Abstract: Knee osteoarthritis (OA), a leading cause of knee pain and chronic disability, is a common type of arthritis. The biomechanics of cartilage is an important indicator of the evaluation of knee OA. However, the biomechanics of cartilage of early knee OA remains to be elucidated. The biomechanical differences among the cartilage of healthy knee, early medial knee OA and early coexisting medial and lateral knee OA were still unknown. Therefore, three knee models with these three different OA situations were established based on fibril-reinforced biphasic cartilage finite element model. The biomechanical differences among the cartilage of healthy knee, early medial knee OA and early coexisting medial and lateral knee OA were investigated in the situation of maximum load and in the situation of maximum flexion angle of a gait cycle. When compared with the results of the healthy knee model, the fluid pressure and solid effective stress decreased while the strain increased in the medial compartment cartilage of early medial knee OA model. The results of the lateral compartment cartilage of early medial knee OA model were almost the same as that of healthy knee model. However, the fluid pressure and solid effective stress decreased and the strains increased in both compartment cartilage of early coexisting medial and lateral knee OA model. In conclusion, the changes of the degenerated cartilage in early knee OA would reduce the load support capability and increase the deformation of cartilage, thereby increasing the risk of further degeneration of cartilage. The proposed knee finite element model considering fibril-reinforced biphasic cartilage could be used to study the biomechanical differences between the cartilage of healthy knee and the cartilage of knee OA. In addition, the proposed model could also be adopted in other biomechanical studies of the joints such as hip, ankle and spine.