[Changes in the visco-elastic properties of the articular cartilage incubated in various kinds of liquid].

The purpose of our experiment was to investigate the way in which the visco-elastic properties of the articular cartilage of a loading joint responded to various liquid environments. Using articular cartilage extracted from the femoral head of a cow, we examined the viscoelasticity of the articular cartilage under a fixed load while it was immersed in distilled water, isotonic salt water, hypertonic salt water, and in hyaluronic acid. A stainless steel rod with a diameter of 1.5 mm was applied directly to the articular cartilage (weighing 25, 50 and 100 grams) and the resultant visco-elastic curves were measured. Results showed that the deformation change to the cartilage was greatest while it was immersed in hypertonic salt solution and smallest while immersed in distilled water. Secondly, when immersed in hyaluronic acid solution, the change in deformation proved to be greater when the solution was denser and the molecular weight heavier and the hyaluronic acid could not penetrate into the cartilage matrix and remained at the surface. These results demonstrated that the visco-elastic property of the articular cartilage was affected not only by the varying osmotic pressures on the internal parts of the cartilage, but also on the density of the solution surrounding the cartilage and on the different water retainability of that cartilage.