Investigators are building an empirical evidence base for real-world data through large-scale replication of randomized controlled trials. The investigators' goal is to understand for what types of clinical questions real-world data analyses can be conducted with confidence and how to implement such studies.

This is a non-randomized, non-interventional study that is part of the RCT DUPLICATE initiative (www.rctduplicate.org) of the Brigham and Women's Hospital, Harvard Medical School. It is intended to replicate, as closely as possible in healthcare insurance claims data, the trial listed below/above. Although many features of the trial cannot be directly replicated in healthcare claims, key design features, including outcomes, exposures, and inclusion/exclusion criteria, were selected to proxy those features from the trial. Randomization is also not replicable in healthcare claims data, but was proxied through a statistical balancing of measured covariates through standard practice. Investigators assume that the RCT provides the reference standard treatment effect estimate and that failure to replicate RCT findings is indicative of the inadequacy of the healthcare claims data for replication for a range of possible reasons and does not provide information on the validity of the original RCT finding.

Inclusion Criteria:

• At least 18 years of age
• Scheduled to undergo elective total knee replacement

Exclusion Criteria:

• Pregnancy or breastfeeding
• Had active bleeding or high risk of bleeding
• Had contraindications for prophylaxis with enoxaparin
• Drug or alcohol abuse
• Concomitant use of protease inhibitors for the treatment of HIV
• Had planned intermittent pneumatic compression
• Had a requirement for anticoagulant therapy that could not be stopped
• Substantial liver disease
• Severe renal impairment (creatinine clearance <30 ml per minute)
• Concurrent use of both drugs

Patients aged 18 years or older undergoing elective total knee arthroplasty.