems in the cocking and follow-through phases.This type of impingement is commonly seen not only asthe sole source of impingement but also as a secondarysource of impingement in other shoulder problems, suchas glenohumeral instability.10,11,20 The serratus and es-pecially the lower trapezius muscles appear to be the firstmuscles involved in inhibition-based muscle dysfunc-tion.8,24 These two muscles form a crucial part of the forcecouple responsible for elevating the acromion. Lack ofacromial elevation and consequent secondary impinge-ment can be seen early in many shoulder problems, suchas rotator cuff tendinitis and glenohumeral instability,and can play a major role in defining the clinical problemsthat are associated with these diagnostic entities.11,16,30

Lack of a stable muscular anchor affects all of the func-tions of the muscles attached to the scapula. Muscleswithout a stable base of origin cannot develop appropriateor maximal torque with a concentric contraction, therebydecreasing their strength and contributing to problemsnot only with strength production but also in muscularimbalance. If the scapula is truly unstable on the thoracicwall, as can be seen in spinal accessory nerve palsies or inextremely inhibited muscles, then an actual reversal ofthe origin and insertion occurs, and the distal end of themuscle becomes the origin. When this phenomenon oc-curs, the scapula is actually pulled laterally by the muscle,which would be contracting from the more stable distalend on the humerus rather than from the proximal end onthe scapula. This phenomenon increases the scapulotho-racic dyskinesis and lateral scapular slide.

One of the most important abnormalities in abnormalscapular biomechanics is the loss of the link function inthe kinetic chain (Fig. 1). The kinetic chain is the mostefficient system for developing energy and force to be

Figure 3. Scapular dyskinesis: abnormal scapular retraction(winging) (A) and abnormal scapular elevation on arm ele-vation (B).


delivered to the hand. The scapula and shoulder are piv-otal links in this chain, funneling the forces from the largesegments, the legs and trunk, to the smaller, rapidly mov-ing small segments of the arm. If the scapula does becomedeficient in motion or position, transmission of the largegenerated forces from the lower extremity to the upperextremity is impaired. This creates a deficiency in result-ant maximum force that can be delivered to the hand orcreates a situation of “catch-up” in which the more distallinks have to work at a higher level of activity to compen-sate for the loss of the proximally generated force. Thiscan be very detrimental to the function of the distal linksas they do not have the size, the muscle cross-sectionalarea, or the time in which to efficiently develop theselarger forces.

Our calculations have shown that a 20% decrease inkinetic energy delivered from the hip and trunk to the armnecessitates an 80% increase in mass or a 34% increase inrotational velocity at the shoulder to deliver the sameamount of resultant force to the hand (Table 1).17 Thisrequired adaptation is large and can cause overload prob-lems with repeated use. In addition, the unstable scapuladoes not create a stable base for glenohumeral rotation asthe link sequencing evolves. Therefore, the arm works offan unstable rather than a stable platform, decreasing themechanical efficiency of the entire motion.

EVALUATION OF THE SCAPULA

The scapula is intimately involved with both performanceand injury conditions of the shoulder. Consequently, thescapula needs to be examined closely as part of the eval-uation of shoulder problems. The scapula needs to beevaluated not only locally but also distantly in relation-ship to its role in the kinetic chain.

Evaluation of the back and trunk is important. Thedegree of lumbar lordosis, any leg-length asymmetry, andany hip rotational abnormalities need to be noted. Be-cause leg and trunk muscle activity is both large andimportant in throwing activities, it should be as-sessed.10,19,31 Inability to achieve normal motions or gen-erate normal velocity in the lower extremity or trunk canaffect the transfer of force to the scapula and the arm.

Thoracic and cervical posture also need to be evaluatedin the back and trunk examination. Excessive thoracickyphosis or scoliosis can have a direct relationship to themotion of the scapula. The presence of cervical lordosisalso can give an indication of the amount of posteriorcervical tightness or anterior clavicular fascia tightness,which can have an effect on scapular retraction and pro-traction (Fig. 5).

Figure 4. Relative glenoid antetilting: normal scapularposition and glenoid tilt (A) and abnormal scapular protrac-tion, with relative glenoid antetilting and anterior humeralshear (B).

