Effects of adding neuromuscular electrical stimulation to functional training on muscle recruitment, pain reduction, and knee joint function in patellofemoral pain syndrome patients

Background: Impaired lower extremity motor function and knee pain are common concerns in patients with patellofemoral pain syndrome (PFPS). It is essential to plan therapeutic techniques to therapy PFPS. The objective of this study was to determine the effect of neuromuscular electrical stimulation (NMES) combined with functional training on pain, lower extremity function and muscle recruitment in patients with PFPS. Methods: Twenty-four PFPS patients (male-13, female-11) were selected to conduct this study finally. Two groups were formed: the control group (n = 12) which included functional training only and the experimental group (n = 12) which functional training along with NMES-in both groups interventions were performed for 45 minutes/session, 3 days/weeks for 6 weeks. The functional training consisted of warm-up activities, strength training, balance training, and relaxation activities. All patients were evaluated with surface electromyography testing system for the root mean square and integrated electromyography of vastus medial oblique (VMO), vastus lateralis (VL), and VMO/VL ratio, visual analog scores (VAS) for pain, and Kujala functional score for knee joint function before and after 6 weeks. Normality was tested for all outcome variables using Shapiro-Wilk test. Nonparametric (Mann-Whitney U test and Wilcoxon signed-rank test) tests were used to analyze data. A 2-way analysis of variance with repeated measures (group*time) was applied to analyze the data. Results: A significant increases (P < .001) root mean square and integrated electromyography of VMO, VMO/VL ratio, and Kujala score in both groups, For VAS scores, significant decreases was observed in both groups. When both groups were compared, greater improvement (P < .05) was observed in the experimental group in comparison the control group for both knee pain, lower extremity function and muscle recruitment. However, there was no difference in VL muscle recruitment between the 2 groups. Conclusions: Functional training and NMES combined with functional training are helpful to improve pain, knee function and muscle recruitment of PFPS patients. NMES combined with functional training was more effective compared to the control group. This may help clinical trialists to use different NMES to synchronize other interventions in future studies to enhance rehabilitation efficacy in PFPS patients through passive training versus active stimulation.