FAMILY MEDICINE® COLUMN
By John C. Wolf, D.O.
Associate Professor of Family Medicine®
Ohio University College of Osteopathic Medicine

DRAINING BAKER'S CYST WILL GIVE TEMPORARY RELIEF

Question: I've been having trouble walking. My knee just doesn't seem to work properly. It hurts a little, but it mostly doesn't work like it should. My doctor ordered an "MRI" that showed a Baker's cyst. What is a Baker's cyst, and why does it keep my knee from working?

Answer: To explain the cause of a Baker's cyst, I need to review for you the normal structure of the knee. As you know, the knee is the flexible connection between the upper leg bone, the femur, and the lower leg bone, the tibia. The connection between the femur and tibia is not mechanically strong. They rest one upon the other with about as much stability as a book lying on the coffee table. The knee is made strong enough to handle the stress of walking and running by the additional support provided by very strong ligaments and by muscles.

The actual area of contact between the bones of the knee is covered with a smooth layer of cartilage. This cartilage is bathed by a small amount of joint fluid that nourishes and lubricates the joint. The fluid, called synovial fluid, is made by a thin tissue sack called the synovial membrane.

In some conditions, the most common of which is rheumatoid arthritis, the "joint capsule" and synovial lining balloon out at their weakest point, which is always at the back of the knee. This bulging tissue becomes filled with synovial fluid and thereby earns the medical label "Baker's cyst." The cyst causes problems walking because it mechanically limits bending the knee. In simple terms, it just gets in the way.

Question: Is the surgery my orthopedic doctor advised the only treatment, or will the draining and cortisone treatment my family doctor suggested help?

Answer: Your family doctor has suggested taking a fairly simple approach to your problem. The doctor puts a needle into the cyst and removes as much fluid as possible. This temporarily shrinks the cyst, and since it is the size that is causing your symptoms, you will have immediate, although temporary, relief. In most cases, however, the abnormally large amounts of fluid your synovial membrane is producing will, in a relatively short period of time, return the cyst to its previous ballooned size.

Your family doctor also suggested you should have a cortisone shot into the cyst. This medication reduces the inflammation of rheumatoid arthritis that is the underlying cause of your Baker's cyst. While using cortisone will prolong the period of relief you get from draining, it won't cure the underlying condition. It is knowledge of the temporary nature of this treatment that led your orthopedic surgeon to recommend surgical removal of the offending cyst.

As you've probably guessed by now, surgical removal usually gives more prolonged relief from the cyst than that obtained from simply draining it. Also, at the time of surgery for Baker's cyst, other underlying knee problems are often addressed. Addressed is the correct term here, since the other underlying problems, often rheumatoid arthritis, aren't totally correctable.

I'm rather conservative in my approach to surgery. I recommend against it until surgery clearly offers an advantage over other types of treatment. Draining a Baker's cyst is a fairly simple procedure that has very little risk associated with it. Therefore, it would seem like the best first step. However, the amount of other underlying knee problems - even those that don't cause constant pain - can swing the balance in favor of surgery first. Ask both of your doctors to explain why they think their preferred method of treatment is best and why the other's approach is less desirable. Then you will have to decide which is best for you.

Family Medicine® is a weekly column. To submit questions, write to John C. Wolf, D.O., Ohio University College of Osteopathic Medicine, Grosvenor Hall, Athens, Ohio 45701.