Two trials, one involving patients undergoing knee arthroscopy and one involving patients with lower-leg casting, evaluated low-molecular-weight heparin as clot prophylaxis. The incidence of symptomatic venous thromboembolism was low, and anticoagulation did not influence it. Patients who undergo arthroscopic knee surgery and patients who are treated with casting of the lower leg are at increased risk for venous thromboembolism (i.e., deep-vein thrombosis or pulmonary embolism). 1 , 2 Venous thromboembolism is an important health problem that is associated with considerable mortality, morbidity, and resource expenditure. 3 – 5 The use of pharmacologic thromboprophylaxis after most orthopedic interventions is well established, because it strongly reduces the risk of thrombosis while only slightly increasing the risk of bleeding. 6 – 8 However, whether such prophylaxis is effective after arthroscopic knee surgery is uncertain, despite the fact that this procedure is the most commonly . . .