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 has signed study-specific informed consent form and agrees to randomization

Exclusion Criteria:

1. No patient undergoing total hip or knee replacement who has been enrolled in this study for a prior hip or knee replacement can be enrolled for a second hip or knee replacement in this study.
2. Women who are pregnant or breastfeeding, as well as those of reproductive potential unless there is a negative urine pregnancy test.
3. A preoperative need for chronic anticoagulation other than with antiplatelet medications
4. A known condition of thrombophilia proven by diagnostic laboratory testing
5. Documented gastrointestinal, cerebral, or other hemorrhage within 3 months of the operation
6. A known hypersensitivity to heparin
7. A known diagnosis of defective hemostasis such as hemophilia
8. A bleeding event within one month of an operative procedure involving the eye, ear, or central nervous system
9. Severe uncontrolled hypertension with systolic BP > 220mmHg and diastolic BP > 120mmHg
10. An absolute body weight of less than 41 kilograms (90.4 lbs) on day of enrollment
11. Vulnerable patient populations including prisoners, minors under age 21, institutionalized individuals, and those who are mentally handicapped