The shoulder joint is a ball and socket joint similar to the hip, though it is extremely shallow and, therefore, unstable. Ligaments help hold the shoulder bone in its socket. If the ligaments become stretched or torn from trauma, or overloading, the required stability of the ligaments throughout the shoulder’s large range of motion is compromised. This is called instability.
Shoulder instability problems are the second most common type of shoulder problems after Rotator Cuff tears. These instabilities can range from subluxation (a malalignment subject to dislocation), to dislocation (actual separation of the humerus from the scapula).
Shoulder instability problems generally result from forceful contact and overhead sports or activities. Patients report an uncomfortable sensation and feeling that their shoulder may slide out of place – which is called apprehension. An unstable shoulder is globally tender and causes a reduction in range of motion – particularly in overhead activities.
Those at Risk
Shoulder instability is most frequently diagnosed in patients who have sustained a prior shoulder dislocation that resulted in torn ligaments. Loose healing of the tendons will result in chronic instability. In patients under the age of 35 sustaining a traumatic dislocation, shoulder instability generally follows in approximately 80 percent of the patients.
Athletes competing in overhead and forceful contact sports, such as swimmers, pitchers and volleyball players, are also at risk for shoulder instability problems.
In young patients, a shoulder dislocation frequently results in future instability and dislocations ultimately requiring surgery. For those in their 30s, future dislocation and instability is rare following a first-time episode. For patients over 40 years of age, a dislocation usually results in a rotator cuff tear as well.
Patient history, a listing of symptoms experienced, and a physical examination are generally all that is necessary to diagnose shoulder instability. An X-ray may be indicated in order to determine which way the shoulder comes in and out of its socket – anterior (front), posterior (back) or both (multidirectional). And magnetic resonance imaging (MRI) can help identify possible causes for the instability or dislocation, such as the presence of torn cartilage or stretched ligaments.
Depending on the severity of the instability, conservative nonsurgical treatment is generally the first course of action and generally involves refraining from overhead activities, cold compression to control pain and swelling and targeted range of motion exercises that strengthen the rotator cuff, the deltoid, and the scapula rotators. Also established are exercises providing both positive and negative force on the muscles while improving cooperation of muscle groups.
If the instability results in a labrum tear, sutures may be required for reattachment. A dislocation may simply require immobilization with a shoulder sling. Arthroscopy or other outpatient procedure may be indicated to assist in stabilizing the shoulder joint.