Children’s bone pain under the knee may be caused by growing pains, excessive exercise, acute injury, synovitis and other factors. 1. Growing pains: children’s physical development is too fast, in the process of development may appear growing pains, belong to physiological factors, usually appear at night, with the gradual development of the body, may be improved by itself, generally do not need to carry out special treatment. 2. Excessive exercise: children in the daytime excessive exercise, may lead to the accumulation of local lactic acid metabolites, will make the knee below the pain, manifested as bone soreness and pain, the symptoms are not obvious, after reasonable rest can be returned to normal. 3. Acute injury: for example, fall, external force, may make the knee bone or soft tissue damage, will cause pain symptoms, may also be accompanied by swelling and subcutaneous bruising. 4. Synovitis: For example, prolonged exposure of the knee to cold or chronic strain injury, resulting in damage to the synovial membrane of the knee joint area, causing synovitis, which will cause pain below the knee, and in severe cases, it will also affect the daily walking. Children with bone pain under the knee, and the symptoms continue to worsen, it is recommended to go to the orthopedic department of the hospital for examination and treatment, to avoid delaying the condition.