The causes of sudden leg cramps include localized cold, hypocalcemia, cervical spondylosis and so on. 1. Localized cold: when the legs get cold, leg muscle spasms are likely to occur, mainly due to poor local blood flow. 2. Calcium deficiency: lack of calcium in the body can cause increased neuromuscular excitability, which can easily trigger involuntary muscle contraction and twitching, mostly in the leg muscles. 3. Cervical spondylosis: such as nerve root cervical spondylosis, spinal cord cervical spondylosis, etc., will compress the nerves. Such as compression of leg nerves may cause leg muscle spasm, numbness and so on. In addition to the above reasons, heavy physical labor and strenuous exercise can also cause the above symptoms. If the above symptoms do not improve, it is recommended to go to the hospital to identify the cause of the disease and carry out targeted treatment.