HPSE and deep vein thrombosis: However, despite prophylaxis, subclinical deep-vein thrombosis develops in approximately 15%–20% of patients shortly after surgery, and symptomatic venous thromboembolism develops in 2%–4% of patients during the first 3 months post-surgery.61 We have recently reported a significant increase in heparanase procoagulant activity observed following orthopedic surgery.39 The study group included 50 orthopedic patients: 31 patients underwent hip surgery, and 19 had knee operation.