Knee Joint Loading And Realtime Vertical Ground Reaction Force Biofeedback With Vest-Borne Loads

Abstract

Realtime biofeedback has been used to modify gait and decrease knee joint loading. Vertical ground reaction force (vGRF) may offer broad utility as a feedback option to alter tibiofemoral joint (TFJ) contact forces during gait. For example, individuals that carry heavy loads experience increased TFJ contact force. vGRF feedback may reduce effect at the TFJ. PURPOSE: To investigate the effectiveness of vGRF feedback for reducing axial TFJ contact force during load carriage. METHODS: Twelve healthy adults (22 + 1.6 yrs), walked for 5 minutes per condition at 1.4 m·s-1 on an instrumented treadmill while carrying vest borne loads of 0%, 15%, and 30% body weight during 3D motion capture, with and without vGRF feedback to reduce peak vGRF below a set threshold. Hip, knee, and ankle kinematic and kinetic data were used as inputs to an inverse dynamics informed musculoskeletal model of axial TFJ contact force. Comparisons of peak TFJ contact force were made via 3x2 repeated measures ANOVA and post hoc paired T-Tests. RESULTS: vGRF feedback led to a total peak TFJ contact force increase of 25% at no load, 55% at 15% load, and 82% at 30% load as compared to no load no feedback. Each load condition with feedback elicited greater peak TFJ contact force than no feedback. (0% [3.44 vs 4.30 Body Weights (BW), p = 0.008]; 15% [3.92 vs 5.34 BW, p = 0.002]; 30% [4.55 vs 6.27 BW, p < 0.001], Figure 1). CONCLUSION: To reduce peak vGRF, participants slightly reduced their stride length and adopted a crouched gait characterized by increased knee and hip flexion. The increase in flexion increased estimated quadriceps and hamstrings force, ultimately leading to large increases in total TFJ contact forces. Although readily available than more sophisticated options to alter TFJ contact force, feedback of peak vGRF is not effective for reducing TFJ contact force with or without load carriage. Realtime feedback of TFJ contact forces would likely be an optimal choice of feedback if attempting to decrease knee joint loads.