Avascular necrosis

Avascular necrosis, also called osteonecrosis, occurs when part of the ball of the hip loses its blood supply. The weakened bone can collapse, damaging the smooth joint surface and causing arthritis.

It may follow injury, steroid treatment or some medical conditions, although sometimes no cause is identified. Symptoms are usually deep groin pain and increasing difficulty walking. Treatment depends on how much bone is affected and whether collapse has occurred. Advanced cases are commonly treated with hip replacement.