Abduction strength was significantly greater in the dominant (affected) shoulder than in the nondominant (unaffected) shoulder in baseball players with partialthickness tears of the isolated supraspinatus tendon or combined supraspinatus and infraspinatus tendons in this study. A possible explanation is that the greater shoulder abduction strength may increase the risk for articularsided partial-thickness supraspinatus tendon tear in baseball players. Also, tearing of the superior shoulder capsule on the superior facet may promote muscle activation of the shoulder abductor muscles. In a future study, we will investigate the mechanism of increased abduction strength in baseball players with an articular-sided partialthickness supraspinatus tendon tear.