A frequent clinical obstacle encountered in patients with knee osteoarthritis (OA) is an inability to achieve full voluntary activation of the quadriceps musculature. This phenomenon has been termed arthrogenic muscle inhibition (AMI) and is an ongoing reflex inhibition of musculature surrounding a joint following distension or damage to the structures of that joint. AMI is a limiting factor in joint rehabilitation as it restricts full muscle activation and therefore prevents restoration of strength. Thus, patients often participate in life activities deficient in strength and neuromuscular control resulting in altered lower extremity mechanics and potentially predisposing patients to further joint degeneration. Neuromuscular electrical stimulation (NMES) has been shown to be successful in reversing quadriceps AMI, however the duration of its effectiveness and its influence on functional outcomes remains elusive. Therefore, the purpose of the proposed study is to examine quadriceps activation and functional outcomes following a 4-week NMES protocol in patients with medial tibiofemoral osteoarthritis. To examine the efficacy of NMES in reversing AMI and improving functional outcomes, 38 subjects will be randomly assigned to either undergo a 4-week NMES program or to undergo no therapeutic intervention. Prior to treatment and at 1, 12, and 24 weeks following treatment, patients' quadriceps central activation ratios will be assessed. Additionally, subjects will undergo gait and stair climb analyses to determine if functional performance during these activities of daily living are improved when compared to the baseline assessment. Patients' perceived level of function will also be tested using the Western Ontario and McMasters Universities Osteoarthritis Index.