Purpose: The efficacy and safety for 250 patients (195 pts after hip arthroplasty and 55 patients after knee arthroplasty) oral drinking Rivaroxaban of group R and 258 pts (185 patients after hip arthroplasty and 73 pts after knee arthroplasty) subcutanously injected Enoxaparin of group E on symptomatic venous thromboembolism (VTE) in SAIGON-ITO Hospital from June 2011 to June 2013.