Which option best describes the typical pharmacologic DVT prophylaxis regimen after hip or knee arthroplasty?

• A. Aspirin started within 24 hours and continued for 2 weeks.
• B. Low molecular weight heparin or DOACs started within 12–24 hours postoperatively and continued for about 10–14 days (hip) or 14 days to 4 weeks per protocol.
• C. Warfarin started after 72 hours for 6 weeks.
• D. No pharmacologic prophylaxis is recommended.

Answer: (B)

The key idea is that after hip or knee replacement there is a high risk of blood clots, so a pharmacologic agent is started early and continued for a defined period to prevent DVT and PE. The evidence and standard practice favor using a low molecular weight heparin or a direct oral anticoagulant, started within the first day after surgery once bleeding risk is acceptable. These agents provide effective protection with predictable dosing and without the need for routine lab monitoring (unlike warfarin).

Starting 12–24 hours after surgery aligns with allowing enough initial hemostasis while promptly reducing clot risk. The typical duration depends on the procedure: for the hip, prophylaxis is commonly about 10–14 days, with some protocols extending to longer periods; for the knee, 14 days up to 4 weeks per protocol is common. This approach balances preventing DVTs with minimizing bleeding risk.

Aspirin alone is used in some settings, but it is not considered the typical standard regimen across all patients after hip or knee arthroplasty. Warfarin requires bridging and monitoring and is less commonly used as the primary immediate post-op prophylaxis in many modern protocols. Omitting pharmacologic prophylaxis altogether would leave patients at high risk for DVT/PE.