Avascular Necrosis (AVN) of the Knee
Avascular necrosis (AVN) is the bone death that occurs as a result of disruption of the blood supply to a part of the bone. Avascular necrosis (osteonecrosis) commonly affects the hip but may also occasionally affect the knee joint.
The management of knee joint osteonecrosis is usually surgical and many patients with advanced-stage surgery may need knee replacement surgery.
The bones in our body are living tissues that require a constant supply of blood that brings oxygen and nutrition for their structure and function. Any disruption of the blood supply leads to bone death (infarct) in the affected area.
MRI of the knee in the coronal section showing AVN lesion along with subchondral fracture in the medial femoral condyle.
The body tries to repair the damage by the formation of new blood vessels that creep in to help bone cells remove dead bone and substitute the dead bone with scar tissue or new bone. The process however is completed in avascular necrosis as in AVN there is usually an increase in pressure of the bone marrow.
The increased pressure inside the bone is detrimental to the formation of new blood vessels and the subsequent repair. Further, in the case of osteonecrosis of the bones of a joint such as knee AVN, the bone death near the joint surface may lead to a collapse of the joint.
The knee joint is the largest weight-bearing joint in the human body. The knee joint is formed by the lower part of the thigh bone (femur), the upper part of the shinbone (tibia), and the kneecap (patella). The lower part of the femur has knobby ends known as condyles that divide the knee joint in the inner and the outer compartment.
The ends of the bones that form the knee joint are covered with a glistening tough tissue known as articular cartilage. The bone just beneath the articular cartilage is known as the subchondral bone. The AVN of the knee commonly occurs in the inner knobby part of the femur known as the medial femoral condyle. AVN may also occur in the lateral condyle of the shin bone (the tibial plateau).
X-ray showing total knee replacement surgery in a patient with AVN knee.
Causes and risks of Knee AVN
The majority of the cases of AVN knee are idiopathic, i.e no single cause has been found that leads to avascular necrosis. Spontaneous osteonecrosis of the knee (SONK) is self-limiting avascular necrosis of the inner side of the knee joint. However, there are risk factors that have been identified to play a role in the development of avascular necrosis.
Long-term consumption and abuse of alcohol have been associated with the risk of avascular necrosis. The consumption of alcohol may lead to an increase in free fatty acids in the bloodstream that may block the blood supply of the bone.
Long-term use of corticosteroids has also been associated with avascular necrosis of the knee joint. The steroid therapy may have been used in various diseases such as lupus nephritis, asthma, rheumatoid arthritis, etc. Abuse of corticosteroids in athletes and bodybuilders has also been associated with knee AVN. Steroid-induced osteonecrosis occurs as the steroids may increase the marrow pressure secondary to edema.
The AVN of the knee may also secondary to any injury to the knee that may occur as a result of a fall/accident or any prior surgery around the knee joint. Certain diseases such as thalassemia may cause avascular necrosis as the deformed blood cells may clog the blood supply.
Certain rare diseases such as Gaucher’s disease may lead to avascular necrosis of the knee joint due to abnormal deposition of tissues in the bone marrow. The knee AVN may also occur in patients with a history of a kidney transplant, and at times in patients with HIV infection.
Symptoms
The symptoms of knee AVN may begin suddenly in the form of sharp pain or may begin insidiously. The pain is frequently located in the inner side of the knee joint. The patients may at times report a trivial fall/accident leading to the start of pain or worsening of previous pain. The fall/trauma may lead to the collapse of the subchondral bone weakened by avascular necrosis.
The pain in the AVN of the knee may be associated with swelling and restricted range of motion of the knee joint. The pain may initially be associated with weight-bearing activity but may also occur at rest. The pain worsens over time and may cause the patient to walk with a limp.
Stages and Diagnosis
The initial stages of the knee avascular necrosis may be asymptomatic or may complain of mild pain and the examination of the knee joint may be normal. Radiological studies such as a plain X-ray may be normal in stage 1. There may be subtle findings suggestive of AVN knee in an MRI and a bone scan.
Stage 2 involves the collapse of the subchondral bone and the patient may complain of severe pain in the knee. The finding of subchondral collapse is bisphosphonates usually apparent on an X-ray but may be confirmed on an MRI.
