Children’s knee pain at night may be caused by excessive exercise, growing pains, synovitis and other factors. 1. Excessive exercise: children exercise for a long time during the day, resulting in mild damage to the knee area, and when they sleep at night, the symptoms of knee pain can occur. 2. Growing pains: children in the process of physical development, there may be growing pains, which will make the knee thigh and calf localized pain symptoms, usually no other clinical symptoms, with age will gradually disappear. 3. synovitis: when children have synovitis, in the process of sleeping at night, the knee area by the cold wind stimulation, may make the synovitis aggravated, will cause the symptoms of knee pain, in the daytime excessive activities, will also appear obvious knee pain. Parents are advised to take their children to the doctor if they have knee pain at night and frequently during the day.