Sore and weak legs during menstruation may be caused by normal physiological phenomenon, calcium deficiency, menstrual syndrome and other reasons. 1. Normal physiological phenomenon: during menstruation, the pelvis is congested, which can easily compress the veins of the lower limbs, causing obstruction of venous return in the lower limbs, which may cause leg soreness and weakness. 2. Calcium deficiency: If the intake of calcium is not enough, it will easily cause calcium deficiency and lead to the phenomenon of weak and achy legs. 3. Menstrual syndrome: during menstruation, women’s resistance will relatively decline, the body is relatively weak, and it is easy to have some symptoms such as lumbar pain and weakness, leg pain and weakness. During menstruation, pay attention to diet, drink more hot water, strengthen nutrition, avoid catching cold, when the symptoms are serious, should go to the regular hospital in time, under the guidance of professional doctors to take targeted treatment measures.