label: Popliteal synovial cyst
label_lc: popliteal synovial cyst
description: "A fluid-filled mass that is a distention of a preexisting bursa in the popliteal fossa, most commonly the gastrocnemio-semimembranosus bursa. This bursa is unique in that it communicates with the knee joint, unlike other periarticular bursae, via an opening in the joint capsule posterior to the medial femoral condyle."