Inclusion Criteria:  Patients requiring hip or knee replacement surgery: i) for 'late' joint prosthesis infection, present for at least 90 days from the date of the arthroplasty (first surgical phase); II) for non-infectious causes (mobilization, wear, instability, misalignment, adverse reactions to local tissues or other aseptic causes), also present for at least 90 days, and which have not had other re-operations on the same joint, and which will be a one-step review; Previous clinical data and laboratory and radiological examinations available.  Exclusion Criteria:  Patients affected by 'early' joint prosthesis infection, with clinical symptom latency of less than 90 days (in this specific subset of patients there is in fact still considerable heterogeneity and little consensus about the diagnostic levels of white blood cell count and percentage of neutrophils). Patients suffering from joint prosthesis infection involving joints other than the hip or knee. Severe cognitive impairment or psychiatric disorders; Pregnant women.