Degradation of articular cartilage is a major common hallmark of different types of arthritis. Collagen type II is possibly the ideal marker of cartilage destruction. Basic information on biochemistry, structure, and degradation of collagen type II is provided in the introduction. Immunochemical markers indicative of degradation of collagen type II fall into three groups according to the localization of the particular epitope within the collagen molecule: (a) denaturation (hidden) epitopes localized to the triple-helical domain, (b) cleavage neoepitopes localized to the collagenase cleavage site, (c) epitopes localized to telopeptides. Currently most promising marker designated as CTX-II belongs to the group (c).

        Key words: collagen II, marker, cartilage degradation, immunoassay, osteoarthritis, rheumatoid arthritis