Bow legs or tibia vara are common in young children. The curvature develops from positioning in utero (in the uterus). This curvature remains until the muscles of the lower back and legs are strong enough to support them in the upright position.
By age five, there may be some improvement with growth but not much. The bowing could actually get worse as he gets larger and puts more weight through the growing but curved bones. The child may have trouble walking without tripping. The way the child walks may not look normal.
Correction of the deformity is about more than just the appearance. The angle, rotation, and length of the bone will be changed toward a more normal alignment. The goal is to restore the normal mechanical axis for the knee joint. The correction of angle will also affect the ankle and hip. Improved alignment can prevent future joint pain and problems from uneven wear.
If the bowing is only on one side or worse on one side, surgery will also equalize any differences in leg length present. Good correction now at a young age can prevent osteoarthritis and disability later.