Abstract
The articular cartilage has a remarkable ability, to soften and spread loads evenly onto the subchondral bone. Smooth joint movement with low friction can be performed, thanks to this "elasto hydrodynamic lubrication". We have examined the mechanical properties of the articular cartilage of rat and rabbit tibia using an experimental apparatus with which the indentation deformation of the cartilage can be measured through micro-transducer. Time-dependent deformation of the articular cortilage under constant loading or repeated loading can be measured with this apparatus. The articular cartilage showed instantaneous deformation just after the application of the load, gradual time-dependent deformation, which is called "creep deformation", and instantaneous recovery of deformation after removal of the load, followed by gradual recovery. Such deformation was, however, not observed, when the indentation test was performed in air rather than in saline. When the indentation test was performed, in silicone oil, morphological changes of the articular surface could be observed microscopically. We could observe the exudation of fluid from the articular cartilage, at the time of indentation, and the simultaneous disappearance of the fluid upon removal of the load. The fluid occupies over 70 percent of the articular cartilage. We could confirm that the exudation and inbibtion of the fluid from and into the articular cartilage was closely correlated with the deformation and with the lubrication mechanism of the articular cartilage. We also examined the deformation behavior of the articular cartilage under repeated loading. These findings should be of great help in the development of a new biomaterial which has all the fine mechanical properties of the articular cartilage and which can be used as artificial articular cartilage.
