Calf thrombosis is generally divided into venous thrombosis and arterial thrombosis. Common causes of venous thrombosis include prolonged bed rest, surgery, tumors, etc. Common causes of arterial thrombosis include diabetes mellitus, immune disorders, inflammatory infections, and atrial fibrillation. 1. Common causes of calf vein thrombosis (1) Prolonged bed rest: Prolonged bed rest leads to slowing down of blood flow and causes blood stagnation, which will lead to the formation of blood clots in the calf. (2) Surgery: Surgery causes damage to the lining of blood vessels, which leads to platelet aggregation and then leads to thrombosis of calf veins. (3) Tumor: Tumor can lead to thrombosis when the body’s anticoagulant system is abnormal. 2. Common causes of arterial thrombosis (1) Diabetes mellitus: In diabetes mellitus, the blood flowing in the body shows high coagulation state, which will lead to blood clots in the calf. (2) Immune diseases: long-term immune diseases can lead to inflammation of the lining of the blood vessels, which can lead to the formation of blood clots. (3) Inflammatory infections: Inflammatory infections lead to a higher amount of certain mixed components in the blood, which aggregate with each other to form blood clots. (4) Atrial fibrillation: In atrial fibrillation, blood clots in the atria can also lead to the formation of blood clots in the arteries of the lower legs. There are many other causes of blood clots in the calf, such as high blood pressure, hyperuricemia, obesity, etc. It is recommended to consult the doctor in time, complete the relevant examinations, and follow the doctor’s instructions to carry out targeted treatment and therapy after clarifying the cause of the disease.