Inclusion Criteria:  Patients undergoing unilateral primary TKA in the outpatient setting. Patients older than 21 years of age. American Society of Anesthesiologists (ASA) physical status I-III. No alcohol or drug dependency. Sufficient understand and co-operation about the perineural catheter.  Exclusion Criteria:  Perioperative complication or discharge delay leading to hospital admission. Chronic opioid use of morphine 30mg equivalent per day for last 2 consecutive weeks. Allergy to the study medications. Coagulopathy and platelet count < 105/μL. Patients with contraindications to the insertion of an epidural or adductor canal catheter (severe anatomic abnormalities or history of previous surgery at the site of catheter placement).