Venous thromboembolism is a serious complication after total hip replacement (THR) and total knee replacement (TKR). Previous studies have reported the incidence of both asymptomatic and symptomatic deep vein thrombosis (DVT) after TKR were higher in Taiwan than other countries in Asia. Therefore, the usage of prophylactic antithrombotics should be considered. The efficacy and safety of Xarelto (Rivaroxaban) for preventing venous thromboembolism has been proved. However, there is a lack of study using prospective design to evaluate the efficacy and safety of Xarelto after THR and TKR for Taiwanese. In this study, the investigators use a randomized controlled trial design comparing the incidence of DVT, pulmonary embolism, and complications between intervention and control groups.