Dissecting popliteal cyst: an unusual complication of Reiter's syndrome.

A case of Reiter's syndrome associated with a dissecting popliteal cyst mimicking deep vein thrombophlebitis is reported. The cyst was diagnosed by arthrography and responded to intra-articular injection of corticosteroids. The diagnosis of a dissecting popliteal cyst should be considered in a patient with arthritis of the knee joint from any cause and who develops signs and symptoms of thrombophlebitis.