Avascular Necrosis (AVN) of the Hip: Stages, X-Rays & Treatment
Avascular necrosis (AVN) of the hip happens when the ball of the hip loses its blood supply and the bone begins to die. It’s staged by what X-rays and MRI show. Early AVN can often be watched. Once the bone has collapsed, a hip replacement is the best operation: it’s predictable, the recovery is short, and AVN can’t come back in a replaced hip.
Key takeaways
- AVN is loss of blood supply to the ball of the hip. The bone weakens and can collapse.
- It’s staged by imaging: early AVN shows only on MRI; later stages show on X-ray as dense bone, cysts, and collapse.
- Stage 1 and 2 can often be watched with X-rays every six months. The deciding factor is your quality of life and function.
- Once the bone has collapsed (stage 3 or 4), a hip replacement is the answer.
- Hip replacement for AVN is predictable, the recovery is short, and AVN can’t come back in the replaced hip.
If you’ve just been told you have avascular necrosis, often shortened to AVN and also called osteonecrosis, you probably have two reactions at once: you’d never heard of it, and the report sounded alarming. Here’s what it is, how it’s staged, and how I decide on treatment.
What AVN is
Bone is living tissue, and it needs a steady blood supply. In avascular necrosis, the blood supply to the ball of the hip (the head of the femur) is disrupted. Without it, the bone in that area dies and weakens, and over time it can collapse, flattening the once-round ball.
That’s different from hip osteoarthritis, which starts as wear of the cartilage. AVN starts in the bone underneath. But once the ball collapses and loses its smooth shape, arthritis follows.
Causes
AVN can have many causes, and often more than one is involved:
- Long-term steroid use. One of the most common causes. I see it in patients who have needed steroids for years, for example for chronic asthma or a chronic inflammatory condition.
- Other medications, including some immune-suppressing drugs.
- Autoimmune and chronic inflammatory conditions, as well as some blood and clotting disorders such as sickle cell disease.
- Heavy alcohol use.
- Injury, such as a hip fracture or dislocation, which can cut off the blood supply directly.
- No clear cause (idiopathic). This is common, and it doesn’t change how we treat it.
Symptoms
Early AVN can cause little or no pain, which is why it’s sometimes found by surprise on an MRI. As it progresses:
- Groin pain, the most common location for hip joint pain.
- Pain with walking and other weight-bearing activity.
- Stiffness and loss of motion in the hip.
- A limp as you protect the hip.
- Pain that builds over time, especially once collapse begins.
Most of my patients with AVN have been living with it for a while and come in at stage 2 or 3, when the pain has started to limit them.
Does AVN show on X-ray or MRI?
- X-ray: not at first. In stage 1, the X-ray looks normal. From stage 2 on, it shows dense, whitened bone (called sclerosis) and small cysts, and later the collapse and flattening of the ball.
- MRI: the most sensitive test. It shows AVN early, before the X-ray changes, and shows how much of the ball is involved.
Once AVN is diagnosed, I usually follow it with X-rays. I order an MRI when the pain changes significantly or when we’re getting close to a decision about surgery.
The stages of AVN
AVN is staged by what the imaging shows, and the stage, together with how you’re living with it, guides treatment.
| Stage | What you feel | What imaging shows | What I usually recommend |
|---|---|---|---|
| Stage 1 | Often mild pain, or none | X-ray looks normal. MRI shows the area of bone that has lost its blood supply. | Usually watch it with X-rays. If pain is severe and limiting your life, we discuss surgery. |
| Stage 2 | Pain with walking and activity | X-ray shows dense, whitened bone (sclerosis) and small cysts. The ball is still round. | Watch it if you’re living well with it. If pain is severe, we discuss drilling vs. replacement, and most patients choose replacement. |
| Stage 3 | Pain, stiffness, often a limp | The bone under the cartilage has started to collapse, and the ball begins to flatten. | Hip replacement. |
| Stage 4 | Pain that limits daily life | The ball has collapsed and arthritis has set in on both sides of the joint. | Hip replacement. |
How I decide on treatment
With AVN, as with any hip or knee problem, the deciding factor is your quality of life and function. The X-ray tells me the stage; you tell me how much it’s limiting you.
- Stage 1 and 2, living well with it: I watch it with X-rays about every six months, and adjust based on your pain.
- Stage 1 and 2 with severe pain: I’ve seen many patients with early AVN who have severe hip pain. Then we discuss surgery: drilling or a hip replacement. Most patients lean toward replacement, because the results are so predictable.
- Stage 3 and 4 (collapse): a hip replacement is the answer. Once the ball has collapsed, it can’t be saved.
