The influence of passive prosthetic knee joints on uneven compliant surface walking among transfemoral amputees under dual-task versus single-task conditions

Individuals with transfemoral amputation (TFA) often experience gait adaptations when walking under environmental and cognitive challenges. This study examined the influence of passive prosthetic knee mechanisms on self-reported mobility and gait biomechanics during single-task and dual-task walking over an uneven compliant surface. Participants were grouped as able-bodied individuals (AB; n  = 15), individuals with TFA using polycentric knees (TFA _P ; n  = 6), and individuals with TFA using fluid-controlled knees (TFA _FC ; pneumatic/hydraulic; n  = 5). The dual-task condition involved walking while performing an auditory Stroop task. Outcome measures included self-report questionnaires, joint kinematics, joint kinetics, and ground reaction forces. Biomechanical variables were analysed using linear mixed-effects models to examine group, task, and group × task interaction effects. Self-reported outcomes indicated reduced functional mobility in individuals with TFA compared with AB. Biomechanical findings showed altered gait patterns in both TFA groups compared with AB, particularly reduced knee flexion and ankle plantarflexion. For kinetic outcomes, significant group effects were observed for selected joint moment and power variables, although Bonferroni-adjusted pairwise differences were identified only for maximum stance hip extension moment (HM1), with lower values in TFA _FC compared with AB. A significant task effect was observed for maximum stance ankle dorsiflexion (AA2) during dual-task walking across all groups. A significant group × task interaction was found for maximum hip eccentric power during late stance (HP2), with increased hip power during dual-task walking in TFA _P . Overall, passive prosthetic knee mechanisms showed limited differences, although task-specific adaptations were evident under combined uneven surface and cognitive demands.