Inclusion Criteria:

1. Males and females 21 years of age or older;
2. Undergoing elective primary or revision hip or knee replacement;
3. Patient has necessary mental capacity to participate and is able to comply with study protocol requirements;
4. Patient is not pregnant;
5. Patient has signed consent form; and
6. Patient is wiling to be randomized and participate.

Exclusion Criteria:

1. Patient is undergoing bilateral hips or knee replacement;
2. No patient undergoing total hip or knee replacement who has been enrolled in this study for a prior hip or knee replacement;
3. Women who are pregnant or breastfeeding;
4. Patient is on chronic anticoagulation other than with antiplatelet medications;
5. Patient is concurrently enrolled in another active interventional clinical trial testing a drug or intervention known or believed to interact with aspirin, warfarin, or rivaroxaban;
6. Patient has a contraindication to two or more of the three prophylaxis regimens;
7. Documented gastrointestinal, cerebral, or other hemorrhage within 3 months of the operation;
8. A known diagnosis of defective hemostasis and past history of clinical bleeding requiring transfusion and treatment;

7) A known condition of thrombophilia proven by diagnostic laboratory testing; 9) An operative procedure involving the eye, ear, or central nervous system within one month; 10) Severe uncontrolled hypertension with systolic BP > 220mmHg or diastolic BP > 120mmHg; 11) An absolute body weight of less than 41 kilograms (90.4 lbs) at baseline; and 12) Vulnerable patient populations including prisoners, institutionalized individuals, and those who are mentally handicapped.