Abstract: The purpose of this study was directly quantify walking stability in elderly female patients with knee osteoarthritis(OA)and healthy elder.Ten female patients with knee OA and ten control subjects(matched by height,mass,and gender)walked on the overground at a self-selected comfortable speed.A motion capture system and two force plates were used to determine locomotion.Dynamic stability during walking was investigated by using the margin of stability.There was no significant difference in speed,step length,step width between the patients with knee OA and normal subjects(all P>0.05).Both groups displayed similar anterior-posterior MoS(P>0.05)at foot contact.The patients with knee OA had a significantly reduced medio-lateral MoS compared to normal subjects(P=0.014).Our findings indicate that OA individuals walked with similar stability in anterior-posterior direction,but greater instability and risk of falls in medio-lateral direction compared to normal subjects.