The purpose of this review is to highlight the most efficient imaging exploratory techniques depicting shoulder instability, to describe its various forms and to point out the findings which can simulate instability. In anterior recurrent dislocation, surgery is indicated and the procedure essentially depends on the importance of glenoid rim lesions. In this case, a standard X-ray evaluation is usually sufficient. The CT arthrography or MRI techniques give more specific details as to the severity of the lesions, particularly soft tissues alterations; however, these data do not alter standard therapeutic protocol. In fixed posterior dislocations, CT scan represents the most pertinent technique to evaluate the size of the humeral head defect and to determine the therapeutic follow-up. In subtle forms of instability, diagnosis or instability direction are not clearly assessed clinically and standard X-ray evaluation is usually unremarkable. In this case, further exploration, such as CT arthrography, MR imaging or MR arthrography, are recommended to confirm the diagnosis of instability and to evaluate its direction. The technique of choice is undoubtedly MR arthrography. Atraumatic voluntary painless subluxations associated with hyperlaxity of the shoulder do not require any specific exploratory method because the findings are generally limited to a capacious axillary pouch.
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