This study evaluates postoperative analgesic efficacy within 48 hours between epidural analgesia and single-shot bilateral adductor canal blocks in bilateral total knee arthroplasty. Half of participants will be received continuous epidural analgesia, while other half of participants will be received single-shot bilateral adductor canal blocks.

Continuous epidural analgesia is effective postoperative pain control but it has some limitations in patients with hypotension, concurrent anticoagulants, technical difficulty, urinary retention.

Adductor canal block is less invasive than continuous epidural analgesia. It provides effective analgesia for total knee arthroplasty and preserves quadriceps muscle strength.

Inclusion Criteria:

• Aged more than 18 years old undergoing bilateral total knee arthroplasty
• American Society of Anesthesiologists physical status classification 1-3

Exclusion Criteria:

• Participants deny to enroll the study
• Allergy to bupivacaine
• Weight less than 50 kilograms
• Hepatic disease
• Contraincation for neuraxial block or adductor canal block
• Uncontrolled cardiovascular disease
• Creatinine clearance less than 50 ml/min