Shoulder impingement syndrome. A critical review.

Impingement syndrome is an ill-defined term for a variety of disorders of the shoulder that manifest as anterior shoulder pain, especially during overhead activities. These disorders each have a common pathologic course that includes rotator cuff tendinitis (RCT), and, if untreated, may proceed to cuff rupture. RCT has at least two distinct etiologies. Primary impingement of the supraspinatus tendon on the coracoacromial arch is responsible in the majority of nonathletic cases. Overhead movements in sports are prone to developing secondary mechanical impingement because of an instability pattern that is common in this population. Information from this review and clinical practice permits differentiation of the two distinct etiologies of RCT which is important in treatment planning. Much work still needs to be done in defining the microscopic pathology of RCT.