Strengthening exercises of the quadriceps femoris muscle (QFM) are of benefit to patients with knee osteoarthritis (OA). Studies reporting short-term effects of neuromuscular electrical stimulation (NMES) of the QFM in this population support the use of this modality as an adjunct treatment. The aims of this follow-up study are to compare the effects of an exercise program with and without NMES of the QFM on pain, functional performance, and muscle strength immediately posttreatment and 12 weeks after completion of the intervention. Sixty-three participants with knee OA were assigned at random to one of two groups receiving 12 biweekly treatments: An exercise-only program or an exercise program combined with NMES. A significantly greater decrease in knee pain was observed immediately after treatment in the NMES group, which was maintained 12 weeks post-intervention in both groups. Although at this stage NMES had no additive effect, both groups demonstrated an immediate increase in muscle strength and in functional abilities, with no differences between groups. Although the improvements in gait velocity and in self-report functional ability were maintained at the follow-up session, the noted improvements in muscle strength, time to up and go, and stair negotiation were not maintained.
Supplementing an exercise program with NMES to the QFM increased pain modulation immediately following treatment in patients with knee OA. Maintenance of the positive post-treatment effects during a 12-week period was observed only for pain, self-reported functional ability, and walk velocity, with no difference between groups. The effects of a comprehensive group exercise program with or without NMES are partially maintained 12 weeks after completion of the intervention. The addition of NMES is suggested mainly for its immediate effect on pain. Further studies are needed to determine the effects of repeated bouts of exercise with and without NMES in this population.