What is Popliteal Artery Entrapment Syndrome?
Popliteal artery entrapment syndrome (PAES) is a rare condition that could lead to serious problems in limbs. It only affects around 0.17%-3.5% of people in the United States. PAES is related to an irregular interaction between the popliteal artery (main artery in the back of the knee and thigh) and nearby muscle and tissue in the same area. Unexpectedly, it primarily impacts active young males who have no previous heart disease risk factors.
Patients with PAES usually complain about on-and-off pain in their feet and calves, which typically happens after exercise and disappears while resting. Thanks to advanced imaging techniques, doctors are now better able to identify and understand PAES. A combination of magnetic resonance imaging (MRI), which uses powerful magnets and radio waves to make detailed images of the inside of your body, and arteriography, an imaging test that uses x-rays and a special dye to see inside the arteries, has proven to be one of the most effective ways to diagnose PAES.
The usual treatment for uncomplicated PAES involves surgery to inspect and release pressure in that area, or to release the popliteal artery by cutting the fibrous bands (tough bands of tissue) that may be affecting it. If not treated, it can lead to problems with the popliteal artery, like narrowing (stenosis), clot formation (thrombosis), or blockage in the artery further down the leg due to a clot (distal arterial thromboembolism).
This article discusses the causes and effects of PAES, emphasizes the importance of a thorough medical history and physical examination to diagnose it and provides information for identifying patients at high risk who urgently need surgical treatment.
What Causes Popliteal Artery Entrapment Syndrome?
Popliteal Artery Entrapment Syndrome (PAES) develops from both inborn (congenital) and acquired factors. Our understanding of how humans develop before birth (embryology) has helped us figure out why some people are born with PAES. Specifically, the popliteal artery—the blood vessel behind your knee—and one part of your calf muscle (medial head of the gastrocnemius) form around the same time. This artery forms from two other arteries, the femoral and sciatic arteries. Later in development, the sciatic artery becomes less prominent, and the femoral artery takes over most of the work of building the popliteal artery.
The development of another muscle in your calf, the plantaris muscle, can also play a role in whether a person is born with PAES. This muscle, which helps point your toes down (plantar flexion), doesn’t do much on its own, and usually works along with the gastrocnemius. However, the way this muscle forms during early development can be unusual in about 10% of cases. If it does develop oddly, it can essentially capture the popliteal artery, leading to symptoms like cramps when walking.
Other abnormalities can contribute to PAES too. The way the popliteal artery, the medial head of the gastrocnemius, and another muscle in your calf called the popliteus are positioned relative to each other can affect whether a person develops PAES. An unusual path the medial head takes while forming can also throw it out of its intended position, causing issues with nearby blood vessels. However, it’s important to realize that many people born with these abnormalities don’t experience any symptoms, indicating there’s probably more than one factor at play in how the disease develops.
Though you’re born with these abnormalities, symptoms often don’t show up until later. This delay might be due to changes related to using your calf muscle in activities like running or walking, which can cause the muscle to grow. This muscle growth can externally compress the popliteal artery, pinching it against the medial head of the gastrocnemius.
Risk Factors and Frequency for Popliteal Artery Entrapment Syndrome
Popliteal artery entrapment syndrome (PAES) is a rather rare but important cause of vascular problems. In fact, more cases have been reported in recent years. According to a recent study, the number of people suffering from PAES is estimated to be anywhere between 0.17% and 3.5% of the population.
- A vast majority of PAES patients, around 85%, are males.
- Young athletes, particularly those in their 30s, tend to be affected the most with almost 60% of cases occurring in this group.
- In about 30% of cases, symptoms are present in both legs.
Signs and Symptoms of Popliteal Artery Entrapment Syndrome
Popliteal artery entrapment syndrome (PAES) is a condition that often affects young athletes who don’t have any history of cardiovascular issues. This condition usually starts to show symptoms between the ages of 10-30, and gradually gets worse over time. The symptoms tend to be quite severe and can affect a person’s ability to move or function normally.
People with this syndrome may experience the following symptoms:
- Severe pain in the leg and foot (claudication)
- Numbness in the lower extremity
- Tingling sensation (paresthesia)
- Changes in skin color
- Pale skin (pallor)
- Cool skin
Physical examination usually reveals enlarged calf muscles. Furthermore, foot movements such as dorsiflexion and plantar flexion (bending the foot up or down) can result in weaker, uneven, or even missing pulses. As the condition progresses, the ankle-brachial index also becomes lower, indicating a problem with blood flow. One study reported that the absence of foot pulses during active bending and passive straightening of the foot is a typical characteristic of PAES.
Testing for Popliteal Artery Entrapment Syndrome
Diagnosing Popliteal Artery Entrapment Syndrome (PAES), a rare condition, can be quite tricky. It requires a proper understanding of the symptoms and signs, along with interpreting the results of different imaging tests. The goal is to accurately identify any issues with the popliteal artery (the artery located at the back of the knee) and the surrounding space, known as the popliteal fossa.