TABLE 1Required Changes in Shoulder Velocity or Mass to Replace a

20% Decrease in Trunk Kinetic Energy to Shoulder Link

Normal Catch-up % Change

Shoulder velocity (m/sec) 3.3 4.43 134Shoulder mass (kg) 9 16.25 180


The evaluation of the scapula itself should be donemainly from the posterior aspect.13,20 The examinationcan then proceed from posterior to anterior to allow ap-propriate examination of all the scapular positions andmotions.

Scapular position may be evaluated in several ways.Abnormalities of winging, elevation, or rotation may firstbe examined in the resting position. In long-standing scap-ular dyskinesis, resting winging may be seen. Isolatedserratus anterior muscle weakness due to nerve palsy willcreate a prominent superior medial border and depressedacromion, while isolated trapezius muscle weakness dueto nerve palsy will create a protracted inferior border andelevated acromion. More commonly, a mixture of thesetwo positions will be present because both muscles areinvolved in microtrauma or inhibition-based muscleweakness.

Motion and position should be examined both in theascending phase and in the descending phase of the arm inboth flexion and abduction (Fig. 6). Muscle weakness andmild scapular dyskinesis will be noted more frequently inthe descending phase of the arm movement. In addition,we use a “muscle assistance” test to see if impingementmay be due to lack of active acromial elevation. The ex-aminer pushes laterally and upward on the inferior me-

dial border of the scapula to simulate the serratus ante-rior/lower trapezius muscle portion of the elevation forcecouple. Impingement symptoms are diminished or abol-ished in cases of muscle inhibition.

A good provocative maneuver to evaluate scapular mus-cle strength is to do an isometric pinch of the scapulae inretraction. Scapular muscle weakness can be noted as aburning pain in less than 15 seconds. Normally, the scap-ula can be held in this position for 15 to 20 seconds withthe patient having no burning pain or muscle weakness.Also, wall push-ups are an effective way of evaluatingserratus anterior muscle strength. Any abnormalities ofscapular winging with 5 to 10 wall push-ups may be noted.

Quantitative measurement of scapular stabilizerstrength can be achieved with the lateral slide test (Fig.7). This semidynamic test evaluates the position of thescapula on the injured and noninjured sides in relation-ship to a fixed point on the spine as varying amounts ofloads are put on the supporting musculature. Three posi-tions are chosen for this testing procedure. The first posi-tion is with the arm relaxed at the sides (Fig. 7A). Thesecond is with the hands on the hips with the fingersanterior and the thumb posterior with about 10° of shoul-der extension (Fig. 7B). The third position is with the armsat or below 90° of arm elevation with maximal internalrotation at the glenohumeral joint (Fig. 7C). These posi-tions offer a graded challenge to the functioning of theshoulder muscles to stabilize the scapula. The final posi-tion presents a challenge to the muscles in the position ofmost common function at 90° of shoulder elevation.

Electromyographic evaluation has shown that very fewmuscles are working in the first position, that the serratusand the lower trapezius muscles are working at low levelsin the second position, and that the upper trapezius, lowertrapezius, serratus, and rhomboid muscles are all workingat approximately 40% of maximum in the third position.In the first position, the inferomedial angle of the scapulais palpated and marked on both the injured and nonin-jured sides. The reference point on the spine is the nearestspinous process, which is then marked with an X. The

Figure 5. A patient with excessive cervical lordosis.

Figure 6. Normal scapular control in shoulder flexion. Checkcontrol in both ascending and descending positions.


measurements from the reference point on the spine to themedial border of the scapula are measured on both sides.In the second position, the new position of the inferome-dial border of the scapula is marked, and the referencepoint on the spine is maintained. The distances once againare calculated on both sides. The same protocol is done forthe third position.

