Effect of neuromuscular electrical stimulation associated with therapeutic exercise on pain, function, and strength of people with knee osteoarthritis: a systematic review with meta-analysis of randomized clinical trials with GRADE recommendations

Objective To determine whether NMES combined with therapeutic exercise improves pain, function, and muscle strength compared to exercise alone in adults with KOA.Methods We searched nine databases (PubMed, MEDLINE-Ovid, EMBASE, Cochrane Library, Web of Science, Scopus, SPORTDiscus, LILACS, SciELO) up to 5 April 2025. Randomized controlled trials comparing NMES + exercise with exercise alone were eligible. Two reviewers independently screened records, extracted data, and assessed methodological quality and risk of bias using the PEDro scale and the RoB 2. Random-effects meta-analyses generated mean differences (MD) or standardized mean differences (SMD). Certainty of the evidence was assessed with GRADE (PROSPERO CRD42023393616).Results Eight trials (354 participants; mean age ≈59 years; 71% women) were included. Immediately post-intervention, NMES + exercise did not reduce pain versus exercise alone (SMD −0.90, 95% CI −1.84 to 0.03; I2 = 84%). At 8–12 weeks, small benefits were observed for pain (SMD −1.30, 95% CI −1.87 to −0.73; I2 = 0%) and TUG (SMD −0.67, 95% CI −0.98 to −0.35). No differences were found for WOMAC total or quadriceps strength. Certainty was very low.Conclusions NMES + exercise may modestly improve long-term pain and mobility in KOA, though evidence certainty is very low.