Anterior-Inferior Capsular Length Insufficiency in the Painful Shoulder

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Anterior-Inferior Capsular Length Insufficiency

in the Painful Shoulder

Rick Hjelm,

PT, ATC

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Chris Draper, PTA Sarah Spencer, PTA

M

any investigators

have reported on the shoulder capsular structures as passive restraints which pre- vent instability. Jobe and Pink linked capsular ligament laxity leading to subluxation, eventually causing im- pingement (5). Jobe and Pink (5) also implicated posterior capsular tightness as causing the humeral head to translate further anterior in conjunction with a weak, lax anterior capsule, leading to impingement. Warner et al (14) reported that tight and lax shoulders presented with im- pingement-like symptoms. Capsular ligament dysfunction has been well documented in the frozen shoulder population (8,9). Little has been writ- ten linking a short anterior-inferior capsule as the primary cause of shoul- der pain, ranging from impingement to frozen shoulder.

To our knowledge, no prior stud- ies have been presented describing the evaluation, treatment, and out- comes of patients with tight capsules or, more accurately, insufficient ante- rior capsular length and shoulder pain. The purpose of this article is to describe the evaluation, physical ther- apy treatment, pathomechanics, and implications of the continuum of an- terior-inferior capsular length insuffl- ciency and shoulder pain.

METHODS

One hundred fifty-six patients were referred for physical therapy

Our clinic's initial attempts to document shoulder capsular laxity made us increasingly aware of the presence of subtle restricted passive shoulder movement in patients with a variety of shoulder diagnoses. The purpose of this study is to describe the evaluation, physical therapy treatment, pathomechanics, and implications of a continuum of anterior-inferior capsular length insufficiency and shoulder pain. One hundred fihy-six patients with the diagnoses of shoulder pain, impingement, rotator cuff tendinitis, and frozen shoulder were found to have capsular length insufficiency and were treated by mobilization techniques deemed as manual decompression. Eighty-three percent displayed good to excellent outcomes for decreasing pain, increasing range of motion, and meeting functional goals. Recent literature has supported the concept that capsular ligaments not only provide restraint, but are specifically oriented to guide and center the humeral head on the glenoid during shoulder movements. These patients presented with abnormal glenohumeral mechanics due to anterior capsular ligament length insufficiency. Glenohumeral ligament length insufficiency can be the primary cause of shoulder pain, ranging from frozen shoulder to impingement-like symptoms. Proper capsular ligament length can be restored with manual techniques. All patients with shoulder pain should have capsular ligament length assessment to ensure proper glenohumera! mechanics. Key Words: capsular length, impingement, shoulder, manual decompression

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Owner, Rosedale Family Physical Therapy, Roseville, MN. Address for correspondence: 65 East Pleasant Lake Road, St. Paul, MN 55127.

Physical Therapy Assistant, White Bear lake Family Physical Therapy, White Bear Lake, MN

'

Physical Therapy Assistant, Claremore, OK

with the diagnoses of shoulder pain, impingement, rotator cuff tendinitis. and frozen shoulder. Ninety-five males and 61 females participated. Age range was 15-80 years. Fifty- seven percent of subjects reported gradual, insidious onset with no epi- sode of trauma. Four of those pa- tients were diabetic. Workers' com- pensation and auto injuries were excluded.

Evaluation consisted of taking a history and performing an examina- tion with a Cyriax basis (1) and spe- cific capsular length and provocation tests developed by the primary author and Maitland (7) (Table 1). Patient pain levels and functional limitations were documented initially and reas-

sessed during and after the course of treatment.

Goniometric measures were taken initially, pre- and postindividual treatment, and for a discharge evalu- ation. Many patients had severe gle- nohumeral restriction beyond the inferior glenohumeral ligament to include the middle posterior capsule. We tracked and documented the an- terior-inferior capsular tightness. Pre- caution was taken to place the hu- merus into 90" of abduction without scapular compensation before exter- nally rotating the shoulder. Passive humeral external rotation performed prior to placing the humerus at 90" resulted in greater measurement of external rotation. The anterior band

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SHOULDER EXAMINATION

Cyriax-based evaluation

1) Active range of motion (standing) Flexion: Pain, asymmetrical movement

2) Passive range of motion (standing, including over-pressure and end feel) Abduction with scapula stabilized

Abduction

External rotation in neutral Reaching behind the back 3) Resisted testing

Abduction, internal rotation, external rotation, adduction, elbow flexion, elbow extension

Capsular length and provocation assessment

1) Active elevation progression involved repeated movements in increasing amounts of abduction and external rotation. These positions put progressive demands on the anterior aspect of the anterior-inferior glenohumeral ligaments. If insufficient capsular length exists, the involved shoulder will ride higher, the taut anterior-inferior glenohumeral ligament will prevent further glide in the joint, and motion will come from the scapulothoracic joint. A painful arc, impingement, catch, or clicking may also occur.

