Dear Doctor Column, March 5, 2007

Baker's Cyst Often Resolves On Its Own

Question:

I have a Baker's cyst. Can it be surgically removed?

Answer:

Yes, if necessary, it can be surgically removed. Some of these cysts, however, disappear on their own or respond well to anti-inflammatory drugs or aspiration of fluid from the cyst.

A Baker's cyst, also called a popliteal cyst, forms when production of fluid that lubricates the knee joint increases, usually because of inflammation or injury to the knee. The excess fluid flows into a bursa, or naturally occurring sack that protects tendons and muscles from irritation, which lies behind the knee. When excess fluid fills the bursa, it expands, causing pain that is worse when bending the knee.

The most common causes of inflammation and fluid accumulation in the knee that lead to popliteal cysts are flare-ups of rheumatoid arthritis or osteoarthritis. Injuries also can cause fluid accumulation, most frequently those that result in a torn cartilage or ligament inside the knee.

Treatment involves identifying the underlying cause of fluid accumulation and treating that. An arthrogram (an X-ray following injection of dye into the joint) or an MRI are often necessary to assess the problem and determine the cause. If the problem is rheumatoid arthritis, for example, medications to control inflammation can help. If an injury is the cause, it may be necessary to surgically correct the injury in order to correct the problem.

Depending on the cause of the cyst, anti-inflammatory drugs or removing fluid from the cyst with a needle may be all that is needed. A shot of cortisone into the joint also may decrease inflammation. As inflammation subsides, the body reabsorbs the fluid, and the cyst decreases in size or disappears. However, Baker's cysts sometimes recur and become larger and more painful. Occasionally, a cyst can extend down into the calf, causing considerable pain. If it becomes extremely large, it can rupture, producing symptoms similar to inflammation of the veins called thrombophlebitis, a serious condition associated with blood clots in the leg.

If initial treatments do not resolve the problem, the physician may recommend removing the cyst surgically. The surgeon makes an incision behind the knee and cuts out the cyst. After recovery and healing takes place, previous activities and exercise can be resumed.