[Popliteal artery aneurysma as an important differential diagnosis].

A common reason for painful lesions of the popliteal fossa are baker's cysts. An important differential diagnosis is the popliteal artery aneurysm, which is rare, but is associated with severe complications. The preferred method of diagnosis is the colour-coded duplex ultrasound. By showing the case of a 58-year-old man, who experienced life-threatening complications caused by an insufficient diagnosis before the operation of a Baker's cyst, we want to underline the importance of preoperative duplex ultrasound diagnosis in this context.