Overuse and impingement syndromes of the shoulder in the athlete.

Overuse and impingement syndromes in the shoulders of athletes are predominantly caused by instability of the glenohumeral joint. Glenohumeral joint instability is usually acquired from repetitive overuse of the rotator cuff and shoulder girdle muscles, or injury of the static and dynamic stabilizers of the glenohumeral joint. Congenital hypermobility of the joint may also contribute to these syndromes in some individuals. The throwing action may lead to a cascade of injuries to the static and dynamic stabilizers of the posterosuperior glenohumeral joint, caused by the repetitive, high-energy nature of the action rather than a specific injury. Injury to the anterosuperior stabilizers of the glenohumeral joint may also lead to anterosuperior impingement syndrome. The role of MR in overuse and impingement syndromes of the shoulder is to accurately diagnose the underlying structural changes and serves to assist the clinician in instituting the appropriate conservative or surgical treatment for individual athletes.