Shoulder Instability / Dislocation

The shoulder is the most mobile joint in the body, and that mobility depends on a shallow socket and soft tissues that hold the ball in place. When those tissues are torn or overstretched, the ball can slip out of the socket, and that is shoulder instability. Most cases follow a traumatic dislocation that tears the rim of the socket. The disrupted tissues do not heal reliably on their own, but the joint can usually be brought back under reliable control.

A first complete dislocation is usually unmistakable. Common symptoms include:

• Sharp pain with the arm locked in a raised position after a dislocation
• A visible deformity at the front of the shoulder where the ball has shifted
• A loose feeling, or a sense that the joint could give way
• Avoiding the arm-raised, rotated-out position where the shoulder feels least secure

The diagnosis rests on the history and a focused exam that tests the stability of the joint in different positions. X-rays show any bone fragment broken from the front of the socket and a dent in the back of the ball where it pressed against the socket rim. An MRI with contrast injected into the joint shows the labral tear in detail, and a CT scan is added when bone loss appears significant, because the amount of bone lost determines which operation is appropriate.

Rehabilitation is a reasonable first step for older or lower-demand patients and for mild or multidirectional instability:

• Strengthening the rotator cuff and shoulder-blade muscles to build active control around the joint

Surgery is appropriate when instability continues despite rehabilitation, when a young active patient faces a high likelihood of repeat dislocation, or when significant bone has been lost. The choice of operation depends on how much bone remains: a soft-tissue repair when the bone is largely intact, or a bone-rebuilding procedure when too much has worn away.

• Shoulder arthroscopyShoulder

For a fuller explanation, including anatomy, diagnosis, and the full range of treatment:

• Chronic Shoulder Instability and Dislocation — AAOS OrthoInfo