Popliteal artery entrapment syndrome, or PAES, is an uncommon but important cause of exertional leg pain in young people. It occurs when the popliteal artery is compressed by the surrounding muscles or tendons behind the knee, particularly during exercise. Left undiagnosed, this repeated compression can lead to popliteal artery occlusion, damage, or thrombosis. Because the symptoms often mimic those of more common conditions, such as a calf muscle strain or chronic exertional compartment syndrome, PAES is often overlooked.
What is popliteal artery entrapment syndrome?
In PAES, the popliteal artery follows an abnormal course or is compressed by adjacent structures—most commonly the medial head of the gastrocnemius. During plantarflexion or knee extension, the artery is dynamically compressed, reducing blood flow to the lower leg. We separate PAES into two types: anatomical and functional.
Over time, repeated compression can cause arterial wall injury, narrowing, aneurysm formation, or complete popliteal artery occlusion.
We typically see PAES in:
- Young athletes
- Runners and footballers
- Military recruits
- People with well-developed calf muscles
Symptoms of PAES
Symptoms usually occur only during exercise and resolve with rest, particularly in early disease. Common symptoms include:
- Calf pain or tightness when running or walking uphill
- Cramping or fatigue in the calf during exertion
- Coldness, numbness, or tingling in the foot during exercise
- Symptoms that are reproducible at a predictable distance or intensity
- Relief of pain within seconds to minutes after stopping — this often distinguishes PAES from chronic exertional compartment syndrome, in which symptoms take many minutes to settle.
In more advanced cases with popliteal artery occlusion, symptoms can become more severe or persistent, including a very low exercise tolerance or pain at rest.
Clinical assessment
Clinical assessment begins with a careful history, focusing on exertional symptoms in a young, otherwise healthy person. Examination at rest is often normal. Key clinical features include:
- Normal pulses at rest
- Reduction or disappearance of the foot pulses with active plantarflexion or resisted calf contraction.
- Symptoms reproduced during dynamic testing rather than static examination
It’s essential to differentiate PAES from other causes of exertional leg pain, including chronic exertional compartment syndrome, stress fractures, nerve entrapments, and lumbar spine disease. Sometimes PAES occurs alongside exertional compartment syndrome.
Investigations
We usually start with the ankle-brachial index (ABI), which compares the blood pressure at the ankle with that at the upper arm. Measurements are taken at rest and immediately after vigorous exercise, such as treadmill running. The ABI is normally 0.9–1.4, and in PAES, it drops by 30–50% after exercise.
Imaging is essential to confirm the diagnosis and assess severity:
- Duplex ultrasound is usually the first investigation. It’s performed dynamically, assessing arterial flow at rest and during provocative manoeuvres such as plantarflexion — a reduction or cessation of flow suggests functional entrapment.
- MRI or MR angiography provides excellent anatomical detail, showing the relationship between the artery and the surrounding muscles or tendons. This helps classify the type of PAES and plan treatment, and is highly accurate.
Most vascular surgeons use a combination of these tests to confirm the diagnosis and determine the type of PAES.
Management of popliteal artery entrapment syndrome
We usually start with conservative management, unless there’s already evidence of arterial damage.
Non-surgical management
In early or functional PAES, non-surgical treatment may be appropriate. This includes:
- Activity modification and a temporary reduction in the provocative exercise
- Physiotherapy to address biomechanical contributors — running gait analysis and a podiatry assessment may help.
- Careful monitoring with repeat imaging
Botulinum toxin (Botox) injections into the medial gastrocnemius (or other compressing muscles) are increasingly used in selected cases. Botox reduces muscle contraction and bulk, decreasing the dynamic compression of the artery. This can relieve symptoms and delay or avoid surgery in some patients — particularly those with functional PAES and no arterial damage. However, Botox isn’t appropriate in cases of popliteal artery occlusion or established arterial damage.
Several studies have examined the use of Botox for PAES. In one approach, doctors injected 50 units of Botox-A into the medial and lateral heads of the gastrocnemius close to the site of entrapment, and about 60% of patients had symptom improvement lasting up to 12 months. Botox is thought to work by causing localised relaxation and mild wasting of the compressing muscle, reducing its bulk and easing the dynamic compression of the artery.
Surgical management
Surgery is recommended for patients with persistent symptoms, anatomical entrapment, or arterial damage. Options include:
- Release of the compressing muscle or tendon
- Arterial reconstruction where there’s significant narrowing or occlusion
- Bypass grafting in cases of complete popliteal artery occlusion
Surgical outcomes are generally good when the diagnosis is made early — particularly in young athletes without established arterial disease — with success rates reported at around 60–100%.
Prognosis and return to sport
With appropriate treatment, most people with PAES can return to sport. Early diagnosis, before arterial damage occurs, is associated with the best outcomes. Delayed diagnosis increases the risk of permanent arterial injury and a prolonged recovery.
Frequently asked questions about PAES
How is PAES told apart from compartment syndrome?
Both cause exertional calf pain, but the pattern of relief is a key clue: in PAES, symptoms typically ease within seconds to a few minutes of stopping, whereas chronic exertional compartment syndrome usually takes many minutes to settle. PAES may also cause coldness or tingling in the foot, and the foot pulses may diminish or disappear during plantarflexion. Dynamic imaging (duplex ultrasound, MR angiography) confirms the difference — and the two can occasionally coexist.
Is PAES dangerous, and what happens if it’s left untreated?
The concern is that repeated compression can progressively damage the artery wall, leading to narrowing, aneurysm, thrombosis, or complete occlusion. When caught early — before arterial damage — the outlook is dgood and non-surgical options may work. That’s why prompt, accurate diagnosis matters.
Can you return to running andsportst after treatment for PAES?
Yes — most patients return to sport with appropriate treatment. The best outcomes come from diagnosing PAES before permanent arterial damage has occurred.
Does Botox cure PAES?
Botox can relieve symptoms in selected cases of functional PAES without arterial damage — around 60% improve for up to 12 months in the studies. It isn’t a cure and isn’t suitable where there’s arterial occlusion or damage, whichrequiresd surgery.
How common is PAES?
It’s uncommon, and the exact frequency is unclear. Functional causes are more common in young women in their 20s, while anatomical causes are more frequent in men in their 30s.
What if narrowing of the popliteal artery is found without symptoms?
A proportion of athletes have asymptomatic popliteal artery compression.Whene changes are found without matching symptoms, the usual advice isto monitor no further unless symptoms develop. It’s currently unclear whether symptomless narrowing raises the risk of future arterial damage, thrombosis, or occlusion.
Final word from Sport Doctor London about popliteal artery entrapment syndrome
Popliteal artery entrapment syndrome is an important but often missed cause of exertional calf pain in young athletes. Awareness of PAES, careful dynamic assessment, and appropriate imaging are essential to avoid progression to popliteal artery occlusion. Early recognition allows non-surgical options, including Botox in selected cases, while timely surgery can prevent long-term vascular complications and allow a safe return to activity.
If you have exertional calf pain that isn’t settling, Dr Masci can assess you in London and, where a vascular cause such as PAES is suspected, arrange the right dynamic testing and onward referral. Contact the team here or call +44 (0) 203 488 0350.
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