Popliteal artery entrapment syndrome, or PAES, is an uncommon but important cause of exercise-leg pain in young individuals. It occurs when the popliteal artery becomes compressed by surrounding muscles or tendons behind the knee, particularly during exercise. If left undiagnosed, this repeated compression can lead to popliteal artery occlusion, damage, or thrombosis. Because symptoms often mimic more common conditions such as calf muscle strain or chronic exertional compartment syndrome, doctors usually overlook PAES. 

What Is Popliteal Artery Entrapment Syndrome?

In popliteal artery entrapment syndrome, the popliteal artery follows an abnormal course or is compressed by adjacent structures, most commonly the medial head of gastrocnemius. During plantarflexion or knee extension, the artery becomes 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

  • Individuals 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 with 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 or minutes of stopping activity – this feature often distinguishes this condition from chronic exertional compartment syndrome, where symptoms take many minutes to settle. 

In more advanced cases with popliteal artery occlusion, symptoms may become more severe or persistent and can include very low exercise tolerance or rest pain.

Clinical Assessment

Clinical assessment begins with a careful history focusing on exertional symptoms in a young, otherwise healthy individual. Examination at rest is often normal.

Key clinical features include:

  • Normal pulses at rest

  • Reduction or disappearance of foot pulses with active plantarflexion or resisted calf contraction

  • Symptoms reproduced during dynamic testing rather than static examination

It is 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 with exertional compartment syndrome. 

Investigations

Generally, we start with the ankle-brachial index, which compares blood pressure at the ankle to that at the upper arm. Measurements are taken at rest and immediately after rigorous exercise, such as treadmill running. ABI is normally 0.9-1.4. In PAES, levels drop by 30-50%. 

Imaging is essential to confirm the diagnosis of popliteal artery entrapment syndrome and to assess severity.

Duplex ultrasound is usually the first investigation. Doctors perform it 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, allowing identification of the relationship between the artery and surrounding muscles or tendons. This imaging helps classify the type of PAES and plan treatment. It is also 100% accurate. 

Generally, most vascular surgeons use a combination of these tests to determine the diagnosis and type of PAES. 

MRI arthrogram showing PAES - narrowed popliteal artery

Management of Popliteal Artery Entrapment Syndrome

Ususally, we start with conservative management first unless there is evidence of arterial damage already. 

Non-Surgical Management

In early or functional forms of PAES, non-surgical treatment may be appropriate.

This includes:

  • Activity modification and temporary reduction in provocative exercise

  • Physiotherapy to address biomechanical contributors. Running gait analysis and 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 dynamic compression of the artery. This approach may provide symptom relief and delay or avoid surgery in some patients, particularly those with functional PAES and no arterial damage. However, Botox is not appropriate for popliteal artery occlusion or damage to the popliteal artery. Multiple studies have examined the effect of botox injecitons on symptoms. Doctors injected 50 units of Botox-A into the medial and lateral heads of the gastrocnemius muscle close to the site of artery entrapment. They found that about 60% of patients experienced symptom improvement lasting for up to 12 months. We think that Botox works by relaxing cuasing localised muscle wasting and relaxing the smooth muscle wall of the artery. 

Surgical Management

Doctors recommend surgery for patients with persistent symptoms, anatomical entrapment, or arterial damage.

Surgical options include:

  • Release of the compressing muscle or tendon

  • Arterial reconstruction if there is 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. Results overll suggest a 60-100% success. 

Prognosis and Return to Sport

With appropriate treatment, most patients with popliteal artery entrapment syndrome 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 prolonged recovery.

Other frequently asked questions about PAES

How common is PAES?

We are unsure. Functional causes are more common in young females in their 20s, while anatomical causes are more frequent in males in their 30s. 

What should we do if we find narrowing of the popliteal artery without true symptoms?

A high percentrage of athletes can have asymptomatic PAES. If patients are found to have changes without corresponding symptoms, doctors suggest no further monitoring unless symptoms develop. We are unsure if narrowing of the popliteal artery without symptoms increases the risk of further artery damage, thrombosis or occulsion. 

Final Word from Sportdoctorlondon 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 consideration of non-surgical options, including Botox in selected cases, while timely surgical intervention can prevent long-term vascular complications and allow safe return to activity.

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