I’ve been to three orthopedic surgeons now about a problem with my pitching arm. It hurts, clicks, and feels like it’s going to pop out of the socket. No one could figure it out. I finally had an arthroscopic exam that showed a posterior tear of the shoulder capsule. Why was this so hard to diagnose?

Posterior instability as a cause of shoulder pain and/or clicking is an uncommon, but not unheard of, condition. Anterior shoulder problems are much more common. In fact, many pitchers or throwing athletes suffer from an anterior instability. Posterior refers to the back of the shoulder. Anterior refers to the front of the shoulder.

In either case, repetitive microtrauma from the action of overhead throwing is the cause of the problem. During the follow-through phase of pitching, the shoulder is close to the body, flexed, and rotated inwardly. This repetitive motion may put stress along the back of the shoulder.

The shoulder capsule and labrum (rim of cartilage around the shoulder socket) can also get pinched causing pain. This is more likely to occur during the late cocking phase of throwing when the arm is drawn back and externally rotated.

The problem is made worse if the athlete has any natural laxity (looseness) or contracture (tightness) of the soft tissues in this area. Repeated stresses from throwing 100s of pitches can lead to labral tears or a stretched capsule.

These types of injuries are not easy to diagnose. There can be different directions of instability at the same time causing confusion. Clinical signs and symptoms and results of testing aren’t always consistent for multidirectional injuries. Diagnosis is delayed when there is more than one lesion (and even a combination of problems).

The surgeon will have to sort out the site of damage and resulting structural and biomechanical problems. Even with history, physical exam, and imaging studies, arthroscopy may be the only way to make the final diagnosis.