(A) Schematic representation of a proteoglycan aggregate solution domain (left) and the repelling forces associated with the fixed charge groups on the glycosaminoglycans (right). These repulsive forces cause the aggregate to assume a stiffly extended conformation, occupying a large solution domain. (B) Applied compressive stress decreases the aggregate solution domain (left), which in turn increases the charge density and thus the intermolecular charge repulsive forces (right) (Reproduced with permission from Mow et al.²²² .)