The diagnosis of a popliteal cyst is usually made on the basis of a history of discomfort and pain in the medial portion of the popliteal region, together with the finding of a palpable mass in the popliteal fossa. The clinical diagnosis can be confirmed by knee arthrography, if the cyst communicates with the knee joint; in recent years, however, noninvasive US has also become an important diagnostic aid to the radiologist. The S. Anna Hospital (Ferrara) experience is here reported in the diagnosis of symptomatic popliteal cysts, with no valve mechanism at the connection with the joint cavity. Arthrography was performed on 438 patients with popliteal cysts to determine their extent and size in relation to the symptoms and to the presence of underlying knee pathology; only 76 patients from this group were then submitted to surgery. The authors confirm that popliteal cyst is a frequent occasional finding during knee arthrography which almost completely lacks any clinical relevance in most cases. Moreover, taking arthrographic findings as a starting point, the authors describe the different anatomotopographic patterns of popliteal cysts.