ABSTRACT
Most shoulder pain involves the soft tissues (e.g., cartilage and muscle-tendon unit) and occurs in the sedentary and active individual. Many shoulder injuries result directly from repetition as in throwing and racquet sports. Similar damage can result from non-sports-related overhead activities such as painting or ladder climbing. In throwing and racquet sports, shoulder problems can account for more than 50% of injuries.26 Anterior shoulder problems in these athletes are usually biomechanical and fatigue related. Unless the injury occurred during a traumatic event, most athletic shoulder problems involve the dominant extremity. In sedentary individuals, however, symptoms in the nondominant or inactive shoulder are not uncommon. In an older population, nonmusculoskeletal sources of symptoms can include cardiac, neurologic, primary neoplastic, and metastatic disease, as well as degenerative changes in the glenohumeral joint, rotator cuff, and cervical spine. Age-related changes, poor conditioning, overtraining, and trauma have common injury features. Studies have shown that rotator cuff and deltoid muscle weakness can cause superior migration of the humerus. This impingement of the humeral head against the subacromial arch is the hallmark event that contributes to bursitis and deterioration of the rotator cuff and biceps tendons. Investigations have repeatedly demonstrated subacromial impingement, whether seen in sports or related to poor conditioning, as one of the most common mechanisms of pain.27
