Popliteal artery entrapment syndrome

Overview

Popliteal artery entrapment syndrome, also called PAES, is an uncommon condition that affects the main artery behind the knee. That artery is the popliteal artery. In this condition, the calf muscle is in the wrong position or is 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.

PAES is grouped into six types. The types depend on the location of the artery and if there are changes in nearby muscle or fiber structures. Type 6 is the most common.

Symptoms

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

• Cold feet after exercise.
• Tingling or burning in the 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.

Symptoms typically affect 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, also called 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 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, also called 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.
• Male sex assigned at birth. PAES can occur in anyone, but it's much more common in young men.
• Extreme 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 very bad cases or when the condition is not diagnosed, the nerves and muscles in the leg can become damaged. Blood clots may occur in the lower leg. Sometimes popliteal artery entrapment syndrome may lead to other artery damage that needs treatment.

Diagnosis

To diagnose popliteal artery entrapment syndrome, also called PAES, a healthcare professional examines you and asks questions about your symptoms and health history. Because most people with PAES are young and usually in good health, diagnosing the condition can sometimes be challenging. The physical exam may not find anything unusual.

The healthcare team typically orders tests to rule out other causes of leg pain, such as muscle strains, stress fractures, chronic exertional compartment syndrome and peripheral artery disease.

Tests

Tests to diagnose popliteal artery entrapment syndrome and conditions that can cause similar symptoms may include:

• Ankle-brachial index measurement, also called ABI, 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 the calf muscle to work.
• Magnetic resonance angiography 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 the lower leg.
• CT angiography also shows which leg muscle is causing the artery entrapment. 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.
• Compartment pressure testing is done to rule out a muscle and nerve condition called chronic exertional compartment syndrome. The syndrome affects specific areas, known as compartments, of muscle in the arms or legs. A doctor places a needle or thin tube called a catheter into a muscle before and after exercise to make the measurements. This test can be mildly painful. It isn't done unless your medical history and other tests strongly suggest you have this syndrome.

Treatment

Treatment of popliteal artery entrapment syndrome, also called PAES, depends on:

• The type of PAES.
• If there is artery damage and, if so, how much damage there is.

If symptoms significantly affect everyday activities or athletic activities, treatment may involve surgery. Surgery is the only way to fix the calf muscle and free the trapped artery.

Surgery or other procedures

Popliteal artery entrapment syndrome surgery is done at a hospital or medical center while you are under general anesthesia. That means you're given medicine that puts you in a sleep-like state during surgery. The surgeon makes a cut on the inner calf just below the knee 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.

The surgery takes about an hour. Most people usually stay in the hospital for at least 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 PAES is diagnosed and treated early, a full recovery is expected. Symptoms should improve.

Preparing for an appointment

If you think you may have popliteal artery entrapment syndrome, also called PAES, make an appointment for a health checkup. If the condition is found early, treatment may be easier and 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

• 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 some 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 someone 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 healthcare team.

For popliteal artery entrapment syndrome, some basic questions to ask are:

• 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?
• Do I need to change or avoid any activities?
• Is there any information that I can take home with me? What websites do you recommend?

Don't hesitate to ask any other questions.

What to expect from your doctor

Your healthcare 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?
• On a scale of 1 to 10, with 10 being the worst, how bad are your symptoms?
• What, if anything, seems to make your symptoms better?
• What, if anything, makes your symptoms worse?