BACKGROUND:Lower limb peri-knee muscle strength training and neuromuscular electrical stimulation are generally safe and effective rehabilitation methods for patellofemoral joint pain,but the mechanism of their intervention is still unclear. OBJECTIVE:To determine the effect of muscle strength training combined with neuromuscular electrical stimulation on pain,lower extremity function and biomechanical characteristics in patients with patellofemoral pain. METHODS:Thirty-seven patients with patellofemoral pain were randomly divided into muscle strength training combined with electrical stimulation group(trial group,n=19)and muscle strength training group(control group,n=18).Both groups underwent intervention training for 6 weeks,three times a week.The visual analog scale and anterior knee pain scale were used to evaluate the pain level and functional level of the knee.Kinematic and kinetics data during running were collected by using an infrared motion capture system and a three-dimensional force platform simultaneously.A two-way analysis of variance with repeated measures(group*time)was applied to analyze the data. RESULTS AND CONCLUSION:(1)After the intervention,the visual analog scale scores of the trial group and the control group were significantly decreased(P<0.001),and the anterior knee pain scale scores were significantly increased(Ptrial group<0.001,Pcontrol group=0.001)in the trial group and control group.The anterior knee pain scale scores of the trial group were significantly higher compared to the control group after the intervention(P=0.001).(2)The peak knee flexion angle(P=0.011),peak knee extension moment(P<0.001),the peak knee internal rotation moment(P=0.008),the peak patellofemoral stress(P<0.001)and the peak patellofemoral contact force(P<0.001)were significantly decreased in the trial and control groups during running after the intervention compared with those before the intervention.(3)In conclusion,both muscle strength training and muscle strength training combined with electrical stimulation training are helpful to improve the subjective pain and lower limb function of patellofemoral pain patients,enhance the movement pattern during running and reduce the stress of the patellofemoral joint.Compared with muscle strength training alone,muscle strength training combined with electrical stimulation can improve lower limb function more significantly.