A Rare Case of Adult Non-traumatic Recurrent Anterior Hip Joint Dislocation.

A 75-year-old woman, who could walk independently with a walker, was incidentally found to have anterior hip joint dislocation on computed tomography. She had a history of anti-signal recognition particle immune-mediated necrotizing myopathy (SRP IMNM), for which long-term oral corticosteroid treatment was administered. Closed reduction was performed immediately after hip dislocation diagnosis; however, the joint easily dislocated again anteriorly. The patient could walk independently with the dislocated joint and did not wish to undergo further treatment. The findings from this case, together with those from previous reports, suggest that long-term corticosteroid administration may be a risk factor for non-traumatic hip dislocation. The underlying myopathy involving significant muscle atrophy may have played a critical role in the pathogenesis of this joint instability.