Children’s thigh pain may be caused by strenuous exercise, or hip synovitis, leukemia and other diseases. 1. Strenuous exercise: children are more active, usually too much exercise, therefore, when the children’s strenuous exercise, resulting in thigh muscle spasms, accumulation of a large number of lactic acid, to a certain extent, the symptoms of thigh pain, is a normal physiological phenomenon. 2. Hip synovitis: the cause of the disease is not clear, may be related to intra-articular injury, trauma, joint infection by pathogenic microorganisms, etc. The main symptoms are hip swelling, pain, restricted movement, etc. However, in some cases, the pain will be launched to the thigh or knee joints, so that the children will have thigh pain. 3. Leukemia: Studies have shown that the cause of this disease is related to chromosomal and genetic mutations, heredity, environment and other factors, including exposure to ionizing radiation and chemical substances, viral infections and so on. When leukemia cells proliferate and infiltrate, the affected child will have symptoms of bone and joint pain, which can manifest as thigh pain. Children’s thigh pain, there may also be other reasons, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.