EFFECTS OF A COMBINED QUADRICEPS STRENGTHENING AND NEUROMUSCULAR ELECTRICAL STIMULATION PROGRAMME ON PAIN, FUNCTIONAL DISABILITY, AND QUALITY OF LIFE IN PATIENTS WITH KNEE OSTEOARTHRITIS: A RANDOMISED CONTROLLED TRIAL

Abstract

Background: Knee osteoarthritis (OA) is a leading cause of chronic pain and functional disability among older adults. While quadriceps strengthening is a cornerstone of conservative management, quadriceps inhibition often limits voluntary activation and reduces training efficacy. Neuromuscular electrical stimulation (NMES) may overcome this limitation by eliciting involuntary muscle contractions, thereby augmenting strength gains and clinical outcomes. This study investigated whether combining NMES with supervised quadriceps strengthening produces superior improvements in pain, functional disability, and quality of life compared with strengthening exercise alone in patients with knee OA.

Objective: To compare the effects of a combined NMES and quadriceps strengthening programme versus conventional quadriceps strengthening alone on pain, functional disability, and health-related quality of life in patients with clinically diagnosed knee OA.

Methods: Twenty participants with knee OA (Kellgren-Lawrence grade II-III) were randomised equally into an intervention group (NMES plus supervised quadriceps strengthening, five sessions per week for six weeks) and a control group (quadriceps strengthening alone at the same frequency and duration). Primary outcomes were pain measured on a Visual Analogue Scale (VAS), physical function on the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) function subscale, and quality of life on the Knee Injury and Osteoarthritis Outcome Score quality-of-life subscale (KOOS-QOL). Secondary outcomes included quadriceps isometric strength, total WOMAC score, Timed Up and Go (TUG) test, 30-second chair stand test, six-minute walk test (6MWT), knee range of motion (ROM), Patient Global Assessment (PGA), analgesic consumption, and treatment adherence.

Results: Both groups demonstrated statistically significant within-group improvements across all outcomes (p < 0.001). However, the NMES combined group exhibited significantly greater between-group improvements in WOMAC function (mean difference -14.5, 95% CI -17.5 to -11.5, p < 0.001), quality of life (14.3, 95% CI 11.1 to 17.5, p < 0.001), quadriceps strength (4.0 kg, 95% CI 3.0 to 5.1, p < 0.001), TUG time (-1.5 s, 95% CI -2.0 to -1.0, p < 0.001), chair stand performance (3.5 repetitions, 95% CI 2.5 to 4.5, p < 0.001), six-minute walk distance (57.7 m, 95% CI 46.7 to 68.7, p < 0.001), and knee ROM (5.0 degrees, 95% CI 3.3 to 6.7, p < 0.001). Seven of ten participants in the NMES group reported being "much improved" on the PGA, compared with none in the control group. Adherence was 94.3% in the intervention group and 88.4% in the control group.

Conclusion: The addition of NMES to a supervised quadriceps strengthening programme significantly enhanced functional recovery, quality of life, and physical performance in patients with knee OA compared with exercise alone. These findings support the incorporation of NMES into standard rehabilitation protocols for knee OA, particularly for patients exhibiting quadriceps inhibition.