Flexion

Elevation in the plane of the scapula (hands in front of trochanter) Abduction with thumbs up (hands begin even with trochanter) Hyperabduction with thumbs up (hands begin behind trochanter)

2) Active motions consisting of flexion with internal rotation and reaching behind the back place primary tension on the posterior capsule and the posterior band of the inferior glenohumeral ligament complex. lnvolved side will show a decrease in active range o i motion and pain.

Reach behind the back

Flexion with maximal internal rotation

3) Quadrant: Maitland (7) described having the patient lie supine in 90" abduction with full external rotation. Allow the arm to hang at its passive limits and slide the arm into full elevation while observing the pathway of the arm movement. Add over-pressure at selective aspects of the arc. lnvolved side will have an arc of movement that rides upward with a leathery end feel. Pain reproduction may be due to compression of suprahumeral structures.

4) Goniometric measures: Ensure 90-f abduction is achieved without scapular compensation before externally rotating the humerus.

9 90190 posterior capsule: Supine, abduct to 90°, internally rotate until anterior shoulder begins to come off the table. Provide over-pressure for end ieel and symptom reproduction. lnvolved side will come off the table earlier with internal rotation and will be firmer and painful with end ieel.

6) Prone external rotation: Lying prone, fingers interlocked with palms down. Forehead rests on dorsal aspect of hands. The deb-acromial groove between acromion and humeral head is visually observed, palpated, and over-pressed for symmetrical depth, end feel, and symptom reproduction. lnvolved side will have smaller fold, less space to palpation between the acromion and humeral head, and will have a firm and possibly painful end feel.

7) Prone maximum external rotation: Same as above except starting position involved interlocking fingers and hands resting on top of the patient's head to place more tension on the inferior glenohumeral ligament complex for increased sensitivity with assessment.

TABLE 1. Shoulder examination and interpretation. Cyriax-based exam and capsular length and provocation assessment.

of the inferior glenohumeral liga- ment is not under tension until the humerus is abducted to at least 90" (1 0,11,15). Therefore, placing the humerus into premature external rotation and then abducting the hu- merus to 90" will give a false pres- ence of anterior capsular length. If the humerus could not be abducted to 90' without the joint locking and the scapula abducting in compensa- tion, the patient was given the mea- sure of 0" external rotation. Treat- ment then consisted of manual

techniques until this position was ac- complished.

Many patients had complaints that related only to throwing o r per- forming overhead sports activities without activity of daily living func- tional compromise. These patients had the least demonstrable capsular shortness limited to the inferior gle- nohumeral ligament complex. Those with subtle capsular length insuffi- ciency did not report stiffness o r re- striction, but only catching, a painful arc. o r movement limitation due to

pain. They were unaware of their lack of capsular flexibility. We think this illustrates how capsular shortness can develop gradually and is compen- sated by a mobile shoulder girdle complex. Patients with less functional movement had less capsular ligament length. This capsular ligament length insufficiency was easily detected by using Cyriax's passive movement as- sessment, and these shoulders fit the capsular pattern for movement limita- tion (1).

Patients' shoulders were primarily treated with mobilization techniques. Manual decompression techniques were performed once the patient achieved 0" of external rotation posi- tion. Modalities, such as ultrasound and hot packs, were used specifically near the anterior border of the axle to invite maximal tissue elasticity by increasing tissue temperature in the anterior capsular structures.

Capsular length was assessed dur- ing treatment sessions by observing active movement for .symmetry and taking passive goniometric measures. Typical subjective comments during the manual decompression technique included the feeling of a dull, non- specific ache, the absence of the mus- cle stretch feeling, and frequent par- esthesia in the hand. Posttreatment active movement was usually more fluid with less scapular compensation and less impingement-like symptoms while performing active elevation movements. This soreness, after a 20- to 30-minute stretching session well into the capsular motion barrier, ranged from being nonexistent to lasting 2 days. We told patients that it was reasonable to be sore for u p to 2-4 hours after treatment. Patients were shown and expected to perform home capsular stretching exercises. T h e number of treatments required was counted and averaged. Factors influencing the number of treat- ments included physician orders, managed care authorizations, and the treatment effectiveness.

