Shoulder Instability

What is Shoulder Instability?

Illustration of shoulder jointThe shoulder joint is made up of two joint surfaces which are held together by ligaments and muscles. It has a ball on one side and a shallow socket on the other. The ball is formed by the upper arm bone called the humerus, and the socket is formed by the outer portion of the shoulder blade and is called the glenoid.

The ball and socket fit smoothly against one another with an outer rim of a cushioning cartilage structure called the labrum surrounding the glenoid. Illustration: End View of ScapulaBecause of the limited contact between these two structures, any loss of the normal integrity of the ligaments will result in the joint slipping out of its normal alignment into an abnormal position creating an unstable shoulder joint.

Minor damage to the capsule can result from recurrent injuries to the ligaments and may lead to mild instability (subluxation). Extensive ligament damage may result in complete dissociation of the two joint surfaces (dislocation).

Signs and Symptoms of Shoulder Instability

An unstable shoulder may cause pain, a sense of arm weakness and the perception of the shoulder slipping out and back into the joint. A complete dislocation is associated with severe pain, inability to relocate the joint, and usually requires and emergency room visit 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 after obtaining an injury history, and doing a physical examination. Certain tests may reproduce some of the symptoms of instability, presenting the patient with the feeling that the joint is about to slip out. This exam differentiates instability from other sources of shoulder pain. Further details of the degree of instability may be obtained 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 full dislocation, a vigorous rehabilitation program is designed to strengthen the supportive muscles. When the shoulder is very painful, a period of rest may be indicated combined with anti-inflammatory medications. The rehabilitation program is advanced as the patient makes progress and the joint demonstrates improved stability over time. A first time shoulder dislocation is frequently treated with rest and immobilization for a short 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 are used to fix shoulder instability depending on the extent and location of the injury.

Before/After Surgery Shot of Torn LabrumThe surgery is done anthroscopically using a thin camera and 1 cm incisions in the shoulder. The torn tissue is anchored back to the glenoid bone, and the stretched ligaments are tightened thereby restoring the shoulder stability. Your surgeon will advise you of the procedure most appropriate for you.