The subsequent stage 3 involves the collapse of the joint surface and osteoarthritic changes in the joint. Stage 4 involves severe osteoarthritis of the knee joint with possible restriction of the range of motion. The findings of stages 3 and 4 are clearly visible on an X-ray. The time between the progression of various stages may vary from weeks to months or years.
Management
The management of the knee AVN depends upon the stage of the disease and the part of the knee involved. AVN of the non-weight bearing part of the knee joint may usually resolve on its own.
Stage 1 management includes protected weight-bearing with the use of crutches, cane, or knee splints. Medications such as bisphonates (anti-resorption) and statins may be used to reduce the progression of avascular necrosis. In the early stages, protected weight-bearing helps to prevent the collapse of the bone. NSAIDs medication may be used to manage the knee pain associated with knee AVN.
In stage 2 of the disease, besides conservative, joint-saving surgical treatment may be used in the form of core decompression, bone and cartilage transplant, autologous chondrocyte implantation, and osteotomy may be used.
In core decompression, multiple small holes are drilled in the area of the AVN to reduce the marrow pressure and increase blood flow. A reduction in marrow pressure helps the new blood vessels to form and start the repair process. Bone graft along with cartilage may also be used to treat the area of bone death after thorough debridement.
Bone cutting surgeries such as osteotomy helps by offloading the joint surface that may stop the progression to joint collapse. Unfortunately, the majority of the cases of knee AVN progress to stages 3 and 4. The treatment option in advanced stages is a total knee replacement surgery that provides excellent relief from the symptoms and improves function.
Rehabilitation and Recovery
Regardless of the treatment option chosen, rehabilitation plays a crucial role in recovering from AVN. Physical therapy can help improve strength, flexibility, and range of motion in the knee, allowing you to regain function and mobility. It’s important to follow your healthcare provider’s recommendations and stick to your rehabilitation plan to achieve the best possible outcome.
Preventing AVN
While not all cases of AVN can be prevented, there are steps you can take to reduce your risk:
- Avoiding excessive alcohol consumption.
- Managing underlying medical conditions such as autoimmune diseases or blood disorders.
- Taking precautions to prevent knee injuries, such as wearing protective gear during sports or activities.
Living with AVN: Living with AVN can be challenging, but with the right treatment and support, many people are able to manage their symptoms and maintain an active lifestyle. It’s important to work closely with your healthcare team to develop a treatment plan that works for you and to seek support from friends, family, and support groups.
Conclusion
Avascular Necrosis (AVN) of the knee is a complex condition, but by understanding its causes, symptoms, and treatment options, you can take proactive steps to manage it effectively. Whether you’re exploring non-surgical treatments, considering surgery, or undergoing rehabilitation, know that you’re not alone in your journey. With the right support and guidance, you can navigate through AVN and continue to enjoy life to the fullest.
Do you have more questions?
How common is Avascular Necrosis (AVN) of the knee?
AVN of the knee is relatively rare compared to other knee conditions, but its prevalence can vary depending on factors such as age, underlying medical conditions, and lifestyle factors.
Can AVN affect both knees simultaneously?
Yes, AVN can affect both knees simultaneously, although it is less common than unilateral (one-sided) involvement.
Is AVN of the knee more common in men or women?
AVN of the knee can affect both men and women, but certain underlying conditions or risk factors may predispose one gender more than the other.
How long does it take for AVN of the knee to progress?
The progression of AVN can vary from person to person and depends on factors such as the underlying cause, the stage of the condition, and how well it responds to treatment. In some cases, AVN may progress slowly over months or years, while in others, it may progress more rapidly.
Can AVN of the knee be cured completely?
Unfortunately, there is no cure for AVN of the knee. However, with proper treatment and management, symptoms can be alleviated, and the progression of the disease can be slowed down.
What are the long-term complications of untreated AVN of the knee?
Untreated AVN of the knee can lead to significant pain, joint deformity, and loss of function. In severe cases, it may result in the need for total knee replacement surgery.
Are there any alternative or complementary therapies that can help manage AVN of the knee?
Some people may explore alternative or complementary therapies such as acupuncture, herbal supplements, or chiropractic care to help manage symptoms of AVN. However, it’s essential to discuss these options with your healthcare provider to ensure they are safe and effective.
Can AVN of the knee recur after treatment?
While treatment for AVN can help alleviate symptoms and slow down the progression of the disease, there is a risk of recurrence, especially if the underlying cause is not addressed or if there is continued stress on the affected knee joint.
