The aim ojthis study was to evaluate serum PIIANP and urinary CTXII as a parwneters oj type II collagen synthesis and degradation. respectively. in patients with OA knees and to investigate whether the use oj these two molecular markers could predict the progression ojjoint damage evaluated by radiography during a period oj3 years. Sixty patients had symptomatic primary knee OA ojKellgren-Lawrence (K-L) grade HII and met ACR criteria. These patients were evaluated prospectively Jor 3 years. Serum PIIANP and urinary CTX-II levels were measured by ELISA at baseline and at study end and their levels compared according to the changes injoint space width (JSW). K-L grade and WOMAC index, over 3 years. Also, we assessed the diagnostic value oj those molecular markers and their performanceJor prediction ojradiological progression. Serum and urinary levels also compared with 40 matched healthy subjects as a control group. There were signifICant decrease in the baseline serum PllANP (P