Shoulder instability and impingement in throwing athletes.

The glenohumeral articulation maintains a fine balance between mobility and stability. In the throwing athlete, this balance is stressed from the repetitive microtrauma incurred to achieve peak performances. The presentation of shoulder pain in the throwing athlete can be confusing, and a thorough understanding of anatomy and biomechanics, in addition to the history and physical examination, are necessary to delineate the correct diagnosis. Specifically, differentiating between instability and impingement is critical to initiate appropriate nonoperative and operative interventions. This paper discusses the anatomy and biomechanics in the shoulder and provides a comprehensive approach to evaluate anterior shoulder pain in throwing athletes. In addition, treatment options will be discussed with specific emphasis or nonoperative interventions.