Magnetic resonance imaging-based inflammation scores shown separately for the three study groups. (A) Magnetic resonance imaging (MRI) inflammation scores (synovitis plus bone marrow edema (BME)). (B) Synovitis scores. (C) Bone marrow oedema scores. The three study groups are the symptom-free controls, the anticitrullinated peptide antibody (ACPA)–negative arthralgia patients and the ACPA-negative rheumatoid arthritis (RA) patients, based on the 1987 criteria for RA . The scores presented are for all participants individually (dots) and the median scores per group (horizontal lines). The red dots indicate the ACPA-negative patients who developed clinically detectable arthritis during the median follow-up of 9 months. The y-axes are split because RA patients had higher scores than the symptom-free controls and ACPA-negative arthralgia patients. The presented P-values were obtained by comparing the scores of ACPA-negative arthralgia patients and symptom-free controls. All P < 0.001 for differences in MRI-based inflammation, synovitis and BME scores between the three groups.