PURPOSE: The aim of this study was to identify differences in knee range of motion (ROM), movement speed, ground reaction forces (GRF) profile, neuromuscular activity, and muscle coactivation during the transition between stair descent and level walking in meniscectomized patients at high risk of knee osteoarthritis (OA) compared with the nonoperated leg and with healthy controls. METHODS: A total of 22 meniscectomized patients (15 men and 7 women (mean±SD), 45.4±5.1 yr, 174.3±7.1 cm, 77.3±15.4 kg) and 26 healthy controls (16 men and 10 women, 45.6±6.1 yr, 174.9±8.1 cm, 78.6±16.8 kg) were tested using synchronous force plate, goniometer, and EMG recording (vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), semitendinosus (ST)) during the transition step between stair descent and level walking. Pain was assessed using the Knee Injury and Osteoarthritis Outcome Score. RESULTS: Patients reported more pain than controls (P≤0.001), but no differences were observed between patients and controls in any variables including knee ROM during stance (operated leg=42.9°, nonoperated leg=44.3°, controls=43.4°, respectively, P=0.42). A shorter stance phase (Tstance; 657 vs 679 ms) was observed for the meniscectomized leg versus the nonoperated leg in patients along with reduced overall medial versus lateral thigh muscle activity in the meniscectomized leg during the weight acceptance phase (P≤0.05) and at peak GRF (P≤0.01). CONCLUSIONS: Patients and controls did not differ in any of the examined variables. However, kinematic differences were observed in the meniscectomized leg compared with the nonoperated leg along with attenuated medial leg muscle activity in the meniscectomized leg. The present findings support the hypothesis that meniscectomized individuals demonstrate early modulations in kinematics and neuromuscular activity that may represent an initial phase in the development of knee OA.