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Overview

Popliteal artery entrapment syndrome (PAES) is an uncommon condition that affects the main artery behind the knee. That artery is called the popliteal artery. In this condition, the calf muscle is in the wrong position or it's larger than usual. The muscle presses on the artery. The artery becomes trapped, making it harder for blood to flow to the lower leg and foot.

Popliteal artery entrapment syndrome is most common among athletes.

Symptoms

The main symptom of popliteal artery entrapment syndrome (PAES) is pain or cramping in the back of the lower leg. The back of the lower leg is called the calf. The pain occurs during exercise and goes away with rest. Other symptoms may include:

• Cold feet after exercise.
• Tingling or burning in your calf.
• Numbness in the calf area.

If the nearby vein, called the popliteal vein, also becomes trapped by the calf muscle, you may have:

• A heavy feeling in the leg.
• Lower leg cramping at night.
• Swelling in the calf area.
• Changes in skin color around the calf muscle.
• Blood clot in the lower leg, called deep vein thrombosis.

Symptoms typically affect young, otherwise healthy people under age 40.

When to see a doctor

Make an appointment for a health checkup if you have any type of leg pain. This is especially important if you have calf or foot cramping during activity that gets better with rest.

Causes

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

The condition may be seen at birth, or it may occur later in life. When it's present at birth, the baby's calf muscle or nearby artery forms in the wrong place during pregnancy. People who get the condition later in life have a calf muscle that is bigger than usual.

The changes in the calf muscle cause it to press on the main artery behind the knee. This reduces blood flow to the lower leg. The lack of blood flow causes pain and cramping in the back of the lower leg during times of activity.

Risk factors

Popliteal artery entrapment syndrome (PAES) is uncommon. The following things increase the risk of the condition.

• Younger age. The condition is most often seen in people who are in their late teens or 20s. It's rarely diagnosed in those over age 40.
• Being male. PAES can occur in anyone, but it's much more common in young men.
• Strenuous athletic activity. Runners, bicyclists, and athletes who try to build muscle fast with weight training routines or high-intensity circuit training are at the highest risk.

Complications

Long-term pressure on the popliteal artery can cause the artery to narrow. This is called artery stenosis. It can cause pain and cramping with just slight activity, such as walking.

In severe cases or when undiagnosed, the nerves and muscles in the leg can become damaged. Blood clots may occur in the lower leg. Older athletes with symptoms of popliteal artery entrapment syndrome should be checked for a ballooning or bulging of the artery. This is called a popliteal aneurysm. It is common in older men.

Diagnosis

To diagnose popliteal artery entrapment syndrome (PAES), the health team checks you and asks questions about your symptoms and health history. But because most people with PAES are young and usually in good health, diagnosing the condition can sometimes be challenging. There are typically no unusual findings from a physical exam.

Tests are done to rule out other causes of leg pain, including muscle strains, stress fractures and peripheral artery disease, which results from clogged arteries.

Tests may include the following:

• Ankle-brachial index (ABI) measurement is usually the first test done to diagnose PAES. Blood pressure measurements are taken in the arms and legs during and after walking on a treadmill. The ABI is determined by dividing ankle pressure by arm pressure. The blood pressure in the legs should be higher than that in the arms. But if you have PAES, your ankle pressure drops during exercise.
• Duplex ultrasound of the calf uses high-frequency sound waves to show how fast blood moves through the leg arteries. This test may be done before or after exercise. You may be asked to flex your foot up and down, which puts your calf muscle to work.
• Magnetic resonance angiography (MRA) shows if the calf muscle is trapping the artery. It also can tell how much of the popliteal artery is narrowed. You may be asked to flex your foot or press it against a board during this test. Doing so helps show how blood is flowing to your lower leg.
• CT angiography also shows which leg muscle is causing the artery entrapment. As with MRA, you may be asked to move your foot during this test.
• Catheter-based angiography shows how blood is flowing to and from the lower leg in real time. It's done if the diagnosis is still unclear after other, less-invasive imaging tests.

Treatment

If popliteal artery entrapment syndrome (PAES) symptoms significantly affect everyday or athletic activities, surgery may be suggested. Surgery is the only way to fix the calf muscle and free the trapped artery.

Surgery is done at a hospital or medical center while you are under general anesthesia. During surgery, the surgeon makes a cut on the inner calf just below or in the back of the knee. This releases the calf muscle to give the artery more room. The calf muscle no longer presses on the artery.

Popliteal artery entrapment syndrome surgery takes about an hour. Typically, you'll need to stay in the hospital for one day.

If you've had the condition for a long time and have severe narrowing of the artery, you may need another surgery called an artery bypass.

Surgery to release the calf muscle and artery usually doesn't affect how the leg works. When the condition is diagnosed and treated early, a full recovery is expected, and symptoms should disappear.

Preparing for an appointment

If you think you may have popliteal artery entrapment syndrome, it's important that you make an appointment with for a health checkup. If it's found early, treatment may be easier, and it may work better.

Health appointments can be brief. But there's often a lot to discuss. So it's a good idea to be prepared for your appointment. Here's some information to help you get ready.

What you can do

• Be aware of any pre-appointment restrictions. Ask if you need to do anything before your appointment. For example, you may be told not to eat or drink for a while before certain tests or surgeries.
• Write down any symptoms you're having, including any that may seem unrelated to popliteal artery entrapment syndrome.
• Write down important personal information. Include any family history of heart disease, stroke, high blood pressure or blood clots, and any major stresses or recent life changes.
• Make a list of all medicines, vitamins or supplements that you're taking. Include the dosages.
• Take a family member or friend along, if possible. Sometimes it can be difficult to understand and remember all the information received during an appointment. The person who goes with you may remember something that you missed or forgot.
• Write down questions to ask your health care team.

Preparing a list of questions to ask the health care team can help you make the most of your time together. List your questions from most important to least important, in case time runs out. For popliteal artery entrapment syndrome, some basic questions to ask include:

• What is likely causing my symptoms?
• What are other possible causes for my symptoms?
• What kinds of tests will I need?
• What's the most appropriate treatment?
• What's an appropriate level of physical activity?
• What are the options to the treatment that you're suggesting?
• I have other health conditions. How can I best manage them together?
• Are there any restrictions that I need to follow?
• Are there any brochures or other printed material that I can take home with me? What websites do you recommend visiting?

Don't hesitate to ask your health care team any additional questions during your appointment.

What to expect from your doctor

Your health care team is likely to ask many questions. Being ready to answer them may save time to go over any points you want to spend more time on. You may be asked:

• When did you first start having symptoms?
• Do you always have symptoms, or do they come and go?
• How severe are your symptoms?
• What, if anything, seems to make your symptoms better?
• What, if anything, makes your symptoms worse?