DEAR DOCTOR K: I just found out I have a Baker's cyst. Is it serious? How is it treated?
DEAR READER: A Baker's cyst is a fluid-filled sac that can form in the popliteal space, the hollow at the back of the knee joint. A Baker's cyst is filled with synovial fluid, a viscous material that lubricates the knee joint. I spoke to my colleague Dr. Celeste Robb-Nicholson, associate professor of medicine at Harvard Medical School, about this condition.