Popliteal cysts in a pediatric patient.

A 12-year-old boy with recurrent complaints of knee pain and swelling for six months, but without diagnosed rheumatological disease, presented with calf swelling and knee pain of several days duration. Examination revealed findings consistent with juvenile rheumatoid arthritis and a ruptured Baker's cyst. This is the sixth reported case of ruptured Baker's cyst reported in a child less than 14 years old and should alert emergency physicians that calf pain and swelling secondary to a ruptured popliteal (Baker's) cyst may be an early manifestation of juvenile rheumatoid arthritis.