Posterior Capsular Tightness

*Video demonstration available* Animation which shows how a tight posterior inferior glenohumeral ligament (PIGHL) damages shoulders to the point the athlete needs surgery.

The capsule of the shoulder is the solid sheet of ligaments that hold the ball (the humeral head) to the socket (the glenoid). This solid sheet of ligaments is white in this diagram, which you can also review on the anatomy page. There are 4 discreet thickenings of this capsule which are called ligaments, specifically, glenohumeral ligaments. The most important one of those four for overhead throwers is the posterior-inferior glenohumeral ligament, A in the diagram.

This is the ligament that restrains the shoulder during the forceful deceleration phase of throwing. Basically, this ligament holds the arm on to the body and keeps it from flying off and landing at the catcher's feet! As you can imagine, this ligament toughens over time, as the thrower develops and gets older and stronger and throws harder and more frequently. If this ligament gets too tough, it becomes contracted, or hardened and shortened. This causes imbalance in the shoulder during motion. During the late cocking and acceleration phases of throwing, the tight posterior inferior ligament "cams up" or pushes up the ball relative to the socket. This makes the ball rub forcefully against the upper or superior labrum. Over time, this causes the superior labrum to tear away from the bone. This is called the "SLAP event," because the labral tear that occurs is a SLAP pattern (superior labrum anterior and posterior), and once this "event" occurs, all shoulders will require surgery to return to effective throwing.