It is understood that deep vein thrombosis is recognized as one of the most difficult to treat and potentially life-threatening common diseases in modern medicine. DVT occurs in the lower extremities and is common after major orthopedic surgery, gynecological and surgical procedures, puerperium, obesity, bed rest, infection, and long flights. Be alert to venous thrombosis after artificial joint replacement. The 69-year-old Ms. Xun, suffering from severe osteoarthritis, is prepared to perform artificial joint replacement in a hospital, because she also suffers from hypertension, the doctor told her before the operation that the possibility of forming deep vein thrombosis in the lower limbs after the operation is greater, to which Ms. Xun and her family members are confused about the doctor’s advice: “What disease is deep vein thrombosis in the lower limbs, and how dangerous it is to the body? “ Venous thromboembolism is the abnormal clotting of blood in the deep veins, which is a venous reflux disorder. Lower extremity DVT is a manifestation of venous thromboembolism in the limbs. Slowed venous blood flow, blood hypercoagulation and endothelial damage are the main causes of DVT formation after artificial joint replacement. In patients with artificial joint replacement, the pain after replacement and the passive position of the limb to prevent dislocation cause the loss of muscle stretching action and reduce the driving force of venous blood flow, which slows down the blood flow and causes blood stagnation and hypercoagulation; the surgical trauma and the long time of the limb being twisted, repeated dislocation and reset can cause the damage to the endothelium of the blood vessels. In addition, blood stagnation can be caused by preoperative water fasting, intraoperative and postoperative blood and fluid loss, which can increase blood viscosity and cause deep vein thrombosis. In addition, surgical anesthesia, blood transfusion, application of intraoperative repellent tourniquet, heat polymerization reaction of artificial joint bone cement and application of electric knife can also cause deep vein thrombosis. Therefore, deep vein thrombosis is very likely to occur after artificial joint replacement. What can be done to prevent and treat lower limb DVT? Professor Wen continued, “The measures to prevent DVT are mainly divided into mechanical methods (including elastic stockings, foot pumps, etc.) and pharmaceutical methods. Thrombolytic drugs are mainly urokinase and streptokinase. The surgical methods of vascular surgery mainly include surgical embolization, direct catheter thrombolysis, balloon catheter dilation and endoluminal intervention techniques such as stent placement.” Acute pulmonary embolism is also a high-risk disease: Ms. Wang said about her brother who passed away has been very sad, she said, “My brother last year due to trauma caused by the right humerus fracture, in a hospital to perform incision reset intramedullary nail internal fixation, the operation suddenly died, the hospital gave the answer is acute pulmonary embolism. At that time, we could not accept this result, but the autopsy result was that thrombus was found in both femoral vein and pulmonary artery, and the medical appraisal agreed with the hospital’s diagnosis, but is this referee result correct?” Professor Wen said after looking at the clinical and autopsy pathology, “Most of the lower limb deep vein thrombosis is secondary to artificial joint replacement or hip fracture, the formation of deep vein thrombosis is related to certain genetic defects, it is formed by chance, but there is also inevitability in it, just that it is not fully discovered at present.” Pulmonary thromboembolism is a disease of pulmonary circulation and respiratory dysfunction due to obstruction of the pulmonary artery or its branches by a blood clot from the venous system or the right heart, commonly referred to as pulmonary embolism. Deep vein thrombosis is the main source of pulmonary embolism emboli, and pulmonary embolism is an acute, high-risk condition caused by thrombus obstruction of the pulmonary arteries. Acute pulmonary embolism leads to rapid death of the patient, which is mostly caused by the rapid obstruction of the pulmonary artery by the larger thrombus; while some non-fatal thrombus only obstructs the pulmonary segment below the blood vessel due to its small size, the patient only shows chest tightness and fever, which does not lead to death. Finally, Professor Wen said that this result is correct. Beware of “economic warehouse syndrome”: Patients of orthopedic surgery, gynecology and post-surgery need to be alert to the interference of deep vein thrombosis, and long-distance flight also needs to pay attention to deep vein thrombosis, which Mr. Zhang, who took a flight to Europe for business last year, knows very well. He said, “The flight transfer had more than ten hours, and I sat all the time. When I got off the plane, my left calf was swollen and in severe pain, and it took me a long time to recover from the rest, and I was told after I returned home that it was “economic warehouse syndrome”, that is, deep vein thrombosis of the lower limbs.” Why would lower limb deep vein thrombosis occur after a long flight? Prof. Wen explained: the main manifestations of peripheral DVT are: pain, heaviness or tension in the back of the calf, pressure pain in the muscles, and mild swelling around the foot and ankle joint. Central deep vein thrombosis mainly manifests as: pain in the groin and inner thigh, some are pain in the whole lower limb, diffuse and sunken edema, pain in the femoral triangle is obvious, a knot-like hard object can be touched, swelling and pressure pain in the affected limb, skin color is deeper than normal, flushing, dark red and cyanotic changes in the affected limb. The skin temperature of the affected side is significantly higher than that of the opposite side; pulsation of the dorsal femoral artery is present; the whole body shows hypothermia, weakness, and a slightly faster heart rate. This condition occurs after a long flight because of venous blood stagnation, and if there is atherosclerosis or venous valve insufficiency, “economic warehouse syndrome” will occur. But is there any sequelae of deep vein thrombosis? Prof. Wen explained: once the lower limb deep vein thrombosis occurs, in the acute stage, as the thrombus reproduction progresses, the venous obstruction further aggravates, from femoral white swelling to femoral cyanosis, causing venous gangrene of the limb. In the chronic phase, the thrombus in the lumen of the vein undergoes the process of adhesion with the luminal surface of the vein, contraction, neovascularization and self-fibrinolysis, and the patient’s vein undergoes the change of “blocking part of the recanalization and complete recanalization”, which eventually causes chronic lower extremity venous hypertension due to the blockage of the proximal vein and/or the destruction of the distal venous valve function, i.e., post-thrombosis Syndrome, mainly manifested as chronic swelling and superficial varicose veins of the lower extremities. Some foreign scholars’ statistical data found that the incidence of post-thrombotic syndrome is 20% to 50%.