The microhardness of articular cartilage.
The standard metallurgical technique of microhardness testing was useful for investigations on the physical properties of articular cartilage. The problem of visco-elasticity of the cartilage was overcome by using a brittle lacquer coating as a memory device. The surface layer was the hardest plane when the superficial layer was intact. Removal of the superficial layer however, made this plane the softest. There was no variation in hardness with depth. The plane at right angles to the vector of movement of the joint was harder than the plane parallel to the vector of movement. This indicates the presence of a secondary fiber system in the middle layer of articular cartilage. The fibers in this system run predominantly at right angles to the direction of motion of the joint.