Background: Knee 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. Methods: Kinematic 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. Findings: After 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. Interpretation: Despite considerable pain and damage to the knee joint, individuals with knee OA showed comparable reactive stepping responses after gait perturbations to healthy participants.

The authors have declared no competing interest.

Smith & Nephew sponsored this study. The funders had no role in the design and conduct of this study.

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Ethical approval was obtained from the CMO Arnhem/Nijmegen (2019-5824).

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes

All data produced in the present work are contained in the manuscript