Avascular Necrosis (Osteonecrosis) of the Knee

Avascular necrosis, or osteonecrosis, is a painful condition that occurs when the blood supply to a section of bone is disrupted. Bone cells need a steady supply of blood in order to stay healthy. So this condition can eventually lead to the destruction of the knee joint as well as severe arthritis.


The knee joint is the largest and strongest joint in the body. There are three bones in the joint, the femur, tibia, and patella. Osteonecrosis usually occurs in the thigh bone on the inside of the knee, a part known as the medial femoral condyle. It can also occur on the lateral femoral condyle or on the tibial plateau.

Avascular necrosis occurs when the blood supply to part of a bone is disrupted. The affected portion of the bone will die and eventually collapse without the nourishment from the blood. Because of this, the articular cartilage that covers the bone will also collapse. This collapse leads to debilitating arthritis.

Avascular Necrosis Causes

It isn’t always known what causes the blood supply to get disrupted to a part of the knee. However, there are certain risk factors that have been identified that make someone more likely to develop this condition. Typically, this condition affects people over the age of 60 and it is also three times more likely to develop in women than men. Other risk factors include:

  • A knee injury that damages the blood vessels of the knee and reduce blood flow to the joint
  • Medical conditions like obesity, sickle cell anemia, and lupus
  • Organ transplants, particularly kidney transplants
  • Excessive alcohol use over time can result in a decreased blood supply to the bone

Avascular Necrosis Symptoms

Avascular necrosis and its symptoms develop in stages. In the first stage, pain on the inside of the knee is very common. The pain might occur seemingly out of nowhere or could be triggered by a specific activity or small injury. However, as the condition progresses, standing and putting weight on the knee becomes very painful. Patients may also notice swelling on the front and inside of the knee, sensitivity to the touch, and limited range of motion. Progression of osteonecrosis can take anywhere from several months to over a year. 

Avascular Necrosis Treatment

When osteonecrosis gets diagnosed early, treatment options may simply involve medications to relieve pain and limiting the use of the knee. For those with advanced osteonecrosis, surgery is almost always required to prevent further damage to the bones. The correct treatment option will be determined based on the stage of the condition, how much bone is affected, and the underlying cause of the disease.

Nonsurgical Treatment

In the early stages, especially if the affected part of the knee is small, treatment will be nonsurgical. Nonsteroidal anti-inflammatory drugs like ibuprofen may be recommended to reduce pain and swelling in the knee. Some patients may find that bearing weight on the knee less often can slow the damage to the knee and even allow for healing. A doctor or physical therapist might also prescribe an exercise program that will help strengthen your thigh muscles and help maintain the range of motion. 

Surgical Treatment 

Surgery is recommended if a patient’s pain doesn’t improve with nonsurgical treatment or a large amount of the bone is affected. There are several procedures possible to treat osteonecrosis. Your doctor will be able to recommend the one that is most appropriate for your situation.

Avascular Necrosis at OAR

Early detection of avascular necrosis is vital to achieving the best possible outcome. If you notice new knee pain, make an appointment at Orthopaedic Associates of Riverside. The earlier we can diagnose the problem and begin treatment, the more successful your treatment will be.

Contact us today!