The relationship between synovitis and erosions in rheumatoid arthritis

If clinically evident synovitis causes erosions, then the two should behighly correlated within individual joints. Separate hand joints (total2064) were examined for the presence of synovitis (the simultaneouspresence of soft-tissue swelling and tenderness) on nine occasions over 2yr. The cumulative synovitis score was compared to the change in the Larsenscore over the same period. The mean correlation between synovitis anderosion progression was r = 0.248 (explained variance = 6%). Of the 216joints which showed progressive X-ray damage, 44% had a cumulativesynovitis score of < 3. When all the joints of one hand were takentogether, the correlation was increased to r = 0.418 and for all the jointsof both hands taken together it was further increased to r = 0.424. Theseresults argue against there being a direct causal relationship betweenclinically inflamed synovitis and erosions in rheumatoid arthritis, andquestion the assumption that erosions and the signs of synovitis representthe same pathological process.