There are two subgroups of metalloproteinases, metalloexopeptidases, and metalloendopeptidases. Metalloproteinases have an enzymatic site that requires a metal ion (often zinc) for activity. For example, cartilage contains two families of metalloproteinases, namely ADAMTSs and MMPs. Because the MMPs and ADAMTSs play major roles in the degradation of cartilage extra-cellular matrix, several MMPs and ADAMTSs are candidate targets for disease modification.