The purpose of this study is to analyse the gait of patients with knee joint disorder, by using the motion analysis system, in order to provide some references for clinical and therapeutic evaluation.Ten patients had been tested: six of them received anterior crucial ligament (ACL) reconstruction. and four received total knee arthroplasty. With cameras of the motion analysis system,the force plate, and the foot switch, raw experimental data were recorded simultaneously from each patient.Fourier analysis, knee angle parameters,ground reaction force parameters,and pressure distribution were then computed with the support of IBM software. The experimental results showed that(1)during the early post-operative poriod,knee joints of the patients receiving ACL reconstruction, unlike other normal subjects, did not have double locking' phenomenon in their single limb stance;(2) after rehabilitation,the ground reaction forces and the motion analysis did not show any significant difference between patients with ACL reconstruction and patients with total knee arthroplasty.