MAGNETIC-RESONANCE IMAGING-DETERMINED SYNOVIAL-MEMBRANE AND JOINT EFFUSION VOLUMES IN RHEUMATOID-ARTHRITIS AND OSTEOARTHRITIS - COMPARISON WITH THE MACROSCOPIC AND MICROSCOPIC APPEARANCE OF THE SYNOVIUM

Objective. To evaluate the relationship between synovial membrane and joint effusion volumes determined by magnetic resonance imaging (MRI) and macroscopic and microscopic synovial pathologic findings in patien ts with rheumatoid arthritis (RA) and osteoarthritis (OA). Methods. Sy novial biopsies were performed, and macroscopic grades of synovitis as signed, at preselected knee sites during arthroscopy or arthrotomy in 17 knees with RA and 25 with OA, Synovial inflammation and 9 separate tissue characteristics were graded histologically. Synovial membrane a nd joint effusion volumes were determined by preoperative MRI, enhance d with intravenous gadopentetate dimeglumine. Results. MRI-determined synovial membrane volumes were correlated with the overall histologic assessment of synovial inflammation (Spearman's sigma = 0.55, P < 0.00 1), with fibrin deposition, with subsynovial mononuclear and polymorph onuclear leukocyte infiltration (sigma = 0.51-0.59), and less signific antly with macroscopic synovitis, vessel proliferation, and granulatio n tissue formation (sigma = 0.40-0.42), No correlation with synovial l ining multiplication, perivascular edema, villous formation, or fibros is was found (sigma < 0.30). Conclusions. MRI-determined synovial volu mes are correlated with synovial inflammatory activity, Synovial volum es probably mainly reflect the mass of cell-infiltrated, vascularized subsynovial tissue, but may also be influenced by the cumulative synov ial proliferative activity, MRT-determined synovial membrane and effus ion volumes may be sensitive makers and/or predictors of disease activ ity and treatment outcome in RA.