Shoulder pain and dysfunction with overhead activities resulting from subacromial impingement syndrome is common. Subacromial impingement syndrome has generally been classified as primary or secondary. A thorough history and physical examination are essential to identifying the etiology of the subacromial impingement syndrome and to direct treatment. Primary subacromial impingement syndrome, resulting from mechanical encroachment into the subacromial space usually by an acromial hook or spurs, occurs in middle age. Individuals with primary subacromial impingement syndrome have symptoms of shoulder pain and weakness with overhead activities. Impingement tests (eg, Neer, Hawkins) are positive. Typically, external rotation, flexion, and abduction of the shoulder are weak and painful. Night pain, usually an inability to sleep on the painful shoulder, is a common symptom of the full-thickness rotator cuff tears that can also occur in this age group. Trauma is usually the mechanism of injury. Persons with secondary subacromial impingement syndrome also have symptoms of pain and weakness with overhead activities. These individuals are usually young and often participate in sports that require repetitive overhead motion (eg, baseball, swimming, volleyball). Symptoms with secondary impingement are attributed to rotator cuff tendinitis. These symptoms are thought to result from overuse of the rotator cuff tendons to compensate for subtle anterior or multidirectional glenohumeral instability. More recently, scapulothoracic muscle weakness has been identified as a cause of secondary subacromial impingement syndrome. Here, the lack of scapular stability is thought to contribute to secondary subacromial impingement syndrome.
J Orthop Sports Phys Ther. 1999;29(1):31-38.
Key Words: shoulder pain, subacromial, tendinitis