Knee replacement pain study aims to cut chronic pain risk

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Adult patient; * Placement of unilateral tricompartmental knee prosthesis for gonarthrosis; * ASA score between I and III ; * Nonseptic scheduled surgery; * Knee replacement scheduled on one of the first 3 days of the week (Monday to Wednesday included) in order to benefit from a homogeneous postoperative physical therapy; * Able to understand the protocol; * Having agreed to participate in the study and having given express oral consent; * Affiliated with a social security system; * Possibility of being followed as part of the protocol. Exclusion Criteria: * Age \>= 86 years old; * BMI \> 35 ; * Revision of knee replacement; * Symptomatic contralateral osteoarthritis; * Anterior of surgery on the operated knee (excluding arthroscopy and meniscectomy); * Vascular surgery on the femoral vessels on the operated side; * Concept of diffuse polyalgia syndrome (fibromyalgia); * Documented neuropathy of the lower limb; * Localized infection at the catheter puncture site (femoral triangle); * Known allergy to Ropivacaine; * Renal insufficiency (Clearance - CKD-EPI formula - creatinine \<30 ml/min) and/or severe hepatic insufficiency (prothrombin blood level \<50%) ; * Inflammatory rheumatic disease (rheumatoid arthritis, ankylosing spondylitis...) ; * Patients on immunosuppressive or systemically administered corticosteroid therapy; * Daily use of level II or III analgesics for more than one month pre-operatively; * Known intolerance to tier III analgesics; * Allergy or contraindications to standard treatments administered per and postoperatively (paracetamol, NSAIDs); * Patient undergoing knee surgery in the year prior to inclusion and participating in the study; * Patients who do not cooperate or do not understand French, difficulties in understanding and evaluating the pain score, preoperative cognitive dysfunction making the interview unreliable; * Patient under guardianship, curators, deprivation of liberty; * Patient already engaged in another interventional clinical study (category 1); * Pregnant or breastfeeding women, or women in a position to procreate who refuse an effective means of contraception; * Refusal to participate; * Inability to understand the protocol and its requirements, and/or to give express oral consent.