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Osteonecrosis of the Knee

Osteonecrosis occurs when a bone loses its blood supply and the cells begin to die. It is more common in older women, occurring three times as much as in men.

Causes and symptoms

The causes of osteonecrosis aren't yet known. Potential causes may include:

  • A stress fracture in the knee that occurs as a result of a specific activity or trauma
  • Fluid buildup within the bones places pressure on blood vessels, reducing circulation
  • Having certain conditions, such as obesity, lupus and sickle cell anemia
  • Certain therapies, such as kidney transplants and steroid therapy, are associated with osteonecrosis

Symptoms of osteonecrosis include:

  • Increased pain at night
  • Swelling in the knee
  • Greater sensitivity to touch
  • Limited range of motion
  • Sudden pain inside the knee as the result of an activity or injury

Diagnosis and treatment

Osteonecrosis in the knee has four stages of progression. Staging of the condition is done through X-rays and examining the symptoms.


Stage I: The symptoms of osteonecrosis are the worst in the earliest stage, and they last for about six to eight weeks before subsiding. Diagnosis is done by positive bone scans, because X-rays will be normal. Treatment in the earliest stage focuses on reducing weight-bearing activities and relieving pain.

Stage II: In this stage, X-rays show that the edge of the thighbone is become flat. Bone and CT scans may be used to further stage the disease and measure the area affected.

Stage III: In the third stage, osteonecrosis is very visible on X-rays. Imaging will show that cartilage covering the bone is loosening, and the bone is beginning to die. At this stage, surgery is a consideration.

Stage IV: The fourth stage is the most advanced stage of the disease. By this time, bone is beginning to collapse, cartilage is destroyed, bone spurs are forming and the space between the joints is very small. This leads to severe osteoarthritis and joint replacement may be needed.


In the early stages of osteonecrosis, treatment is conservative. Depending on the condition of your knee, treatment may include:

  • Pain medication
  • Strengthening exercises
  • Activity modification
  • Knee brace

If your condition worsens or pain is not relieved by conservative treatment, surgery is often the next step. There are several options for surgery:

  • Arthroscopic cleansing of the joint
  • Drilling to relieve pressure on the bone
  • Shifting the weight-bearing of the leg away from the affected knee
  • Total knee replacement

Your surgeon will work with you to determine a treatment plan that is unique to your personal needs and goals.

To learn more, call 714-456-7012 or schedule an appointment online ›

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