OBJECTIVE: This study aimed to investigate differences in knee joint kinematics, ground reaction force kinetics and neuromuscular activity including muscle coactivation, and medial versus lateral muscle activity during a forward lunge between the operated and contralateral legs of meniscectomized patients. Such differences may represent early changes in neuromuscular function potentially contributing to the development of knee osteoarthritis. METHODS: Twenty-two unilaterally meniscectomized patients (15 men and 7 women; age = 45.4 ± 5.1 yr, height = 174.3 ± 7.1 cm, weight = 77.3 ± 15.4 kg (mean ± SD)) were investigated on their operated and contralateral legs during a forward lunge using synchronous goniometer, force plate, and EMG recording (vastus lateralis, vastus medialis, biceps femoris, and semitendinosus). RESULTS: During impact loading, an increased level of muscle coactivation (38.0% (29.8%-46.3%) vs 30.1% (23.6%-36.6%), P = 0.02; mean (95% confidence interval)), reduced range of motion (59.4° (54.5°-64.2°) vs 64.9 (60.8°-70.0°), P = 0.01), and increased loading rate (985% BW·s(-1) (653-1317% BW·s(-1)) vs 696% BW·s(-1) (525-868% BW·s(-1)), P = 0.01) were observed in the operated leg compared with the contralateral leg. In addition, different patterns of medial versus lateral neuromuscular activity were observed in the operated and contralateral legs, along with minor differences during the other phases of the forward lunge. CONCLUSIONS: The findings of increased muscle coactivation, reduced range of motion, and increased loading rate in the operated compared with the contralateral leg support the hypothesis that meniscectomized patients demonstrate modulations in kinetics, kinematics, and neuromuscular activity, which may represent early changes in neuromuscular function that precede and affect development of knee osteoarthritis. The results also indicate that the forward lunge test is a sensitive measure to identify leg-to-leg differences in neuromuscular function after surgical interventions.