Leg pain in a seven-year-old child may be caused by trauma, growing pains, synovitis and other factors. 1. trauma: children can feel pain in their legs when they play sports, accidentally fall down or suffer injuries to their legs due to other reasons. 2. Growing pains: Growing pains are characterized by pain in the legs, knees and other parts of the body, and are common in children under the age of 12 or 13. They are usually caused by rapid growth and other factors that cause pain in the leg muscles, which can be relieved by applying hot compresses or massaging the legs. 3. Synovitis: Sprains of the legs and overuse of the joints can lead to damage of the synovial membrane of the joints, which in turn leads to synovitis. Common manifestations are joint pain, swelling, etc., and in severe cases, it will also lead to joint flexion and extension difficulties. If your child’s leg pain is more serious, we recommend that you go to the hospital for an examination and a clear diagnosis, and treat the symptoms according to the specific conditions under the guidance of the doctor.