Outcome data were gathered by assessing the patient's pre- and post-

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Average Range of = 156 Percentage of Average Number of Motion

N Treatments (decrees) " Excellent 78 50 12 40.5 Good Fair Poor

TABLE 2. Summary of treatment results.

range of motion, pain levels, and functional abilities. The outcome was scored by assigning 1 point for an increase in passive range of motion with a goniometer, decrease in pain, and meeting functional goals. A score of 3 was considered excellent, 2 was

good, 1 was fair, and 0 was poor. Functional goals related to combined movement of elevation with external rotation included reaching to the back of the head for grooming, reaching to the top shelf of a c u p board, donning an overcoat, and get- ting into the cocking phase of throw- ing. Pain levels were rated 1-10. We associated a lower patient pain rating with diminished pain. When patient.. who previously reported interrupted sleep due to pain reported that they could now sleep through the night, we considered their pain to be de- creased (Table 2).

RESULTS

Eighty-three reported good to excellent results. Regarding an excel- lent result, the average beginning external rotation was 56" and the av- erage ending external rotation was 9'7". Most patients reported some dis- comfort during and, for a brief pe- riod, after stretching sessions. Pa- tients with a poor result frequently did not tolerate the manual stretch- ing and some had involuntary muscle guarding during stretching. Insur- ance restrictions, low tolerance to manual stretching, and involuntary muscle guarding were the major fac- tors limiting patient progress.

Manual Decompression Technique

The term manual decompression is used to describe manual capsular stretching techniques used to restore normal glenohumeral biomechanics and decompress the suprahumeral space (Figure 1). The technique in- volves simply pushing the humeral head into the shortened ligamentous structure to increase its length and create more suprahumeral space. We believe it is extremely effective in stretching the anterior-inferior gleno- humeral ligaments as the technique of depressing the humeral head causes a "bowing force" of the liga- ment rather than a parallel force as with physiological stretching. The technique also allows for subtle alter- ations of the humerus to maximize stretch. While continually assessing end feel firmness, humeral position is

frequently adjusted in abduction, horizontal abduction, and external rotation during the stretching ses- sion. The basis for these techniques rests in understanding how glenohu- meral motion is allowed and con- trolled by specifically oriented fibers of the glenohumeral ligaments (Fig- ure 2).

Literature Review

O'Brien et al (10) describe the anatomy and histology of the inferior glenohumeral ligament complex. Briefly, they describe the attachment of the inferior glenohumeral liga- ment complex as a hammock with insertions from 3 o'clock to 9 o'clock on the glenoid. Its anatomy consists of anterior and posterior bands that have a distinct parallel orientation of collagen fibers and a axillary portion that is thicker, but has a less orga- nized collagen matrix. Functionally, the inferior glenohumeral ligament complex becomes taut in increasing amounts of abduction. Abduction combined with internal rotation causes increased tension in the poste- rior band of the inferior glenohu- meral ligament complex. Abduction with external rotation increases ten-

FIGURE 1. Patient is supine with shoulder abducted to 90'. Available capsular length is taken up, hanging the shoulder in maximum external rotation and horizontal abduction. The clinician supports the arm and uses the web space to decompress the humeral head by pushing caudally into the hammock-like anterior band of the inferior glenohumeral ligament complex.

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ER MOBILIZATION FORCE

ANTERIOR BAND

\

I

FIGURE 2. Manual decompression is done by lying the patient supine on the edge of the table, abducting the humerus to 904 and taking the slack out of the capsular structures by externally rotating and placing the shoulder in horizontal abduction. From that position, the therapist uses the web space to push the humeral head into the shortened capsular structures while maintaining the position of horizontal abduction and external rotation. ER =

External rotation.

sion in the anterior band of the infe- rior glenohumeral ligament complex

(Figure 3).

Teny et a1 (13) demonstrated how capsular ligaments control and guide the humeral head throughout movement by use of a strain gauge analysis. Eight aspects of the capsular ligaments were studied with a shoul- der motion device to describe pri- mary restraint, tension sharing, and transference of tension. The primary restraint ligament is that ligament under the most tension during a spe- cific movement. In Terry et al's study, movements reveal a ligament loaded substantially more than a secondary or an antagonistic ligament. The first ligament is the primary restraint liga- ment and the second ligament is part of the tension sharing concept. Com- bined movements such as abduction and external rotation reveal changes in the tension known as transference of tension of the ligaments. This re- flects how certain aspects of the c a p sule are always under various

amounts of tension to control the humeral movement.

