The causes of leg cramps at night are mainly caused by overwork, cold and osteoporosis. 1. Overwork: When the calf is overworked during the day, it will lead to the accumulation of lactic acid in the calf, which may produce muscle spasms, thus making it easy for cramps to occur at night. 2. Cold: Calf cramps are caused by cold stimulation of the soft tissues of the calf during sleep at night; 3. Osteoporosis: the bone quality of middle-aged and old people is decalcified faster due to ageing, resulting in lower blood calcium, which is prone to cause leg cramps at night. In daily life, it is necessary to reduce the level of leg fatigue, pay more attention to warmth, and avoid leg cold at night. It is also possible to improve bone density by strengthening anti-osteoporosis treatment, such as calcium supplementation and activation of vitamin D, so as to reduce the occurrence of leg cramps at night.