Prognostic ability of key markers for separating healthy non-progressors from early progressors. Early progressors were defined by whether the KL score increased from a baseline score of 0. For each marker, the population was divided into quartiles and each quartile was compared with the lowest quartile in terms of the odds ratio (OR) for predicting the progressors. Each OR is given with the 95% confidence interval and with the significance level: *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001. Cartilage longevity-tib proved superior to the individual markers (P < 0.05) except for roughness/homogeneity (P = 0.2/0.3) with OR of 20.0 for the highest quartile. JSW = joint space width; uCTX-II, urinary marker of collagen type II C-telopeptide fragment.