The present invention provides a composition comprising an antibody or fragment thereof against oxidized Collagen II (CII) in which the antibody or fragment thereof is conjugated to a pharmaceutically active moiety. The invention also provides a composition comprising an antibody or fragment thereof against oxidized Collagen II (Gil) and a detectable label. The invention further provides the use of such compositions in medicine, in particular for the treatment of an arthropathy, and in methods of diagnosis.