Anterior-superior internal impingement of the shoulder: an evidence-based review

Purpose  

Internal impingement syndrome is a painful shoulder condition related to the impingement of the soft tissue, including the rotator cuff, joint capsule and the long head of the biceps tendon and glenoid labrum. Two types of internal impingement syndrome can be differentiated: posterior-superior impingement and anterior-superior impingement (ASI). The aetiology of ASI in particular is not clear. The purpose of this paper is to discuss the different aetiological theories relating to ASI, try to clarify the clinical, radiological and arthroscopic findings and, finally, suggesting treatment for this complex shoulder syndrome.