What is a Baker’s Cyst?

A Baker’s Cyst, also referred to as a popliteal cyst, is a small benign (non-cancerous) cyst that forms on the back of the knee joint. A cyst is a small sac filled with clear, thick fluid. It may range in size, and causes a bulge and feeling of tightness behind the knee. The condition, which has nothing to do with baking, is named after Dr. William Morrant Baker who is the British surgeon who first described it. The pain can get worse when fully extending the knee or when active or after standing for an extended period of time. A Baker’s cyst is usually the result of a problem with the knee such as arthritis or a cartilage tear. The clear, thick fluid that builds up is called synovial fluid which helps your leg to move smoothly, however when there is an injury (such as a cartilage tear) or swelling of the knee joint (such as arthritis) then the knee may produce too much fluid. The resulting building of fluid in the area on the back of the knee (popliteal bursa) causes the Baker’s cyst.

Symptoms

In some cases, a Baker’s cyst causes no pain or discomfort and may go unnoticed. If you do have signs and symptoms, they might include:

  • Swelling behind your knee, and sometimes in your leg
  • Knee pain
  • Stiffness and inability to fully flex or extend the knee

Baker’s Cyst treatment

Treatment is often not necessary, except to continue to observe the cyst to be sure that it does not continue to grow larger and normally the cyst will go away by itself. However, if the cyst is large and causes pain, treatments may include:

  • Medication. Your doctor may inject a corticosteroid medication, such as cortisone, into your knee to reduce inflammation. This may relieve pain, but it doesn’t always prevent recurrence of the cyst.
  • Fluid drainage. Your doctor may drain the fluid from the knee joint using a needle, called aspiration.
  • Physical therapy. Icing, a compression wrap and crutches may help reduce pain and swelling. Gentle range-of-motion and strengthening exercises for the muscles around your knee also may help to reduce your symptoms and preserve knee function.

As mentioned above, there may be an underlying cause of the cyst. If a cartilage tear is causing the overproduction of synovial fluid, surgery may be recommended to remove or repair the torn cartilage. Baker’s cysts associated with osteoarthritis usually improve with treatment of the arthritis. Surgical intervention is rarely needed for a Baker’s cyst.

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