Electromyographic biofeedback or neuromuscular electrical stimulation added to isometric quadriceps exercise does not improve pain and functional outcomes in knee osteoarthritis: a randomized controlled trial

Quadriceps muscle weakness is a common clinical feature in individuals with knee osteoarthritis (KOA) and contributes to pain, functional limitations, and reduced quality of life. While quadriceps strengthening exercises are well-established, the additional benefits of electromyographic biofeedback (EMG-BFB) and neuromuscular electrical stimulation (NMES) remain inconclusive. This single-blind randomized controlled trial investigated whether EMG-BFB or NMES provides added benefits when combined with isometric quadriceps strengthening exercises in patients with mild-to-moderate KOA. Ninety-three participants aged over 55 years, meeting the American College of Rheumatology criteria and classified as Kellgren-Lawrence grades 1-2, were randomly assigned to three groups: exercise only, exercise plus EMG-BFB, and exercise plus NMES. All participants completed 15 supervised sessions over 3 weeks. Pain intensity (Visual Analogue Scale) was the primary outcome. Secondary outcomes included physical function (Western Ontario and McMaster Universities Osteoarthritis Index), muscle activation (raw EMG amplitude), and quality of life (36-Item Short Form Health Survey), assessed at baseline, immediately after the intervention, and at 3- and 6-month follow-up. All groups demonstrated significant improvements in pain, knee function, muscle activation, and quality of life following the intervention, with benefits maintained at follow-up. However, no significant differences were observed between groups at any time point. These results suggest that isometric quadriceps strengthening exercises alone are effective in managing KOA, while the addition of EMG-BFB or NMES does not yield superior clinical outcomes. Given the simplicity, accessibility, and effectiveness of exercise alone, it may serve as a first-line intervention, while the specific clinical indications for adding EMG-BFB and NMES to isometric exercises remain to be determined.