Objective To evaluate the biomechanical effects of lateral meniscus posterior root (LMPR) tears fixed at different suture positions, so as to investigate the optimal suture method for repairing LMPR tears. Methods Eight fresh cadaveric knees were used. Each knee was tested under 6 conditions: intact knee, ruptur of LMPR, suture of LMPR to the center point of root insertion, suture of LMPR posterior, interior and later 5 mm to the center point of root insertion, respectively. The peak contact pressure, the average contact pressure and contact area were evaluated using a Tek-scan sensor positioned between the meniscus and tibial plateau, under 1 kN compressive loading, at 0 degree knee extension. Results In the lateral compartment, the average contact pressure and peak pressure significantly increased under rupture of LMPR compared with the intact state (P<0.01), and the contact area decreased significantly (P<0.05). For LMPR tears fixed by four different suture methods, both the average pressure and peak contact pressure reduced, and the contact area increased. The average contact pressure, peak pressure and contact area were closer to the knee joint in the intact state when the suture positions of LMPR tears was posterior 5 mm to the center point of root insertion (P<0.05). In the medial compartment, there were no significant differences in contact pressure, peak contact pressure and contact area with the knee joint at 0 degree (P>0.05). Conclusions The average contact pressure, the peak contact pressure and the contact area between the lateral meniscus and the tibial plateau changed obviously due to the LMPR tears. When the suture position was 5 mm lateral to the center point of root insertion, similar biomechanical function with the intact knee could be obtained.