As mentioned earlier, most patients who develop pulmonary embolism are caused by dislodged venous thrombosis in the lower extremities. Patients often have swollen and painful legs at the beginning of the disease. People usually do not take leg swelling seriously, guessing that they may be too tired or have drunk too much water, so they ignore the step of going to the hospital for examination and plant a time bomb for themselves. Many people do not understand why leg swelling and leg pain are related to lower limb vein thrombosis. There are many veins in the lower limbs of the human body, just like the traffic network. The veins are supposed to be unobstructed one-way streets, and the venous valves are the traffic police, which control the blood flow back to the heart only from the bottom up. When they are in order, the lower extremities are healthy. When one day a venous thrombosis appears, it controls the traffic cop so that he cannot perform his duties, causing a traffic jam, and the blood flow takes advantage of the opportunity to go backwards. The retrograde blood stagnates in the lower extremities and sneaks out of the vessel walls, and the symptoms of swelling and leg pain in the lower extremities occur. Figure 2 Thrombus dislodged, forming pulmonary embolism The first reaction of patients with swollen legs and pain is “rubbing”. By rubbing the leg to promote blood flow back, can the swelling be reduced? In fact, this is an extremely wrong and dangerous act. The newly formed thrombus is not firmly bonded with the blood vessel wall, so it can be easily separated from the vessel wall and fall off after squeezing and rubbing. When the thrombus sticks to the blood vessel wall, it only causes leg swelling and pain, which is relatively safe and controllable. Once dislodged, it will drift to the heart with the blood flow and block the important intrapulmonary vessels, and pulmonary embolism will occur, endangering the patient’s life. Therefore, for people who have just undergone surgery, trauma, pregnancy, long-distance travel, suffer from cardiovascular disease or are older, it is important not to blindly rub the lower limbs when they suddenly appear swollen and painful. For patients with pulmonary embolism (especially the elderly) who have just been treated and discharged home, proper activities can promote blood flow and prevent the formation of blood clots again. However, many middle-aged and elderly people like to go to the park or neighborhood fitness equipment for massage, and some of them often put one leg on the bar or railing for back and forth rubbing (as shown below), this kind of exercise can cause blood vessels to rupture and bleed, while forming large hematomas, causing difficulties in treatment. Therefore, it is recommended that patients on anticoagulants avoid strenuous exercise and take exercises such as walking and playing Tai Chi for exercise. Pay attention to measuring the thickness of the legs and when there is a difference in the thickness of the two legs, go to the hospital for examination as soon as possible to prevent the disease from progressing. Figure 3 Exercises that promote the dislodgement of blood clots or cause blood vessel rupture