Poro-viscoelastic mechanical characterization of healthy and osteoarthritic human articular cartilage.

Articular cartilage serves an important mechanical function in the human body. For the design of implants for cartilage repair after injury or disease, it is key to thoroughly understand the unique mechanical properties of the native tissue. Here, we use multimodal mechanical testing combined with poro-viscoelastic modeling, finite element simulations, and histology to characterize the region-specific macroscopic large-strain mechanical properties of healthy and osteoarthritic human articular cartilage as well as their relation to the underlying microanatomy. We individually characterize tissue from medial and lateral sides, respectively, of the human femoral condyle and tibial plateau. Our results show that there are no significant differences between the medial and lateral sides, but tissue from the tibial plateau is slightly softer than tissue from the femoral condyle. Osteoarthritis leads to a significantly softened mechanical response, which correlates with corresponding microstructural changes. Through the presented combination of experiments and poro-viscoelastic material parameter identification for healthy and osteoarthritic cartilage, we confirm a reduction in stiffness and an increase in permeability due to the disease. The parameters can be valuable for future finite element simulations of the knee joint The presented results will help guide the design of implants that are able to restore cartilage structure and function, bridging biomechanics and regenerative medicine for osteoarthritis treatment.