School ager with a palpable mass in the popliteal fossa

US of popliteal cyst
Transverse (above) and sagittal (below) US of the popliteal fossa shows it to contain an anechoic mass which upon closer scanning had a neck at its deepest extent that extended into the joint space between the semimembranosus tendon and medial head of the gastrocnemius tendon.

The diagnosis was popliteal cyst.