Four-year-old babies always say leg pain may be related to excessive exercise, calcium deficiency, osteosarcoma or bone tumor and other factors. 1. Excessive exercise: If the baby has recently had strenuous exercise, it may lead to excessive stretching of the leg muscles, which will be relieved after resting. 2. Calcium deficiency: Some babies with calcium deficiency may also have growing pains, accompanied by night terrors and occipital baldness. 3. Osteosarcoma, bone tumor: a small number of babies in the above situation, may be related to osteosarcoma and bone tumors and other diseases, the need for further X-ray examination. Four-year-old baby always say leg pain may also have other reasons, it is recommended to go to the hospital in a timely manner to carry out relevant examinations, clear causes and then actively treat the symptoms.