###### Abstract  
The lower limbs play an important role in daily human activities. Therefore, a 3D tibial model is constructed, and finite element analysis is performed to investigate the biomechanical characteristics and injury tolerance of lower limb flexion movement. The maximum equivalent stress at 30 deg flexion was 19.1 MPa and 31.2 MPa in the normal and dynamic even positions, respectively, of the knee joint, 1.4 MPa and 1.1 MPa in the medial tibial plateau, and 1.8 MPa and 1.2 MPa in the lateral tibial plateau. The peak contact force was generally approximately 4000 N when different positions of the tibia were impacted. The maximum contact force of the frontal impact was larger than that of the external impact at 4109 N and 3927 N, respectively. The dynamic knee valgus posture and lateral impacts are more likely to cause tibial injury. The findings of this study provide information for the prevention of sports injuries and rehabilitation treatment. tibia; flexion movement; finite element model; biomechanics; damage tolerance +
Footnote †: journal: applied sciences  
00242024141760  
Some abnormal movement postures of the human body can have a weak but sustained impact on human bones, which can evolve into more serious injuries over time. Due to the fact that the tibia is the main load-bearing bone in the human body, the vast majority of sports require the participation of the tibia, and the damage caused by sports to the tibia is much higher than other bones in the human body [3; 4]. Buckling exercise is the most common exercise in people's daily life and physical exercise. The so-called flexion movement refers to the joint moving around the coronal axis, causing the two bones of the relevant joint to approach each other. Therefore, studying the biomechanical characteristics of the tibia during flexion exercise and abnormal posture exercise has important theoretical and practical value for preventing sports injuries, assisting rehabilitation treatment, etc. Impact load is the most common type of load that can cause tibial fracture injury, and the damage caused by impact load is generally more severe. However, currently, the main method for studying the biomechanical properties of the tibia under impact load in different countries is to conduct relevant experiments on the tibia of cadavers. These experiments are predominantly confined to mid-tibial impact experiments. The tolerance limit of the tibia under other impact conditions has not been sufficiently studied. Therefore, a comprehensive analysis of the impact tolerance limit of the tibia can help understand the load-bearing capacity of the lower limbs and prevent injuries. Furthermore, it can provide a foundation for the development of human rehabilitation treatments and related care. [PERSON] et al. used 3D CT simulation technology to identify different injury modes of tibial plateau fractures in flexion and analyzed the correlation between each injury mode and accompanying injuries. The research results showed that the incidence of lateral quadrant collapse fractures after type IIB fractures was significantly higher than that of type IIC fractures (_p_ < 0.001). The incidence of posterior lateral quadrant fractures, anterior lateral quadrant fractures, and proximal fibular fractures in type IIC fractures was significantly higher than that in type IIB fractures (_p_ < 0.001). There was a significant difference in the number of accompanying injuries between type IIB and type IIC fractures (_p_ < 0.001) [5]. [PERSON] et al. diagnosed anterior cruciate ligament (ACL) avulsion using data from computed tomography and magnetic resonance imaging and analyzed the 3D quantitative measurement results of tibial plateau fractures. The research results showed that there were more ACL tear and displacement during knee flexion (_p_ < 0.05). The incidence of ACL tear in the flexion outward rotation injury mode was higher than that in other injury modes of the same level (_p_ < 0.05).