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Osteonecrosis means “bone death”. The bone cells can die due to blood flow reduction, lack of oxygen to the cells, and the bone then begins to cause pain. Pain can occur at rest and with weight bearing, unlike osteoarthritis pain that occurs mostly with weight bearing, and is relieved with rest.

Osteonecrosis can occur in any bone, but it is commonly seen in the knee and hip joints. In the knee, osteonecrosis can occur in the end of the femur or the top of the tibia bone. It can occur in just one bone and on just one side of the bone, but it can also occur in both bones and throughout the entire end of the bones. Bone death can start off in a small area and can progress to a large area of bone. Sometimes the process stops early, and the pain can go away.

In the early stages the condition is not seen on x-ray but can be seen with MRI. In these early phases, there are some potential non-joint replacement options that attempt to stop the progression of the process. As the osteonecrosis process worsens, the cartilage surfaces can collapse into the dead bone area causing more significant pain and disability. Once the process goes on to joint surface collapse, joint replacement is the only solution to relieve the pain and restore function.

knee osteonecrosis MRI
Osteonecrosis of the Medial Femoral Condyle
MRI View
x-rays of a knee joint with osteonecrosis
Osteonecrosis of the Medial Femoral Condyle
X-ray View
x-rays of knee osteonecrosis

What Are the Causes of Osteonecrosis​?

Primary osteonecrosis is also called Spontaneously Osteonecrosis of the Knee or “SONK”. This is more commonly seen on the medial femoral condyle. It is usually thought to be lack of oxygen and blood supply to the bone. It is also thought to be secondary to microfractures that cause swelling in the bone and then loss of blood flow and death. Pain is more commonly of sudden onset. It is commonly seen on the inner side of the knee (medial side).

Secondary osteonecrosis of the knee is not as common. This form occurs more commonly in younger patients <50. It is thought to occur from corticosteroid use, excessive alcohol use/abuse, from sickle cell disease, from deep sea diving called Caisson disease, from tobacco use, from myeloproliferative disorders. It is also commonly seen in both knees and can be seen in other bones in the body.

Osteonecrosis After a Knee Arthroscopy is the third cause of this condition. This can present 1-2 months after a knee arthroscopy for a meniscus tear or cartilage procedure and is associated with a sudden onset of pain at this interval after surgery. This is a very infrequent cause of osteonecrosis.

MRI of knee osteonecrosis

What Are The Signs And Symptoms Of Osteonecrosis​?

The most common symptom of knee osteonecrosis is pain in the knee. This pain can occur with weight bearing, but it can also occur when not weight bearing, like sitting or lying down in bed. The pain can be a dull aching pain, or a sharp stabbing pain. The symptoms can include loss of motion and swelling in the knee joint.

Dr. Buechel performing physical exam

Can You Leave Knee Osteonecrosis Untreated?

You can treat osteonecrosis of the knee conservatively in the early stages. This means protecting the joint from excessive pressure by using canes, crutches, walkers when walking. It also means using NSAID medications and in some cases prescription medications.

In the later stages the pain is generally debilitating, and patients seek out treatment to relieve their pain.

Healed knees of a patient after robotic knee surgery

How Do You Treat Osteonecrosis Surgically?

Treating osteonecrosis surgically depends on the stage of the disease, how extensive it is, and knowing the cause of osteonecrosis. The different surgical options for painful osteonecrosis of the knee are provided below. Dr. Buechel can help you understand your condition and provide you with the best options to treat your osteonecrosis. The most common surgical treatments and descriptions are provided below.

Core Decompression

Early in the process a “core decompression procedure” can be used to drill into the bone area that has died, attempting to bring new blood supply to the region.

Osteochondral Allograft

Sometimes cutting out the bad zone and inserting a cadaver bone with cartilage and bone into the bad area can work. This is called an “osteochondral allograft”.


Sometimes cutting the bone and changing the loading angle to take pressure off one side of the knee joint that is affected can help. This is called an “osteotomy”. This requires cutting the bone, changing the angle, and holding it with a plate and screws until it heals over a couple months.

Partial Knee Replacement

Partial Knee Replacement is a surgical procedure that places new surfaces on the end of the bones on one side of the knee joint that is affected by the osteonecrosis.

Total Knee Replacement

Total Knee Replacement is a surgical procedure that places new surfaces on all the surfaces on the ends of the bones of the knee joint because the disease is more extensive than in cases that can be fixed with just a partial knee replacement alone.

Contact the Robotic Joint Center today to schedule your consultation with Dr. Frederick Buechel, Jr. M.D.

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