The swelling of the back of the left foot is clinically common for the following reasons: First, a sprain of the left foot can cause local soft tissue damage, and the symptoms may affect the normal activities of the patient in the more severe cases. At this time, the patient should fully rest in bed, swollen parts of the ice for 24 hours to reduce tissue exudation, 24 hours later can be given local hot compresses, topical bruising oil to promote the inflammation, the absorption of swelling. Second, deep vein thrombosis of the lower extremity will cause impaired blood flow to the lower extremity, and excessive blood will accumulate in the ankle and dorsum of the foot, causing swelling of the extremity, at this time, the patient can have no obvious symptoms of pressure pain, and can be given subcutaneous injection of low molecular heparin, intravenous use of dextran and other drugs to improve blood circulation, and oral rivaroxaban to promote the dissolution of blood clots to reduce the symptoms of swelling of the foot.