Effect of forefoot strike and toe-out running on hip contact forces: A musculoskeletal modelling-based study

Hip osteoarthritis (OA) is an increasingly significant public health concern, contributing to substantial economic and societal burden worldwide. Emerging evidence suggests that running may promote cartilage health through optimal joint loading. However, it remains unclear how modifications to running posture, such as altering footstrike patterns or adjusting foot progression angles, affect hip contact forces (HCF). This study investigated HCF differences across three running conditions: natural running, forefoot strike (FFS) modification, and toe-out modification. FFS may enhance shock attenuation through increased lower limb flexion and altered ankle mechanics, while toe-out running laterally shifts the center of pressure, reducing the lever arm. Ten healthy participants ran along a 20-meter walkway under the three running conditions in a randomized order. Running biomechanics were recorded using an 8-camera motion capture system synchronized with four force plates. Kinematic and kinetic data were used to calculate right-limb HCF during early and late stance using a musculoskeletal model and the software OpenSim. Within-subject differences in HCF across the three running conditions were analyzed with one-way repeated measures ANOVA. FFS running resulted in a significantly lower vertical HCF during early stance and a significantly higher vertical HCF during late stance compared to both natural running (early stance: p = 0.011; late stance: p = 0.004) and toe-out running (early stance: p = 0.028; late stance: p = 0.013). No statistically significant differences were observed in medial-lateral HCF during either early stance or late stance (p > 0.220) across the three conditions. No significant differences in vertical or medial-lateral HCF were found between toe-out and natural running during either early or late stance (p > 0.366). Footstrike modification appears to be a viable strategy to alter vertical HCF compared to natural and toe-out running. However, none of the selected strategies effectively modified HCF in the frontal plane. These findings have implications for developing targeted interventions to manage hip OA.