Analgesic Efficacy of Different Liposomal Bupivacaine Doses in the Adductor Canal Block for Total Knee Arthroplasty

Inclusion Criteria: * ASA I-III * Age 18-80 years old * Scheduled for elective primary unilateral total knee arthroplasty (TKA) with robotic surgery * Able to speak and understand Cantonese or Mandarin or English * Able to provide informed oral and written consent Exclusion Criteria: * Revision TKA * Single-stage bilateral TKA * Complex primary TKA requiring use of stem/augment/constrained liner * Surgeries with significant intraoperative complications which may alter rehabilitation protocol eg 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 * Chronic use of glucocorticoids * Chronic opioid use (morphine, fentanyl, hydromorphone, ketobemidone, methadone, nicomorphine, oxycodone, or meperidine) * History of congestive heart failure (NYHA 2) * Alcohol or drug abuse * Impaired renal function (defined as effective glomerular filtration rate \< 30ml/min/1.73m2 * Impaired liver function (defined as plasma bilirubin over 34mol/L; international normalized ratio \[INR\] \>= 1.7, alanine aminotransferase \[ALT\] over 100U/L, aspartate aminotransferase \[AST\] over 100U/L) * Coagulopathy (platelet count \<100,000/ml and/or INR \>= 1.5) or the use of anticoagulants (not including aspirin) that precludes the use of adductor canal blocks * Pre-existing neurological or muscular disorders * Psychiatric illness * Impaired mental state * Pregnancy * Local infection * On immunosuppressants * High body mass index (BMI) (\>=40) * Patient refusal for regional nerve blocks or to conduct clinical trial