Hip synovitis in children may be related to infection, trauma, congenital developmental abnormalities and other causes. 1. Infection: prolonged inflammatory stimulation can lead to hip synovitis in children. Some children have a history of upper respiratory tract infection, such as cold and flu, 1-2 weeks before the onset of the disease, and some children may have infections in other parts of the body. 2. Trauma: If children’s hip joints are stimulated by external forces leading to localized injuries, such as sprains of the knee joint, it can also cause hip synovitis. 3. Congenital developmental abnormalities: If children have congenital growth and developmental abnormalities, such as synovial lesions, it is also easy to cause hip synovitis. There are other causes of hip synovitis in children, so parents are advised to take their children to the hospital as soon as possible to clarify the cause of the disease and carry out regular treatment.