Stride width independently reduces knee abduction moment but not medial contact force

Gait modification targeting the internal peak knee abduction moment (PKAM1) is proposed as a conservative strategy to reduce medial compartment loading in knee osteoarthritis. However, prior studies have not isolated stride width effects from concomitant changes in spatiotemporal or kinematic changes or determined whether PKAM1 reductions translate to decreased medial contact force (MCF). This study investigated the independent effect of increased stride width on PKAM1 after controlling for covariates, with narrow gait as a directional mechanistic comparator. Sixteen healthy males performed five trials of baseline, narrow, and wide gait conditions. Mixed-effects models evaluated condition effects on temporospatial, kinematic, and kinetic outcomes with spatiotemporal and kinematic covariates included in kinetic models. Wide gait significantly reduced PKAM1 after covariate adjustment, driven by a lateral shift of the GRF line of action relative to the knee joint center. However, this did not translate to a significant reduction in estimated MCF. Narrow gait shifted the moment arm medially and did not reduce PKAM1 after covariate adjustment, suggesting its modest descriptive reduction was attributable to reduced walking speed. Wide and narrow gait produced opposing effects across frontal and sagittal plane moments, with neither achieving a net MCF reduction independent of temporospatial changes. Stride length was independently associated with sagittal plane loading, warranting further investigation as a modification target.