Finally, we propose to characterize the repertoire of specific active proteases in the SF of arthritic patients concomitantly to the use biomarkers (neoepitopes of cleaved collagens) previously associated with cartilage destruction and synthesis to identify new targets for the development of protease inhibitors for the treatment of arthritis. Furthermore, our project will also provide the opportunity to test the potential of measuring the net proteolytic activity by Fluorescent-Activated Substrate Conversion as a method of monitoring disease activity and treatment efficiency in a clinical setting.