Causes

Popliteal artery entrapment syndrome (PAES) is caused by an abnormal calf muscle, usually the gastrocnemius muscle.

The condition may occur from birth (congenital) or develop later in life (acquired). In the congenital form, the calf muscle or nearby artery is abnormally positioned while the baby grows in the mother's womb. People with the acquired form of PAES have a calf muscle that is bigger than normal (enlarged).

The abnormal calf muscle presses on the main artery behind the knee (popliteal artery), reducing blood flow to the lower leg. The lack of blood flow results in pain and cramping in the back of the lower leg during times of activity.