Relationship between knee adduction moment and knee contact forces during walking and running with modified foot progression angles

Knee osteoarthritis (KOA) is a leading cause of disability, influenced by both systemic and mechanical factors. Gait modifications, such as toe-in (TIN) and toe-out (TOUT) foot progression angles, can alter knee adduction moment (KAM) and knee contact forces (KCF), but the task-specific relationship between these measures in walking and running remains unclear. Twenty healthy adults (age 18–35 years) were randomly assigned to walking or running groups. Participants completed natural and modified gait trials: TIN for walking and TOUT for running. KAM was calculated using a clinically feasible inverse-dynamics workflow in Visual3D, while musculoskeletal modelling in OpenSim estimated KCF. Correlations between KAM and medial KCF were assessed, and paired t-tests or linear mixed models examined the effects of gait modifications. During natural walking, early stance KAM was moderately correlated with medial KCF (r = 0.484; p = 0.011), but this relationship disappeared during TIN walking. Both KAM and medial KCF decreased with TIN walking (p < 0.040). In natural running, peak KAM did not correlate with medial KCF, whereas a strong correlation emerged during TOUT running (r = 0.619; p < 0.001). TOUT running increased medial KCF (p = 0.041) without altering KAM. The relationship between KAM and medial KCF is task- and modification-dependent. KAM is a reasonable surrogate for medial loading during natural walking but not during modified gait or running. Toe-in walking reduces both KAM and KCF, supporting its use in gait interventions for knee OA. Conversely, toe-out running can increase medial KCF despite unchanged KAM, highlighting gait modifications beneficial during walking may not translate to running.