Does neuromuscular electrical stimulation enhance the effectiveness of an exercise programme in subjects with knee osteoarthritis? A randomized controlled trial.

OBJECTIVE: To determine whether neuromuscular electrical stimulation applied to the quadriceps femoris muscle will enhance the effectiveness of an exercise programme in patients with knee osteoarthritis.

DESIGN: A randomized trial with parallel intervention treatment groups.

SETTING: Outpatient physical therapy clinic.

SUBJECTS: Fifty participants (mean age (SD) 68.9 (7.7) years) with symptomatic idiopathic knee osteoarthritis and radiographic evidence (grade ≥ II Kelgren's classification).

INTERVENTIONS: Participants were randomized into one of two groups receiving 12 biweekly treatments: An exercise-only group or an exercise combined with neuromuscular electrical stimulation group (biphasic pulses, at 75 Hz and 250 µs phase duration).

MAIN MEASURES: Knee pain intensity; maximal voluntary isometric contraction and voluntary activation of the quadriceps femoris muscle; measures of functional performance.

RESULTS: A significant interaction effect (P = 0.01) indicated greater improvement in pain for the electrical stimulation group. The mean (SD) change in pain intensity was from 7.5 ± 2 to 5 ± 2.2 and from 7.4 ± 1.9 to 3.3 ± 2.4 in the exercise and electrical stimulation groups, respectively. A significant treatment effect was also noted for the voluntary activation of the quadriceps femoris, which increased by 22.2% in the electrical stimulation group and by 9.6% in the exercise group (P = 0.045). Significant improvements were observed in both groups in all remaining measures, with no differences between groups.

CONCLUSIONS: Electrical stimulation treatment to the quadriceps femoris enhanced the effectiveness of an exercise programme in alleviating pain and improving voluntary activation in patients with knee osteoarthritis, but did not enhance its effect on muscle strength or functional performance.