Unicondylar surgery generally refers to unicondylar knee replacement surgery. The foot on the affected side stays swollen after the surgery, which may be due to slowed venous return, deep vein thrombosis, hypoproteinemia, etc., and you should consult the doctor to find out the cause of the disease in time. 1. Slowing down of venous return: due to the tissue damage around the incision during surgery, postoperative pain and activity limitation, decreased activity and other factors, resulting in weakening of muscle strength of the lower limbs, obstruction or slowing down of venous and lymphatic return of the lower limbs, leading to swelling of the lower limbs. 2. Deep vein thrombosis: due to surgical trauma, prolonged bed rest and other reasons, resulting in slow blood flow in the lower limbs, vascular endothelial damage, vascular hypercoagulability, which is prone to deep vein thrombosis, manifested as swelling of the affected limbs, accompanied by persistent pain and pressure pain. 3. Hypoproteinemia: due to blood loss during surgery, traumatic exudation and other causes of excessive loss of plasma proteins, as well as postoperative loss of appetite and insufficient protein intake, can lead to hypoproteinemia, which can cause swelling of the limbs, especially the affected limbs of the swelling performance is more obvious. There may be other reasons for the swelling on the affected side of the foot after unicondylar replacement surgery, which should be consulted in time to clarify the specific cause and then targeted treatment.