What is Shoulder Instability?

The shoulder joint is made up of two joint surfaces which are held together by capsular ligaments and some surrounding musculature. The shoulder joint itself is not a "ball and socket" joint but is made up of a large articular ball on one side and a shallow "dish" on the other. The ball portion of the joint is formed by the upper arm bone called the humerus and the dish is formed by the outer portion of the scapula or shoulder blade called the glenoid. These two surfaces fit smoothly against one another within an outer rim of a "cushioning cartilage" structure called the labrum at the attachment of the capsular ligaments to the glenoid. Because of the limited contact surface between these structures, any loss of the normal integrity of the capsular ligaments will result in tendency of the joint to slip out of its normal alignment into an abnormal, incongruent position creating an unstable shoulder joint.

Small degrees of damage to the capsule can result from recurrent injuries to the capsular ligaments or their attachments to either side of the joint, and may lead to smaller degrees of instability (subluxation).

With larger degrees of capsular ligamentous damage, the joint may become more unstable resulting in complete dissociation of the two joint surfaces (dislocation).

Signs and Symptoms of Shoulder Instability?

A shoulder which is unstable may subluxate in different provocative positions, or during certain provocative activities may be associated with sudden pain, a sense of arm deadness or a perception of the shoulder.slipping out and back into "joint".

A complete dislocation is associated with severe pain, inability to "relocate" the joint, and usually requires the aid of a knowledgeable person to restore the shoulder to its proper alignment. The joint may dislocate anteriorly (towards the front), inferiorly (downward), or posteriorly (towards the back).

How is Shoulder Instability Diagnosed?

The diagnosis of shoulder instability is made by the examining physician after taking a thorough diagnostic history and doing a careful physical examination. Certain maneuvers the examining physician puts the arm through may reproduce some of the symptoms of subluxation, presenting the patient with an uncomfortable feeling that the joint is about to "slip out". This careful examination differentiates instability from other sources of shoulder pain. Further details of the degree of instability may be enhanced through a variety of x-rays and imaging studies.

Common Treatments for Shoulder Instability?

When shoulder instability is diagnosed and there has not been a frank dislocation, a vigorous rehabilitation program is designed to strengthen some of the supportive musculature while limiting positioning of the arm into provocative positions. When the shoulder is exceptionally painful, a period of rest may be indicated combined with some anti-inflammatory medication. The rehabilitation program is advanced as the patient makes progress and the joint demonstrates improved dynamic stability over time. A first time shoulder dislocation is frequently treated with rest and immobilization over a period of time followed by progressive rehabilitation, based on the severity of the injury. When recurrent dislocations occur or an unstable shoulder fails to respond to conservative management, surgery may be indicated. A number of surgical techniques exist which may be employed, depending on the extent and location of the problem causing the instability. These range from arthroscopic stabilization techniques to open reconstruction of the joint capsule. Your surgeon will advise you of the procedure most appropriate for you.

Following surgery, a period of rest and rehabilitation follows over a period of time designed to return the individual to function, work and sports.

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