People can become bow legged for a number of reasons, but some common disorders or diseases, such as Blount's disease, rickets and lead poisoning, are often the culprit behind bowed legs. Most cases of bowed legs are not serious, and many people can live normal lives with this condition, but extreme bowleggedness can lead to issues such as arthritis.
Most infants are actually born with bowed legs, since they are in the fetal position for such a long period of time in the womb. As the child grows and begins to walk, at anywhere from 12 to 18 months, the bowed legs usually correct themselves, straightening out naturally to the point that the toddler can stand with their feet slightly apart and still touch their knees. In some instances, the child does not outgrow the bowed legs, and when the child stands with feet together, there is still noticeable space between the knees. If the child does not naturally correct the bowleggedness by age three, the child is considered to have bowed legs. Certain diseases and illnesses can also cause legs to be bowed, according to the National Institutes of Health. These include rickets, which is a result of vitamin D deficiency, lead or fluoride poisoning, Blount's disease or abnormal bone development. Fractures and broken bones that do not heal correctly can also lead to bowleggedness.