Drilling vs. hip replacement
Over the years, surgeons have tried to save the hip in early AVN. Core decompression drills channels into the dead bone to relieve pressure and encourage new blood flow, and fibula grafting moves a piece of bone from the leg into the hip. Neither comes close to the success of a hip replacement.
I mainly consider drilling for very young patients. For most people, the worst outcome is having the drilling, and then needing a hip replacement anyway. Nobody wants two surgeries.
Hip replacement for AVN
For most patients with AVN, I perform a direct anterior hip replacement, which works between the muscles rather than cutting through them. The dead bone is removed along with the ball of the hip, so AVN can’t come back in that hip.
- Up and walking the day of surgery. My patients are up and walking the same day.
- Home the same day for most. Many of my hip replacements are done at an ambulatory surgery center, and most patients go home the same day. See outpatient (same-day) joint replacement.
- Built to last. Modern hip replacements can last 30 years or more. See how long a hip replacement lasts.
“Am I too young?”
AVN often affects younger adults, and it’s one of the most common questions I hear. Age alone rarely decides it. What matters is how much the hip is limiting your life. See am I too young for a hip or knee replacement?
The other hip
AVN can affect both hips. Usually, when patients come in with one painful hip, the other side hurts much less. I watch it with X-rays and order an MRI if the pain picks up. If both hips need replacing, see double hip replacement: what to expect.
What patients commonly tell me
“I had never heard of AVN before my MRI.”
“My X-rays were normal, but the MRI showed something.”
“I’m worried I’m too young for a hip replacement.”
“I don’t understand why this happened.”
If that sounds like you, the next step is the same for everyone: find out your stage and talk about how the hip is affecting your life. I see patients in Washington, D.C. and Germantown, Maryland. Bring your X-rays or MRI if you have them. Request an appointment.
Frequently asked questions
Can you see avascular necrosis on an X-ray?
Not at first. In stage 1, the X-ray looks normal and only an MRI shows it. From stage 2 on, an X-ray shows dense, whitened bone and small cysts, and later the collapse and flattening of the ball of the hip.
What are the stages of avascular necrosis of the hip?
Stage 1 shows only on MRI. Stage 2 shows dense bone and cysts on X-ray while the ball is still round. Stage 3 is collapse of the bone, with the ball starting to flatten. Stage 4 is collapse with arthritis on both sides of the joint.
Does AVN of the hip always need a hip replacement?
Not always. Stage 1 and 2 can often be watched with X-rays every six months if you’re living well with it. Once the bone has collapsed, at stage 3 or 4, a hip replacement is the answer. And if an earlier stage is causing severe pain, replacement is usually the most predictable option.
What causes avascular necrosis of the hip?
Common causes include long-term steroid use (for example, for chronic asthma or inflammatory conditions), some immune-suppressing medications, autoimmune and chronic inflammatory conditions, heavy alcohol use, and injuries such as a hip fracture or dislocation. Often, no cause is found.
Can avascular necrosis come back after a hip replacement?
No. AVN is dead bone in the ball of the hip, and that bone is removed and replaced during surgery. It can’t come back in the replaced hip. AVN can occur in other bones, including the other hip, which is why we keep an eye on it.
Is core decompression (drilling) better than a hip replacement for AVN?
Drilling tries to save the hip in early AVN, but its success is far lower than a hip replacement’s, and many patients end up needing a replacement anyway. I mainly consider it for very young patients. For most people with severe pain, replacement is the more predictable choice.
Am I too young for a hip replacement for AVN?
AVN often affects younger adults, so this is a common concern. Modern hip replacements can last 30 years or more, and age alone rarely decides it. What matters most is how much the hip is limiting your life.
References
This article is for general education and is not a substitute for personalized medical advice. Please consult Matthew Harb, M.D. about your specific condition.
What patients say
“A really smooth operation — I was discharged the same day and basically able to walk easily within a day.”
“A world-class orthopedic surgeon who performed flawless hip replacement surgery on me. Life changer, and forever thankful.”
“No more pain — I was moving around and driving within two weeks, and back at work at two months.”
Where to go from here
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Read articleHip ReplacementDouble (Bilateral) Hip Replacement: What to Expect
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Read articleHip ReplacementAm I Too Young for a Hip or Knee Replacement?
One of the most common questions I hear is whether someone is too young — or too old — for a hip or knee replacement. The answer surprises many patients: the decision is rarely about age at all. It’s about how much arthritis is affecting your life, your overall health, and whether conservative treatments still help.
Read articleWondering what’s causing your hip or knee pain?
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