Effect Of Minimalist Shoe And Gait Retraining On Patellofemoral Joint Load

Purpose In view of the high incidence of patellofemoral joint pain syndrome(PFPS)in runners,the purpose of this study was to investigate the effect of different shoes on biomechanical characteristics of patellofemoral joint and the changes in strike pattern,knee sagittal angle and moment,patellofemoral joint force,and stress before and after 12-week gait retraining.Methods A total of 30 healthy male rearfoot strike runners were divided into control group(n=15)and experimental group(n=15).The 15 runners in the experimental group were required to complete 3 overground running trials at 3.33 m/s(±5%)in two shoe conditions(cushioned vs.minimalist shoes).Ten Vicon infrared cameras(100 Hz)and two Kistler force plates(1000 Hz)were used to collect kinematics and ground reaction force(GRF)data simultaneously.The two groups were subjected to 12-week gait retraining.The experimental group was required to wear minimalist shoes(INOV-8 BARE-XF 210 v2;heel-toe drop 0mm;227 g)for gait retraining with the forefoot strike pattern,and the control group was required to wear minimalist shoes and train with the same intensity and duration as the existing foot strike habit.Quadriceps strength,patellofemoral contact force,patellofemoral contact area,and patellofemoral contact stress were calculated by inverse dynamics.A repeated measures two-way ANOVA(group× time)was used to compare knee flexion angle,knee extensor moment,patellofemoral joint force,and patellofemoral joint stress.The level of significance,α,was set at 0.05.Results 1.Compared with cushioned shoes,when wearing minimalist shoes: 1)The maximum flexion angle of the knee was significantly reduced(P < 0.01);2)The contact area of patellofemoral joint was significantly reduced(P < 0.01);3)The peak knee extension moment decreased significantly(P < 0.01);4)Peak patellofemoral contact force and stress decreased significantly(P < 0.05).2.After 12-week gait retraining,a total of 17 runners(control group n=8,experimental group n=9)met the training standard.In the experimental group the 12-week gait retraining combined with minimalist shoes can transform the rearfoot striker into forefoot striker(78%).After 12-week gait retraining.There were no differences in all parameters of the control group before and after training;the knee angle,patellofemoral joint contact area,and patellofemoral joint contact force of the experimental group did not change significantly before and after training,while the peak knee extension torque was reduced by 13.8%(P <0.05).The peak stress of the hip joint was reduced by 13.3%(P <0.05).Conclusion Compared with cushioned running shoes,while maintaining the peak impact force,wearing minimalist shoes significantly reduced the patellofemoral contact force(17.02%)and patellofemoral joint stress by reducing the moment of knee extension,effectively reduce the load of patellofemoral joint during the support phase.Gait retraining using only minimalist shoes didn’t change the characteristics of the patellofemoral joint during running,but 12-week gait retraining can effectively reduce the patellofemoral joint load,thus reduce the occurrence of patellofemoral joint pain caused by running.