Avascular Necrosis of the Hip: When Blood Flow to the Femoral Head  Is Disrupted

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Avascular Necrosis of the Hip

Avascular necrosis of the hip (AVN) occurs when there is a lack of blood supply to part of the hip bone. Over time, the affected bone can weaken and become damaged.

AVN usually affects the femoral head, the rounded upper part of the thigh bone that forms the ball of the hip joint. The condition is also known as osteonecrosis of the hip.

Some people have no symptoms early on. When symptoms appear, you may feel pain in the hip, groin, or upper thigh. It may first occur when you walk or put weight on the affected leg. Over time, the pain may become harder to ignore, making everyday activities such as walking or climbing stairs more difficult.

Without treatment, continued damage may weaken the femoral head and change its shape. This can affect the hip joint surface and eventually lead to arthritis.

Treatment options can vary depending on the stage of AVN. Identifying AVN before major changes occur in the hip joint may provide more options for managing the condition.​

What Is Avascular Necrosis of the Hip?

The hip is a ball-and-socket joint. The femoral head forms the ball at the top of the thigh bone and fits into a socket in the pelvis.

Bone is living tissue and needs a steady blood supply to remain healthy. In avascular necrosis, blood flow to an area of the femoral head is reduced or interrupted. The affected bone gradually loses strength and may become damaged.

These changes do not always cause symptoms right away. In some people, doctors find the condition before significant pain develops. In others, hip or groin pain is the first noticeable sign.

Symptoms of Avascular Necrosis of the Hip

AVN pain is commonly felt around the hip or groin. It may also spread to the thigh or buttock. The pain often worsens with walking, standing, or putting weight on the affected leg.

As the condition progresses, pain may become more frequent and can eventually occur even at rest. The hip may also become stiff or harder to move, making everyday activities more difficult.

Common symptoms of AVN may include:

  • Pain in the hip or groin
  • Hip pain when walking or bearing weight
  • Pain that may spread to the thigh or buttock
  • Hip stiffness or limited movement
  • Difficulty walking or a noticeable limp
  • Pain at rest as the condition progresses

Symptoms can develop differently from person to person. Pain when walking or hip movement may become more noticeable as the condition advances.

Causes and Risk Factors

Avascular necrosis develops when the blood supply to the femoral head is reduced or disrupted. This may happen after an injury that damages the blood vessels around the hip. In many cases, however, AVN is linked to other factors rather than a direct injury.

Common risk factors include:

  • Hip injury: A fracture or dislocation may damage the blood vessels that carry blood to the femoral head.
  • Corticosteroid use: Long-term use or high doses of corticosteroids can increase AVN risk.
  • Heavy alcohol use: Drinking large amounts of alcohol over time is associated with a higher risk of developing AVN.
  • Certain medical conditions: Blood disorders and some autoimmune diseases can affect blood flow to the bone.
  • Certain medical treatments: Radiation therapy and some treatments that affect bone health may also increase the risk.

AVN can also occur without an identifiable cause. When no clear cause or risk factor is found, it is called idiopathic avascular necrosis.

Diagnosis of Avascular Necrosis of the Hip

Diagnosing AVN starts with understanding the pattern of hip pain and looking for factors linked to the condition. The assessment usually starts with a discussion about your symptoms, past hip injuries, current medications, and overall health. During the examination, the doctor will gently move the hip to look for stiffness, discomfort, or a limited range of motion.

Imaging tests are important because changes inside the bone may begin before symptoms become severe.

  • X-ray: This test gives the doctor a clear view of the hip joint and can reveal changes in the femoral head, including signs of bone collapse or joint damage. Early AVN may not always appear on an X-ray.
  • MRI: An MRI provides a closer look inside the bone and can detect early changes that may not appear on an X-ray. It can also help show the location and extent of the affected area.

The imaging results help determine how far AVN has progressed and whether the femoral head still keeps its normal shape. This distinction matters because treatment options can differ before and after the bone begins to collapse.

Stages of Avascular Necrosis of the Hip

Avascular necrosis can progress from early changes within the bone to more advanced damage of the hip joint. The stage is based on imaging findings and the condition of the femoral head.

In the early stages, the femoral head still keeps its normal shape, although changes may already be developing inside the bone. These early changes may be easier to detect with an MRI than with a standard X-ray.

As AVN progresses, the affected bone becomes weaker. Small changes can develop beneath the joint surface, and the femoral head may begin to lose its rounded shape.

In the advanced stages, part of the femoral head may collapse. Once this happens, the smooth surface of the hip joint becomes uneven, and the joint can gradually develop arthritis.

