What gives tendons and ligaments their tensile strength?

Tendons and ligaments derive their remarkable tensile strength primarily from their composition of collagenous fibers, specifically type I collagen. These proteins form the structural scaffolding of the connective tissue, providing high resistance to stretching and enabling the tissues to withstand the mechanical stresses imparted by force and movement.123

In addition to this composition, the tensile strength of tendons is attributed to a specific hierarchical organization. These tissues are structured with a parallel orientation of fibers, which are organized into primary, secondary, and tertiary bundles. This arrangement allows them to effectively transmit mechanical forces, such as those generated by muscle contraction. While elastin fibers are also present in ligaments to provide limited flexibility, it is the dense, organized network of collagen that serves as the primary source of their strength and resistance to tension.123