Objective:To quantify the effects of different touchdown methods on the knee joint during barefoot running us-ing a validated finite element model of the knee joint,providing a theoretical basis for reducing sports injuries in runners.Method:Kinematics and ground reaction force data were collected from 22 participants during forefoot land-ing,midfoot landing and hindfoot landing at 4 m/s±5％respectively.Knee joint reaction forces were calculated using Visal3D inverse dynamics.The numerical simulations were performed for each of the three ground con-tact processes based on a 3D finite element model of the knee joint.Result:There were significant kinematic differences in the knee joint during forefoot/midfoot touchdown mode and hindfoot touchdown,with a larger peak flexion when using midfoot touchdown.Compared to forefoot touchdown,the midfoot touchdown mode during barefoot running produced a smaller peak in vertical ground reaction force.At the peak vertical ground reaction force,the peak patellofemoral cartilage contact stress(4.83 MPa)and the peak meniscal contact stress(5.98 MPa)in the midfoot touchdown mode were the lowest com-pared to the other two touchdown modes.Conclusion:When running barefoot,using a midfoot landing may reduce the risk of knee injury.It is recom-mended to use the midfoot touch pattern for rehabilitation involving barefoot running.

Objective:To quantify the effects of different touchdown methods on the knee joint during barefoot running us-ing a validated finite element model of the knee joint,providing a theoretical basis for reducing sports injuries in runners.Method:Kinematics and ground reaction force data were collected from 22 participants during forefoot land-ing,midfoot landing and hindfoot landing at 4 m/s±5％respectively.Knee joint reaction forces were calculated using Visal3D inverse dynamics.The numerical simulations were performed for each of the three ground con-tact processes based on a 3D finite element model of the knee joint.Result:There were significant kinematic differences in the knee joint during forefoot/midfoot touchdown mode and hindfoot touchdown,with a larger peak flexion when using midfoot touchdown.Compared to forefoot touchdown,the midfoot touchdown mode during barefoot running produced a smaller peak in vertical ground reaction force.At the peak vertical ground reaction force,the peak patellofemoral cartilage contact stress(4.83 MPa)and the peak meniscal contact stress(5.98 MPa)in the midfoot touchdown mode were the lowest com-pared to the other two touchdown modes.Conclusion:When running barefoot,using a midfoot landing may reduce the risk of knee injury.It is recom-mended to use the midfoot touch pattern for rehabilitation involving barefoot running.