Popliteal artery entrapment syndrome

Overview

Popliteal artery entrapment syndrome (PAES) is a rare vascular condition that occurs when the popliteal artery, which supplies blood to the lower leg, becomes compressed by surrounding muscular or tendinous structures. This compression typically occurs behind the knee in the popliteal fossa and can lead to reduced blood flow, particularly during physical activity. PAES most commonly affects young, otherwise healthy individuals—often athletes or military recruits—who experience calf pain during exercise that resolves with rest. If left untreated, the condition can result in long-term vascular damage, blood clots, or limb ischemia.

Causes

PAES is caused by abnormal anatomical relationships between the popliteal artery and the muscles or tendons of the leg, particularly the medial head of the gastrocnemius muscle. These anomalies can be either congenital or acquired:

• Congenital causes: Most commonly due to developmental abnormalities in the positioning of the popliteal artery or surrounding musculature. There are several recognized types of congenital PAES based on specific anatomical variants.

• Functional or acquired causes: Occur in individuals with normal anatomy who develop arterial compression due to muscle hypertrophy or overuse, particularly in highly active individuals.

Repeated arterial compression may cause thickening of the arterial wall, stenosis, or even thrombosis over time.

Symptoms

The hallmark symptom of popliteal artery entrapment syndrome is intermittent claudication in the calf—pain, cramping, or tightness that occurs during exercise and resolves with rest. Other symptoms may include:

• Coldness or numbness: In the foot or lower leg during activity.

• Weak or absent pulses: In the affected limb, particularly during leg movement or flexion.

• Swelling or tightness: In the calf, sometimes mistaken for compartment syndrome.

• Paresthesia: Tingling or a pins-and-needles sensation in the foot.

• Visible muscle fatigue or weakness: In the lower limb after exertion.

Symptoms are typically unilateral but can be bilateral in up to 25–30% of cases. The pain pattern often mimics other conditions like chronic exertional compartment syndrome or deep vein thrombosis, leading to misdiagnosis.

Diagnosis

Diagnosing PAES requires a high index of suspicion, particularly in young patients without typical risk factors for vascular disease who present with exercise-induced leg pain. Diagnostic steps include:

• Physical examination: May reveal diminished pulses during active plantar flexion or dorsiflexion of the foot.

• Ankle-brachial index (ABI): May be normal at rest but drops significantly after exercise.

• Doppler ultrasound: To assess blood flow in the popliteal artery during rest and dynamic leg positioning.

• Magnetic Resonance Angiography (MRA) or Computed Tomography Angiography (CTA): Non-invasive imaging to visualize arterial narrowing or occlusion and anatomical relationships.

• Conventional angiography: Considered the gold standard for detailed vascular imaging, often combined with leg movement to reveal positional compression.

Additional tests such as MRI of the knee may be used to delineate the muscular structures contributing to entrapment.

Treatment

Treatment of PAES depends on the severity of symptoms and the degree of arterial damage. Options include:

• Conservative management: In mild or functional cases, activity modification and physical therapy may provide relief. However, this is rarely sufficient for true anatomical entrapment.

• Surgical intervention: The mainstay of treatment for anatomical PAES, typically involving:

  • Release or resection of the abnormal muscle or tendon compressing the artery

  • Arterial repair, such as endarterectomy, vein patch angioplasty, or bypass grafting in cases with arterial damage or thrombosis

• Postoperative rehabilitation: Gradual return to physical activity under medical supervision, with monitoring for recurrence of symptoms.

In some cases where the artery has been severely damaged, long-term vascular follow-up is necessary to prevent further complications.

Prognosis

With early diagnosis and appropriate surgical treatment, the prognosis for popliteal artery entrapment syndrome is generally excellent. Most patients experience complete relief from symptoms and are able to return to full physical activity. However, delays in diagnosis can lead to irreversible arterial damage, chronic pain, or even limb-threatening ischemia.

Outcomes are best when the condition is treated before permanent changes such as arterial fibrosis or thrombosis occur. Long-term follow-up is advised, especially in athletes or those with bilateral involvement, to ensure adequate blood flow and prevent recurrence.