Fig. 2

Association between WOMAC pain and the CTX-II biomarker of cartilage turnover. Association between geometric mean concentration of uCTX-II (creatinine corrected) and pain intensity in the full study population (N = 1241) and by gender (male: N = 399, female: N = 842). Groups of pain intensity consist of tertiles of WOMAC pain sub-score intensity of each knee (ranging from 0 to 100), resulting in six groups ranging from mild pain in both knees (“Low-Low”) to severe pain (“High-High”) in both knees. Error bars represent ± 1sem range. “a” p < 0.05 compared to the “Low-Low” group. WOMAC, Western Ontario and McMaster Universities Osteoarthritis Index