Have you ever heard of a Baker's cyst from Lyme disease? Our son was diagnosed with this earlier this year.

Baker's cyst (sometimes called a popliteal cyst) has been reported with Lyme disease. It is a rare presentation of this disease. Boys are affected more often than girls.

The cyst is located behind the knee. It fills with synovial fluid from the joint. There usually isn't any infection present in the joint.

Antibiotic therapy is the main treatment for this problem. Treatment with oral antibiotics may not clear up the swelling. Sometimes two or three series of antibiotics are required. Intravenous antibiotics may be needed if the symptoms don't go away with the oral antibiotics.

The Centers for Disease Control and Prevention (CDC) recently reported over 23,000 cases of Lyme disease in the United States. Most cases occur in the New England area, the mid-Atlantic states, Minnesota, and Wisconsin.

Only a handful of cases involving popliteal cyst have been reported. Because of its unusual presentation, it may be missed or misdiagnosed.