Poromechanical Modeling of Porcine Knee Joint Using Indentation Map of Articular Cartilage

The knowledge of site-specific properties of articular cartilage of a knee joint may be important for understanding the onset of cartilage degeneration in the knee. Few earlier studies have focused on the rate-dependent poromechanical response of knee joints to site-specific material properties across the joint. The objective of the present study was to develop a methodology to implement the in-situ cartilage mechanical properties in an anatomically accurate computational model of the porcine knee joint. Fresh porcine knee joints were used to reconstruct the knee geometry using magnetic resonance imaging. An automated indentation test was used to determine the site-specific cartilage properties. The variations of the recorded reaction forces over different sites were not solely due to nonuniform cartilage thickness. The nonfibrillar matrix and fibrillar network of the tibial cartilage had higher stiffness compared to that of the femoral cartilage as determined in the data fitting procedure. Considering the site-specific properties in finite element simulations, the force-compression relationship of the joint was determined by both compression-magnitude and compression-rate. The preliminary results indicated that a realistic implementation of site-specific tissue properties may be necessary for understanding the load distribution in the joint. The methodology will be further refined and tested.

Articular cartilage, Fibril-reinforced model, Finite element, Image based modeling, Indentation test