After a hip, knee or shoulder arthroplasty, the evolution is not always favorable. It can be marked by an infectious or non-infectious complication, most often implant failure. In this context, joint fluid aspiration (JFA) is indicated to document a prosthetic joint infection (PJI) or to bring to light arguments for implant failure. Nevertheless, opinions differ on its indication for microbiological identification. Some teams perform it systematically when faced with a prosthesis dysfunction. Others, only in the presence of suggestive signs of PJI. Finally, others never perform it.

Based on clinical, radiological and biological (CRP) signs, at the preoperative stage and before JFA, we classify our patients into 3 groups: supposedly septic (chronic joint infection), supposedly aseptic (implant failure) or intermediate (Unknown). This last group, often encountered in consultation, poses a diagnosis problem more than the others.

In our experience, JFA is an essential diagnosis tool in these 3 groups of patients. It helps to choose the surgical strategy. In addition, the dosage of biomarkers in the joint fluid as the alpha defensin, the leucocyte esterase and the CRP could provide an additional argument to investigate the infectious origin or not, in particular in difficult cases.

In summary, the disagreement on the usefulness of JFA in case of PJI suspicion and any other prosthetic dysfunction, the lack of data on large prospective studies and our questioning about the contribution of JFA in the aseptic and intermediate group of patients, motivated us to set up this study to evaluate the interest of the JFA for the preoperative diagnosis, as well as that of the dosage of biomarkers in the joint fluid.

Visit V0: corresponds to the first consultation. After informing and obtaining the consent of the patient, the investigator will collect the anamnesis, clinical, radiological and biological data, then will indicate the anticipated medico-surgical strategy. The FJA will be prescribed during this consultation, as well as the dosage of the CRP in blood the same day as the FJA.

Then, the investigator will classify the patient (primary classification) in one of the three groups the groups: supposedly septic, supposedly aseptic or intermediate.

A reclassification of patients (secondary classification) will be done, based on the bacteriological results of the FJA (positive, negative and doubtful). Biomarker results will not be disclosed or considered for patient care.

Visit V1: corresponds to the day of the FJA in the x.ray department and the blood sample in the central laboratory for the CRP dosage.

During FJA, 2 ml of additional joint fluid will be collected in addition to the volume usually collected for CRP, Leukocyte Esterase and alpha defensin dosage in joint fluid. Alpha defensin dosage will be performed only in patients in the intermediate group with a negative FJA.

Visit V2: Day of prosthesis revision in the event of chronic PJI or mechanical prosthesis dysfunction (Implant failure) requiring surgery.

Inclusion Criteria:

• Patient consent to participate in the study.
• Patient aged over 18 years
• Patient with hip, knee or shoulder joint prosthesis
• Patient who has the Indication to perform a FJA, whatever the cause of revision (mechanical, septic)
• Over one-month symptoms evolution for patients suspected of infection

Exclusion Criteria:

• Acute prosthesis infection with less than one-month symptoms' duration
• Antibiotic therapy between preoperative FJA and intraoperative samples
• Pregnant or breastfeeding woman.