Condition in which bone death occurs because of inadequate blood supply to it. Two common risk factors include chronic use of steroids and or heavy alcohol consumption. The hip joint is most commonly affected; however, the knee and shoulder may also be involved. Symptoms appear suddenly if it’s a result of an injury. In other situations, the pain and stiffness may gradually appear over a period of time. Diagnosing the condition is mainly by imaging modalities such as X-ray, MRI, and occasionally bone scan to rule out other causes. Treatment depends on the stage of the disease, in the early stages it may include rest, activity modification, bone decompression, or osteotomy, in the late-stage joint replacement is the prefered method.