Baker's cyst connected to popliteal artery cyst.

A patient with compression of the left popliteal artery by cystic adventitial disease is presented. The adventitial cyst was connected to a Baker's cyst. The patient suffered severe ischemia only after heavy exercise, because the mucous fluid of the Baker's cyst shifted into the popliteal artery cyst when the Baker's cyst was compressed. The etiology of cystic adventitial disease of the popliteal artery in this patient is discussed.