The stage of AVN is an important part of treatment planning. Treatments aimed at preserving the natural hip joint are generally considered before significant collapse, while more advanced joint damage may require a different approach.

Treatment for Avascular Necrosis of the Hip

Treatment depends on the stage of AVN, the amount of bone affected, symptom severity, and whether the femoral head has started to collapse. Clinicians also consider age, overall health, and the condition of the hip joint when planning treatment.

H3: Treatment in the Early Stages

When the femoral head has not collapsed, treatment may focus on relieving symptoms and reducing stress on the affected hip. Depending on the individual case, this may include:

  • Medication: Pain-relieving or anti-inflammatory medicines may be used to manage discomfort.
  • Reducing strain on the hip: Activities that place repeated stress on the hip, such as running, jumping, or walking for long periods, may need to be limited to help manage pain.
  • Walking support: Crutches or other walking aids may be recommended for a period of time to reduce weight on the affected hip.
  • Physical therapy: Exercises may help maintain hip movement and support the muscles around the joint.

For some patients, surgery may be considered to preserve the femoral head before collapse occurs. One option is core decompression, a procedure that removes a small amount of bone from the affected area to reduce pressure and support blood flow within the femoral head. In selected cases, other procedures may be used together with core decompression depending on the extent of bone damage.

Treatment for Advanced AVN

When the femoral head has collapsed, or the hip joint has developed significant damage, procedures that preserve the natural joint may no longer be suitable.

Total hip replacement may be considered when pain and joint damage significantly affect walking, movement, or daily activities. During the procedure, surgeons remove the damaged joint surfaces and replace them with implants that allow the hip to move more comfortably.

Treatment decisions are based on more than symptoms alone. Imaging findings and the condition of the femoral head help the orthopedic surgeon determine whether preserving the natural hip is still possible or whether joint replacement is more appropriate.

Specialized Hip Treatment  at Vejthani International Hospital

The Hip and Knee Center at Vejthani International Hospital in Thailand provides specialized care for hip conditions, with orthopedic surgeons experienced in total joint reconstruction and hip arthroplasty.

When avascular necrosis affects the hip, treatment is planned based on symptoms, imaging findings, and the stage of bone damage. When the femoral head can still be preserved, joint-preserving treatment may be considered. If AVN has progressed and caused significant joint damage, hip replacement, including minimally invasive approaches, may be an option.

Care continues through treatment and recovery to reduce pain, improve hip function, and help patients return to daily activities.

AVN Can Progress to Femoral Head Collapse or Hip Joint Damage  

Without appropriate treatment, the affected bone may continue to weaken. Over time, the femoral head can lose its rounded shape and eventually collapse, making the hip joint surface uneven.

As the joint becomes more damaged, pain and stiffness may increase, and walking or moving the hip can become more difficult. Damage to the joint surface can also lead to secondary osteoarthritis.

Once the femoral head has collapsed, treatments that aim to preserve the natural hip may become less suitable. This is why identifying AVN before significant joint damage develops can be important when considering treatment options.

Frequently Asked Questions About Avascular Necrosis of the Hip

Can Avascular Necrosis of the hip heal on its own?

AVN generally does not heal on its own once the bone has been damaged. The condition can progress differently, so accurate diagnosis is important to determine the stage of AVN and which treatment options may be suitable.

Does AVN always require hip replacement?

No. Hip replacement is not necessary for every patient with AVN. When the condition is found before the femoral head collapses, doctors may consider treatments that aim to preserve the natural hip. Hip replacement is more commonly considered when there is significant collapse or joint damage.

Can Avascular Necrosis affect both hips?

Yes. AVN can affect one or both hips. Even when symptoms are present on only one side, imaging tests may sometimes identify changes in the other hip.

Can I walk or exercise with AVN of the hip?

This depends on the stage of AVN and the condition of the hip. Activities that involve repeated impact on the hip, including running and jumping, may need to be reduced. A doctor or physical therapist can advise which activities are appropriate and how much weight can safely be placed on the affected hip.

How quickly does Avascular Necrosis of the hip progress?

There is no single timeline. AVN may progress at different rates depending on how much of the bone is involved and where the damage has developed. Regular follow-up and imaging can help monitor changes in the femoral head over time.

For more information, please contact

Hip and Knee Center, Vejthani Hospital
Call: (+66)2-734-0000 Ext. 2222
English Hotline: (+66)85-223-8888

Medically Reviewed by

DR. WACHARA MANEERATROJ
DR. WACHARA MANEERATROJ

Orthopedics

Total Joint Reconstruction (Arthroplasty)

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