MMP13 and disease of the tendon: Several studies selected candidate genes on the basis of pre-existing association analyses for Achilles tendon ruptures (TNC, Col5A1, and MMP-3) [35–37], tendinopathies of the elbow (Col5A1) [38], ruptures of the posterior tibial tendon (MMP-1) [39] and matrix metalloproteinase genes MMP-1, MMP-2, MMP-3, MMP-9, MMP-13, TIMP-1 that are specifically expressed in torn rotator cuff.