Subacromial impingement with rotator cuff tendinitis is probably the commonest shoulder condition seen by the orthopedic surgeon. If left untreated or misdiagnosed, partial-thickness and full-thickness rotator cuff tears may result. The impingement process can be caused by several mechanisms. The cause can range from mechanical factors to glenohumeral instability. Understanding the pathophysiology and the treatment of this disorder is the keystone to understanding all other aspects of shoulder rehabilitation.

Impingement rehabilitation focuses on strengthening the humeral head depressors, while ignoring the deltoid and supraspinatus muscles. Later treatment includes specific retraining of scapular balancing muscles. The final phase of treatment includes strengthening of the prime humeral movers in positions that avoid further stress to the previously injured rotator cuff tendons and, last of all, specifically strengthening the supraspinatus muscle.