What lifestyle modifications can help manage AVN of the knee?
Lifestyle modifications such as maintaining a healthy weight, avoiding excessive alcohol consumption, quitting smoking, and engaging in low-impact exercise can help manage symptoms and improve overall knee health.
Are there any dietary changes that can help prevent or manage AVN of the knee?
While there is no specific diet that can prevent or cure AVN of the knee, maintaining a balanced diet rich in fruits, vegetables, lean proteins, and whole grains can support overall bone and joint health.
How does AVN of the knee affect daily activities and quality of life?
AVN of the knee can significantly impact daily activities and quality of life, leading to pain, stiffness, difficulty walking, and limitations in mobility. It’s essential to work closely with your healthcare team to develop strategies to manage these challenges effectively.
Can AVN of the knee lead to other complications or secondary conditions?
In some cases, AVN of the knee can lead to secondary complications such as osteoarthritis, joint instability, or bone fractures. These complications may require additional treatment and management.
What is the success rate of surgical treatment options for AVN of the knee?
The success rate of surgical treatment options for AVN of the knee can vary depending on factors such as the stage of the condition, the patient’s overall health, and the surgeon’s experience. However, many patients experience significant improvement in symptoms and function following surgery.
Are there any experimental treatments or clinical trials available for AVN of the knee?
Researchers are continually exploring new treatment options for AVN of the knee, including stem cell therapy, gene therapy, and biologic agents. Participation in clinical trials may be an option for some patients, but it’s essential to discuss these options with your healthcare provider.
How long does it take to recover from surgery for AVN of the knee?
The recovery time from surgery for AVN of the knee can vary depending on the type of procedure performed, the patient’s overall health, and other factors. In general, rehabilitation and recovery may take several months, with gradual improvement in symptoms and function over time.
Are there any support groups or resources available for people with AVN of the knee?
Yes, there are several online support groups, forums, and resources available for people with AVN of the knee. Connecting with others who are going through similar experiences can provide valuable support, information, and encouragement.
Can AVN of the knee be prevented in people at risk?
While it may not be possible to prevent AVN entirely, certain measures can help reduce the risk, such as avoiding excessive alcohol consumption, managing underlying medical conditions, and taking precautions to prevent knee injuries.
How often should follow-up appointments be scheduled after treatment for AVN of the knee?
Follow-up appointments after treatment for AVN of the knee may vary depending on factors such as the type of treatment received, the stage of the condition, and the patient’s overall health. Your healthcare provider will typically schedule follow-up appointments as needed to monitor your progress and adjust your treatment plan accordingly.
Can AVN of the knee affect children or adolescents?
Yes, AVN of the knee can affect individuals of any age, including children and adolescents. In younger patients, AVN may be related to factors such as trauma, infection, or certain medical conditions.
How does AVN of the knee differ from other knee conditions such as osteoarthritis or rheumatoid arthritis?
While AVN of the knee involves the death of bone tissue due to a lack of blood supply, osteoarthritis and rheumatoid arthritis are inflammatory conditions that affect the joints differently. Osteoarthritis is characterized by the breakdown of cartilage in the joints, while rheumatoid arthritis is an autoimmune disorder that causes inflammation and damage to the joints.
Are there any specific exercises or physical activities that should be avoided with AVN of the knee?
It’s essential to consult with your healthcare provider or physical therapist before starting any new exercise or physical activity regimen with AVN of the knee. In general, high-impact activities or exercises that put excessive stress on the knee joint should be avoided, while low-impact exercises that promote strength, flexibility, and range of motion may be beneficial.
What are the potential complications of surgery for AVN of the knee?
Like any surgical procedure, surgery for AVN of the knee carries risks, including infection, blood clots, damage to surrounding tissues, and complications related to anesthesia. Your surgeon will discuss these risks with you in detail before the procedure and take steps to minimize them during and after surgery.
Can AVN of the knee affect other joints in the body?
While AVN most commonly affects the knee joint, it can also occur in other joints such as the hip, shoulder, ankle, or wrist. The underlying causes and risk factors for AVN may vary depending on the affected joint.
My name is Dr. Suhirad Khokhar, and am an orthopaedic surgeon. I completed my MBBS (Bachelor of Medicine & Bachelor of Surgery) at Govt. Medical College, Patiala, India.
I specialize in musculoskeletal disorders and their management, and have personally approved of and written this content.
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