Anatomical Classification of PAES
There are five recognized anatomical types of popliteal artery entrapment syndrome (Types I, II, III, IV, and V), with Type IV representing functional rather than anatomical entrapment. 1
Classification Framework
The ACR Appropriateness Criteria (2019) provides the authoritative classification system for PAES 1:
Anatomical PAES (Types I, II, III, and V)
These types involve extravascular structures within the popliteal fossa that compress the popliteal artery and/or popliteal vein, resulting in compression, stenosis, or occlusion during plantar flexion 1.
- Type I: Popliteal artery deviates medially around a normally positioned medial head of gastrocnemius
- Type II: Medial head of gastrocnemius has abnormal lateral insertion, causing arterial compression (most common anatomical type, found in 51.4% of cases) 2
- Type III: Aberrant accessory slip of gastrocnemius muscle entraps the artery (found in 20% of cases) 2
- Type V: Entrapment of both popliteal artery and vein
Functional PAES (Type IV)
Type IV results in popliteal artery compression despite an anatomically normal popliteal fossa, with unclear etiology 1. This represents a distinct entity where compression occurs without developmental anatomical abnormalities 3.
Additional Anatomical Considerations
Research has identified that gastrocnemius lateral head anomalies can also cause PAES, though this is less commonly discussed in traditional classification systems. Studies show aberrant accessory slips of the lateral gastrocnemius head entrapping the popliteal artery and vein in up to 28.6% of cases 4, 2.
Clinical Pitfall
The traditional classification focuses on medial gastrocnemius anomalies, but lateral head anomalies are an underrecognized cause of entrapment that may not fit neatly into the standard five-type system 4.
Bilateral Presentation
Bilateral involvement occurs in approximately 83% of patients (40 of 48 patients in one large series), making it critical to evaluate both limbs even when symptoms are unilateral 3.