What is Avascular Necrosis of the Hip?
Avascular necrosis (AVN) of the hip is a condition where the bone tissue in the ball of your hip joint dies because it loses its blood supply, eventually causing the hip joint to collapse and leading to severe arthritis if left untreated. 1
How It Happens
The bone in your hip needs constant blood flow to stay alive and healthy. When this blood supply gets interrupted or blocked, the bone cells and bone marrow die 1. Think of it like a plant that doesn't get water—it eventually withers and dies. Three main ways this happens include: 2
- Blood vessels get physically cut off (like after a hip fracture or dislocation)
- Blood vessels get clogged (similar to how arteries can get blocked in heart disease)
- Pressure builds up inside the bone that squeezes the blood vessels shut (often from fat cells getting larger) 2
Where It Affects You
The "ball" part of your hip joint (called the femoral head) is the most common location, accounting for over 75% of all AVN cases 3. However, AVN can also affect other bones in your body including your shoulder, knee, ankle, and certain bones in your hand and foot 2, 1.
What Puts You at Risk
Several factors significantly increase your chances of developing AVN: 4, 1, 5
- Steroid medications (like prednisone), especially high doses or long-term use
- Heavy alcohol consumption
- Hip injuries such as fractures or dislocations
- Sickle cell disease and other blood disorders
- High cholesterol (hyperlipidemia)
- Blood clotting disorders (hypercoagulability)
- HIV infection and its treatments
- Cancer treatments including chemotherapy and radiation
- Certain rare diseases like Gaucher disease
A critical fact: when AVN happens without trauma, both hips are affected 70-80% of the time, even if you only feel pain in one hip. 5
What You'll Experience
Pain is the main symptom—it typically starts gradually in your groin or buttock area and gets worse when you put weight on the hip (walking, standing, climbing stairs) 5. The pain is usually severe and doesn't improve with rest 5.
However, here's an important caveat: about 5% of people at risk have AVN that shows up on imaging tests but causes no symptoms at all 4, 1. This is why doctors sometimes screen high-risk patients even without pain.
Why Early Detection Matters
The size of the dead bone area determines your outcome. 1, 5
- If less than 30% of the femoral head is affected, only 5% of cases progress to collapse
- If 30% or more is affected, 46-83% of cases will progress to collapse 1, 5
Once the bone collapses, joint-preserving treatments no longer work, and you'll likely need a hip replacement. 1 This is particularly devastating because AVN typically affects people in their 30s to 50s—much younger than typical arthritis patients 2. In fact, AVN causes up to one-third of all hip replacements in people under age 60 4.
Additional Risk Factors for Worse Outcomes
Beyond the size of the affected area, certain factors predict faster progression: 5
- Being over 40 years old
- Body mass index over 24 kg/m²
- Fluid around the joint (joint effusion)
- Swelling in the bone marrow around the dead area
The Bottom Line
Without treatment, AVN inevitably leads to early severe arthritis and joint destruction. 4 The key is catching it early—before the bone surface collapses—when treatments can still preserve your natural hip joint. Once you have symptoms, the disease process is already underway, which is why screening high-risk patients before symptoms develop is so important 5.