To date, there remains a need for highly selective MMP inhibitors and for better information on the disease-specific substrates, which could be therapeutically targeted as shown by recent studies with MMP-13 in osteoarthritis (Li et al., 2011) as well as for more efficient and reliable techniques to sensitively measure condition-specific MMP activity potential (not just MMP expression levels). This evidence concerns the gene MMP13 and osteoarthritis.