It is a multicenter, prospective, observational study of standard care. This study analyses the care of patients on long term effective anticoagulation therapy (ADELC) during a primary hip or knee arthroplasty.

The objectives of the study are to:

1. Identify clinical practices set up for patient care
2. Assess the type and the frequency of perioperative complications
3. Look for factors, related to patients or treatments, associated with the occurrence of these complications.

The main objective is to estimate the risks, adjusted and not, of postoperative complications associated to a long term anticoagulation by comparing patients under anticoagulation to a control group of patients having the same interventions but who are not under anticoagulation.

Inclusion Criteria:

• Adult ≥ 18 years
• Programmed for primary hip or knee arthroplasty.
• Effective dose of anticoagulant drugs intake for more than 1 month with the intention to resume it after the intervention for ADELC cohort; no effective dose of anticoagulant drugs intake for the control cohort.

Exclusion Criteria:

• Patient non opposition

Patients on long term effective anticoagulation (ADELC) or not undergoing a primary hip or knee replacement