Load partitioning influences the mechanical response of articular cartilage.

The role of the fluid within articular cartilage as affected by the load-sharing mechanism and its potential, beneficial effects were assessed with the u-p finite element method. The mechanical behavior of cartilage as it covers the surface of a diarthrodial joint was evaluated when the partitioning of an applied stress to the solid and fluid phases of the tissue was varied. Comparisons were made in the response of the cartilage when 0%, 25%, 50%, or 75% of the applied stress was supported by the fluid at the surface. Substantial changes in the behavior of the tissue were observed for each load case. As the fluid sustained a larger portion of the applied stress, several parameters were affected; the fluid pressure within the cartilage layer remained at a higher value, the stress and strain generated in the solid matrix decreased while the compression of the cartilage layer decreased. These findings indicate that an increased load-partitioning to the fluid phase in cartilage may perform the function of shielding the solid matrix from excessive stresses. This could also potentially alter the mechanical environment around the chondrocytes, influencing metabolic activity and homeostasis.