Osteonecrosis of the Knee

Osteonecrosis is a condition in which death of a section of bone occurs because of lack of blood supply.  Women over the age of 60 years of age are most commonly affected, three times more often than men.

Osteonecrosis of the knee is most commonly seen in the femoral condyle, usually on the inner side of the knee (the medial femoral condyle). However, the condition can also occur on the outside of the knee (the lateral femoral condyle) or on top of the shin bone (the tibial joint surface), known as the tibial plateau.

The exact cause of the osteonecrosis of the knee is unknown.  The most common theory suggests that a stress fracture or trauma results in altered blood supply to the bone.  Another theory says that fluid buildup within the bone increases the pressure on the blood vessels resulting in decreased circulation.  If the condition is not diagnosed and treated early, it can result in severe osteoarthritis.  Conditions and treatments that are associated with osteonecrosis of the knee are obesity, sickle cell anemia, lupus, kidney transplants, and steroid therapy.   Steroid-induced osteonecrosis can affect multiple joints and is usually seen in younger patients.

Osteonecrosis in the knee results in sudden onset of pain inside the knee that is activated with a specific activity or minor injury. The pain may worsen with activity and at night.  Osteonecrosis may also cause swelling of the knee, be sensitive to touch and pressure, and can result in limited motion due to pain and swelling.

Treatment

In the early stage of the disease, non-surgical treatment options that include anti-inflammatory medications, braces, strengthening exercises for thigh muscles, and activity modification may be recommended to reduce the knee pain.

Surgical treatment is considered in advanced stages where more than half of the bone surface is affected. Surgical treatment options include:

• Arthroscopic debridement
• Drilling or microfracture in the area of osteonecrosis to decrease pressure and stimulate healing
• Unicompartmental or total knee replacement

Dr. Fischer will discuss all the surgical options and will recommend the one appropriate for you.