Anticoagulation, the use of sequential compression devices on the lower extremities perioperatively, and early ambulation are thought to reduce the incidence of venous thromboembolism (VTE) postoperatively and are recommended to reduce VTE risk. However, the evidence on which this recommendation has been based is not particularly strong. We have demonstrated that even a large, multicenter cohort with carefully collected prospective data is inadequate to provide sufficient evidence to support, or refute, this recommendation.