Tests for reliability and validity of this measuring sys-tem have been done. Studies on the accuracy of markingthe inferomedial border of the scapula in comparison withradiographic evaluation of the same point when markedby a lead shot have shown a correlation of 0.91 with thedifferent positions. Therefore, it does appear that the po-sition that is marked on the skin does correspond wellwith the actual position of the inferomedial border of thescapula. Test-retest and intertest reliability has shownthat the test-retest (intratester) relationship is between0.84 and 0.88, and that the intertester reliability is be-tween 0.77 and 0.85 depending on the position (Table 2).23

The third position is the most difficult to measure accu-rately because of the muscle activity. Even so, this posi-tion achieved a test-retest and intertester reliability ofgreater than 0.78. Therefore, it appears that the lateralslide test 1) does reproduce the desired scapular pointsand the desired measurements, 2) is a reliable test interms of reproducibility, and 3) does test muscles that areactually working to stabilize the scapula.

The lateral slide test is not a true dynamic test in thatit does not measure scapular mobility during the throwingmotion and it does rely on static positions. However, thethird position does accurately reproduce the position offunction of the shoulder and produces a significant load onthe scapular muscles. In addition, by keeping the shoulder

at or below 90°, the position of impingement is avoided,and, therefore, pain-based inhibition of the musculature isless likely to occur. Investigations of this testing proce-dure show that in asymptomatic throwing athletes, as theprogression of muscle activity goes from the first to thethird position, the amount of asymmetry of the scapularpositions becomes less, indicating the increasing role ofthe scapular stabilizing muscles in controlling the retrac-tion of the scapula as the arm abducts.

In a group of injured patients, this change in symmetrydoes not occur, and the degree of asymmetry actuallyincreases when going from the first to the third position(Table 3). The side-to-side differences in the injured ath-letes are consistently greater than 0.83 cm, with a range of0.83 to 1.75 cm. For purposes of clinical evaluation, wehave established 1.5 cm asymmetry as the threshold ofabnormality and accept this in any of the positions, al-

Figure 7. Lateral scapular slide measurement. A, the first position, with arms at side; B, the second position, with hands on hips;C, the third position, with arms at or below 90° abduction, with glenohumeral internal rotation.

TABLE 2Test-Retest and Intertest Reliability of Lateral

Slide Measurements

PositionShoulder

Dominant Nondominant

Intratester reliability

1 0.85 0.872 0.84 0.883 0.86 0.85

Intertester reliability

1 0.83 0.852 0.77 0.813 0.78 0.83


though it is more commonly seen in the third position.However, in long-standing cases, abnormalities of asmuch as 2 to 3 cm in any of the positions have also beenseen. Although this test does not solve all of the problemsabout measuring scapular strength, it is a semiquantita-tive and reproducible test that can be used as part ofevaluation and rehabilitation of these problems and doesallow an objective set of criteria to determine the scapularabnormalities.

Other testing that can be done to objectively measurescapular position include Moire topographic analysis,30

which involves stroboscopic evaluation of the contours ofthe back. This test shows the abnormalities of scapularposition very well, but this is limited by the availability ofthese facilities. Few clinical centers have the equipment orthe personnel to use the test in a clinical situation.

Evaluation techniques for other structures that are per-tinent to the scapular evaluation include evaluation of theacromioclavicular joint, the acromioclavicular angle inboth retraction and protraction, and glenohumeral rota-tion and muscle strength.13 All of these play a role in themotion and position of the scapula.

TREATMENT CONSIDERATIONS FORSCAPULAR ABNORMALITIES

Most of the abnormalities that exist in scapular motion orposition may be treated by treating the source of theproblems.20 Very seldom is surgical treatment directed atthe scapula itself; rather, it is usually directed at thesource of the underlying problems.

If there is a primary neurologic problem, such as a torn,stretched, or lacerated spinal accessory nerve or long tho-racic nerve, then appropriate nerve repair or muscletransfers may be used. Scapular stabilization in serratusanterior muscle dysfunction due to nerve palsy can beachieved by transfer of the pectoralis major muscle with afascial extension to the scapula,27 or can be achieved intrapezius muscle dysfunction due to nerve palsy by rhom-boid muscle transfer and levator scapulae muscle ad-vancement.2,20 In advanced cases, actual stabilization ofthe scapula to the ribs by arthrodesis may be considered.

