**4. Postoperative pain in total knee arthroplasty**

Postoperative pain is caused by neuronal damage that occurs during the surgical procedure and the stimulation of the nociceptors. In postoperative period, total knee arthroplasty (TKA) is painful and pain management is quite difficult. The main purpose of postoperative pain relief is to reduce the pain of the patient, to contribute to the healing process, to shorten the length of hospital stay, and to reduce hospital costs.

Techniques such as intravenous analgesia, epidural analgesia, and peripheral nerve blocks are used to prevent postoperative pain. In addition, oral and parenteral analgesics, patientcontrolled analgesia, nerve blocks, and periarticular injection methods are used as multimodal analgesia method. Systemic opioids, nonsteroidal anti-inflammatory drugs, and local anesthetics are frequently used for postoperative analgesia.

Pain scales such as visual analogue scale (VAS), verbal descriptive scale (VDS), numerical rating scale (NRS) are used as standard methods in the evaluation of pain of patients.

Total knee arthroplasty (TKA) is known to be a very painful orthopedic procedure [5]. For this reason, effective pain control is important to optimize the rehabilitation process in order to ensure patient satisfaction, hospital stay, and cost reduction [6]. However, the difficulty of postoperative pain management after TKA is to maintain adequate motor function with adequate analgesia. The patient is informed about the surgery to be performed before the operation, and a training program and the physical preparation are recommended. Patients undergoing preoperative exercise and training showed significant improvements in function, quadriceps strength, and duration of stay. After the surgical intervention is performed, the patient can continue the rehabilitation program to speed up the healing process in the home under the supervision of a physiotherapist. Rehabilitation therapy depends on many factors such as patient characteristics, prosthesis characteristics, and postoperative complications.

More than 1.1 million joint arthroplasty (TJA) are performed annually in the USA, and more than 700,000 of them are primary TKA [7, 8].
