Load sharing in articular cartilage

The load sharing of an applied load at the articular surface between the solid and fluid phases of articular cartilage in diarthrodial joints was investigated.;In the experimental component of this effort, the in situ mechanical conditions of cartilage in the articulated knee were quantified during joint loading. Six porcine knees were subjected to a 445 N compressive load while cartilage deformations and contact pressures were measured. Results showed that the medial side of the lateral femoral condyle had higher contact pressures as well as deformations.;In the modeling component of this effort, the u-p finite element model was used to simulate the loading of six separate porcine knee joints and to predict surface deformations of the cartilage layer on the lateral femoral condyle. It appeared from the comparison that approximately 75% of the applied load was borne by the fluid phase at the articular surface under this loading regime. It appeared that the solid phase was shielded from the total applied stress on the articular surface by the fluid and could be a reason for the excellent durability of the tissue under the demanding conditions in a diarthrodial joint.;In the last phase of the study, the in situ mechanical environment of repair and normal cartilage in articulated porcine knees were compared during joint loading. Repair cartilage was grown in lateral femoral condyles of Yorkshire pigs by creating 5mm defects to bleeding bone in both lateral femoral condyles and allowing healing for 12 weeks. Normal and repair knees were subjected to a 445 N compressive load while cartilage deformations and contact pressures were measured. To begin to correlate the pressures and resulting deformations, the intrinsic material properties of normal and repair cartilage on the lateral condyle were obtained from indentation tests. Experimental measurements in conjunction with theoretical predictions using the u-p finite element model were used to determine the extent of load supported by the fluid phase of cartilage at the articular surface for both normal and repair tissues. Results showed that, for small defects, although some differences in applied pressure on the cartilage surface and deformations of the cartilage layer existed between the normal and repair knees, the differences in load sharing between the solid and fluid phases were insignificant between normal and repair tissues. (Abstract shortened by UMI.).