The viscoelastic behaviors of articular cartilage, such as stress-relaxation, depend on its biphasic material properties. These material properties are directly related to the composition and the structure of the tissue . It is known there are four zones within the tissue, i.e. superficial zone, middle zone, deep zone and calcified zone. These zones can be identified, from the articular surface to the subchondral bone, according to the morphological appearances of the chondrocytes and the collagen ultrastructure within its organic matrix. This zonal organization appears to be related to the inhomogeneous biphasic material properties of the tissue.