MMP9 and rheumatoid arthritis: The lack of association with RA of seven of the regulatory SNPs in ECM proteases was somehow unexpected because they affect proteases with a recognized role in RA [7-9] and because the size of the study allowed for detection of modest effects (for example, the post hoc power to detect an excess of the T allele of the MMP9 SNP was 87% for a risk ratio of 1.2).