DEAR DR. DONOHUE: About four months ago, a bulge appeared behind my right knee. It didn't hurt at first, but then it started to give me a little pain. I saw a doctor. He poked around and finally said it was a cyst. He told me to put a hot, wet towel on it. I did this three times a day for the next three months. Nothing happened. It's still there, and it might be bigger. How does a cyst get there? Is there something else I can do for it?
ANSWER: That's a Baker's cyst. It's a soft bulge on the back of the knee. It's sort of like housemaid's knee, a swelling on the front of the knee, something that happens to people who are on their knees a lot — carpet layers, gardeners and people who scrub floors.
Behind the knee is a bursa. Bursas are small, flat discs that act like ball bearings. Nature placed them between tendons and bones to prevent friction as the tendon rubs across the bone. The behind-the-knee bursa is connected to the knee joint by a small tunnel. Any process that causes inflammation of the knee joint increases fluid production inside the joint. Excess fluid drains into the bursa, and it swells. The drainage tunnel has a one-way valve, so fluid can't drain out of the bursa. Housemaid's knee is the same process, but the front bursa does not connect to the knee joint.
Moist heat is a valid treatment for a Baker's cyst. It's obviously not working for you. Anti-inflammatory medicines like Advil and Aleve can be helpful. However, after four months without any improvement, you now ought to see an orthopedic surgeon.
The doctor can drain the bursa and inject cortisone into it to prevent fluid from reforming. And he or she can examine your knee to see if there is real trouble there.
You should make the appointment soon. Baker's cysts can break, and that is a painful experience.
Incidentally, other conditions in the same location look very much like Baker's cysts but are much more worrisome. An aneurysm of a leg artery or a clot in a deep leg vein has an appearance similar to that of a Baker's cyst.
DEAR DR. DONOHUE: I just had a physical examination and some blood tests for a new job. Everything turned out fine, except I have a positive ANA. The doctor who examined me isn't my regular doctor, but he told me I should see my regular doctor about this. He made it sound like I am at death's door. I feel fine and have never been sick. I'm only 32 and have two young children, keep house and do all the cooking. I also do the yard work. (My husband doesn't like doing it.)
ANSWER: "ANA" is an abbreviation for "anti-nuclear antibody." Antibodies are products of the immune system, somewhat like the immune system's ammunition. They're fired at incoming germs and any other foreign invader.
Sometimes antibodies are made that work against the body's own cells and tissues. In this case, the antibody is directed against the cell nucleus — the heart of a cell.
ANAs are found in rheumatoid arthritis, lupus, scleroderma, some kinds of hepatitis, thyroid inflammation and Lyme disease.
You are a healthy person who happens to have a positive ANA test. A number should follow the ANA notation. Numbers of 1:80 or less indicate a low level of ANA, and those tests can be false-positive tests. Your doctor can clear this up for you, but a positive test in a healthy person often has little significance.
DEAR DR. DONOHUE: I am five months into my first pregnancy. My vision is a bit blurry. I meant to ask my OB doctor if it was due to pregnancy, but I forgot, so I'll ask you. Can pregnancy affect vision?
ANSWER: Pregnant women retain water, and water retained in the eye's cornea can make vision a little less than perfect. If you can read and drive without trouble, you can wait until you see your doctor again. If it is due to a slightly swollen cornea, the swelling leaves when you deliver the baby.
• Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475.