A dislocated shoulder is one of the most common shoulder injuries, especially in young athletes and people who play contact sports.
To understand the injury, it helps to understand the shoulder's structure. The shoulder is a ball-and-socket joint, yet the shoulder's anatomy allows for an amazing amount of flexibility. The head of the humerus (upper arm bone) is a ball that sits in the glenoid cavity (shallow socket) of the shoulder blade. Because the socket is so shallow, the shoulder relies on the surrounding soft tissues for stability. The labrum (cartilage lining the socket) and capsule (containing joint fluid and several ligaments) provide a majority of the shoulder's stability. The muscles of the rotator cuff and shoulder blade also help.
Shoulder dislocation most commonly occurs when the arm is moving forcefully away from the body and rotating externally, as in the motion of throwing a baseball. The humeral head is pulled out of the front of the glenoid cavity – either partially, which is called a shoulder subluxation, or entirely, which is called a shoulder dislocation. Although some people are able to get the humerus back into the joint themselves, many need to have it done in an emergency room.
A shoulder dislocation usually also injures the front of the labrum (resulting in what doctors call a Bankart lesion) and the humeral head (a Hill-Sachs lesion).
Vulnerability to a repeat dislocation or related shoulder injuries depends on a person's age. Athletes under the age of 30 have a high risk of dislocating the shoulder again. This risk decreases with age. People over 50, however, have a higher chance of a shoulder dislocation causing a rotator cuff tear.
Our Approach to Shoulder Dislocation
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UCSF Health medical specialists have reviewed this information. It is for educational purposes only and is not intended to replace the advice of your doctor or other health care provider. We encourage you to discuss any questions or concerns you may have with your provider.