Recurrent Shoulder Dislocation
February 16, 2005
By: Steve Siwy for Shoulder1
If you’ve ever experienced the pain of a dislocated shoulder, once was probably more than enough. Shoulder dislocations often recur, however, and the risk of it happening again can be influenced by various factors.
Most dislocated shoulders are the result of trauma to the joint, but recurrence is much more likely to occur if that trauma is caused by twisting, or sharp abduction (when the arm is lifted up and out from the body), than from a blow directly to the front of back of the shoulder or a fall. Interestingly, if the trauma is so severe that it causes a complication like a fracture that requires a longer period of immobilization than normal (usually, a dislocated shoulder is immobilized for one to three weeks), the additional time without movement may help prevent recurrence by allowing additional scar tissue to form, which can contribute to stability.
The more often a shoulder is dislocated, the more likely it is to dislocate again. Also, young people are far more likely to have subsequent dislocations, and the risk of recurrence decreases as patients get older (though the risk of the shoulder joint stiffening, or “freezing” while immobilized increases). Athletes, who are at a higher risk for traumatic injury in general, also have a greater than usual chance of recurrent dislocation. Recurrence is also more likely in men than women.
A dislocated shoulder is extremely painful, and it is thus desirable to have it diagnosed as quickly as possible, at which point the doctor can place the shoulder back in its socket (a procedure technically known as “reduction”). Analgesics or other painkillers may be used to dull the pain while the shoulder is being x-rayed, or during reduction itself. Once the shoulder is back in its socket, the most intense pain will quickly subside.
The shoulder is one of the most flexible joints in the body. The area of contact between the head of the humerus (upper armbone) and the glenoid fossa (the socket on the scapula into which the humeral head fits) is small, and the glenoid fossa is shallow, allowing for the joint’s wide range of motion. These features also contribute to its instability, however, making the shoulder the easiest joint to dislocate.
The shoulder is stabilized by the shoulder capsule, which surrounds the joint and includes the synovial membrane, various ligaments, the labrum (which cushions the joint and anchors several ligaments), and the rotator cuff muscles. Also surrounding and stabilizing the joint are the larger muscles of the upper arm, the triceps, biceps, and deltoid.
The shoulder usually dislocates anteriorly (in the forward direction), because the glenoid restrains it from the rear. In a full dislocation, the humeral head slips all the way out of its socket, often tearing ligaments, and sometimes the rotator cuff or the labrum, along the way. When the humerus is pushed only partway out of the shoulder socket, it’s known as “subluxation.”
Last updated: 16-Feb-05