The effect of adding whole-body electromyostimulation to hip and knee strengthening exercises on pain, muscle strength, and function in women with patellofemoral pain syndrome: A randomized controlled trial

Introduction Strength training is a key treatment for patellofemoral pain syndrome (PFPS). Although conventional strengthening exercises offer important benefits, whole-body electromyostimulation (WB-EMS) may provide complementary advantages; however, its additive effects in PFPS remain unclear.Purpose This study investigated the short-term effects of adding WB-EMS to hip and knee strengthening exercises on pain and self-reported function in women with PFPS. It also assessed immediate post-treatment effects on muscle strength and objective function.Methods In this single-blind randomized controlled trial, 36 women with unilateral PFPS were randomized to strengthening exercises alone (control) or combined WB-EMS and strengthening exercises (intervention). All performed strengthening exercises three times weekly over 7 weeks (21 sessions); the intervention group additionally received WB-EMS twice weekly (14 sessions). Primary outcomes – worst pain in the previous week (visual analog scale (VAS)) and knee-related symptoms and function (Kujala scale) – were assessed at baseline, 7 weeks, and 3-month follow-up. Secondary outcomes (muscle strength, step-down test repetitions) were measured at baseline and 7 weeks.Results Significant group-by-time interactions were found for VAS (F(2,33)=6.41, p = .003, ηp2 = 0.16) and the Kujala scale (F(2,33)=3.86, p = .026, ηp2 = 0.15). VAS was significantly lower in the intervention group at 3 months (mean difference [MD] = −7.64, 95% CI: −9.36 to −3.16, p = .014). Kujala scores were significantly higher at 7 weeks (MD = 5.61, 95% CI: 2.33 to 8.88, p = .001) and 3 months (MD = 7.32, 95% CI: 3.82 to 10.83, p < .001). Significant interactions were also shown for step-down test repetitions (F(1,33)=10.33, p = .003, ηp2 = 0.23), knee extensor strength (F(1,33)=8.06, p = .008, ηp2 = 0.19), and knee flexor strength (F(1,33)=9.21, p = .005, ηp2 = 0.21).Conclusion Adding WB-EMS to strengthening exercises may improve pain, knee muscle strength, and function in women with unilateral PFPS. Larger, adequately powered trials with appropriate blinding and longer objective follow-up are warranted.