The main reasons for a child’s sudden leg pain include: growing pains, localized inflammatory stimuli, muscle strains and so on. 1. Growing pains: If a child’s bone growth rate is relatively fast, and the growth and development of the surrounding tendons, muscles and other tissues are not coordinated, it is easy to cause a kind of physiological pain, also known as growing pains, manifested as a sudden pain in the legs. With age, this pain can be slowly relieved. 2. Local inflammatory stimulation: for example, synovitis, usually due to repeated stimulation of the local synovial membrane, extrusion, resulting in local congestion and edema, and the production of some inflammatory factors to stimulate the peripheral nerves and produce pain. Usually after overwork, cold and flu, pain can suddenly appear or pain symptoms become more obvious. Children suddenly said leg pain, there may be other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.