Effects Of Neuromuscular Electrical Stimulation Combined Strength Training In Patients With Patellofemoral Pain Syndrome

Objective: Patellofemoral pain (PFP) is a common knee joint injury among runners. The purpose of this study was to investigate the effects of a 6-week neuromuscular electrical stimulation combined with muscle strength training on pain, knee function, muscle strength, and patellofemoral joint stress during running in patients with PFP. Methods: Sixty patients with patellofemoral pain (15 females and 45 males, age: 21.9 ± 2.6 years, height: 1.75 ± 0.08 m, and weight: 71.5 ± 12.2 kg) were randomly assigned to the neuromuscular electrical stimulation combined with muscle strength training (EMS) group, the muscle strength training (MST) group, and the health education (HE) group. The EMS and MST groups received interventions three times per week for 6 weeks. Pain score, knee function (anterior knee pain scale, AKPS), muscle strength, and patellofemoral joint stress during running were measured before and after the intervention. Two-way repeated ANOVA was applied to determine the main effects of groups, time, and their interaction on the measurements. Results: Significant interaction were detected in pain score (P < 0.001, η2p = 0.459), AKPS score (P < 0.001, η2p = 0.559), knee extensor strength (P = 0.001, η2p = 0.222), and patellofemoral joint stress (P < 0.001, η2p = 0.390). Post-hoc indicated that compared with week 0, EMS and MST groups showed significant decrease in pain score (EMS: from 4.98 ± 0.98 to 2.13 ± 0.87, p < 0.001; MST: from 4.75 ± 1.29 to 2.45 ± 0.69, p < 0.001) and patellofemoral joint stress(EMS: from 5.93 ± 1.39 Mpa to 4.19 ± 0.99 Mpa, p < 0.001; MST: from 5.59 ± 1.61 Mpa to 4.37 ± 1.39 Mpa, p < 0.001), significant increase in AKPS score (EMS: from 76.65 ± 7.13 to 86.65 ± 6.14, p < 0.001; MST: from 75.70 ± 5.25 to 80.40 ± 3.94, p < 0.001) and knee extensor strength (EMS: from 1.88 ± 0.58 N*m/kg to 2.42 ± 0.60 N*m/kg, p < 0.001; MST: from 2.06 ± 0.68 N*m/kg to 2.59 ± 0.73 N*m/kg, p < 0.001) at week 7. Additionally, compared to the MST and HE groups, the EMS group exhibited greater improvement in AKPS scores at week 7(PEMS,MST = 0.003, PEMS,HE < 0.001). Conclusion: Neuromuscular electrical stimulation combined with muscle strength training could be recommend as one of the clinical treatments for patellofemoral pain to relieve pain, improve knee functional level and reduce patellofemoral joint stress.