Failure in cartilaginous tissues

Cartilaginous tissues high load bearing capacity is explained by osmotic prestressing putting the collagen fiber reinforcement under tension and the proteoglycan gel under compression. The osmotic forces are boosted by a further 50 % by the affinity of the collagen with the aquous solution. The high osmolarity of the tissue provides a strong protection against crack propagation. Degeneration results in degradation of the prestressing and hence to internal damage. 3D visualisation of a discontinuity of the collagen struction of the disc is achieved by confocal laser scanning microscopy. The collagen and the cells are visualised by means of a two fluorescent probes. The discontinuity is shown to open and close depending on the osmotic loading of the tissue. The process of internal degradation is presently modelled using Partition of Unity method in a osmotically prestressed fluid-solid mixture.