Impingement syndrome describes a painful mechanical irritation of soft tissues, in particular the supraspinatus tendon and the subacromial bursa, in the subacromial space of the shoulder.
Clinically there is often a painful arc when lifting the arm sideways between roughly 60 and 120 degrees, and discomfort during overhead movements. Anatomical narrowing, dysfunction of the rotator cuff and dyskinesis of the shoulder blade are discussed as causes. Besides subacromial impingement there are other forms, such as internal posterosuperior impingement.