Objectives. To investigate the effect of 8 weeks of NMES + Ex (neuromuscular electrical stimulation combined with exercises) on pain and functional improvement in patients with knee osteoarthritis (OA) compared to exercise (Ex) alone. Design. Randomized controlled trial. Setting. A specialty outpatient clinic. Participants. Patients (N = 100; women = 86, men = 14; age range, 50–75 years) with knee OA. Interventions. Participants were randomly assigned to NMES + Ex or Ex group. Outcome Measures. Numerical Rating Scale 0 to 10 (NRS) and the Timed Up and Go (TUG) test were the primary outcomes. The secondary outcomes used were the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Results. Following the interventions, a statistically significant improvement in both groups was observed in all outcomes assessed. For the comparison between the groups, no statistically significant difference was found between the NMES + Ex and the Ex groups in NRS (P = 0.52), TUG test (P = 0.12), and aspects of WOMAC: pain (P = 0.26), function (P = 0.23), and stiffness (P = 0.63). Conclusion. The addition of NMES to exercise did not improve the outcomes assessed in knee OA patients. This study was registered at the Australian Clinical Trials Registry (ACTRN012607000357459).