The association between quadriceps strength and synovitis in knee osteoarthritis: an exploratory study from the Osteoarthritis Initiative

The aim of this study was to explore the association between quadriceps strength and synovitis in the knee osteoarthritis (KOA).This study was derived from the Osteoarthritis Initiative (OAI) cohort which recruited adults with or at risk of KOA. Knees with complete records of isometric quadriceps strength, effusion-synovitis and Hoffa-synovitis assessments were included. Quadriceps strength was measured isometrically at baseline. Effusion-synovitis and Hoffa-synovitis were measured using Magnetic Resonance Imaging Osteoarthritis Knee Score (MOAKS) at baseline, 1-year and 2-year follow-ups. Generalized estimating equations were used to analyze the associations of baseline quadriceps strength with the effusionsynovitis and Hoffa-synovitis changes in multivariable analyses. Additionally, analyses were stratified on synovitis-driven inflammatory phenotype.1513 knees were included in this study. 61.0% of the subjects were female, with an average age of 61.9 years and mean BMI of 29.4 kg/m2. In the whole population, baseline quadriceps strength was negatively associated with the baseline effusion-synovitis and follow-up changes in effusion-synovitis (OR: 0.77-0.86), but no significant association was observed in terms of Hoffa-synovitis. Stratified by synovitis-driven inflammatory phenotypes, baseline quadriceps strength was significantly associated with follow-up changes in effusion-synovitis in the population with existed effusion-synovitis (OR: 0.75-0.79), but not in Hoffa-synovitis.Higher baseline quadriceps strength was negatively associated with the changes in effusion-synovitis instead of Hoffa-synovitis, especially in the population with existed effusion-synovitis. Our finding suggested a potential protective role of quadriceps in effusion-synovitis.