Immediate effects of valgus knee bracing on tibiofemoral contact forces and knee muscle forces

Background Valgus knee braces have been reported to reduce the external knee adduction moment during walking. However, mechanistic investigations into the effects of valgus bracing on medial compartment contact forces using electromyogram-driven neuromusculoskeletal models are limited. Research question What are the immediate effects of valgus bracing on medial tibiofemoral contact forces and muscular loading of the tibiofemoral joint? Methods Sixteen (9 male) healthy adults (27.7 +/- 4.4 years) performed 20 over-ground walking trials at self-selected speed both with and without an Ossur Unloader One (R) brace. Assessment order (i.e., with or without brace) was randomised and counterbalanced to prevent order effects. While walking, three-dimensional lower-body motion, ground reaction forces, and surface electromyograms from eight lower-limb muscles were acquired. These data were used to calibrate an electromyogram-driven neuromusculoskeletal model of muscle and tibiofemoral contact forces (N), from which muscle and external load contributions (%) to those contact forces were determined. Results Although walking with the brace resulted in no significant changes in peak tibiofemoral contact forces at the group-level, individual responses were variable and non-uniform. At the group-level, wearing the brace resulted in a 2.35% (95% CI 0.46-4.24; p = 0.02) greater relative contribution of muscle to lateral compartment contact loading (54.2 +/- 11.1%) compared to not wearing the brace (51.8 +/- 12.1%) (p < 0.05). Average relative contributions of muscle and external loads to medial compartment loading were comparable between brace and no brace conditions (p >= 0.05). Significance Wearing a valgus knee brace did not immediately reduce peak tibiofemoral contact forces in healthy adults during normal walking. It appears this population may modulate muscle activation patterns to support brace-generated valgus moments, thereby maintaining normal walking knee moments and tibiofemoral contact forces. Future investigations are warranted to better understand effects of valgus knee brace in people with medial knee osteoarthritis using an electromyogram-driven neuromusculoskeletal model.