In this study, the sensitivity of MARS MRI for the preoperative diagnosis of PJI was 80.65% and the specificity was 75%, which was not a statistically significant difference compared with conventional diagnostic indices (culture, CRP, ESR, SF WBCs, SF PMNs%) (p > 0.05), indicating that the diagnostic efficacy of MARS MRI is not inferior to the commonly used diagnostic indicators. The gene discussed is CRP; the disease is juvenile polyposis syndrome.