The shoulder is most commonly dislocated when the arm is abducted and externally rotated, in a position as if you were throwing a baseball. When there is a strong force with the arm in this position, the humeral head can dislocate out the front of the glenoid. When this occurs, it can either come partially out, which is termed a shoulder subluxation, or come entirely out, which is termed a shoulder dislocation. Although some people are able to reduce their shoulder (put it back into joint), many others need to have their shoulder reduced in an emergency room.
When a shoulder dislocates, there is most often an injury to the front of the labrum, termed a Bankart Lesion. There is also an injury to the humeral head termed a Hill-Sachs Lesion. The Bankart lesion is what is repaired during surgery for a unstable shoulder.
The natural history of athletes with a shoulder dislocation depends on the age of the athlete. In younger athletes (less than 20 years old), there is a very high risk of re-dislocating the shoulder. However, as we get old, the risk decreases. In people over the age of 50, there is a chance that the shoulder dislocation occurs along with a rotator cuff tear.
Reviewed by health care specialists at UCSF Medical Center.