Nine-year-old boy leg cramps may be due to fatigue, cold stimulation and other physiological factors, may also be due to calcium deficiency and other conditions. 1. Physiological factors: usually nine-year-old boys living habits are poor, often stay up late, resulting in overwork, or the child’s legs by the cold stimulation, there may be cramps, is a normal physiological phenomenon. 2. Calcium deficiency: If the nine-year-old boy usually poor eating habits or excessive weight loss, there may be a lack of calcium. And the child’s lack of calcium will have an impact on the organism, may appear cramps, anorexia, weakness and other symptoms. In addition to the above factors, leg cramps in nine-year-old boys are also related to epilepsy, tetanus and other conditions, and it is recommended that patients clarify the cause of the disease in time and treat it reasonably.