The invention relates to the identification and selection of novel biomarkers and the identification and selection of novel biomarker combinations which are differentially expressed in osteoarthritis and/or in a particular stage of osteoarthritis, as well as a means of selecting the novel biomarker combinations. The measurement of expression of the products of the biomarkers and combinations of biomarkers demonstrates particular advantage in one or more of the following: (a) diagnosing individuals as having arthritis, (b) differentiating between two stages of osteoarthritis (OA) and (c) diagnosing individuals as having a particular stage of OA. Polynucleotides and proteins which specifically and/or selectively hybridize to the products of the biomarkers are within the scope of the invention as are kits containing the polynucleotides and proteins and the use of the polynucleotides and proteins. The biomarker products can be used to identify therapeutic targets for osteoarthritis, and compounds that bind and/or modulate gene activity.