To analyse the relationship between the levels of urinary biochemical markers of type II collagen degradation and the clinical and radiological severity and progression of knee osteoarthritis (OA).
Seventy-five patients with primary knee OA were included in this 3-year follow-up study. Mean joint space width (JSW) of the medial compartment of the femorotibial joint was measured with a computer assisted method on standardized radiographs taken at baseline and after a 3-year follow-up. Pain, stiffness, and physical function subscales of the Western Ontario and McMaster Universities (WOMAC) were assessed at the same time points. Type II collagen peptides Coll 2-1 and Coll 2-1 NO(2), as well as pyridinoline (Pyr) and deoxypyridinoline (D-Pyr) were measured in urines at baseline, after 1 year and 3 years, with specific immunoassays.
At baseline, significant correlations were found between the urinary Coll 2-1 and Coll 2-1 NO(2) levels and the global WOMAC score (Coll 2-1: r=0.28, P=0.01; Coll 2-1 NO(2): r=0.27, P=0.02) and its subscales for pain (Coll 2-1: r=0.27, P=0.01; Coll 2-1 NO(2): r=0.30, P=0.01) and function (Coll 2-1: r=0.29, P=0.01; Coll 2-1 NO(2): r=0.27, P=0.02). Pyr and D-Pyr levels were not significantly correlated with the WOMAC scores. One-year change in Coll 2-1 and Coll 2-1 NO(2) urinary levels were negatively correlated with a 3-year change in JSW (Coll 2-1: r=-0.31, P=0.03; Coll 2-1 NO(2): r=-0.31, P=0.03), indicating that an increase of Coll 2-1 or Coll 2-1 NO(2) over 1 year is predictive of subsequent joint space narrowing. Neither Pyr nor D-Pyr was correlated with radiological OA progression.
At baseline, Coll 2-1 and Coll 2-1 NO(2) urinary levels were indicative of the clinical activity of knee OA and the increase of these peptides over 1 year was predictive of the radiological progression of knee OA.