Until the '90s, research in Biomechanics and Biorheology mainly focused on tissues and cell priorities, so as to identify the bioclinical problems linked to the rheology properties of cells and tissues or to develop substitutes. Advances in molecular biology and new knowledge in cellular biology over the last ten years have given access to a more physiological approach to the effects of stress on cells and tissues. All cells and tissues in the body are constantly exposed to physical forces and these forces can influence the biological behaviour of cells and hence affect gene expression, phenotype, paracrine or autocrine factor secretion and metabolism. These mechanically-induced cellular alterations may constitute major factors affecting the physiological and pathological condition of the organism. This new approach could be called Mechanobiology because it requires, in parallel with theoretical concept development at the cellular level, the use of molecular biology methods to identify the various steps or stages whereby changes are brought about by the mechanical forces permanently applied to cells and tissue. This book focuses on cartilage and chondrocytes, which are the cells particularly subject to wide range pressure stress.