Septic arthritis associated with avascular necrosis of the femoral head.

Avascular necrosis may predispose joints to a septic process particularly in the immunosuppressed individual. The clinical and radiographic presentation may not be diagnostic in the patient with pre-existing joint disease. Suspicion of infection and early aspiration of the involved joint are the keys to early diagnosis. Four patients with avascular necrosis of the femoral head, secondary to renal transplantation and corticosteroids in 3, and systemic lupus erythematosus and corticosteroids in one, presented with super-imposed joint infections. All were treated with intravenous antibiotics and frequent joint aspirations and the infection was resolved.