Following this rationale, and considering the need for a reliable marker in day-to-day clinical routine with high sensitivity and specificity for preoperative planning, we here present the IL-6 as a potential biomarker to differentiate between a painful total arthroplasty without signs of loosening and infection and aseptic loosened prosthesis on the one hand and PJI on the other hand. The gene discussed is IL6; the disease is infection.