The incidence of lower extremity venous thrombosis after arthroplasty is around 10% and is thought to be higher after knee arthroplasty than hip arthroplasty. Bleeding during arthroplasty, postoperative bed rest, and reduced activity of the lower extremity can lead to slow blood flow and hemodynamic changes that induce the formation of lower extremity venous thrombosis. Small, localized thrombosis is usually not clinically symptomatic. Ultrasound examination is non-invasive, and its safety and efficacy provide a reliable and easy method for clinical diagnosis and observation of anticoagulation effect. Prevention and treatment of lower extremity venous thrombosis: 1.Accurate and rapid surgical operation, avoid intravenous injury, and standardize the use of lower extremity tourniquet; 2.Pay attention to cardiopulmonary function monitoring and timely rehydration during the perioperative period to avoid dehydration and increase blood viscosity; 3.Elevate the affected limb after surgery, encourage patients to move their toes and move to the ground as early as possible; 4.Take anticoagulant drugs routinely after surgery to inhibit the formation of thrombosis; 5.Use 5. Use elastic stockings and intermittent inflatable compression devices as mechanical preventive measures to promote venous return of blood to the lower extremities; 6. Routine postoperative ultrasound examination, once thrombosis is detected, active anticoagulation therapy and regular review. Lower limb venous thrombosis is a common complication after arthroplasty. In the vast majority of cases, after close observation and regular treatment, the thrombus eventually mechanizes and disappears, and the patient’s discomfort is relieved and he is discharged smoothly. Therefore, people should not worry excessively.