The child’s old legs tense, can be considered to be cold legs, clothes are too tight and other physiological reasons, but also can be considered to be local eczema, urinary tract infections, the body lack of calcium and caused, according to the specific cause of the daily warmth, medication, reasonable diet and other measures. 1. Physiological reasons: after the legs are cold, it is easy to cause muscle spasm contraction, so the legs will be taut. Secondly, wearing tighter clothes will make the child have a sense of constriction, which will also be manifested as tense legs. In daily life, pay attention to keep warm, wear loose and comfortable clothes after the symptoms can be relieved. 2. Localized eczema: Eczema can be itchy, and there are many small red dots or plaques on the skin surface, which can make the child uncomfortable, so the legs will be tense. It can be treated by applying glyphosate lotion under the guidance of the doctor. 3. urinary tract infection: urethritis, will show the legs tense when urinating, and there will also be redness of the urethral opening. You can use penicillin or cephalosporin under the guidance of a doctor. 4. Calcium deficiency: Calcium deficiency can cause twitching of the hands and feet, tightness and stiffness of the calf muscles. Pay attention to give the child to eat more calcium-rich food, if necessary, follow the doctor’s advice to supplement calcium supplements, such as calcium carbonate D3 granules. There are more reasons that lead to the tightness of the child’s old legs, when the child has the above symptoms, it is recommended to go to a professional hospital, and through a reasonable way of treatment, to avoid leading to other complications.