ABSTRACT
Articular cartilage is a porous medium, structured by collagen fibers and saturated by an electrolyte, with water as solvent and metallic ions as solutes. Charged macromolecules, the proteoglycans, intermingled with collagen fibers, give rise to electro-chemomechanical couplings that allow moderate deformation to take place, and ensure an optimal adaption of the tissue to physiological loads. In other words, the chemical and mechanical loadings are performed with characteristic times much larger than the times characterizing the material response. For unloaded cartilage under physiological salinity, intrafibrillar water represents up to 25% of total water, the extrafibrillar water furnishing the complement. The latter can be moved by mechanical loading and osmosis with water external to the cartilage.
