Effect of wider step-width gait on hip joint contact force.

Hip joint contact force (HJCF) overloading is a primary mechanical cause of hip osteoarthritis. Hip adduction moment (HAM) is a surrogate measure for estimating HJCF. Gait modification, especially wider step-width (SW), can significantly decrease the peaks and impulses of HAM, suggesting a possible strategy for preventing joint overloading. However, the effectiveness of a wider SW in directly reducing HJCF remains to be determined. In our study, fourteen healthy young participants comfortably walked with normal SW, double SW and triple SW. The neuromusculoskeletal simulation, calculation of HJCF peak values and impulse were carried out using Opensim during gait tasks. 3D motion capture system and surface electromyography assessed HAM peak values, impulse and muscle activities around the hip. Variations in HJCF, HAM, muscle activities, correlations between HJCF and HAM peaks were evaluated across walking conditions. We found that increasing the SW to double and triple significantly diminished the 2nd peaks and impulses of HJCF and HAM. Under the triple SW condition, the 1st peak of HAM notably decreased, whereas the activities of the gluteus medius and rectus femoris muscles markedly increased. Correlation analyses revealed that the 1st peak of HJCF was significantly associated with the 1st peak of HAM across all walking conditions. Moreover, the 2nd peak showed a significant correlation with both double and triple SW conditions. Increasing SW markedly improves dynamic HJCF, with changes in gluteus medius activity and HAM explaining this effect. This finding supports wider SW as a viable strategy for mitigating hip joint overload.