Avascular necrosis of the hip is a condition where bone tissue in the femoral head (the ball of your hip joint) dies because its blood supply is disrupted. More than 20,000 people are diagnosed with it annually in the United States, and it most commonly affects adults between their 30s and 50s. Without treatment, the bone weakens, collapses, and eventually destroys the joint.
How Blood Supply Fails in the Hip
The ball-shaped top of your thighbone sits inside a socket in your pelvis, forming the hip joint. This bone gets its blood from three sources: a ring of small arteries at the base of the femoral neck, branches that climb up along the neck’s surface, and arteries running through a small ligament inside the joint itself. Because these vessels are small and have limited backup routes, any significant interruption can starve the bone of oxygen.
When blood flow stops, bone cells begin to die. The internal scaffolding of the bone, a lattice of tiny structural beams called trabeculae, can no longer repair itself through the normal cycle of breaking down and rebuilding. Under the constant load of walking and standing, these weakened trabeculae start to fracture. Eventually, the layer of bone just beneath the joint surface buckles inward, a stage visible on imaging as a crescent-shaped line. Once that happens, full collapse of the joint surface typically follows.
In cases caused by something other than trauma, the central event appears to be abnormal clotting inside the blood vessels feeding the femoral head. This clotting can be triggered by swollen fat cells in the bone marrow compressing the vessels, by direct damage to vessel walls from medications or radiation, or by fat particles lodging in the vessels and blocking flow.
Common Causes and Risk Factors
The causes split into two broad categories: traumatic and nontraumatic. A hip fracture or dislocation can physically tear the arteries feeding the femoral head, cutting off blood supply in an instant. This is one of the most straightforward paths to avascular necrosis and can develop in the weeks or months after a serious hip injury.
Nontraumatic cases are far more common, and over 90% of them have been linked to just two factors: corticosteroid use and excessive alcohol consumption. Corticosteroids, the type prescribed for conditions like lupus, asthma, and inflammatory bowel disease, appear to enlarge fat cells within the bone marrow, compressing the tiny blood vessels from the outside. The risk increases with higher doses and longer courses. Alcohol, in heavy or prolonged use, contributes through a similar mechanism of fat buildup and vessel damage.
Other recognized risk factors include sickle cell disease, HIV infection, radiation therapy, certain chemotherapy drugs, organ transplantation (partly because of the steroids used to prevent rejection), and autoimmune conditions like lupus itself, independent of its treatment. In some cases, no clear cause is found, and the condition is classified as idiopathic.
What It Feels Like
Early avascular necrosis often produces no symptoms at all. The bone is dying, but you may not feel anything because the damage hasn’t yet reached a point where the structure is compromised. This is one of the reasons it’s sometimes caught incidentally on an MRI done for another reason.
When symptoms do appear, the first sign is usually a dull ache or throbbing pain in the groin or front of the hip. It may start only when you put weight on the leg and gradually become more persistent. Some people notice the pain spreading to the buttock or down the thigh toward the knee, which can lead to an initial misdiagnosis of a knee problem. As the bone weakens and begins to collapse, pain typically worsens, range of motion decreases, and you may develop a limp. In the vast majority of cases, the condition worsens over time, and without treatment the affected bone collapses over a period of months to a few years.
How It’s Diagnosed
Standard X-rays can show avascular necrosis once the bone has already started to change shape or collapse, but they often look completely normal in the earliest stages. MRI is the most sensitive tool for early detection. It can pick up changes in blood flow and bone marrow composition before any structural damage is visible, making it crucial for catching the condition when treatment options are broadest.
Staging systems help classify how far the disease has progressed. The most commonly referenced system divides it into four stages: Stage I shows MRI changes but normal X-rays, Stage II shows visible bone changes on X-ray but no collapse, Stage III involves early collapse of the bone surface (the crescent sign), and Stage IV means the joint itself has developed arthritis from the damaged bone.
Treatment by Stage
The stage at diagnosis heavily determines what treatment looks like and how well it works.
Early Stages (I and II)
The goal in early disease is to preserve the natural hip joint for as long as possible. The most established surgical option is core decompression, a procedure where a surgeon drills one or more channels into the femoral head to relieve pressure inside the bone, restore blood flow, and encourage new bone growth. Research published in the Journal of Bone and Joint Surgery found that none of the hips treated at Stage I needed a total hip replacement during the study period. For Stage II hips, about 65% survived without needing a replacement at just over four years.
Nonsurgical approaches like limiting weight bearing, using anti-inflammatory medications, and physical therapy may be tried alongside or before surgery, but there’s limited evidence that they can reverse the underlying process on their own. They primarily manage symptoms.
Later Stages (III and IV)
Once the bone surface has started to collapse, joint-preserving procedures become much less reliable. Core decompression at Stage III showed only a 21% survival rate at four years in the same study, meaning roughly four out of five hips still progressed to needing replacement. More complex procedures like bone grafting, where a piece of healthy bone with its own blood supply is transplanted into the femoral head, may offer somewhat better outcomes at this stage but involve longer recovery.
By Stage IV, when arthritis has set in, total hip replacement is the standard treatment. Modern hip replacements are durable and effective at restoring function and eliminating pain, but because avascular necrosis tends to strike younger adults, some patients may need one or more revision surgeries over their lifetime as the implant wears out. Surgeons sometimes recommend delaying replacement as long as symptoms are manageable to reduce the total number of surgeries a person faces.
Stem Cell Therapy: Where It Stands
Injecting a patient’s own stem cells (harvested from bone marrow) into the damaged femoral head is an area of active investigation for early-stage disease. A long-term clinical trial found that patients experienced meaningful pain reduction within the first month, with scores continuing to improve through the first year. Hip function scores also improved significantly over 12 months.
The radiological picture was more modest. About 62.5% of patients showed stabilization of the damaged area during the first year, meaning the disease stopped progressing. Only 12.5% showed signs of actual bone regrowth, while 25% continued to worsen despite treatment. These results suggest stem cell therapy may help slow or halt the disease in some patients but is not yet a reliable way to reverse it. It remains largely experimental and is not widely available outside of clinical trials or specialized centers.
Living With the Condition
If you’ve been diagnosed early, the practical priorities are reducing mechanical stress on the hip and addressing any modifiable risk factors. If corticosteroids are the likely cause, your prescribing doctor may explore whether the dose can be lowered or an alternative medication used. If alcohol is a contributing factor, reducing or stopping consumption is one of the few things within your direct control that can influence the disease course.
Low-impact exercise like swimming, cycling, and water aerobics can help maintain muscle strength and joint mobility without the repeated pounding of running or jumping. Physical therapy focused on hip range of motion and strengthening the muscles around the joint can also reduce pain and improve daily function. Some people find that using a cane on the opposite side takes enough load off the affected hip to make walking significantly more comfortable.
Because avascular necrosis affects both hips in a substantial number of patients, your doctor will likely monitor the opposite hip as well, even if it’s currently pain-free. Bilateral involvement is especially common in steroid-related and alcohol-related cases.