Fig. 1.

Quasi-static mechanical behavior of tendon and ligament and the macro- and microscale. (a) Representative stress–strain curves for human MCL strained at a rate of 10 mm/s, demonstrating the high degree of anisotropy observed in ligament and tendon. Linear moduli during longitudinal (axial) and transverse tensile tests were reported to be 332.15±58.27 MPa and 11.02±3.57 MPa, respectively (Adapted with permission from Quapp and Weiss [7]. Copyright 1998 by American Society of Mechanical Engineers). (b) Representative stress–strain curves and tangent lines (used to calculate toe and linear moduli) for the human ACL and patellar tendon strained at a rate of 100%/s. Linear moduli for ACL and patellar tendon in males were reported to be 128±25 MPa and 479±141 MPa, respectively (Adapted with permission from Chandrashekar et al. [8]. Copyright 2008 by Elsevier). (c) Collagen fibrils uncrimp in the toe region (Adapted with permission from Miller et al. [9]. Copyright 2012 by Elsevier), while fibril sliding, demonstrated by shearing of a grid photobleached onto the ECM (Adapted with permission from Cheng and Screen [10]. Copyright 2007 by Springer Nature), is the predominant mechanism of tissue deformation at high strains in the linear region.