Hip pain is common problem, and there are many causes. Arthritis is among the most frequent causes of hip pain. If conservative treatments fail, hip replacement surgery is an option. Hip pain can also be caused by pirifomia syndrome, trochanteric bursitis and tendonitis. Osteonecrosis, or avascular necrosis, is a condition that occurs when blood flow to an area of bone is restricted. Patients usually experience pain and coldness as a result. If an inadequate amount of blood flow reaches the bone, the cells will die and the bone may collapse. One of the most common places for osteonecrosis to occur is in the hip joint.