We describe the expression of eight interleukins commonly used to identify infectious diseases (including IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, and IL-17) in the synovial fluid of these diseases and explore the value of these interleukins in distinguishing PJI from active RA. The gene discussed is IL1B; the disease is rheumatoid arthritis.