In the group with arthritis, an increase in the thickness of the digital extensor tendon was correlated with the swollen joint count (r = 0.301, p = 0.044) and CRP concentration (r = 0.268, p = 0.038) and the ESR increase (r = 0.521, p = 0.041), but it was not correlated with the tender joint count or the disease activity as measured by the DAS28. This evidence concerns the gene CRP and arthritic joint disease.