MRI appearance of popliteal cysts in childhood.

Popliteal cysts are soft fluid-filled lesions of synovial origin which result from extrusion of joint fluid into the gastrocnemiosemimembranous bursa. They may occur in any age group, but 22-33 % occur in the first 15 years of life. In this age group they are rarely associated with intraarticular abnormalities and therefore rarely require treatment. This case report shows the magnetic resonance imaging (MRI) appearances of a popliteal cyst in two children.