The calf bone is curved, this condition may be caused by both physiological reasons, but also due to disease. The common causes are as follows: 1, due to genetic factors. Because the normal human body, the calf part of the bone itself has an outward curvature. Some patients due to the influence of genetic factors, may cause the curvature is more obvious compared to the normal people, so in the body surface looks and feels more curved calf. This condition is overwhelmingly physiological and is not a disease. This condition is particularly noticeable in younger women. The condition should be treated if there is limited or abnormal movement of the knee joint. 2. It may be caused by prolonged upright weight bearing. During the evolution of the human body, the need for upright weight-bearing of the lower extremities has led to an appropriate physiological bending of some of the bones in the lower extremities to accommodate this weight-bearing. This is a manifestation of biological evolution.3. This condition is caused by the overuse of the lower leg. For example, if the patient has to walk long distances or carry heavy weights, this will gradually lead to overuse of the lower leg and excessive wear and tear on the knee and ankle joints, followed by bending of the lower leg. Finally, the condition can also be caused by osteoporosis or old damage to the calf, both of which may cause bony deformities in the calf, resulting in a curved calf.