Osteonecrosis occurs when something restricts or cuts off blood flow to a bone. Bone tissue starts to die, and as it loses its structural integrity, tiny breaks called microfractures begin to form. These microfractures can cause the collapse of the weight-bearing surface of the bone, causing pain. Most people with osteonecrosis need surgery to treat the problem. Sometimes, joint replacement is the best option.
Healthcare providers may refer to osteonecrosis as avascular necrosis or aseptic necrosis. Osteo means “bone,” while necrosis refers to “tissue death.”
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How common is osteonecrosis?
Between 10,000 and 20,000 Americans develop osteonecrosis every year. It can affect all ages and genders.
Where does osteonecrosis develop?
Osteonecrosis typically affects the ball-part of the thighbone (femur) where it joins the hip (femoral head). But it can affect any bone, most commonly those in the:
- Ankles.
- Jaw.
- Knees.
- Upper arm (humerus) and shoulders.
What are the types of osteonecrosis?
Types of osteonecrosis include:
- Traumatic osteonecrosis occurs when a bone breaks into two or more pieces and those pieces no longer align. The misalignment can disrupt blood flow to the bone. This kind of injury is a displaced fracture. Osteonecrosis may also result from a dislocated joint.
- Nontraumatic osteonecrosis occurs when medical conditions or problems restrict blood flow to bone. Nontraumatic osteonecrosis often affects the same bones on both sides of the body. If you have osteonecrosis in one shoulder or hip, you’re likely to have it in the opposite shoulder or hip, too.
What causes osteonecrosis?
Your skeletal system continually makes new bone to replace aging bone. This process requires a healthy blood supply. In people with osteonecrosis, something slows or stops blood flow to bone. As a result, old bone breaks down before the body can replace it. If blood flow isn’t restored, bone tissue dies.
About 20% of the time, osteonecrosis occurs without any obvious cause.
Older women (and occasionally men) who have osteoporosis may experience spontaneous osteonecrosis of the knee (SPONK). Normal wear and tear on a weakened bone causes an insufficiency/stress fracture that leads to osteonecrosis.
What are the risk factors for osteonecrosis?
People older than 65 are more prone to hip fractures and dislocations that lead to traumatic osteonecrosis. About 20% of people who dislocate their hips develop osteonecrosis afterward.
Risk factors for nontraumatic osteonecrosis include:
- Blood disorders like sickle cell anemia.
- Cancer treatments, such as radiation therapy.
- Decompression sickness in scuba divers.
Other less common risk factors for nontraumatic osteonecrosis include
- Alcohol misuse and smoking.
- HIV.
- Lupus.
- Organ transplants.
- Prolonged use of corticosteroids to treat conditions like lupus.
What are the symptoms of osteonecrosis?
You might not notice when osteonecrosis first develops. In the early stage, the disease rarely causes pain or other symptoms. As bone tissue dies, tiny fractures form. The bone starts to compress and collapse. You might first notice pain when you put pressure on the damaged area. This pain lessens when you rest.
Gradually, the bone and the surrounding joint surface start to decay. This process can take weeks or months. As it continues, the pain intensifies. You may experience joint stiffness and have limited, painful range of motion. You may limp if the problem affects the hips or knees. It can also be difficult to stand or walk.
How is osteonecrosis diagnosed?
Your healthcare provider will assess your symptoms and perform a physical exam. You may get one or more of these tests:
- Blood tests: A blood test can check for underlying disorders or causes.
- X-rays: These tests detect bone fractures and arthritis.
- Imaging tests: MRIs provide images of bones, muscles and tissues to detect bone collapse. An MRI is better than X-rays at detecting osteonecrosis early.
What are the complications of osteonecrosis?
Very rarely, osteonecrosis leads to limb loss (amputation). More commonly, the condition increases your chances of developing severe, painful osteoarthritis.
How is osteonecrosis managed or treated?
Regardless of whether you have traumatic or nontraumatic osteonecrosis, treatments focus on improving mobility. Your care will also aim to preserve bones and joints. Your healthcare provider will develop a treatment plan based on:
- Affected bone.
- Disease stage (early or late).
- Extent of bone damage.
- Underlying cause.
- Your age.
If you catch the disease early and it affects a small area that isn’t weight-bearing, you may get better with home care. Nonsteroidal anti-inflammatory drugs (NSAIDs), rest and physical therapy can help. These treatments are most effective for small bones that don’t bear a lot of weight.
In most cases, you’ll need surgery. Surgical options include:
- Core decompression: Your surgeon drills one or more small holes (cores) into the affected bone to relieve pressure. In two out of three people, this procedure delays or prevents the need for joint replacement surgery.
- Bone grafting: During a bone graft, your surgeon takes healthy bone from one part of your body and transplants it to take the place of diseased bone.
- Osteotomy: This procedure reshapes and repositions the bone to take stress off of a damaged joint.
- Joint replacement: If you have significant bone collapse, your provider may replace the damaged joint with an artificial one. Hip replacements and knee replacements are 95% effective at relieving pain and restoring mobility in people with osteonecrosis.
How can I prevent osteonecrosis?
Cutting out alcohol and smoking can lower your risk of osteonecrosis. If you take corticosteroids for a chronic medical condition like lupus, talk to your healthcare provider. You may be able to reduce the dosage or length of treatment. In many instances, there isn’t anything you can do to prevent osteonecrosis.
What is the prognosis (outlook) for people who have osteonecrosis?
Most people with osteonecrosis eventually need surgery to ease pain and improve mobility. The outlook may be better with a faster diagnosis. Your prognosis for recovery is better the earlier you begin treatment.
When should I call the healthcare provider?
You should call your healthcare provider if you experience:
- Pain that doesn’t improve with rest or pain relievers.
- Pain that makes walking or movement difficult.
- Unexplained limping.
What questions should I ask my healthcare provider?
You may want to ask your healthcare provider:
- Why did I get osteonecrosis?
- What is the best treatment for me?
- What are the treatment risks?
- What type of follow-up care do I need after treatment?
- Should I look out for signs of complications?
