EP9.26 Changes in Hip Joint Moments Relative to Knee and Ankle Moments During a 16-Minute Walking Protocol in Individuals With Suspected Femoroacetabular Impingement (FAI)

Abstract

Abstract Background Biomechanical factors play a central role in symptomatic hip conditions, yet the influence of fatigue on inter-joint kinetic coordination during walking remains poorly defined. Evaluating how hip, knee, and ankle joint moments evolve under sustained load may provide mechanistic insight into gait compensation patterns relevant to hip preservation. Purpose To characterize fatigue-related changes in sagittal-plane joint moments and quantify proximal-distal inter-joint coupling during prolonged walking. Methods Participants completed a 16-minute walking protocol with kinetic data collected at 5, 10, and 15 minutes. Sagittal-plane hip, knee, and ankle joint moments were extracted across stance, and peak and mean values were calculated at each timepoint. Inter-joint coupling was quantified using linear regressions between mean hip moments and mean ankle or knee moments. Coupling slope and coefficient of determination (R2) were used to assess the strength and structure of proximal-distal moment relationships across fatigue. Results Sustained walking produced consistent reductions in inter-joint coordination. Hip-ankle coupling slope decreased from 1.75 at 5 minutes to 1.04 at 15 minutes (-41%), with R2 decreasing from 0.16 to 0.07. Hip-knee coupling showed a similar decline, with slopes decreasing from 0.25 to 0.16 (-36%) and R2 reducing from 0.17 to 0.07. Most changes occurred between 5 and 10 minutes. Joint moment patterns demonstrated preserved hip moment output relative to declining ankle and knee contributions, indicating altered load distribution across proximal and distal joints. Conclusion Fatigue induced measurable decoupling of sagittal-plane kinetics, characterized by weakened coordination between hip, knee, and ankle joint moments. The disproportionate reduction in hip-ankle coupling suggests diminished distal drive and a compensatory shift toward proximal moment generation as fatigue accumulated. These findings provide mechanistic evidence of emerging proximal-dominant gait strategies and highlight the sensitivity of inter-joint coupling as a marker of kinetic adaptation. Scientific Significance This study advances fundamental understanding of fatigue-related kinetic control in walking and establishes inter-joint coupling as a sensitive biomechanical metric for evaluating movement adaptations relevant to hip preservation research.