Elucidation of the relationship between synovitis and bone damage: A randomized magnetic resonance imaging study of individual joints in patients with early rheumatoid arthritis

Objective To simultaneously image bone and synovium in the individual joints characteristically involved in early rheumatoid arthritis (RA). Methods Forty patients with early, untreated RA underwent gadolinium‐enhanced magnetic resonance imaging (MRI) of the second through fifth metacarpophalangeal joints of the dominant hand at presentation, 3 months, and 12 months. In the first phase (0–3 months), patients were randomized to receive either methotrexate alone (MTX) or MTX and intraarticular corticosteroids (MTX + IAST) into all joints with clinically active RA. The MTX‐alone group received no further corticosteroids until the second phase (3–12 months), when both groups received standard therapy. Results In the first phase, MTX + IAST reduced synovitis scores more than MTX alone. There were significantly fewer joints with new erosions on MRI in the former group compared with the latter. During the second phase, the synovitis scores were equivalent and a similar number of joints in each group showed new erosions on MRI. In both phases, there was a close correlation between the degree of synovitis and the number of new erosions, with the area under the curve for MRI synovitis the only significant predictor of bone damage progression. In individual joints, there was a threshold effect on new bone damage related to the level of synovitis; no erosions occurred in joints without synovitis. Conclusion In early RA, synovitis appears to be the primary abnormality, and bone damage occurs in proportion to the level of synovitis but not in its absence. In the treatment of patients with RA, outcome measures and therapies should focus on synovitis.