An estimated 27 million Americans suffer from osteoarthritis (OA). Symptomatic OA is often treated with total knee replacement, a procedure which is expected to increase in number by 673% from 2005 to 2030, and costs to perform total knee replacement surgeries exceeded $11 billion in 2005. Subject-specific modeling and finite element (FE) predictions are state-of-the-art computational methods for anatomically accurate predictions of joint tissue loads in surgical-planning and rehabilitation. Knee joint FE models have been used to predict in-vivo joint kinematics, loads, stresses and strains, and joint contact area and pressure. Abnormal cartilage contact pressure is considered a risk factor for incidence and progression of OA. For this study, three subject-specific tibiofemoral knee FE models containing accurate geometry were developed from magnetic resonance images (MRIs). Linear (LIN), Neo-Hookean (NH), and poroelastic (PE) cartilage material models were implemented in each FE model for each subject under three loading cases to compare cartilage contact pressure predictions at each load case. An additional objective was to compare FE predictions of cartilage contact pressure for LIN, NH, and PE material models with experimental measurements of cartilage contact pressure. Because past studies on FE predictions of cartilage contact pressure using different material models and material property values have found differences in cartilage contact pressure, it was hypothesized that different FE predictions of cartilage contact pressure using LIN, NH, and PE material models for three subjects at three different loading cases would find statistically significant differences in cartilage contact pressure between the material models. It was further hypothesized that FE predictions of cartilage contact pressure for the PE cartilage material model would be statistically similar to experimental data, while the LIN and NH cartilage material models would be significantly different for all three loading cases. This study found FE and experimental measurements of cartilage contact pressure only showed significant statistical differences for LIN, NH, and PE predictions in the medial compartment at 1000N applied at 30 degrees, and for the PE prediction in the medial compartment at 500N applied at 0 degrees. FE predictions of cartilage contact pressure using the PE cartilage material model were considered less similar to experimental data than the LIN and NH cartilage material models. This is the first study to use LIN, NH, and PE material models to examine knee cartilage contact pressure predictions using FE methods for multiple subjects and multiple load cases. The results demonstrated that future subject specific knee joint FE studies would be advised to select LIN and NH cartilage material models for the purpose of making FE predictions of cartilage contact pressure.

To extend the use of computational techniques like finite element analysis to clinical settings, it would be beneficial to have the ability to generate a unique model for every subject quickly and efficiently. To this end, we previously developed two mapped meshing tools that utilized force and displacement control to map a template mesh to a subject-specific surface. This work is an extension of those methods; the objective of this study was to map a template block structure, common to multi-block meshing techniques, to a subject-specific surface. The rationale was that the blocks are considerably less refined and may be readily edited, thereby yielding a mesh of high quality in less time than mapping the mesh itself. In this paper, the versatility and robustness of the method was verified by processing four datasets. The method was found to be robust enough to cope with the variability of bony surface size, spatial position and geometry, producing building block structures that generated meshes comparable to those produced using building block structures that were created manually.