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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.
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.
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:
Symptoms can develop differently from person to person. Pain when walking or hip movement may become more noticeable as the condition advances.
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:
AVN can also occur without an identifiable cause. When no clear cause or risk factor is found, it is called idiopathic avascular necrosis.
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.
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.
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 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.
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:
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.
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.
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.
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.
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.
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.
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.
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.
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.
Hip and Knee Center, Vejthani Hospital
Call: (+66)2-734-0000 Ext. 2222
English Hotline: (+66)85-223-8888
Orthopedics
Total Joint Reconstruction (Arthroplasty)
