An innovative randomly oriented laminated composite model for articular cartilage tissue

Articular cartilage is a three-dimensional biphasic, fiber-reinforced composite material in which fiber orientation changes along the depth. The fibers have key asset in tolerating the applied stresses to cartilage by reinforcing the proteoglycan matrix of articular cartilage. This study is aimed to establish an innovative model based on microstructure of articular cartilage for stress distribution anticipation in cartilage constituents. To do this, articular cartilage is modeled as a laminated composite with randomly oriented fibers with depth dependent fiber volume fraction in superficial zone. Furthermore, the nonlinear strain dependent permeability model is used for all zones. Finite element simulation is carried out for further study on articular cartilage behavior under confined compression loading. The reaction force, time, and depth dependent stress distribution of our presented model are compared to classic isotropic model. Although isotropic model has been basically used to characterize the mechanical behavior of articular cartilage under different loading directions, our results reveal that it fails to calculate the mechanical behavior of articular cartilage tissue thoroughly. In addition, comparing the reaction force in confined compression of CSM model with the experimental results indicate the importance of collagen fibers' role in reducing the stresses applied to proteoglycan matrix in all cartilage depth. The findings of this study may have implications not only for developing progressive damage model of articular cartilage but also of potential ability to predict osteoarthritic cartilage behavior in different cartilage-related diseases.