Blood clots can cause pain. Blood clots in the legs are mainly divided into arterial clots and venous clots, both of which cause pain in the lower extremities, but the symptoms and manifestations of pain differ depending on the clot. Arterial thrombosis in the leg is mainly an ischemic manifestation caused by the ischemia of the arteries in the leg, which is accompanied by pain, pale skin color, cold skin temperature, numbness, abnormal sensation and other symptoms in the lower limbs. The pain caused by venous thrombosis is mainly caused by swelling and discomfort, which is mainly due to the thrombus blocking the channel of venous return, and this symptom will be aggravated after prolonged standing and exertion, which is accompanied by symptoms such as red skin color and increased skin temperature of the lower limbs, so the thrombus can cause pain. To clarify whether the thrombus causing pain is an arterial thrombus or a venous thrombus, it is recommended to go to the vascular surgery clinic for ultrasound examination to clarify the diagnosis and further treatment for the thrombus under the guidance of a specialist.