Adaptations of the Shoulder to Overhead Throwing in Youth Athletes.

Context: The high number of repetitions and high forces associated with overhead throwing lead to anatomical adaptations, such as humeral retrotorsion and posterior-capsule thickness, in elite and professional baseball athletes. However, little is known about the origin and progression of these changes that may account for the increasing trend of chronic shoulder injuries in youth baseball and precipitate subsequent pathologic conditions throughout a young athlete's lifetime.

Objective: To investigate the relationship of age and upper extremity dominance on humeral retrotorsion, posterior-capsule thickness, and glenohumeral range of motion.