Synovitis in children may be caused by over-activity of joints, joint injuries, infections and other factors. 1. Over-activity of joints: frequent strenuous activities in children may lead to congestion and edema of synovial tissues, which may easily induce synovitis. 2. Joint injury: for example, external blows may cause damage to bone, synovium, muscle, ligament and other tissues, which may lead to synovitis, which may cause joint pain, swelling, and in severe cases, activity restriction. 3. Infection: such as bacterial infection or periosteal tuberculosis infection, etc., may induce infectious synovitis, the child may also appear fever, fatigue, joint pain and tenderness and other symptoms. When the symptoms of synovitis appear in children, parents are advised to take their children to the doctor for examination and treatment as soon as possible to avoid aggravation of the disease.