Internal impingement of the shoulder in the overhead athlete.

Internal impingement of the shoulder refers to a constellation of pathologic conditions, including, but not limited to, articular-sided rotator cuff tears, labral tears, biceps tendinitis, anterior instability, internal rotation deficit, and scapular dysfunction. Physiologic adaptations to throwing include increased external rotation, increased humeral and glenoid retroversion, and anterior laxity, all of which may predispose an individual to internal impingement. Nonoperative treatment should always be attempted first, with a focus on increasing the range of motion and improving scapular function. When an operative intervention is chosen, it is important to address microinstability in order to have a good outcome and prevent failure.