Pedal Musculovenous Pump Activation Effectively Counteracts Negative Impact of Knee Flexion on Human Popliteal Venous Flow

Knee scooters are commonly used for mobility instead of other devices. However, passive popliteal venous flow impedance has been observed with knee scooter usage ostensibly as a result of deep knee flexion. This study aimed to characterize the magnitude of impact knee flexion has on popliteal venous flow in relation to the degree of knee flexion when walking boot immobilized. Furthermore, the countervailing effect of standardized pedal musculovenous pump (PMP) activation was observed. Popliteal venous diameter and flow metrics were assessed with venous ultrasonography in 24 healthy individuals. Straight leg, crutch, and knee scooter positioning while wearing a walking boot and non–weight-bearing were compared. Flow was assessed with muscles at rest and with PMP activation. Of 24 participants, 16 (67%) were female. Twelve limbs (50%) were right sided. The mean age was 21.9 (SD = 3.0) years, and the mean body mass index was 21.9 (SD 1.9) kg/m². Observer consistencies were excellent (intraclass correlation range = 0.93 to 0.99). No significant differences in mean vessel diameter, time-averaged mean velocity, and total volume flow occurred (all P > .01). Corresponding knee flexion effect sizes were small (range = −0.04 to −0.26). A significant decrease (−24%) in active median time-averaged peak velocity occurred between upright and crutch positions (20.89 vs 15.92 cm/s; P < .001) with a medium effect size (−0.51). PMP activation increased all flow parameters (all P < .001), and effect sizes were comparatively larger (>0.6) across all knee flexion positions.

Clinical Significance: Knee flexion has a small to medium impact on popliteal venous return in healthy patients. Active toe motion effectively counters the negative effects of gravity and knee flexion when the ankle is immobilized.

Levels of Evidence: Therapeutic, Level IV