The effectiveness of 6-week superimposed neuromuscular electrical stimulation in knee osteoarthritis: an assessor blinded randomized controlled clinical trial

Conservative treatment of knee osteoarthritis (KOA) is crucial for alleviating patient complaints and postponing disability from the onset of symptoms until the disease progresses to the point where surgery is inevitable. Although as a part of conservative management, Superimposed Neuromuscular Electrical Stimulation (sNMES), which combines electrical stimulation with voluntary contraction, has gained popularity in clinical practice, the effects of sNMES in KOA are unknown. Therefore, the study aimed to investigate the effects of sNMES in patients with KOA. Fifty-eight participants with KOA were randomly divided into three groups (sNMES + CP (conventional physiotherapy), NMES (Neuromuscular Electrical Stimulation) + CP, and only CP). The treatments lasted 3 times for 6 weeks. Before and after treatments, the quadriceps and femoral cartilage thickness, sensorimotor function (balance and proprioception), physical function (quadriceps muscle strength, knee range of motion, and 30-second sit-to-stand test), and functional status (Short Form-36 (SF36) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC)) were evaluated. Regarding timeXgroup effect when comparing groups, the sNMES + CP showed significant improvements over NMES + CP and only CP in quadriceps muscle strength (p < 0.01), SF36_Energy (p < 0.01), and SF36_Social Functioning (p < 0.01). Both the sNMES + CP (p < 0.01) and only CP groups (p < 0.01) showed significant changes in SF36_Pain scores, while all groups had significant reductions in WOMAC Scores (p < 0.05), with the sNMES + CP group showing the greatest improvement (p < 0.01). No adverse effects were reported in all treatment groups. sNMES + CP proved more effective than NMES + CP or only CP in enhancing quadriceps muscle strength and improving functional status. Incorporating sNMES instead of NMES into CP could be a more effective intervention for treating KOA, particularly when the goal is to enhance quadriceps strength, thereby improving functional status. In conservative management of KOA, collaboration between orthopedists and physiatrists is crucial for addressing functional improvement regarding the effect of sNMES.