BACKGROUND: Quadriceps activation failure is common in patients with tibiofemoral osteoarthritis (TFOA) and has been reported to occur bilaterally following acute and chronic knee injuries. Sensory transcutaneous electrical stimulation (TENS) applied to the knee has increased ipsilateral quadriceps activation, yet it remains unknown if repeated sensory TENS treatments affect activation in the contralateral quadriceps. OBJECTIVE: To determine the effects of unilateral TENS treatment to the involved leg, in conjunction with 4-weeks of therapeutic exercise, on volitional quadriceps activation in the contralateral leg. METHODS: Thirty-three patients with radiographically diagnosed TFOA were randomly assigned to the TENS, placebo, and the control groups. The involved leg was defined as the knee with highest degree of radiographically assessed TFOA. All participants completed a supervised 4-week lower extremity exercise program for the involved leg only. TENS and placebo TENS were worn throughout the rehabilitation sessions as well as during daily activities for those groups on the involved leg. Quadriceps central activation ratio (CAR), a measure of volitional muscular activation, was assessed in the uninvolved leg at baseline, 2-weeks and 4-weeks following the initiation of the intervention. RESULTS: There were no differences between groups for quadriceps CAR (p = 0.3). DISCUSSION: Although significant differences were not found, strong to moderate within group effect sizes were calculated for the TENS group at 2 (d = 0.87) and 4 weeks (d = 0.54), suggesting that significant differences may be found in a larger population. CONCLUSIONS: Contralateral quadriceps CAR was not affected following a 4-week unilateral disinhibitory intervention in this sample.

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