Internal impingement is a term used to describe the pathologic contact of the undersurface of the rotator cuff with the glenoid. It typically occurs in overhead athletes, particularly throwers. In these athletes, the bones and soft tissues adapt to allow these athletes to have a supraphysiologic range of motion. In many athletes, these changes may lead to symptoms of internal impingement. This article discusses the background, biomechanics, pathophysiology, clinical and radiographic assessment, treatments, and outcomes of this disorder.