Osteonecrosis of the hip is a disabling condition that can lead to the collapse of your hip joint. It is estimated that doctors see about 10,000-20,000 new cases of osteonecrosis (ON) each year. Osteonecrosis most often occurs in those aged 20-50 and have any of the following risk factors:

• Hip dislocation or fracture.
• Alcoholism.
• Corticosteroid use
• Glandular problems and diseases including rheumatoid arthritis, sickle cell disease, myeloproliferative disorders, Gaucher's disease, chronic pancreatis, Crohn's disease, Caisson's disease or systemic lupus erythematosus

Causes
No one knows exactly what causes it. If you have osteonecrosis of the hip, your blood vessels gradually cut off nourishment to the top of the thighbone (femur) where it fits in the hip socket. Without blood, the head of your femur dies and collapses. This can make it painful to move your hip, and you may develop arthritis and a limp. Cartilage in your hip's socket may also break down. Osteonecrosis in one hip usually indicates you will develop the same problem in your other hip, eventually.

Symptoms
Although the condition may start with few signs or warnings, you may develop a sharp pain in the groin or buttocks that may radiate down the back of the leg; a decreased exercise tolerance; stiffness of the hips; and increased pain and difficulty in walking after exercise.

Treatment
If you have ON and the head of your femur is not yet collapsed, certain medical procedures (such as decompression and bone grafting) may help your body build new blood vessels and bone cells to reverse the damage done.

Surgical Options
If ON has already collapsed your hip, total hip replacement surgery (arthroplasty) may eliminate your pain and give you better hip mobility. This will involve replacing your hip with a two-piece ball and socket joint for your natural hip joint. This will relieve your pain and improve your ability to walk. You may need crutches or a walker for a period after surgery. Rehabilitation is important to restore your hip's flexibility and work your muscles back into shape.