Harvard Women's Health Watch

Ask the doctor: How do you treat a Baker's cyst?

Q. I have a Baker's cyst in my right knee. It has been drained twice and recurred. Are there any other treatments for it?

A. Your situation is fairly common. A Baker's cyst (also called a popliteal cyst) is a fluid-filled sac that can develop in the popliteal space, the hollow at the back of the knee joint. It's named for William Morrant Baker, a 19th-century surgeon who first described the condition. The cyst is filled with synovial fluid, a viscous material that lubricates the knee joint, reducing friction among the components of the joint and allowing the knee to flex and extend freely. There are several ways to treat a Baker's cyst, but it will often recur if the underlying cause hasn't been addressed.

A Baker's cyst may occur as a result of an injury to the knee, such as a tear in a meniscus, or damage to the cartilage from conditions such as rheumatoid arthritis or osteoarthritis. These conditions may cause the synovial cells lining the knee joint to produce excess fluid. If the fluid bulges into the popliteal space, a cyst can develop (see the illustration). The excess fluid can also cause the whole knee to become swollen.

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