Consistent with O'Brien et al's description of the anterior and poste- rior band of the inferior glenohu- meral ligament complex, Terry et al's results confirmed that the anterior and posterior aspects of the inferior capsule are the primary restraint liga- ments when the shoulder is abducted to 90" and externally and internally rotated, respectively.

Harryman et al (3) coined the term "the law of the capsular con- straint" to describe how an asym- metrically tight capsule causes exces- sive translation of the humeral head on the glenoid in the opposite direc- tion of the tightness. "Obligate glen* humeral translations are not the re- sult of ligamentous insufficiency or laxity; instead, they result when the capsule is asymmetrically tight." For example, a tight anterior capsular structure will cause excessive poste- rior translation of the humeral head on the glenoid during external rota- tion (Figure 4).

In seven cadaveric glenohumeral joints with the capsule intact, flexion was accompanied by an average of 4

mm anterior translation that could not be prevented when opposed by an opposite force of 30-40 N. Trans- lation in these joints began at around 50" flexion. Joints without passive restraints show translation consistent with the current osteokinematic prin- ciple of the convex on concave rule

(translation or glide in the opposite direction of roll). These control joints stripped of capsular ligaments

showed 0 to 2 mm of posterior trans lation. When a surgical stitch was placed, causing a now tight posterior capsule, flexion was accompanied by 10 to 12 mm of anterior translation beginning immediately from 0" flex- ion (Figure 5).

These articles have focused on how capsular structures play a greater than previously appreciated role in allowing and controlling normal ar- ticulation between the humeral head and the glenoid (3,lO,l3). Excessive translation of the humeral head on the glenoid occurs with rotator cuff dysfunction and can be caused by anterior-inferior glenohumeral liga- ment length insufficiency. This taut- ness prevents the desired roll and gliding that is necessary to prevent suprahumeral space compression.

Proposal for Normal Glenohumeral

Arthrokinematics

A much larger humeral head needs to roll and glide simulta- neously on the glenoid. Beginning range of motion involves mostly roll- ing. The rotator cuff functions to compress the humeral head against the glenoid, preventing superior mi- gration, leading to impingement (6). Research indicates those with shoul- der dysfunction, specifically rotator cuff disease, have excessive amounts of translation superiorly. The average humeral head translates 3 mm ini- tially when the deltoid vector of force is nearly perpendicular with the hu- merus. It then settles down to ride 1 mm superior of its initial resting place relative to the glenoid (12).

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FIGURE 3. O'Brien et al's schematic shows how the inferior glenohumeral ligament complex functions like a hammock to support the humeral head. It becomes taut at 90' of abduction fa). As the arm is internally rotated (b, c), the posterior band of the inferior glenohumeral ligament complex becomes increasingly taut to support the humeral head posteriorly. When the arm is internally rotated (b, d), the anterior band of the inferior glenohumeral ligament complex becomes increasingly taut to support the humeral head anteriorly. Laxity of this structure can lead to subluxation or dislocation. Insufficient length of the inferior glenohumeral ligament complex leads to excessive translation of the humeral head on theglenoid, leading to impingement and a host of shoulder symptoms. Abd = Abduction, IR = Internal rotation, ER = External rotation. (Reprinted from O'Brien et a1 (101, with permission).

The maintenance of the relation- ship between the humeral head and glenoid during elevation is due to many factors. First, the articular shapes show a glenoid that is shallow, but made approximately 50% deeper by the labrum (4). The humeral head is convex and much larger than the glenoid. The rotator cuff func- tions to dynamically depress the hu- meral head while the deltoid powers

would roll up posterosuperiorly and would glide 1-4 mm in the same di- rection. Proper capsular length would allow this translatoric move- ment to occur without excessive translation, leading to subluxation. The result is full and free elevation with the humeral head and glenoid maintaining its relationship (Figure 6)

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the humerus into elevation. The non-

contractile structures. ~rimarilv n , c a p

.

