Fortunately, with the development of medicine, various detection methods have been found for the diagnosis of PJI, such as laboratory tests (e.g., white blood cell count, erythrocyte sedimentation rate, C-reactive protein, interleukin-6, alpha-defensin, procalcitonin, D-dimer, and fibrinogen), synovial fluid characteristics, histopathological studies, microbiological studies (e.g., conventional synovial fluid and tissue cultures, and SFC), and radiological studies. The gene discussed is CRP; the disease is juvenile polyposis syndrome.