Batter’s Shoulder Rehabilitation

Batter’s shoulder causes posterior instability leading to episodic subluxation of the lead shoulder during the baseball swing (Wanich 2012). A subluxation is defined as an incomplete dislocation. Posterior shoulder instability is typically the result of a posteriorly directed load to the shoulder in a position of forward flexion, adduction, and internal rotation (Wanich 2012). Posterior instability affects only 2% to 12% of patients with shoulder instability. There has been recent research in posterior shoulder instability as a cause of disability in the athletic population. Posterior instability in the athletes is usual caused from contact sports and this occurs from acute trauma or repetitive microtrauma. In the case of batter’s shoulder, the major rotational forces about the shoulder are believed to be the cause of the instability (Wanich 2012). The symptoms from posterior shoulder pain occur during batting and this causes the inability to generate power during the baseball swing. It is unknown impossible to pinpoint the exact mechanism of injury in batter’s shoulder; the problem is thought to be the result of repetitive microtrauma. This repetitive microtrauma could be cause by a swing and a miss on an outside pitch. During a missed pitch, it is presumed there is no counterforce to the momentum from the baseball swing leading to overdynamics in the shoulder and an excessive pulling force (Wanich 2012). Some studies have found an average shoulder abduction angle of 105° for outside pitches versus 90° for inside pitches. The American Sports Medicine Institute (ASMI) group suggested the increased shoulder abduction angle may increase shear forces across the joint (Fleisig 2009).