Radiological assessment of shoulder instability

Shoulder instability is a common problem which is defined as symptomatic motion of the glenohumeral joint, which can present as pain or sense of displacement [1]. There are several systems of classification in the literature of shoulder instability. Recently, to introduce some consensus, the FEDS system has been proposed [2]. The symptoms are classified according to Frequency (solitary, occasional or frequent), Etiology (traumatic or atraumatic), Direction of instability (anterior, inferior or posterior) and the Severity, based on subluxation or dislocation. The etiology of shoulder instability is likely multifactorial. Though trauma is the most common cause, repetitive or habitual use and structural or congenital factors contribute in varying degrees. Advances in arthroscopy and radiological imaging have revealed a variety of lesions associated with shoulder instability. Confusing acronyms are often used in practice and in the literature to describe many of these abnormalities. The objectives of this review are to facilitate the understanding of the relevant anatomy and anatomical variations, discuss the imaging techniques used to assess the unstable shoulder, describe the various pathologies whilst attempting to clarify some of the confusing terminology and discuss the key imaging findings that influence clinical management.