Figure 5.

Molecular mechanism of cartilage dynamic mechanical behavior is governed by electrostatic and solid–fluid interactions between GAG chains. (a) Cross section of neighboring GAG chains is shown. The mechanical function of aggrecan in quasi-static loading is controlled by the electrostatic and steric interaction between GAG side chains. (b) In dynamic loading, as it happens during fast rate of loading such as in running, solid–fluid interaction determines the mechanical functions of aggrecan by viscous drag effects and fluid pressurization. (c) The fluid pressurization due to solid–fluid viscous interaction (simulated and shown by the blue line) results in self-stiffening, which is the increase in dynamic modulus by loading frequency (experimentally measured and shown by black line; the shade around the black line is the 95% confidence interval).