Ultrasound grayscale histogram analysis for early rheumatoid arthritis cartilage assessment

Objective To evaluate the feasibility of ultrasound grayscale histogram analysis in detecting metacarpal head (MH) cartilage damage in rheumatoid arthritis (RA) and its correlation with clinical parameters. Methods This cross-sectional study enrolled 50 RA patients and 50 healthy controls (HCs). Bilateral MH2-5 cartilages were scanned using a Mindray Resona R9 ultrasound system. Grayscale values were quantified via histogram analysis in standardized regions of interest. Intraclass correlation coefficients (ICC) assessed reliability. Mann-Whitney U tests compared groups; Spearman correlation analyzed associations with disease duration and body mass index (BMI). Results RA patients exhibited significantly higher grayscale values in total MH (median: 48.6 vs. 44.8, P < 0.001), MH2 (46.4 vs. 42.7, P = 0.015), and MH3 (48.6 vs. 43.4, P = 0.006) compared to HCs. ICC demonstrated excellent intra- (0.905–0.945) and inter-observer (0.861–0.908) reliability. Weak correlations were observed between grayscale values and disease duration (r = 0.120, P = 0.001) or BMI (r = − 0.136, P < 0.001). Conclusion Quantitative grayscale histogram analysis of the metacarpal head cartilage demonstrates promising feasibility and provides valuable imaging evidence to support the early diagnosis of rheumatoid arthritis. Clinical trial number Not applicable.