Fig. 2

Unsupervised classification discriminates controls from knee osteoarthritis (KOA) patients. A Clustergram showing the Z-scores of variables (as indicated in rows) of the subjects (as indicated in columns), color-coded as indicated. Hierarchical clustering of the variables was performed in ClustVis (https://biit.cs.ut.ee/clustvis/) using the Ward method [52]. Distances of the bonds on the left side to the color-coded clustergram grow with the dissimilarity between variables across subjects, while the distances of the bonds shown on the top increase with the dissimilarity between subjects across the space of variables. Diagnosis group (1 = control; 2 = KOA) and sex of the subjects (1 = male; 2 = female) were not used for clustering. B Scatter plot showing the controls and KOA patients as single dots, projected in the space of the two major principal components (PC1–2). One KOA patient was not included in these analyses due to missing values of cartilage thickness