Also known as Genu varum, this is due to bowing of the tibiae causing the knees to be wide apart when standing with the feet together. It is a relatively common problem in toddlers and in children up to 3 years old and usually resolves without treatment.

Severe bow legs may be caused by rickets. Another cause is Blount disease (infantile tivia vara), an uncommon condition seen predominantly in children of African background.