This study evaluate the efficacy of adding popliteal sciatic nerve block with low concentration bupivacaine and dexamethasone to abductor canal block for total knee arthroplasty in patient with NSAIDs prescribing precaution. Half of participants will receive popliteal sciatic nerve block, abductor canal block and periarticular injection, while the other half will receive a sham block, abductor canal block and periarticular injection.

After informed and consent, all patients will be devided into two groups, Sciatic group (group S) and Controlled group (group C). All patients will receive adductor canal block, then patients in group S will receive Sciatic nerve block with low concentration bupivacaine and dexamethasone while partients in group C will receive sham block. All patient will receive spinal anesthesia and intraoperative periarticular injection.

Postoperative pain score, muscle strength, total morphine consumption and adverse events will be record in case record form.

Inclusion Criteria:

• patient scheduled for single total knee arthroplasty
• patient with NSAIDs prescribing precautions such as history of NSAIDs allergy, Chronic kidney disease (GFR< 50 ml/min), history of ischemic heart disease or cerebrovascular disease

Exclusion Criteria:

• patient refusal
• body weight less than 45 kg
• history of allergy to bupivacaine or dexamethasone
• uncontrolled diabetes mellitus
• contraindicated for spinal block, adductor canal block or sciatic nerve block
• inability to assess pain score (cognitive or psychiatric history)
• patient scheduled for revision TKA
• preexisting neuropathy or neurological deficit in lower extremity
• preexisting chronic pain (prolonged use of oral morphine 20 mg/day or equivalent)