Objectives To introduce a comprehensive and reliable scoring system for the assessment of whole-knee joint synovitis based on contrast-enhanced (CE) MRI.
Methods Multicenter Osteoarthritis Study (MOST) is a cohort study of people with, or at high risk of, knee osteoarthritis (OA). Subjects are an unselected subset of MOST who volunteered for CE-MRI. Synovitis was assessed at 11 sites of the joint. Synovial thickness was scored semiquantitatively: grade 0 (<2 mm), grade 1 (2–4 mm) and grade 2 (>4 mm) at each site. Two musculoskeletal radiologists performed the readings and inter- and intrareader reliability was evaluated. Whole-knee synovitis was assessed by summing the scores from all sites. The association of Western Ontario and McMaster Osteoarthritis Index pain score with this summed score and with the maximum synovitis grade for each site was assessed.
Results 400 subjects were included (mean age 58.8±7.0 years, body mass index 29.5±4.9 kg/m2, 46% women). For individual sites, intrareader reliability (weighted κ) was 0.67–1.00 for reader 1 and 0.60–1.00 for reader 2. Inter-reader agreement (κ) was 0.67–0.92. For the summed synovitis scores, intrareader reliability (intraclass correlation coefficient ( ICC)) was 0.98 and 0.96 for each reader and inter-reader agreement (ICC) was 0.94. Moderate to severe synovitis in the parapatellar subregion was associated with the higher maximum pain score (adjusted OR (95% CI), 2.8 (1.4 to 5.4) and 3.1 (1.2 to 7.9), respectively).
Conclusions A comprehensive semiquantitative scoring system for the assessment of whole-knee synovitis is proposed. It is reliable and identifies knees with pain, and thus is a potentially powerful tool for synovitis assessment in epidemiological OA studies.
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Funding The MOST Study is supported by National Institutes of Health (NIH) grants from the National Institute on Aging to Drs Torner (U01-AG-18832), Nevitt (U01-AG-19069) and Felson (U01-AG-18820). NIH grants AR053161 and K23AR053855.
Competing interests AG is the president of Boston Imaging Core Lab, LLC (BICL), Boston, Massachusetts, a company providing radiological image assessment services. He is a shareholder of Synarc, Inc. and is a consultant to MerckSerono, Facet Solutions and Stryker. FWR, MDC and MDM are shareholders of BICL. None of the other authors have declared any possible conflict of interest.
Ethics approval This study was conducted with the approval of the institutional review board at Boston University School of Medicine.
Provenance and peer review Not commissioned; externally peer reviewed.