Since the discovery of a gene encoding ADAMTS1 in 1997 [1], a total of 19 similar genes have been found in the human genome [2], numbered ADAMTS1-20; there is no ADAMTS11 because early reports of an ADAMTS11 [3] were later found to describe ADAMTS5. Many of these genes have been implicated in a variety of diseases, including connective tissue disorders [4], cancer [5-7], osteoarthritis [3,8], and possibly Alzheimer's disease [6,9]. Here, ADAMTS5 is linked to osteoarthritis.