Emphasis on OA-related mechanics has included the effects of traumatic joint injuries, such as rupture of the ACL (a,b), which leads to altered joint contact mechanics (c), initiation of degeneration of cartilage matrix (d) and accompanying changes to other joint hard and soft tissues, altered biomechanical properties of cells (e) and extracellular/pericellular matrices (f), and changes in specialized load bearing matrix molecules that can be quantified at the nanoscale (g). Images adapted from: (a,b) http://www.quincymedgroup.com/adam/dochtml/surgery; (c) Kindly provided by Dr. Guoan Li, Massachusetts General Hospital; (d) Johnson, DL, et al., Am. J. Sports Med. 26:409–414, 1998; (e) Ng, L, et al., J Biomechanics, 40:1011–1023, 2007; (f) Han, L, et al., Annu Rev Mater Res, 41:133–168, 2011; (g) Lee, H-Y, et al., Osteoarthritis Cartilage, 18:1477–1486, 2010.