The inner side of the thigh suddenly shows pain between the following diseases are common: First, acute embolism of the arteries of the lower extremities, mostly seen in patients with coronary heart disease and atrial fibrillation, who will have a history of arteriosclerotic occlusive disease of the lower extremities. Embolus formation with blood circulation, can embolize to the arteries of the lower limbs. In the acute stage, the patient will show sudden pain, numbness, coldness and progressive aggravation of the lower limbs, also accompanied by nausea and vomiting, and ultrasound examination can make a clear diagnosis. Secondly, when venous thrombosis is caused by venous system disease, the patient will experience pain along with swelling of the limb, especially distal congestion and edema, as well as exudation and obvious tension blisters.