There are many reasons for the swelling of one leg of the elderly, and the common causes are deep vein thrombosis, phlebitis, and proliferative arthritis. Elderly people should go to the hospital in time for relevant examination, and take targeted treatment after clarifying the cause of the disease. 1, deep vein thrombosis: elderly people are bedridden for a long period of time, or the amount of exercise is relatively small, it will slow down the speed of venous blood flow, the local blood is not smooth, so that the blood in the deep venous cavity of the abnormal coagulation, which can cause deep vein thrombosis, blocking the venous cavity resulting in venous return obstruction, blood stagnation in the legs, can cause elderly people to have one leg swollen. Swelling. Elderly people can take anticoagulant drugs for treatment under doctor’s guidance, such as warfarin sodium tablets, rivaroxaban tablets, and when the condition is more serious, it can be treated by surgical venous thrombectomy; 2, phlebitis: phlebitis may be caused by venous puncture injury, catheter mechanical damage to the vein wall, and prolonged exposure to irritating drugs, etc. Phlebitis will make the blood vessels of the lower limbs be squeezed, which affects the blood flow of the lower limbs, causing stagnation of blood, resulting in the swelling of one leg of the elderly. As a result, the blood stagnates, causing one leg to swell in the elderly. Elderly people can apply anticoagulant drugs under doctor’s guidance for treatment, such as toluenesulfonic acid edoxaban tablets, apixaban tablets, if the pain is more serious, you can take non-steroidal anti-inflammatory drugs for treatment, such as ibuprofen extended-release capsules, etc.; 3. Proliferative arthritis: proliferative arthritis is also known as osteoarthritis, which may be caused by a variety of causative factors, such as the interaction of mechanical and biological factors, and can be caused by age, trauma, fatigue, and other factors, including the use of a variety of drugs and other factors. It can be caused by age, trauma, obesity, genetics, inflammation, metabolism and other factors. For the elderly with proliferative arthritis, the blood circulation in the joints is affected, which can obstruct the venous return of the lower limbs, and also stimulate the synovial membrane inside the joints, resulting in swelling of the joints, which can lead to the problem of swelling of one leg in the elderly. Elderly people can take non-steroidal anti-inflammatory drugs (NSAIDs), such as diclofenac sodium extended-release tablets and ibuprofen extended-release capsules, under the guidance of a doctor to relieve pain and improve joint function. If the condition continues to deteriorate, joint fusion and artificial joint replacement can be chosen as a treatment option.