Osteonecrosis of the hip, also called avascular necrosis, is a disabling condition that can lead to the hip joint collapsing. It is estimated that doctors see about 10,000-20,000 new cases of osteonecrosis each year.

If you have osteonecrosis of the hip, the blood vessels gradually cut off nourishment to the top of the thighbone (head of the 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 the hip's socket may also break down. It often happens that if there is osteonecrosis in one hip, it will be seen in the other hip.

Sometimes, the cause is not known.

• Hip dislocation or fracture
• Alcoholism
• Use corticosteroids
• Have 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.

Your doctor may flex and rotate your hips to check for pain. Your hips may be X-rayed and possibly scanned by MRI (magnetic resonance imaging) to see if bone marrow is dying or dead, and how much the head of your femur may have collapsed.

If you have osteonecrosis and the head of your femur is not yet collapsed, certain medical procedures (i.e., decompression and bone grafting) may help your body build new blood vessels and bone cells to replace the dead ones.

If osteonecrosis has already collapsed your hip, total hip replacement surgery (arthroplasty) may eliminate your pain and give you better hip mobility. A ball and socket replaces your hip joint. Your thighbone is fitted with the ball piece, which takes the place of the head of your femur. Your hip socket is fitted with the socket piece (cup).