It was aimed to evaluate the postoperative analgesic efficacy of the suprainguinal fascia iliaca block applied in the postoperative period in terms of 24-hour opioid consumption, pain score, additional analgesic need, and side effects and complications in the postoperative period, and to see the postoperative analgesic effectiveness of this block in patients who underwent knee arthroplasty.

Total knee arthroplasty (TKA) is one of the major orthopedic surgeries that cause severe postoperative pain. A successful post-operative outcome is possible with strong and effective pain control followed by early mobilization and a good functional recovery.

There are many studies in the literature showing successful results regarding the effectiveness of suprainguinal fascia iliaca block on postoperative pain in pain control after hip surgery. However, there is not enough information about the use of suprainguinal fascia iliaca block in knee arthroplasty. With this study, the investigators aim to contribute to the literature on the use and effectiveness of suprainguinal fascia iliaca block in knee arthroplasty.

An identification number (ID) number will be randomly assigned to each participants, whose written consent was obtained before the surgery, when they are admitted to the postoperative recovery room. In the postoperative period, participans will be followed up with these numbers in patient follow-up. Which group the participants will be included in will be determined by the closed envelope method.

Participants who underwent unilateral knee arthroplasty will be included in the prospective and randomized study. The participants will be divided into two groups and suprainguinal fascia iliaca block and patient-controlled analgesia (Group SFI) will be applied to one group and patient-controlled analgesia (Group PCA) will be applied to the other group.

No block attempt will be made to the participants in the patient-controlled analgesia group (Group PCA), and when the patient is taken to the recovery room after surgery, patient-controlled analgesia will be administered and transferred to the ward.

Group SFI; the block procedure will be applied to the participant lying in the supine position under sterile conditions with a high-frequency linear probe (ESAOTE Fixed Color Doppler Ultrasonography Device, Italy).In the block method, 0.25% bupivacaine (Buvasin Vem İlaç, Turkey) (15 ml physiological saline + 15 ml 0.5% bupivacaine) total amount of 30 ml, same volume and same concentration will be used. The participant with the block will be followed in the recovery room and if the block is successful, PCA treatment will be started and the participant will be taken to the ward.

Evaluation of postoperative pain will be done with numerical rating scale (NRS).Pain levels will be questioned in two different ways as rest and passive moving.

Inclusion Criteria: Patients,

• Having undergone unilateral knee replacement surgery under elective conditions,
• Age range of 18-75 years,
• ASA score I and II,
• Body mass index < 35kg/m²,
• written consent who agreed to participate in the study.

Exclusion Criteria: Patients,

• who do not want to be included in the study by not signing the voluntary consent form,
• Body mass index > 35 kg/m²,
• Local infection, hematoma, hernia, neoplasm etc. in the area to be blocked. found,
• Coagulopathy, hepatic or renal failure,
• Allergic to a local anesthetic agent or one of the drugs used in the study,
• Having a history of chronic opioid and corticosteroid use,
• who cannot use the patient-controlled analgesia system and have a psychiatric disease,
• with operative time less than 20 minutes and more than 120 minutes for better standardization of studies.

Researched data and statistical analyzes will be available from the journal in which the clinical study was published.

The patient will not know which study group he is in. The anesthetist, who will perform the regional block, will give the block to be applied in a sealed envelope by an assistant staff outside the study, and at the same time, the patient will not know which block has been made. The anesthesiologist who made the block will not participate in the pain follow-up of the patients. Postoperative pain assessment and data collection will be performed by another investigator blinded to the study.