Foot progression angle modifications alter hip joint contact forces and femoral growth plate mechanics in children.

Introduction: Bony deformities of the lower limbs are prevalent in both children and adults and are associated with pain, gait impairments, and increased risk of osteoarthritis. While severe torsional deformities are commonly treated surgically, bone growth is regulated by mechanical stimuli, suggesting potential for non-invasive interventions. In children, longitudinal bone growth occurs at epiphyseal growth plates through endochondral ossification, where chondrocyte activity is modulated by biochemical and mechanical cues. Mechanobiological theories indicate that compressive and shear stresses influence local growth rates. Gait modifications are practical, coachable strategies to alter lower-limb loading in vivo, yet direct evidence that such modifications acutely affect growth-related mechanical stimuli within paediatric growth plates is lacking. Most prior studies report joint moments rather than subject-specific joint contact force (JCF) or micro-scale stresses. The present study addresses this gap by integrating MRI-based, electromyography (EMG)-informed musculoskeletal (MSK) modelling with subject-specific finite element (FE) analyses to quantify how gait modifications alter growth-related stresses in femoral growth plates. Methods: Three typically developing children walked on an instrumented treadmill under preferred gait and bilateral in-toeing and out-toeing conditions. MRI-based MSK models combined with EMG-informed optimization were used to estimate muscle forces and hip, knee, and patellofemoral JCFs, which were applied as loading conditions in FE models of the proximal and distal femoral growth plates. Hydrostatic compressive and octahedral shear stresses were quantified as mechanobiologically relevant growth stimuli. Results: In-toeing increased hip JCF magnitude and shifted its orientation anteriorly across all participants, accompanied by increases in hydrostatic compression and more heterogeneous shear stress distributions in the proximal femoral growth plate. Changes at the knee, patellofemoral joint, and distal growth plate were smaller and more variable between participants, likely reflecting anatomical and neuromuscular differences. Overall gait kinetics and estimated forces aligned with previous reports. Discussion: These findings provide proof-of-concept that modifiable gait patterns can acutely alter mechanobiologically relevant stresses in paediatric femoral growth plates. While responses were subject-specific, the results support the feasibility of personalised gait retraining as a low-risk, non-invasive strategy to influence growth-related mechanical loading. Larger longitudinal studies are required to determine whether such acute changes can steer bone development during maturation.