Popliteal artery entrapment syndrome occurs when the popliteal artery, the main artery for the lower body, is compressed by muscles behind the knee, restricting blood flow through the legs.

The disease presents in two ways: congenitally and developmentally.

Congenital variations are present at birth when the course of the artery is altered by one of the muscles in the area behind the knee. This can remain without symptoms or can cause significant problems if the artery becomes compressed and eventually blocked.

Developed conditions are usually seen in athletes and competitive runners when the muscles are in the correct position but compress the artery as they grow.