Sudden swelling, thickening and hardening of the calves are related to cold, strenuous exercise, kidney disease, heart disease, liver disease, varicose veins of the lower limbs and so on. Sudden swelling, thickening and hardening of the calves are related to the following factors: 1. Cold: Calf in a cold and wet environment can lead to poor blood circulation in the legs, which causes swelling, hardening and thickening of the calves. 2. Strenuous exercise: prolonged strenuous exercise can cause muscle spasms in the legs, resulting in swelling, hardening and thickening of the calves. 3. Kidney disease: such as nephrotic syndrome, the loss of protein in the urine, plasma osmolality decreases, the phenomenon of edema can occur, the legs can be swollen and thickened. Sudden swelling and hardening of the calves may also be liver disease, heart disease, varicose veins of the lower extremities, etc. It is recommended to go to the hospital, improve the examination to determine the cause of the disease, and then give targeted treatment or treatment.