Elderly people with knee pain at night can not sleep during the day to get better may be due to a variety of reasons, such as osteoarthritis, synovitis, femoral head necrosis, cold and so on. It is recommended to go to the hospital to do a comprehensive examination to determine the cause of the disease to treat the cause. Specific instructions are as follows. 1. Osteoarthritis is a kind of degenerative disease, due to age, strain, trauma, joint deformity and many other factors caused by degenerative damage to the articular cartilage, joint edges and subchondral bone reactive hyperplasia. Clinical manifestations are joint pain, stiffness, swelling, joint deformity, etc., often aggravated at night. 2. Synovitis is a joint disease in which the synovial membrane is irritated and produces inflammation, resulting in the formation of fluid accumulation due to the imbalance of fluid secretion. When the joints are affected by various factors, the synovial membrane reacts and causes congestion or edema, which can be manifested as joint swelling, pain and joint cavity fluid accumulation. 3. Patients with femoral head necrosis can have reflex knee pain, which can be aggravated at night. 4. When the temperature drops at night, some old people may get cold legs due to the big change of temperature, which can be relieved when the temperature is higher during the day. So if you have knee pain at night and can’t sleep and get better during the day, you should consult a doctor in time to diagnose the cause of the disease and then treat the cause of the disease.