(ii) The classification of shoulder instability: new light through old windows!

Abstract Shoulder instability is a phenomenon, which has a variety of clinical presentations. Its complex nature has until recently been poorly understood. Inadequate understanding of the pathology of instability has been confounded by confusion over definitions and inadequate classification systems. As a result treatment failures have been observed in many of the specific pathologies. We propose a classification system, which challenges previous systems by being all inclusive and recognises that more than one pathology can occur in an individual shoulder. The system takes the form of a triangle with polar groups at each corner and specific subgroups mapped along each axis. It provides a usable framework for clinicians in the management of what can be complex problems.