Proposal for Abnormal Glenohumeral

sular structures, share tension to

Arthrokinematics

maintain the humeral head and gle-

noid relationship of rolling and glid- Rotator cuff dysfunction with in- ing. For example, the combined adequate humeral head depression movement of abduction and external will cause excessive superior transla- rotation means the humeral head tion (12). Motion asymmetry due to

FIGURE 4. Effect of asymmetrical tightening of the capsule. Rotations of the humeral head that produce tension in the tissues of an operatively tightened c a p sule predictably cause translation in a direction oppo- site to the tight-tissue constraint. This constraint o p poses loads and displacement that are directed toward itself and acts to translate the humeral head on the glenoid in a direction away from itself. This mecha- nism of translatory motion is referred to as the capsular constraint mechanism.

rotator cuff insufficiency usually pre- sents early in the elevation attempt due to the nearly vertical force the deltoid exerts to overcome gravity. The combined movement of abduc- tion and external rotation with an excessively tight anterior band of the inferior glenohumeral ligament com- plex will cause excessive glide of the humeral head on the glenoid in the posterior and superior direction. The effect is posterior and superior com- pression of the suprahumeral space. This compression will begin near

150" of flexion and will occur earlier if elevation of the humerus is per- formed in greater amounts of hori- zontal abduction as greater capsular length is required. The joint may catch, pinch, or lock in the quadrant position of abduction and external rotation where capsular length must be sufficient to allow glide of the hu- merus (Figure 6).

In subtle cases, these symptoms may only occur when the patient is performing tasks requiring maximal

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The magnitude of capsular shortness related closely with the amount of reported functional compromise. Lit- tle relationship was found between pain and capsular shortness.

2) People who have developed shoulder pain of an insidious nature may have anterior-inferior capsular ligament dysfunction that has been present but has not manifested itself Control

due to the shoulder girdle's inherent

i

-20 0 20 40 60 00 100 120

FLEXION ANGLE (degrees)

FIGURE 5. Representative graph comparing translation during flexion in shoulders with an intact capsule, a vented capsule, and a tightened capsule. After operative tightening ofthe posterior part of the capsule, anterior translation occurred at lesser angles and to a much greater extent than in shoulden with an intact or vented capsule. (Reprinted from Harryman et a1 (3), with permission).

capsular mobility such as throwing and reaching into the back seat of the car. If the condition progresses and capsular length is further com- promised, many of the patient$' activ- ities of daily living requiring shoulder excursion will be affected, such as putting on a coat and reaching into the cupboard.

Implications

1) Subtle anterior-inferior capsule length insufficiency causes impinge- ment-like symptoms. Those with full active motion and little activity of daily living functional compromise may have pain with dynamic activi- ties, such as swimming or throwing.

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90 DSGRRES ABDUCTION

FIGURE 6. Abduction to 90" takes the slack out of the inferior glenohumeral ligament complex, and external rotation (ER) further increases tension in the anterior band. This tension pushes the humeral head into the suprahumeral space. This translation is consistent with Harryman et al's "law of the capsular restraint."

flexibility which compensates for the glenohumeral joint.

3) Capsular length assessment is a practical tool in determining if capsu- lar ligament dysfunction is present.

4) The manual decompression technique restores proper capsular length and facilitates a normal g l e n e humeral interaction.

5) Increasing capsular length (as measured by passive goniometric reading) resulted in less painful, more symmetrical active and passive movements and ultimately allowed patients to have less shoulder pain and greater function.

6) Shoulder pain caused by asym- metrical capsular tightness may be on the same continuum as frozen shoul- der, where a greater portion of the capsule becomes restricted. An asym- metrically tight capsular ligament structure may be the predisposing factor for the development of a host of shoulder problems, including bur- sitis, impingement, and rotator cuff tears.

Implications for the Throwing Athlete

Many of the athletes in our study doing overhead sports had subtle capsular tightness located in the ante- rior band of the inferior glenohu- meral ligament complex. These ath- letes had difficulty getting back into the fully cocked phase. Dillman et al (2) report that range of shoulder ab- duction remains between 90 and 110" throughout the throwing mo- tion. The maximum amount of exter- nal rotation occurs just after foot contact and averaged 178" (some of which is contributed from the t h e

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racic spine). Although specific quan- tification of this external rotation was not assigned, it is reasonable to be- lieve a tremendous amount of ten- sion exists in the anterior band of the inferior glenohumeral ligament complex. Athletes with tight anterior bands of the inferior glenohumeral ligament complex will report they can throw a short toss, as in an in- field-type of throw, where maximal cocking is not required and forces are generated from the elbow and wrist cocking rather than shoulder winding, but cannot produce maxi- mum velocity, as in an outfield long toss, where the shoulder is maximally positioned in preparation to begin the acceleration phase. These ath- letes usually throw with short move- ments in a near side arm fashion and will use the elbow and wrist exces- sively to create velocity.

