Total knee replacement surgery can be associated with a significant postoperative pain burden and an inability to mobilize adequately, which can lead to the failure of the ambulatory course.

Indeed, early mobilization is beneficial in this context in order to prevent complications related to immobility.

The optimization of postoperative analgesia is therefore a key issue for the success of this intervention in an outpatient setting or during a short-term hospitalization since an adequate pain relief facilitate the earlier mobilization of the operated joint. Modern postoperative analgesia protocols recommend a multimodal approach, including the use of acetaminophen, anti-inflammatories, opioids and others as well as the use of nerve blocks.

Some nerve blocks used for total knee replacement surgery, such as the femoral nerve block, do not preserve the motor skills of the operated limb, which may alter the clinical trajectory due to delayed mobilization due to weakening of the quadriceps, one of the extensor muscles of the knee. Currently, one of the blocks used to spare the motor functions is the block of the femoral triangle.

Unfortunately, this block of the femoral triangle does not fully cover the skin component of the surgical incision used for a total knee arthroplasty. A solution to obtain a better quality of pain relief at the level of the cutaneous incision would be to add a block of the para-sartorial compartment, which makes it possible to cover the nerve territories not covered by the femoral triangle block.

The hypothesis of this study is that the addition of the para-sartorial compartments (PACS) block, which aims to block the intermediate cutaneous femoral nerve, will improve the postoperative analgesia after total knee replacement surgery, compared to the classical isolated approach of the femoral triangle block (FTB).

Despite many advances, the postoperative analgesia offered by the present techniques remains imperfect, the femoral triangle block does not make it possible to completely cover the cutaneous component of the classic midline incision used for a total knee arthroplasty. This incision would fall more under the anterior cutaneous femoral nerves, more specifically the intermediate and medial cutaneous femoral nerves. A recently described approach offers the prospect of better covering this skin incision, by specifically blocking these nerves using the same needle path as for the femoral triangle block. Although the feasibility of this approach has been studied in healthy volunteers and in a few clinical cases, no randomized controlled study has been conducted to determine whether the addition of cutaneous femoral nerve blocks offers an analgesic benefit in the population undergoing total knee replacement surgery. This is therefore necessary in order to assess whether this approach improves the clinical trajectory of patients receiving a total knee arthroplasty.

Inclusion Criteria:

• 18 years and over, requiring a primary total knee arthroplasty
• 'American Society of Anesthesiologists' classification 1 to 3

Exclusion Criteria:

• Refusal or unable to consent
• Contraindications to a peripheral nerve block;
• Inability to communicate with the healthcare team or the research team;
• Inability to understand follow-up instructions or questionnaires;
• Chronic pain requiring the intake of the equivalent of more than 60 mg of morphine daily;
• Pregnancy;
• Patients weighing less than 50 kg (to limit the risk of intoxication with local anesthetics).