Abstract:Objective To investigate the effects of electrical stimulation combined with muscle strength training on knee joint biomechanical characteristics in patients with patellofemoral pain (PFP). Methods Forty-six patients with PFP were recruited and randomly assigned to the muscle strength training (MST) and electrical muscle stimulation with strength training (EMS) groups. The intervention was performed three times a week for six weeks. The anterior knee pain scale (AKPS) was used to measure the knee pain degree. Knee kinematics, dynamics, and surface electromyography (sEMG) data were collected using an infrared motion capture system, force platform, and sEMG system during drop jumps before and after the intervention. Two-way analysis of variance with repeated measures was applied to determine the differences between the dependent variables of the two groups before and after the intervention. Results Compared with pre-intervention, the AKPS score, vastus medialis oblique (VMO)activation, VMO/vastus lateralis (VMO/VL) activation, maximum knee flexion angle, and peak knee extension moment increased significantly in the EMS group; the maximum knee abduction, external rotation angle, and peak knee external rotation moment decreased significantly in the EMS group after intervention. Compared with pre-intervention, the AKPS score, maximum knee flexion angle, and peak knee extension moment increased significantly in the MST group after intervention, the peak knee abduction and external rotation moment significantly decreased in the MST group after intervention. Post-hoc comparisons indicated that compared with the MST group, the AKPS score, VMO activation, VMO/VL activation were significantly higher and the maximum knee abduction angle was significantly lower in the EMS group. Conclusions EMS helped in the better balance muscle activation of the VMO and VL and corrected the excessive knee abduction angle during jump landing, which may be helpful in relieving pain and improving lower limb function in patients with PFP.