Scatterplots depicting synovitis, defined as synovial perfusion by maximal systolic colour fraction and by magnetic resonance imaging using the rheumatoid arthritis magnetic resonance imaging score for synovitis vs. synovial explant release after 72 hours in culture. The statistically significant plots are shown. For the remaining plots, see Additional file 3. Rheumatoid arthritis magnetic resonance imaging scores (RAMRIS) for synovitis are shown in (a) and (b). (a) Interleukin 6 (P = 0.04, approximate ρ = 0.50). (b) Macrophage inflammatory protein 1β (P = 0.02, approximate ρ =0.63). Maximal systolic colour fraction (CFmax) values are shown in (c) and (d). (c) Monocyte chemoattractant protein 1 (P = 0.009, approximate ρ = 0.41). (d) Macrophage inflammatory protein 1β (P = 0.02, approximate ρ = 0.38).