The matrix metalloproteinase (MMP) enzymes, in particular the collagenases interstitial collagenase (MMP-1), neutrophil collagenase (MMP-8), and collagenase-3 (MMP-13), which can all be produced by chondrocytes, have been proposed to be the main enzymes accountable for cleaving type II collagen during arthritis [87], [88]. This evidence concerns the gene MMP1 and arthritic joint disease.