Popliteal artery entrapment syndrome (PAES) is a rare condition affecting the artery in the back of the knee. It causes pain in the lower legs during exercise.

The popliteal artery runs behind the knee, providing the lower half of the body with blood from the heart. It is the main blood supply to the knees and legs. Rarely, pressure on this artery from the calf muscles can cause pain during movement. Without treatment, it may cause serious problems with blood circulation.

Popliteal artery entrapment syndrome (PAES) mainly affects active young male athletes.

The symptoms of PAES generally improve after rest. Surgery may also help.

Read on to learn more about the symptoms and causes of PAES, how doctors diagnose the condition, treatment options, and more.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.

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People with PAES usually report to a doctor with severe and disabling leg and foot pain that gets worse with physical activity but gets better with rest.

They may also note the following symptoms in the legs and feet:

  • calf pain
  • numbness
  • cool, pale skin
  • pins and needles, prickling, or skin-crawling sensations
  • swollen calf muscles
  • reduced or absent pulse in the foot when flexing it inward

Learn about other causes of numbness and tingling in the legs and feet.

PAES usually occurs when the head of the gastrocnemius muscle traps or increases pressure on the popliteal artery. The muscle sits at the top of the calf and the back of the knee and is vital for walking.

Sometimes, PAES may develop due to issues with the plantaris muscle, which supports ankle flexing.

Congenital PAES might occur due to problems with development before birth. Functional PAES can happen when issues develop over time.

Congenital PAES

When a fetus develops, the gastrocnemius and popliteal arteries develop simultaneously. If the gastrocnemius moves into an abnormal position during development, this can trap the artery, leading to PAES.

This is the most common cause of PAES. People who have PAES from birth do not often show symptoms until they are teenagers or in their 20s.

Functional PAES

Some people may find that regular participation in sports can lead to PAES developing over time.

As the calf muscles grow, they can develop bands of scar-like tissue that can start to increase pressure on the artery.

Learn about the anatomy of the lower leg.

Several types of congenital and functional PAES can develop depending on their cause, including:

  • Type I: The popliteal artery takes an unusual path around the typically positioned calf muscle.
  • Type II: The calf muscle attaches in the wrong spot on the thigh bone, causing the popliteal artery to move inward and downward.
  • Type III: An abnormal fibrous band or extra muscle wraps around the popliteal artery.
  • Type IV: The popliteal artery is in a deep position, and the popliteus muscle or fibrous bands trap it.
  • Type V: Any of the causes in types I to IV can trap both the popliteal artery and the vein that runs along with it.
  • Type VI: The calf muscle enlarges, squeezing the popliteal artery and vein.

Being male and involved in athletics are significant risk factors for PAEP.

According to a 2018 case study, up to 85% of people diagnosed with PAEP are male. However, the case study explains that this may be due to underreporting in females.

Around 60% of people with PAES are athletes in their 20s.

If a doctor suspects PAES, they will order imaging tests. Typically, the first test they order is a duplex ultrasound (DUS). This helps evaluate the flow of blood through the arteries and veins.

Other tests that can help diagnose PAES include CT angiography (CTA) and MRI. They may order an MRI with or without a magnetic resonance angiogram (MRA).

A person’s doctor can advise on what tests they recommend and what they involve.

PAES treatment involves surgery to relieve symptoms by releasing the artery, usually by removing part of the popliteal muscle. This usually produces excellent outcomes without needing to reconstruct the muscle.

During surgery, the medical team checks whether:

  • damage to the artery walls has occurred
  • a bulge known as an aneurysm has developed
  • there is a blockage

If they identify significant damage, the team can carry out a bypass that moves a vein to the area to reroute blood flow. They may also place a stent, which helps keep the vein open.

People may require follow-up monitoring every 3 months for a year after the procedure, then every year after that.

PAES can lead to a permanently narrowed popliteal artery or blood clots that block it.

The outlook of PAES improves with early detection and treatment, but if artery damage has occurred, an individual may have permanent pain during movement.

Without treatment, people with PAES may require the amputation of a leg. However, this is very rare, as even severe PAES develops slowly. Doctors usually identify and treat PAES long before a person loses a leg.

PAES is a rare condition.

The condition occurs in 0.17% to 3.5% of people in the United States. However, it may be more common than official figures suggest, as a significant number of people may not report having PAES, or misdiagnosis may happen.

How do you fix PAES?

Surgeons can treat PAES by removing part of the calf muscle and relieving pressure on the artery. People with advanced or severe PAES may need bypass surgery to allow blood to flow to the legs and feet through a different vein.

PAES vs compartment syndrome: What is the difference?

Compartment syndrome means that the space in the tissues below the knee has become too small, meaning the muscles inside no longer fit. PAES happens when a muscle behind the knee puts pressure on the popliteal artery.

Compartment syndrome resembles PAES because it causes similar symptoms, is common in athletes, and may result from excess calf muscle growth.

What does PAES feel like?

People with PAES may experience severe pain in their calves and feet during exercise. The pain usually gets better during rest.

Popliteal artery entrapment syndrome (PAES) is a rare blood vessel condition that is most likely to develop in young male athletes. It causes pain while walking, which improves while at rest.

PAES occurs due to increased pressure from the calf muscles on a blood vessel that supplies the lower leg. Congenital PAES is due to changes during fetal development. Functional PAES develops over time with regular participation in sports.

Diagnosis for PAES can involve duplex ultrasound (DUS), MRI, and CT angiography (CTA). Treatment usually involves surgery to reduce the calf muscle and release the artery. For people who have blood vessel damage resulting from PAES, a bypass may be necessary to prevent complications.