**2.2.2 Extraction of ADM in joint tissues**

For measuring ADM levels of acquired joint fluids, samples were acidified with acetic acid to a final concentration of 1.0 M and centrifuged at 3000 rpm for 5 min, while synovium and cartilage specimens were acidified with acetic acid to a final concentration of 1.0 M and boiled for 10 min to inactivate proteases. The samples were then homogenized and centrifuged for 90 min at 12,000 rpm. The supernatant of samples was applied to a Sep-Pak C18 cartridge (Millipore-Waters, Milford, MA, USA). After the cartridge was washed with 10% CH3CN in 0.1% trifluoroacetic acid, the absorbed materials were eluted with 50% CH3CN in 0.1% trifluoroacetic acid. The eluted samples were dried by speed vacuum, freeze-dried and stored at –30°C until assayed.
