Bowed Legs

Children are commonly referred to our office for us to check the alignment of their legs. The parents may feel their legs are too bowed or too knock-kneed. Our job is figure out if the alignment of their legs is physiologic (part of development) or pathologic (caused by some disease process).

The term we use for bowed legs is genu varum and the term for knocked knees is genu valgum.

To understand if the child has an abnormal leg alignment, you have to first understand what is a normal leg alignment and this depends on the age of the child.

Infants are generally born with bowed legs secondary to their positioning prior to birth. A child’s legs will generally straighten by eighteen to twenty-four months of age. Children will then become knock-kneed by three to four years of age. By five to six years of age, the degree of knock knees will decrease, leaving the average pattern of mild knock kneed alignment which carries on into adulthood.

What I just described is for the average child, but as with anything, no one thing is “normal”. Normal is a range of things and can be quite variable as is seen with siblings and friends.

Physiologic bowing, which is part of a child’s development, will improve over time. Pathologic bowing, which is due to some disease process, will get worse over time.

The image to the left is of a fourteen month old male who was brought in for the evaluation of bowed legs. Is this physiologic or pathologic bowing? First, you have to take into account his age. At fourteen months of age many children normally have bowed legs. Children’s legs will usually straighten out by eighteen to twenty-four months of age. Second, this child has a lot of internal tibial torsion, which will make bowing appear worse.

The x-rays in the image are from the same child. The legs in the left x-ray looks bowed because the child’s legs are rotated outward. The right x-ray was taken correctly with the child’s kneecaps facing straight up, thereby, removing any effect of internal tibial torsion. Notice how the legs look pretty straight. This child has physiologic bowing and his legs did straighten out as he got older. Many disease entities can cause pathologic bowing. Some are generalized bone disorders such as rickets or bone dysplasias, and some a localized bone disorders, such as Blount’s disease.