The severity of calf vein thrombosis is not very serious, because the volume of calf vein thrombosis is relatively small, even once it is dislodged, the blockage to the pulmonary artery trunk is almost zero, so it will not block the pulmonary artery very seriously, even if the patient has symptoms of pulmonary embolism, it is not very serious, the patient may have symptoms of chest tightness and chest pain, but it will not endanger the patient’s life. If the patient has a blockage in the pulmonary artery and then a new thrombus grows into the main pulmonary artery, the patient’s symptoms will be aggravated. The symptoms in the lower leg are not very obvious because the area of the lower leg is relatively small and the collateral circulation is established quickly, so the patient may have gastrocnemius muscle pressure or slight edema in the lower leg, which can be controlled by medication.