Immediate postoperative pain after Total Knee Arthroplasty(TKA) remains an unsolved problem, and a substantial proportion of patients experience moderate to severe postoperative pain. Patient controlled analgesia(PCA) using opioid is an effective and safe modality for postoperative pain relief after TKA and remains an integral part of pain management after TKA. However, Opioid is associated with high incidence of postoperative nausea and vomiting(PONV) which is the most frequent complication during the first 24 hour after surgery.PONV has been reported to be more distressing than postoperative pain and to be the most undesirable negative outcome. Despite advances in prevention and treatment of PONV, PONV remains a continuing problem with an incidence of 20-30% in unselected patients and up to 70% in "high-risk" patients. As results of current researches, some risk factors of PONV have been identified and indications of prophylactic antiemetics and strategies to reduce baseline risk have been recommended.The recommended modalities to reduce baseline risk includes regional anesthesia, oxygen supplement, use of midazolam and propofol and avoid use of inhaled anesthesia and neuromuscular blockade. In addition,published evidence suggests that appropriate antiemetic prophylaxis should be considered for patients with 2 or more risk factors and to reduce opioid consumption, preemptive multimodal pain management such as preemptive analgesic medication, continuous regional nerve block is recommended.Ramosetron is a newly developed serotonin receptor antagonist with a higher affinity and longer duration of action than that of the previously developed serotonin receptor antagonist such as ondansetron and granisetron. Thus, this prospective blinded randomized study was conducted to document the antiemetic efficacy of multimodal antiemetic protocol to reduce baseline risk, using regional anesthesia, midazolam and propofol, hydration and oxygen supplement and multimodal pain control protocols using the continuous femoral nerve block, PCA and preemptive oral medications and to determine whether Ramosetron prophylaxis would provide additional antiemetic effect in patients after TKA for whom covered by this multimodal antiemetic protocols.