Influence of Limb Position on Venous Blood Flow After Total Knee Arthroplasty: A Prospective Randomized Study

Abstract

Previous studies have suggested a clinical advantage when placing the limb in flexion after total knee arthroplasty (TKA). We sought to measure venous flow compared with control values after TKA. Our hypothesis was that the knee flexed positioning would not adversely affect venous flow. Two cohorts were prospectively evaluated. First, volunteers were randomized to positions with the knee flexed to approximately 90° or placed in a fully extended (control) position. Venous flow velocity was measured in the femoral vein every 15 minutes for 2 hours. Subsequently, 32 patients were randomized to 1 of these 2 positions after TKA, and venous flow velocity was measured in both the operative and the contralateral limb. In the healthy volunteer cohort, mean venous flow velocity was significantly higher at all time points in the flexion group compared with the extended control group ( P <.05). After TKA, mean flow velocity for an extended knee (control) was 28.5 cm/s. Mean flow velocity for the flexed knee, foot-dependent group was 47.2 cm/s ( P =.036) and for the flexed knee, foot-elevated group was 30.4 cm/s ( P =.618). Placing the limb in a flexed position after TKA is not detrimental to venous flow velocity and resulted in higher velocities relative to the extended position. Placing the limb at 90° flexion does not cause venous stasis and should not increase the risk of deep venous thrombosis. [ Orthopedics . 2023;46(1):8–12.]