Fig. 6. The fibrous and mineral architectures of the tendon enthesis provide multiscale toughening mechanisms for a resilient attachment between tendon and bone.

Enthesis toughness is achieved over multiple length scales through unique fibrous and mineral architectures. At the millimeter-length scale, (A) the fibrous architecture of the tendon enthesis allows for fiber recruitment and reorientation to optimize toughness over strength across a range of loading directions. At the micrometer-length scale, (B) the enthesis actively adapts its mineral architecture to maintain its strength along the axis of loading. At the micrometer-to-nanometer–length scale, (C) a spatial gradient in mineral across the enthesis reduced stress concentrations (16). At the nanometer-length scale, (D) collagen damage localization protects against damage prorogating to higher length scales. Created with Biorender.com.