Avascular necrosis after a steroid injection

I read with interest the Clinical Vista Brief about bilateral hip avascular necrosis.1 I note that the corticosteroid injection was given 8 months before the condition was diagnosed, but the patient had complained of hip pain for 13 months. Cortisone injections (particularly bursa and tendon sheath infiltrations) are extremely common treatments in primary care, but avascular necrosis is rarely seen. Although one always has to be careful when using steroid infiltrations, they are usually quite safe. In this particular case, the connection between the cortisone injection and the development of avascular necrosis is not clear, given the chronology of events.