The investigators compared continuous epidural infusion with combined continuous femoral and single-shot sciatic nerve blocks. The primary outcome was the incidence of side effects, and secondary outcomes were pain relief, motor blockade,morphine consumption, and rehabilitation indices.

The parcicipants were randomly assingned to epidural infusion group and femoral sciatic block. In epidural infusion group, a lumbar epidural catheter was placed at the L3-4 level using loss-ofresistance procedure. ropivacaine 0.2% and fentayl 2mcg/ml were infused at a rate of 5ml/hr from the end of operation. In femoral sciatic group, the femoral and sciatic nerve are located using ultrasound and 0.2% ropivacain is injected. A catheter is inserted to femoral nerve. From the end of operation, 0.2% ropivacaine was infused through the femoral catheter at a rate of 5ml/hr. The incidence of side effects is measured.

Inclusion Criteria:

• American Society of Anesthesiologists Physical Status Classification I-II
• total knee arthroplasty
• 18-90 years

Exclusion Criteria:

• allergic to the local anesthetics
• cognitive impairment such as dementia
• coagulopathy
• motor and sensory impairment
• patient refusal
• BMI >39