The aim of this study is to assess the effect of different analgesic effects on the outcome of patients undergoing total knee arthroplasty. Patients who will have primary unilateral total knee replacement between September 2016 to June 2018 at Peking Union Medical College Hospital and meet the inclusion criteria will be included. They are randomized into two groups. The total knee arthroplasty is performed by one surgeon and adductor-canal block is performed by one anesthesiologist who is not responsible for follow-up. Patients on both groups will have intravenous patient control analgesia with 1 mg morphine/bolus. One residency is responsible for the follow-up.