CD68 total stained area within the sublining was identified as the most reliable marker to discriminate between RA and OA (AUC 0.94, CI 95 % 0.84–1.00, p = 0.001) followed by the CD68-stained area in the upper and middle sublining (both AUC 0.93, CI 95 % 0.82–1.00, p = 0.001). This evidence concerns the gene CD68 and rheumatoid arthritis.