Sonomorphologic variants of popliteal cysts

Since sonography of popliteal cysts was first described in 1972 by McDonald and Leopold, it has proved to be a valuable diagnostic tool for the detection of these lesions.(2-9) Popliteal cysts can appear clinically as a posterior mass, mimicking a solid tumor or vascular lesion,(3,4,6-9) and they may cause pseudophlebitis, cellulitis, deep vein thrombosis, or isehemia.(4,6,7,9,10) Although various studies have shown that not all popliteal cysts meet the typical sonographic criteria for cyst, little is known about the different sonomorphologic variants that may complicate the differentiation of popliteal cysts from other lesions.(2-4,6,7,9) This pictorial essay illustrates the normal anatomy of the fossa poplitea, variants of popliteal cysts, and their differential diagnosis, focusing on the value of sonography. Familiarity with these sonomorphologic variants will permit a more accurate diagnosis.