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Written by: Dr. Frederick Buechel, Jr.

What Is Osteonecrosis​?

Osteonecrosis means bone death. The bone cells die due to blood flow reduction, lack of oxygen to the cells, and the bone begins to cause pain. This can occur in any bone, but it is commonly seen in the knee and hip joints. Pain can occur at rest and with weight bearing, unlike osteoarthritis pain that occurs mostly with weight bearing and is relieved with rest. Bone death can start off in a small area and can progress to a large area of bone. Sometimes the process stops, and the pain can go away. Initially, in the very early stages, the condition is not seen on x-ray. It can, however, be seen with MRI, in the very early phase. In these early pre-collapse 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 surface 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 usual solution to relieve the pain and restore function.

What Is Knee Osteonecrosis​?

Knee osteonecrosis is bone death that occurs in the region of the knee, the location where the end of the femur and the top of the tibia meet, called the knee joint. Osteonecrosis can occur across the entire end of either bone in the knee.

What Are The Causes Of A Condition?

  • 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. It is also more common over the age of 60 but can be seen younger as well.
    • Pain is more commonly of sudden onset
    • Commonly 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 which are slow-growing blood cancers where bone marrow makes too many abnormal cells.
    • Each of these in some way make blood flow difficult in the bone cells and cause ischemia leading to bone death.
    • Pain is more commonly slower in onset
    • 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.

What Are The Signs And Symptoms Of A Condition?

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.

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.

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.

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.

Sometimes cutting out the bad zone and inserting a cadaver bone with cartilage 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 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 is a surgical procedure that places new surfaces on all the surfaces on the end 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.

How Do You Treat Osteonecrosis Of The Knee Non-Surgically?

In the early pre-collapse stages, patients can consider protecting the joint from excessive pressure by using canes, crutches, or walkers when walking.

There has also been evidence that using NSAIDs and in some cases prescription medications called Bisphosphonates can be effective. You need to discuss this with your doctor to see what options might be beneficial for your case.

Frederick F. Buechel, Jr. MD

Meet Frederick F. Buechel, Jr. MD

Frederick Buechel, Jr., MD is an internationally renowned orthopedic knee surgeon, an international instructor, and an expert in the field of Robotic Partial Knee Replacement and Robotic Total Knee Replacement.

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Meet Frederick F. Buechel Jr. MD

Frederick F. Buechel Jr. MD is an internationally renowned Orthopaedic Surgeon who is Fellowship Trained in Knee and Hip Joint Replacement and specializes in robotic partial knee replacement, robotic total knee replacement, and knee meniscus surgery. Learn More »

Select Relevant Publications

Buechel F., Buechel F., Conditt M. (2016) Robotic-Arm Assisted Unicompartmental Knee Arthroplasty (MAKO). In: Scuderi G., Tria A. (eds) Minimally Invasive Surgery in Orthopedics. Springer, Cham. Link to Article

Buechel FF Sr, Buechel FF Jr, Pappas MJ, Dalessio J. Twenty-year evaluation of the New Jersey LCS Rotating Platform Knee Replacement. The journal of knee surgery. 2002 Spring;15(2):84-9. Link to Article

Buechel, Frederick F. Sr. MD; Buechel, Frederick F. Jr. MD; Pappas, Michael J. PhD; D'Alessio, Jerry MS. Twenty-Year Evaluation of Meniscal Bearing and Rotating Platform Knee Replacements. Clinical Orthopaedics and Related Research. July 2001 - Volume 388 - Issue - pp 41-50. Link to Article

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