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Shoulder Instability

It is important to make a distinction between laxity and instability. Shoulder laxity is a translation of the humeral head on the glenoid (socket) in the absence of clinical symptoms or pathologic changes. This means that normal shoulders may be lax without being unstable. When the laxity results in clinical symptoms and is associated with pathologic changes, instability results. Shoulder instability is mostly a chronic, recurrent condition. The direction of the shoulder instability can be anterior and inferior, posterior and inferior, posterior, or multidirectional. The degree can also vary from dislocation to subluxation.
Shoulder instability and impingement are a continuum of shoulder disease. Too many classification systems exist but a practical one in sport could be:
– type I is pure impingement;
– type II is secondary impingement and primary instability caused by capsular trauma;
– type III is secondary impingement with primary instability from associated hyperelasticity;
– type IV is pure instability.

Chronic shoulder instability is most common in athletes participating in sports involving throwing or other overhead activities. Chronic fatigue of the dynamic anterior shoulder stabilizers seems to initiate most
problems. As these dynamic stabilizers fatigue, increased and repetitive stress is placed on the static anterior, glenohumeral (shoulder joint) stabilizers which results in gradual stretching of these stabilizers. A
relative imbalance between the anterior and posterior capsule may be the result. This fatigue may result in changes in the throwing or hitting mechanism, which may include scapula lag and/or a dropped elbow. In
the early phases there is mostly fatigue or loss of consistency, but no major decrease in performance. At this stage a training program may have good effects with time. Gradual stretching of the anterior structures will occur with anterior subluxation. This will allow the rotator cuff to impinge on the posterior superior surface
of the glenoid in the abducted and externally rotated position of the arm, which may eventually progress to fraying of the undersurface of the rotator cuff. This pattern can be seen in throwing athletes, and in baseball, volleyball, and tennis players. Swimmers have similar shoulder problems. Stress combined with laxity predisposes to internal impingement. Exercises at this stage are very important. The gliding of the joint within the socket may cause pain during and after sporting activity. The athlete often feels as if the shoulder has almost slipped out of the socket in sports such as pole-vault, ice hockey, team handball, volleyball, basketball, American football, and in throwing and racket sports. In order to treat these injuries successfully, it is important to determine the direction and the magnitude of the instability.

Symptoms and diagnosis

– Pain in the shoulder joint occurs during and after exercise and competition.
– ‘Dead arm’ sign is present. This sudden onset of weakness, numbness and tingling in the arm is provoked by certain actions and can be due to a sudden transient subluxation of the shoulder.
– A feeling of dislocation is experienced when the arm is lifted above the horizontal plane and externally (outwards) rotated.
– The diagnosis can be made with the aid of the apprehension and stability tests.
– An X-ray examination reveals skeletal changes along the anterior edge of the joint socket.
– An MRI or preferably an MR arthrogram may show a labral tear, intra-articular changes, and the redundant capsule. This test is excellent but expensive.
– Arthroscopy and examination under anesthesia will confirm the diagnosis.


The athlete should improve the function of the joint with active strength exercises.
The doctor may operate in cases of prolonged problems. It is often enough to stabilize a tear of the labrum, but if there is multidirectional instability, open surgery with a capsular shift procedure may still be

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