Internal fixation of scapular or clavicular fractures maybe necessary to restore normal anatomy or angulation ofthe glenoid or to restore the normal length to the strut ofthe clavicle.6 Acromioclavicular joint separations shouldbe evaluated in terms of their contributions to scapular

stability. If a third or fourth degree acromioclavicularseparation creates a loss of the strut function and exces-sive scapular protraction or dyskinesis, then functionalconsequences may include rotator cuff impingement andabnormalities in strength production. Acromioclavicularjoints may need to be anatomically repaired in this situa-tion. Acromioclavicular joint arthrosis with consequentpain or acromioclavicular joint instability may need to besurgically corrected to stabilize the scapula or eliminatethe problem that is causing pain at the joint.

More commonly, the underlying source of muscle inhi-bition or muscle imbalance needs to be addressed,whether this is the predominant glenohumeral internalderangement, such as instability, labral tears, or rotatorcuff injury, or rotator cuff tendinitis with muscle weak-ness and inhibition. Superior glenoid labral tears andmicrotrauma-based glenohumeral instability are commonpainful contributors to scapular dyskinesis. Once the in-ternal derangement is corrected, scapular muscle rehabil-itation may begin.

REHABILITATION CONSIDERATIONS INSCAPULAR DYSKINESIS

Once the complete and accurate diagnosis of all of thefactors that are causing or contributing to scapular andshoulder problems is established, scapular rehabilitationshould be accomplished in the context of all of itsroles.18,22,25,32 Rehabilitation may be indicated beforesurgical intervention if rehabilitation may create morefavorable postoperative conditions. Good preoperativescapular control can improve postoperative rehabilitationfor rotator cuff repairs and glenohumeral instability re-constructions by creating a more stable, neurologicallycoordinated base for muscle rehabilitation. In addition,preoperative scapular rehabilitation may eliminate theneed for surgery. A surprisingly large percentage of “im-pingement” problems can be corrected by proper scapularmuscular re-education and conditioning. By restoring thenormal motor organization and force couples, rehabilita-tion can improve scapular position and motion to decreaseacromial impingement and increase rotator cuff efficiency.

In the postoperative phase, proximal kinetic chain re-habilitation may be started early in the legs and trunk,even while shoulder protection is desired. Scapular reha-bilitation, especially isometric or closed-chain exercises,may also be instituted before shoulder rehabilitation,within the limits imposed by the need for shoulderprotection.

Because scapular dyskinesis due to altered physiologyoccurs early in the injury or postoperative phases, accel-erated rehabilitation should be emphasized to restore nor-mal physiologic patterns. Rehabilitation should start atthe base of the kinetic chain. This usually means correct-ing any strength or flexibility deficits that exist in thelower back and thoracic level as a prelude to starting workon the scapular component. This phase includes exercisesfor flexibility in both AP and rotational directions,strengthening of the trunk in flexion, extension, and ro-

TABLE 3Change in Scapular Slide Asymmetry with Different

Testing Positionsa

PositionAthletes

Symptomatic Asymptomatic

1 0.83 0.472 1.41 0.393 1.75 0.27

a Mean asymmetry (injured side 2 uninjured side) meas-urements in centimeters.


tation, and correction of postural abnormalities with ap-propriate postural exercises for the thoracic area.

Abnormalities in back alignment can be corrected withproper exercises or postural corrections (Fig. 8). Range ofmotion of the glenohumeral joint can be improved by ap-propriate stretching that emphasizes stretching of theposterior capsule rather than stretching of the entire up-per limb (Fig. 9). In this situation, care must be taken tomake sure that the stretching does not occur at the scapu-lothoracic articulation but at the glenohumeral articula-tion. If the stretching occurs at the scapulothoracic artic-ulation, it will increase rather than solve thebiomechanical problem by allowing too much scapularprotraction.

Specific scapular rehabilitation activities should be bro-ken down into scapular stability exercises, closed-chainexercises, and open-chain exercises. Scapular stability canbe started early in the rehabilitation sequence. At thebeginning, these exercises involve isometric exercises,such as scapular pinch and scapular shrug exercises forelevation. In this early stage, help with control of scapularposition may be provided by scapular taping in a retractedor elevated position and the use of a figure eight collar,which is normally used for clavicular fractures (Fig. 10).This helps to retract and elevate the scapula and createsconditions for normalization of scapular muscle firing pat-terns, which are often quite disorganized and inhibited inthe injured state.

