Serum COMP levels correlate with the severity of systemic lupus erythematosus and knee OA. In systemic lupus erythematosus patients (n = 30), serum COMP levels are significantly higher (p < 0.05) than serum from normal non OA affected patients (n = 30). This demonstrates the variable involvement of inflammation in disease processes in some sub-types of knee joint OA. The gene discussed is COMP; the disease is systemic lupus erythematosus.