Popliteal artery entrapment syndrome (PAES) refers to symptomatic compression or occlusion of the popliteal artery due to a developmentally abnormal relationship with the medial head of gastrocnemius (MHG) or less commonly with popliteus or fibrous bands.
The anatomic anomalies may be seen in up to 3% of the population and are often bilateral 2 (~2/3 of cases). Most individuals; however, are asymptomatic and the true clinical syndrome is far less common. Individuals with well-developed muscles are more likely to be symptomatic, which probably explains why the syndrome is most often found in young sports persons (~60 % in those <30 years) with a male to female ratio of 15:1 3.
Symptoms are typically those of intermittent claudication. Physical examination can reveal signs of arterial compromise particularly when the ankle is plantarflexed. Chronic repeated arterial compression can lead to acute thrombus formation and presentation with acute limb-threatening ischaemia in those with poorly developed collateral vessels.
Arterial compression can result in chronic vascular microtrauma, local premature arteriosclerosis, and thrombus formation. This can result in distal ischaemia. Stenosis and turbulent flow may lead to poststenotic ectasia or aneurysm formation.
Five anatomic types of entrapment are typically described 1:
- type I: popliteal artery has aberrant medial course around MHG (see case 1)
- type II: artery is not displaced but the MHG inserts more lateral than usual ; the artery passes medial and beneath the muscle
- type III: accessory slip of MHG slings around the artery
- type IV: artery lies deep in popliteal fossa entrapped by popliteus or fibrous band
- type V: both popliteal artery and vein are entrapped
May show arterial compression elicited by maneuvers such as plantar flexion and dorsiflexion 5. Doppler may demonstrate an increase in peak velocity 8.
Lower limb angiography usually demonstrates medial deviation/compression of the popliteal artery when the ankle is plantar flexed. Occlusion of the vesssls with thrombus can be seen in acute presentation. Usually, collateral vessels are present. Even slight irregularity of the vessel can indicate a degree of entrapment 2.
MRI is the best imaging modality to demonstrate the underlying anatomic type of entrapment, which helps guide surgical management 4. A medial slip of the medial head of the gastrocnemius may be seen, compressing the popliteal artery.
Treatment and prognosis
Acute limb-threatening thrombosis requires urgent bypass surgery. Intermittent occlusion can usually be cured with release of the popliteal artery alone or with saphenous vein bypass 2.
Imaging differential considerations include
The knee is a complex synovial joint that can be affected by a range of pathologies:
- bone and cartilage
- distal femoral condyle fracture
- tibial plateau fracture (classification)
- patella fracture
avulsion fractures of the knee
- Segond fracture
- reverse Segond fracture
- anterior cruciate ligament avulsion fracture
- posterior cruciate ligament avulsion fracture
- arcuate complex avulsion fracture (arcuate sign)
- biceps femoris avulsion fracture
- iliotibial band avulsion fracture
- semimembranosus tendon avulsion fracture
- Stieda fracture (MCL avulsion fracture)
- patella fracture
- chronic avulsion injuries
- chondromalacia patellae
- osteoarthritis of the knee
- osteochondral defects
- osteochondritis dissecans of the knee
- pattern of bone contusion in knee injuries
- knee fractures
- meniscal lesions
- synovial lesions
- fat pad
- popliteal fossa
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