Osteonecrosis (ON) of the hip is an important cause of musculoskeletal disability and finding therapeutic solutions has proven challenging. Patients who are affected with ON are often relatively young, usually in the third to sixth decade of life. ON of the hip is an increasingly common cause of musculoskeletal disability. It can cause pain with or without loss of function of the joint and often ends in substantial use of health care resources and disability. ON of the hip usually progresses to severe destruction of the femoral head with resultant degeneration of the hip joint, in most cases requiring joint replacement.