Recent research points to the combination of two types of imaging tests as being most effective for diagnosing PAES. These are magnetic resonance imaging (MRI) and duplex ultrasonography (DU), a kind of ultrasound test.
Duplex arterial ultrasonography (DAU) is especially helpful because it is quick, affordable, and non-invasive. During this test, you will first rest your leg or foot in a neutral position, then press it downwards as if you were pushing a pedal. If the test shows any issues with the artery or unusual branching blood vessels in the fossa area, this could indicate PAES.
Another imaging method, angiography, can also be used, again with your foot in active positions. This can show if the popliteal artery is deviating from its regular path, narrowing, forming a bulge (called an aneurysm) or blocking.
Finally, computed tomography (CT) angiography or magnetic resonance angiography (MRA) can help confirm the diagnosis when the artery is blocked. However, these tests are not suitable for the active positioning needed for the provocative testing.
Treatment Options for Popliteal Artery Entrapment Syndrome
When dealing with Popliteal Artery Entrapment Syndrome (PAES), a condition where calf muscle or tendon positions put pressure on the main artery in the leg, treatment depends on whether the patient has symptoms or not. Those without symptoms, or “asymptomatic” patients, who were diagnosed by chance, are usually monitored as many won’t experience symptoms or their condition won’t worsen.
If the placement of muscle insertions in the leg, or where the muscle attaches to the bone, is what’s causing the pressure on the artery (even in a patient without symptoms), surgery is offered as the primary treatment.
For patients who are experiencing symptoms, surgery to release the popliteal artery, the main artery they’re experiencing pressure on, is the preferred treatment method. This surgery aims to restore the normal anatomy of the leg, often with successful results. This involves either a surgical approach from behind the knee (posterior) or from the inside of the knee (medial). The responsible calf muscle or tendon causing the entrapment can then be cut to release pressure. Then, the surgeon will feel the artery to see if it’s functioning as it should and decide if a bypass surgery might be needed. Incidentally, there’s no need for the surgeon to reconstruct the nearby muscles, as your body can function just fine without them.
For the most effective results in treating PAES, and to evaluate the artery for any necessary repairs or bypasses, open surgical procedures are usually the best choice. Depending on the severity and location of the damage to the artery, such as extreme damage to the artery wall, blockage, or aneurysm development, there are certain types of bypass surgeries that have been recommended.
Managing functional PAES, where the muscle contractions from normal leg movements cause the artery entrapment, remains a topic of debate. Some success has been found through a procedure that reduces the size of the calf muscle.
Once surgery is completed, patients are followed-up using arterial duplex imaging, which uses ultrasound to see how blood is flowing through your arteries. This is typically carried out after 1, 3, 6, and 12 months, and then yearly from that point forward.
What else can Popliteal Artery Entrapment Syndrome be?
When trying to diagnose a severe leg condition known as popliteal artery entrapment syndrome (PAES), doctors need to rule out other conditions that can cause similar symptoms. These might include:
- Chronic exertional compartment syndrome, a condition caused by excessive physical activity
- Medial tibial stress syndrome, also known as shin splints
- Fibular stress fractures, which are small cracks in the fibula bone
- Tibial stress fractures, similar small cracks but in the tibia bone
- Fascial defects, or problems with the connective tissues
- Nerve entrapment syndrome, a condition in which a nerve is compressed
- Referred pain from lumbar disc herniation, where a problem with a disc in the lower back causes pain in the leg
These other conditions can make it harder for doctors to correctly diagnose PAES.
What to expect with Popliteal Artery Entrapment Syndrome
The future outcome of the condition known as Popliteal Artery Entrapment Syndrome (PAES) largely depends on the timing of its discovery. If PAES is found and addressed early, the general outlook is usually positive. However, if PAES is discovered too late, after significant damage to the arteries has occurred, the patient may be at risk of persistent leg pain or even limb loss.
Nonetheless, the loss of a limb in patients with PAES is extremely uncommon, even in severe cases, because the blockage of the artery tends to develop slowly over time.
Possible Complications When Diagnosed with Popliteal Artery Entrapment Syndrome
Popliteal Artery Entrapment Syndrome (PAES) is a serious vascular condition that affects the limbs and requires quick detection and treatment. If it goes unnoticed, PAES can result in different problems such as:
- Narrowing of the popliteal artery (Popliteal artery stenosis)
- Blood clot in the popliteal artery (Popliteal artery thrombosis)
- Blood clot that has traveled to a distant artery (Distal arterial thromboembolism)
- Limb amputation
Preventing Popliteal Artery Entrapment Syndrome
For individuals diagnosed with PAES, it is important to understand the condition and their treatment options. The first step is understanding what has caused PAES in their particular case, the more detailed the better.
The next thing to know is that early surgical intervention is the best way to halt the disease’s progression. This means that surgery often provides the best treatment outcome compared to other options.
After surgery, it is vital to know how to recognize the signs and symptoms of compartment syndrome, a possible post-surgery complication. Knowing what to look for can make a big difference in ensuring a successful recovery.
