Intra- and Extrafibrillar Fluid Exchange in the Disc

The mechanical properties of the intervertebral disc are regulated by its biochemical composition. With ageing and degeneration the water content of the disc decreases which highly influences the mechanical properties. The disc is subjected to a combination of elastic, viscous and osmotic forces. Osmotic forces are shown to have a major impact on crack opening and propagation [1] and on cellular responses [2]. In particular, osmosis provides an understanding on why fissures in the degenerating disc are so poorly related to external mechanical load [3].