Objective <p>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.</p> Methods <p>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).</p> Results <p>RA patients exhibited significantly higher grayscale values in total MH (median: 48.6 vs. 44.8, <i>P</i> &lt; 0.001), MH2 (46.4 vs. 42.7, <i>P</i> = 0.015), and MH3 (48.6 vs. 43.4, <i>P</i> = 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 (<i>r</i> = 0.120, <i>P</i> = 0.001) or BMI (<i>r</i> = − 0.136, <i>P</i> &lt; 0.001).</p> Conclusion <p>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.</p> Clinical trial number <p>Not applicable.</p>