Inclusion Criteria:  ASA I-III Age 18-80 years old Scheduled for elective primary unilateral total knee replacement Chinese patients BMI < 40 Able to speak and understand Cantonese Able to provide informed oral and written consent  Exclusion Criteria:  Revision total knee replacement Single-stage bilateral total knee replacement Complex primary total knee replacement requiring the use of stem/augment/constrained liner Surgeries with significant intraoperative complications which may alter rehabilitation protocol e.g. collateral ligament injury, fracture requiring fixation Known allergy to opioids, local anaesthetic drugs, paracetamol, non-steroidal anti-inflammatory drugs (NSAIDs) including COX-2 inhibitors History of chronic pain other than chronic knee pain History of immunosuppression Daily use of glucocorticoids Daily use of strong opioids (morphine, fentanyl, hydromorphone, ketobemidone, methadone, nicomorphine, oxycodone, or meperidine) History of severe heart disease (NYHA 2) Alcohol or drug abuse Impaired renal function, defined as preoperative serum creatinine level over 120 micromol/L Pre-existing neurological or muscular disorders Psychiatric illness or neurologic or psychiatric diseases potentially influencing pain perception Impaired or retarded mental state Difficulties in using patient-controlled analgesia (PCA) Pregnancy Local infection On immunosuppressants High BMI (>=40) Patient refusal