anterior instability

What is it?
The ligaments in the shoulder are formed by thickenings of the capsule. The capsule is the white sheet-like structure that holds the ball (humeral head) into the socket (glenoid), in this diagram, which can be seen on the anatomy page along with some others. These ligaments can stretch out and this allows the ball to slide around too much during throwing. This is called instability, and is usually because of loosening of the anterior (front-side) ligaments, B and C in the diagram.

What does it feel like?
Throwers with this "anterior instability" have loss of control and velocity of their pitches, but usually not much pain. Sometimes, they complain of a "dead arm." Or, they may feel like their shoulder is slipping or sliding in and out, or even like it is dislocating. This is normally felt in the late cocking or follow-through phases of throwing. It can also be felt during normal daily activities involving the same shoulder position as the cocking position. Subtle anterior instability can be associated with "internal impingement syndrome."

How is it treated?
Nonoperative treatment is sometimes successful for instability that does not allow the ball to come completely out of the socket, or completely dislocate. This treatment is going to be physical therapy designed to strengthen and better coordinate the rotator cuff muscles that hold the ball in the socket during motion.

Operative treatment is required for instability that is so bad that the ball comes out of the socket, or dislocates. It is also needed for cases where there is incomplete return to throwing after nonoperative treatment. It is arthroscopic surgery with very small skin incisions and many advantages over older open surgery techniques.

How long will I be out of throwing?
If nonoperative treatment is successful, about 3 months.
If surgery is required, about 9-12 months.