Whether a 4mm thrombosis of the intermuscular vein in the calf is serious or not depends on the symptoms and the patient’s own condition. If the symptoms are mild, it is usually not serious, but if the thrombus is dislodged, it will be more serious. Calf interosseous vein thrombosis 4mm, may be manifested as swelling and accompanied by local pain symptoms, symptoms will be aggravated when walking. Clinical symptoms are relatively mild, it is recommended to soak feet in hot water, avoid strenuous exercise, while oral anticoagulant drugs, is not too serious. In addition, with the body’s muscle movement, the thrombus may be squeezed off, into the deep veins, and then into the heart to form a pulmonary embolism leading to death. In addition the sequelae of chronic thrombosis can also cause long-term illness, affecting the patient’s life and work. It is recommended that patients avoid squeezing the thrombosed area. If the symptoms are serious, patients should consult a doctor immediately and receive anticoagulation and thrombolytic therapy under the guidance of the doctor.