For lower extremity venous thrombosis, the considerations for filter implantation must pay attention to the size of the inferior vena cava implantation. Not all patients with deep vein thrombosis need to have a filter placed, depending on the indications, such as when anticoagulation is contraindicated in the patient, when the thrombus is large in the proximal iliac segment, or when there is a floating thrombus on ultrasound. For example, if the thrombus is contraindicated by anticoagulation, if the proximal iliac segment is large, or if there is a floating thrombus on ultrasound, a filter should be placed in advance. Major orthopedic surgeries, such as hip and knee, which may cause thrombus dislodgement, should also be done prophylactically. If it is necessary, try to put temporary filters or convertible filters, and try to recycle the filters within the best time after the whole treatment procedure or surgery.