Fig. 1

Tukey’s box-and-whisker plots showing the concentration of serum COMP (a), HA (b), and PIICP (c) by OA severity (Kellgren-Lawrence (KL) score). Patients with late osteoarthritis (LOA) were divided into the mild (KL of 2 in at least one knee) and severe (KL of 3 and 4 in at least one knee) groups. Data are presented as medians (IQR). Kruskal Wallis test followed by Dunn’s multiple comparisons test was used for statistical analysis. Only statistically significant differences are shown and indicated with asterisks: ** p < 0.01, ****p < 0.0001. The number of participants in each K&L score is shown in parentheses