Avascular necrosis of the hip

Avascular necrosis (osteonecrosis) of the hip happens when the blood supply to the ball at the upper end of the thighbone is reduced or cut off. Without enough blood, areas of bone die and can gradually weaken and collapse, damaging the cartilage over them and causing arthritis. It most often affects adults in midlife and can involve both hips.

• No symptoms at all in the earliest stage
• An aching pain in the groin, thigh, or buttock
• Pain that first appears with standing and walking and later occurs at rest
• Stiffness and loss of hip motion
• A limp

Pain can worsen suddenly if the weakened bone collapses. The time from first symptoms to significant joint damage varies from weeks to more than a year.

An injury, such as a hip fracture or dislocation, can disrupt blood flow to the bone directly. Many cases occur without an injury, and the exact cause is not always known.

Factors linked to avascular necrosis include:

• Long-term use of high-dose corticosteroid medications
• Heavy alcohol use
• Tobacco use
• Sickle cell disease and some other blood disorders
• Lupus and other autoimmune conditions
• Treatments such as chemotherapy, radiation, or organ transplantation
• Other conditions, including Gaucher disease, HIV, and decompression sickness

Some people develop it with no known risk factor.

A clinician asks about your symptoms, medications, alcohol use, and medical history, and examines which hip movements cause pain.

X-rays may look normal early on but can show collapse of the ball of the hip in later stages. An MRI can detect bone changes before they appear on X-rays and may also reveal early involvement of the other hip. A CT scan is used in some cases. Imaging shows the stage and size of the affected area, which guides treatment.

Treatment depends on the stage of the disease, the size of the affected area, and whether the ball of the hip has collapsed.

Non-surgical measures can relieve pain and may slow progression in some cases, though they usually do not stop the disease:

• Crutches or a cane to take weight off the hip
• Anti-inflammatory and other pain-relieving medications
• Physical therapy to maintain motion
• Addressing underlying factors, such as cutting back on alcohol, stopping tobacco, and reviewing steroid use with the clinician who prescribes it

Many people eventually need surgery. Before the bone collapses, joint-preserving procedures may be considered. In core decompression, the surgeon drills one or more channels into the ball of the hip to relieve pressure and encourage new blood vessels to grow, often combined with a bone graft. Other options for selected patients include a bone graft that brings its own blood supply, or an osteotomy that shifts weight onto healthier bone.

Once the ball of the hip has collapsed or arthritis has developed, total hip replacement is usually the recommended treatment.

Recovery depends on the treatment. After core decompression, a period of protected weight-bearing with crutches is common, and grafting procedures may involve a longer recovery. Recovery after hip replacement follows the usual path for that operation. Because the other hip can also be affected, follow-up visits and imaging may continue over time.

Not every case can be prevented, but lowering known risks may help:

• Limiting alcohol
• Not using tobacco
• Taking corticosteroids only as prescribed, and never stopping them on your own — ask your clinician whether the lowest effective dose is being used
• Managing conditions such as sickle cell disease or lupus with your care team