CRP and infection: In 2011, the Musculoskeletal Infection Society (MSIS) categorized PJI “major” criteria (existence of a communicating sinus tract and two positive periprosthetic cultures), and “minor” criteria (increased ESR/CRP levels, synovial leukocyte count, and synovial polymorphonuclear cell levels, presence of purulent material, isolation of a single organism in a culture, and intraoperative frozen sections with histology) [10].