Muscle contributions to knee extension in the early stance phase in patients with knee osteoarthritis.

•We evaluated knee extension mechanics in the early stance in patients with knee OA.•Muscle contributions to knee acceleration were calculated using a simulation model.•In knee OA, knee extension acceleration by vasti was lower.•Higher knee extension acceleration by hip adductors was also found in knee OA.•Hip adductors partly compensate for weak knee extension by the vasti in knee OA.