This prospective observational study aims to evaluate whether rebound pain after peripheral nerve block is associated with the development of chronic postsurgical pain following elective total knee arthroplasty. Adult patients undergoing unilateral total knee arthroplasty under spinal anesthesia and receiving a peripheral nerve block as part of routine multimodal analgesia will be included. No additional intervention, drug administration, or biological sampling will be performed beyond standard clinical care.

Rebound pain will be assessed during the early postoperative period using pain diaries, numeric rating scale pain scores, and analgesic consumption records. Chronic postsurgical pain and related outcomes will be evaluated at postoperative 3 and 6 months using validated instruments assessing pain severity, neuropathic pain features, psychological status, functional outcomes, and health-related quality of life. The primary outcome is the presence of chronic postsurgical pain at 3 months after surgery. Secondary outcomes include chronic pain at 6 months, pain intensity, neuropathic pain characteristics, opioid consumption, rescue analgesic requirements, sleep disturbance, and quality-of-life measures. The study also aims to explore demographic and clinical factors associated with rebound pain and chronic postsurgical pain.

Inclusion Criteria:

• Age 18 years or older
• ASA physical status I to III
• Scheduled for unilateral elective total knee arthroplasty
• Planned to undergo spinal anesthesia
• Planned to receive a peripheral nerve block as part of routine multimodal analgesia
• Able to provide informed consent and complete study assessments

Exclusion Criteria:

• Chronic opioid use (60 mg oral morphine equivalent per day or more, or use for 3 months or longer)
• Significant neuropathy or radiculopathy
• Bilateral or two-stage total knee arthroplasty during the same hospitalization
• Contralateral total knee arthroplasty within the previous 6 months
• Severe cognitive impairment or major psychiatric disorder
• Chronic analgesic dependence

Adult patients undergoing unilateral elective total knee arthroplasty at Konya City Hospital under spinal anesthesia and receiving a peripheral nerve block as part of routine multimodal analgesia.