ABSTRACT Objective: To investigate the effect of root injury on the knee biomechanics and the finite element analysis. Methods:(1) Establishment and verification of the three-dimensional model of the knee joint. Four patients with normal knee joints were enrolled as the study subjects. The left knee joint was scanned by MRI to establish the geometric model of articular cartilage, meniscus, anterior and posterior cruciate ligament and medial lateral collateral ligament, respectively loading 1000N axial compression load and 134N forward thrust. The results of the analysis were compared with the results of digital simulation analysis. (2) The influence of posterior root injury of the lateral meniscus on the biomechanics of the knee joint. Based on the three-dimensional model of the knee joint, the posterior root injury model of the medial and lateral meniscus was established under finite element. As an observation group, the established normal knee model was used as a control to investigate the physiological and mechanical conditions of different parts of the knee joint after posterior root injury of the medial and lateral meniscus.RESULTS: 1 For normal knee joints, the medial femoral condyle and lateral anterior cartilage have higher stress. When the human body walks normally, the anterior part of the femur and the lateral part of the femur will bear a large force. The force is relatively small; femoral condyle, tibial plateau cartilage, meniscus, etc. are also low weight and high weight bearing area; 2 observation group femoral condyle, femoral condyle, medial tibial plateau, lateral tibial plateau cartilage, lateral meniscus maximum compressive stress , higher than the control group (P<0.05); 3 observation group femoral condyle, femoral condyle, medial tibial plateau, lateral tibial plateau cartilage, lateral meniscus maximum shear force, higher than the control group (P<0.05);Conclusion: Based on MRI images, the normal model of human knee joint and the posterior root injury model of meniscus can be successfully established. The finite element analysis shows that the biomechanical change of knee joint in the posterior root injury of lateral meniscus is not equivalent to the knee joint of lateral meniscus resection. The treatment should be different from the medial meniscus injury.