Fig. 2.

Synovial fluid concentrations of C4d, C3bBbP and soluble terminal complement complex (sTCC). a Box plots with subjects ordered by the diagnostic groups: reference, osteoarthritis (OA), rheumatoid arthritis (RA), pyrophosphate arthritis (PPA), and knee injuries split into recent injury and old injury. b Knee injury samples ordered by days after injury in subgroups of 24–46 subjects (Table 1), showing recent injury and old injury groups. Boxes show the quartiles (median, 25th and 75th percentiles) with error bars and whiskers for the 10th and 90th percentiles. The quartiles of the reference group are extended as thin horizontal lines in both panels for comparison. Statistically significant group differences, determined by Mann-Whitney U test, versus the reference group are indicated by asterisks (*) and are presented in Additional file 1: Table S1. CAU Complement activation units