Objective:A three-dimensional (3D) finite element model of the ankle joint of marathon runners was constructed to simulate the changes of the lateral collateral ligament (LCL) injury on the stability of the ankle joint and the force distribution of talar talus cartilage during exercise.Methods:The 3D MRI images of the right ankle joint of one marathon runner were acquired and imported into Mimics software in DICOM format for preliminary 3D model reconstruction of the images. The boundary conditions and loads were loaded on the model using Ansys Workbench software, and the ankle joint forces were analyzed by Ansys Workbench for marathon runners in the sports condition, and four kinds of ankle LCL injury finite element models were established, i.e., the normal model of LCL, the injury model of anterior talofibular ligament (ATFL), the injury model of AFTL merged with the calcaneofibular ligament (CFL), and the injury model of AFTL merged with the CFL and the posterior talofibular ligament (PTFL). The peak talus slide cartilage stress and its distribution were observed under the four models, and one-way ANOVA was used to compare the values of talus advancement, and the SNK- q test was used for two-by-two comparisons. Results:In the LCL normal model, the maximum stress peak of the talar slide was 0.21 MPa, which was mainly distributed in the junction area of the anterior medial (MA) and anterior lateral (LA) parts and part of the LA region. In ATFL injury, the peak stress of talar cartilage increased compared with the normal model, with a maximum value of 0.65 MPa, which was mainly distributed in the MA region. In ATFL combined with CFL injury, the peak stress increased, and the peak was mainly distributed in the MA region, and was shifted from the MA to the LA region. In ATFL combined with CFL and PTFL injuries, the peak cartilage stress in the talus slide was up to 2.29 MPa, and the maximum stress was mainly distributed in MA and LA, which had a comparable range of distribution. The anterior talar displacement values were (3.2±0.4), (3.4±0.4), (3.7±0.5), and (6.5±0.7) mm for normal LCL, AFTL injury, AFTL combined with CFL injury, ATFL combined with CFL, PTFL injuries, respectively, with a statistically significant difference ( F=109.08, P<0.001). The anterior talar displacement of ATFL combined with CFL, PTFL injuries was larger than those of normal LCL, AFTL injury, and AFTL combined with CFL injury ( P<0.05). Conclusions:A 3D finite element model is successfully constructed based on 3D MRI of the ankle joint in marathon runners. The peak and range of cartilage stresses in the talar glide change during LCL injury, and the talar glide displaces anteriorly.