Page "Tendon" Paragraph 10

The proteoglycan components of tendons also are important to the mechanical properties.

While the collagen fibrils allow tendons to resist tensile stress, the proteoglycans allow them to resist compressive stress.

The elongation and the strain of the collagen fibrils alone have been shown to be much lower than the total elongation and strain of the entire tendon under the same amount of stress, demonstrating that the proteoglycan-rich matrix must also undergo deformation, and stiffening of the matrix occurs at high strain rates.

These molecules are very hydrophilic, meaning that they can absorb a large amount of water and therefore have a high swelling ratio.

Since they are noncovalently bound to the fibrils, they may reversibly associate and disassociate so that the bridges between fibrils can be broken and reformed.

This process may be involved in allowing the fibril to elongate and decrease in diameter under tension.