Impact of Sustained Synovitis on Knee Joint Structural Degeneration: 4‐Year MRI Data from the Osteoarthritis Initiative

Background Synovial inflammation is a risk factor for osteoarthritis (OA). But to date, there is limited information on how inflammation impacts progression of knee OA. Purpose To investigate how sustained synovitis, assessed with semi‐quantitative magnetic resonance imaging (MRI) scores, impacts progression of knee degenerative changes over 4 years. Study Type Retrospective cohort study. Subjects In 249 participants ( N = 132 women [53%]), from the Osteoarthritis Initiative (OAI) two definitions for synovitis were used resulting in two groups of participants with sustained synovitis at baseline, 2‐year, and 4‐year follow‐up ( N = 80 and N = 132), and two groups without synovitis at all three time points ( N = 81 and N = 47). Field Strength/Sequence 3 T intermediate‐weighted (IW) turbo spin‐echo (TSE) sequence and three‐dimensional (3D) dual‐echo steady‐state (DESS) sequence. Assessment Synovitis was scored semi‐quantitatively using the Anterior Cruciate Ligament Osteoarthritis Score (ACLOAS), MRI Osteoarthritis Knee Score (MOAKS), and synovial proliferation score (SPS). Two MRI‐based definitions of synovitis were used: (i) score ≥2 based on cumulative score of MOAKS and ACLOAS, and (ii) score ≥3 based on the cumulative score of ACLOAS, MOAKS, and SPS. Changes in structural abnormalities from baseline to year 4 measured using the whole‐organ MRI score (WORMS) were defined as outcomes. Statistical Tests Linear regression models were used to compare the differences in longitudinal changes in WORMS scores between participants with and without sustained synovitis for each definition of sustained synovitis. A P ‐value of <0.05 was considered statistically significant. Results Significantly higher rates of progression were found in participants with synovitis for patellar (Beta coeff. = 0.29) and medial tibial cartilage abnormalities (Beta coeff. = 0.29) for definition (i). For definition (ii), patellar (Beta coeff. = 0.36) and medial femoral cartilage (Beta coeff. = 0.30) abnormalities demonstrated significant differences. Data Conclusion Greater progression of structural degenerative disease was observed in individuals with sustained synovitis compared to those without sustained synovitis, suggesting that sustained synovitis is associated with progressive OA. Level of Evidence 3 Technical Efficacy Stage 2