Effect on postoperative pain and local inflammation factors PGE2 and IL-6 for total knee arthroplasty

INTERVENTION: 1:receive parecoxib 40mg IV at the completion of surgery and 40mg iv bid for 3 days after surgery;2:receive normal saline 2ml; CONDITION: osteoarthritis PRIMARY OUTCOME: Morphine consumption; SECONDARY OUTCOME: Range of motion (ROM);The PGE2 and IL‐6 level in drainage;VAS Pain score; INCLUSION CRITERIA: With Institutional Ethic Committee approval and patient's signature on consent, 100 patients will be enrolled who have an ASA physical status of I to II, between 55–75 years of age, scheduled undergoing routine total primary arthroplasty for unilateral knee with a standardized regimen of general anaesthesia.