Individuals with knee osteoarthritis show few limitations in reactive stepping responses after gait perturbations

BackgroundKnee osteoarthritis (OA) causes structural joint damage. The resultant symptoms can impair the ability to recover from unexpected gait perturbations, contributing to an increased fall risk. This study compared reactive stepping responses to gait perturbations between individuals with knee OA and healthy individuals. MethodsKinematic data of 35 individuals with end-stage knee OA, and 32 healthy individuals in the same age range were obtained during perturbed walking on a treadmill at 1.0 m/s. Participants received anteroposterior (trip or slip) or mediolateral perturbations during the stance phase. Changes from baseline in margin of stability (MoS), step length, step time, and step width during the first two steps after perturbation were compared between groups using a linear regression model. Extrapolated center of mass (XCoM) excursion was descriptively analyzed. FindingsAfter all perturbation modes, XCoM trajectories overlapped between individuals with knee OA and healthy individuals. Participants predominantly responded to mediolateral perturbations by adjusting their step width, and to anteroposterior perturbations by adjusting step length and step time. None of the perturbation modes yielded between-group differences in changes in MoS and step width during the first two steps after perturbation. Small between-group differences were observed for step length (i.e. 2 cm) of the second step after trip and slip perturbation, and for step time (i.e. 0.02 s) of the second step after slip perturbations. InterpretationDespite considerable pain and damage to the knee joint, individuals with knee OA showed comparable reactive stepping responses after gait perturbations to healthy participants.