Anatomy and Biomechanics of the Unstable Shoulder.

PURPOSE: To review the anatomy of the shoulder joint and of the physiology of glenohumeral stability is essential to manage correctly shoulder instability. METHODS: It was reviewed a large number of recently published research studies related to the shoulder instability that received a higher Level of Evidence grade. RESULTS: It is reviewed the bony anatomy, the anatomy and function of the ligaments that act on this joint, the physiology and physiopathology of glenohumeral instability and the therapeutic implications of the injured structures. CONCLUSION: This knowledge allows the surgeon to evaluate the possible causes of instability, to assess which are the structures that must be reconstructed and to decide which surgical technique must be performed.