DISCUSSION

In throwing athletes as well as in people performing everyday tasks, the glenohumeral capsular ligaments p r e vide restraint while keeping the hu- meral head centered during normal functional movement. In our study, patients had several different diag- noses, but a common element of an- terior-inferior glenohumeral ligament length insufficiency in varying degrees. With an average external rotation in- crease of 40.5" (excellent result) and 34.8" (good result), these patients ex- perienced significant changes in their capsular flexibility. Identifying and treating by restoring capsular length produced good to excellent outcomes in 83% of the patients.

SUMMARY

Through clinical experience of treating and restoring symmetrical

capsular extensibility in the shoulder and studying recent literature, we think that more emphasis needs to be placed on the capsular structures' role in allowing and guiding normal motion. The glenohumeral ligaments may play a critical role in centering the humeral head on the glenoid during a variety of complex motions. Glenohumeral motion is guided by passive tissue restraints which are un- der various amounts of tension throughout movement. Capsular dys- function can be detected by assessing the length of passive capsular re- straints. Insufficient length of the anterior-inferior glenohumeral liga-

The technique involves

simply pushing the

humeral head into the

shortened ligamentous

structure to increase its

length and create more

suprahumeral space.

ments may be a critical mechanical factor causing impingement and shoulder pain. Treatment goals may include restoration of normal capsu- lar tissue length through specific mo- bilization techniques directed at the anterior-inferior glenohumeral liga-

ments. JOSFT

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1. Cyriax 1 0 : Textbook of Orthopedic Medicine (3rd Ed), p 728. London: Bay- lor Tindall, 1978

2. Dillman C, Fleisig G, Andrew J: Biome- chanics ofpitching with emphasis upon shoulder kinematics. 1 Orthop Spom Phys Ther 2:402-408, 1993

3. Harryman D, Sidles J, Clark J, Mc- Quade K, Gibe T, Matsen F: Translation of the humeral head on the glenoid with passive glenohumeral motion. J Bone Joint Surg 72A(9): 1334

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1343, 7 990

4. Howell S, Galinat B: The glenoid-labral socket-A constrained articular sur- face. Clin Orthop 243: 122- 125, 1989

5. Jobe F, Pink M : Classification and treat- ment of shoulder dysfunction in the overhead athlete. J Orthop Sports Phys Ther 8:427-432, 1993

6. Kronberg M, Nemeth G, Brostrom L: Muscle activity and coordination in the normal shoulder. Clin Orthop 8: 76-85, 1990

7. Maitland GD: Peripheral Manipulation (2nd Ed), pp 66-67. London: Butter- worth-Heinemann, 1977

8. Moren-Hybbinette I, Mortiz U, Scher- sten B: The painful diabetic shoulder. Acta Med Scand 2 19:507-5 14, 7 986 9. Moren-Hybbinette I, Mortiz U, Scher-

sten B: The clinical picture of the pain- ful diabetic shoulder-Natural history, social consequences and analysis of concomitant hand syndrome. Acta Med Scand 22 1 :73-82, 7 987

10. O'Brien S, Neves M, Arnoczky S, Rozbruck R, Dicarlo E, Warren R, Sh- wartz R, Wickiewicz T: The anatomy and histology of the inferior glenohu- meral ligament complex of the shoul- der. Am 1 Sports Med 5:449-457,

7 990

11. O'Connell P, Nuberg G, Mileski R, Lautenschlager E: The contribution of the glenohumeral ligaments to anterior stability of the shoulder joint. Am J Sports Med 6:579-584, 1990

12. Poppen N, Walker P: Normal and ab- normal motion of the shoulder. J Bone Joint Surg 3:195-200, 1976

13. Terry G, Hammon D, France P, Nor- wood L: The stabilizing function ofpas- sive shoulder restraints. Am J Sports Med l9(1):26-34, 199 1

14. Warner J, Micheli L, Anlanian L, Kennedy I, Kennedy R: Patterns of flex- ibility, laxity and strength in normal shoulders and shoulden with instability and impingement. Am J Sports Med 4:366-375, 1990

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