The most physiologic way to reorganize and reestablishnormal motor firing patterns for the scapula is with the

exercises that involve closed-chain activities.3,18,25 Theseexercises simulate the normal functional patterns in thatthey work the arm at 90° of glenohumeral elevation. Inthis fashion, they reproduce the normal physiologic pat-terns of co-contractions of the scapular stabilizing musclesand of the muscles of the rotator cuff. They allow normalmotor patterns that create scapular elevation, depression,retraction, and protraction to occur with minimal stressand allow normal biomechanics of concavity/compressionand rotation to occur. These are usually done with thehand stabilized on a wall, or on a ball on the wall, andspecific scapular maneuvers of elevation, depression, re-traction, and protraction are performed (Fig. 11).

The closed-chain exercises may be done safely withinthe parameters set by the need for healing of the under-

Figure 8. Postural exercises should include correction ofthoracic kyphosis.

Figure 9. Posterior shoulder capsular stretching. A, motionis mainly between the scapula and thoracic wall, which ex-acerbates scapular slide. B, exercise with scapula stabilizedallows stretch at appropriate location.


lying injury and can be started as early as 3 weeks aftersurgery for glenoid labral repair or instability repair andas early as 5 weeks after rotator cuff repairs.18 The exer-cises may be started at elevations of 60° or less and then

moved up to 90° as tissue healing allows. They can be donethroughout the early and middle stages of rehabilitation,and can be combined with lower extremity exercises.18

Further progressions to create more load on the scapularmuscles include push-ups, quadriped and biped exercises,and press-up exercises.25,32

Open-chain activities may be initiated on the base es-tablished by the isometric and closed-chain activities.These more strenuous exercises include vigorous proprio-ceptive neuromuscular facilitation patterns, diagonals, ex-ternal rotation and retraction activities, and plyometrics(Fig. 12), all of which create muscles ready to return tomore normal physiologic function. Machines may be usedin this phase to allow pull-downs, upright rows, push-ups,and push-up-plus activities for the complete rehabilitationof the scapula.

Most of the scapular rehabilitation exercises should bedone before emphasis on rotator cuff-strengthening exer-cises. The scapula is the base from which the rotator cufforiginates, and complete scapular rehabilitation allows formore normal scapular positioning and, therefore, more nor-mal patterns of activation of the rotator cuff. In addition,control of elevation of the acromion decreases the chances of

Figure 10. Use of a figure eight clavicle collar helps withscapular retraction.

Figure 11. Closed-chain scapular exercises to simulate elevation (A), depression (B), retraction (C), and protraction (D).


impingement and allows the rotator cuff muscles to pull in acompression fashion into the glenohumeral joint.

Lateral scapular slide measurements may be used as aguide for progressing through these activities. Criteria forinitiating specific rotator cuff and open-chain arm activi-ties would include a lateral slide asymmetry of less than 1cm in the third position and smooth motion of the scapulaon the injured and noninjured sides with both ascent anddescent.18

If scapular stabilization is achieved by this strengthen-ing program, it is often found that there are fewer prob-lems in rotator cuff rehabilitation because the rotator cuffis activated in a more physiologic fashion in the closed-chain rehabilitation. Also, the scapular base is much bet-ter prepared for activity of the rotator cuff muscles aftersuch a strengthening program.

To summarize, the scapula has a major and pivotal rolein normal shoulder function. Its motion and position cre-ate the parameters to allow normal physiology and biome-chanics of the shoulder to occur. Its roles include being astable part of the glenohumeral articulation, retractionand protraction around the thoracic wall, active acromialelevation, a base for muscle origin and insertion, and as alink in the kinetic chain delivering energy and force fromthe trunk and legs to the hand. Abnormalities in scapularposition and motion are very common and can be seen in

a variety of pathologic states, some intrinsic in theglenohumeral joint or scapula and some far from the scap-ula. These abnormalities alter the roles of the scapula,and can decrease performance, or cause or contributeto shoulder abnormalities. Evaluation of the scapulashould be an integral part of the evaluation of shoulderabnormalities, and rehabilitation of the scapula shouldbe one of the early points emphasized in shoulderrehabilitation.

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