The causes of newborns’ calf bones look bent include physiologic and pathologic, and the pathologic factors include rickets, etc. The treatments include medication such as vitamin D, surgery, and so on. 1. Physiological factors: newborns’ legs will be flexed to adapt to the environment because they have been in the mother’s stomach for a long time before birth. Therefore, the calves of newborns will look more bent for a period of time after birth, and the symptom will be gradually relieved with the growth of age. 2. Pathological factors: rickets is a disease caused by abnormal calcium and phosphorus metabolism as well as ossification disorders. Symptoms such as chicken breasts, rotund legs and irritability will appear when vitamin D absorption or conversion is impaired. Treatment includes medication such as oral vitamin D, if the bone deformity is serious, surgery is needed in time to correct. The choice of medication should be made under the supervision of a doctor. When a child becomes ill, he or she should go to the hospital immediately.