857 patients having undergone total knee arthroplasty (TKA) were randomized to receive either short term thromboprophylaxis, where therapy would stop at day 10 +/- 2, or extended thromboprophylaxis, where therapy would stop at day 35 +/- 5. Patients were assessed for proximal or symptomatic deep vein thrombosis (DVT), pulmonary embolism (PE), major bleeding, thrombocytopenia, and mortality up to day 35 +/- 5 (primary outcome). The secondary outcome was ultrasonographic distal deep vein thrombosis at day 35 +/- 5. The rates of the primary and secondary outcomes were found to be higher in the short therapy group.