Popliteal vein compression, obesity, and chronic venous disease

Obesity is a known risk factor for the development of chronic venous disease (CVD). However, some obese patients with lower limb skin changes suggestive of venous disease do not demonstrate venous reflux or obstruction. Popliteal vein compression (PVC) caused by knee hyperextension during standing has been postulated by others to be more common in the obese due to the increased adipose content of the popliteal fossa. This compression may contribute to the development of venous disease. The objective was to examine the prevalence of PVC in obese and nonobese subjects, with and without venous disease.

Participants were recruited across the range of Clinical-Etiology-Anatomy-Pathophysiology (CEAP) clinical classifications and body mass. Those referred for venous studies had full venous ultrasound assessments. To assess for PVC, the popliteal vein was assessed via B-mode ultrasound whilst the subject stood and performed two maneuvers: knee hyperextension and a bilateral toe stand. Video clips of each maneuver were analyzed offline.

There were 309 limbs (158 subjects), of which 131 were nonobese (body mass index [BMI]: 26 ± 3 kg/m²) and 178 obese (BMI: 43 ± 8 kg/m²). PVC with toe stand (PVC(toe stand)) was more common in obese limbs (89% vs 64%, P < .001). It occurred mainly in the distal popliteal vein, associated with contraction of the gastrocnemius muscles. PVC with knee hyperextension (PVC(lock)) was also more frequent in obese limbs (39% vs 10%, P < .0001) and was distinct as it occurred more proximally in the popliteal vein. PVC(lock) was significantly more frequent in all C classes of obese patients, most notably in the obese with C4-6 CVD (41% vs 4%, P < .0001), and was associated with more severe Venous Clinical Severity Score (median 8 [range: 0-19] vs 5 [0-21], P = .034). There were 19 limbs with skin changes (C4-6) with no venous reflux or obstruction on ultrasound, exclusively obese limbs. These limbs, designated CEAP Pn limbs, were in older, shorter participants with a higher BMI than their counterparts demonstrating reflux, and they also had more frequent PVC(lock) (63% vs 37%, P = .036).

PVC(toe stand) and PVC(lock) are both functional effects and more common in obese limbs. PVC(toe stand) is likely associated with normal functioning of the calf muscle pump. Although PVC(lock) may contribute to CVD in some obese limbs, the demonstration of PVC(lock) alone is insufficient evidence for direct intervention.