Bow-legs means that there is a gap between the knees when the ankles are pressed together and knock-knees are present when there is a gap between the ankle bones with the knees are pressed together.
Babies are born with ‘bow-legs’ which gradually straighten out up till age two years. After this they become gradually ‘knock-kneed’ and the degree of knock-knee is most obvious between age 3-6. The legs then slowly straighten to the normal adult shape by age 10-12 years. Many babies have big calf muscles and lots of baby fat, which can make the leg seem quite bent even when the bones are only slightly curved. Heavy children and children with loose ligaments can stretch out their knee joints and can appear to have a greater deformity. If a child has bow-legs beyond the age of two, or knock-knees before age two or after age 10-12 years, this may indicate a problem and further investigations may be necessary, particularly if one side is different to the other or there are associated symptoms such as pain
The great majority of symmetrical bow legs and knock-knees will resolve as the child grows. Treatment with exercises, special diets, physiotherapy, special shoes or braces will often make no difference. If any concerns consult your local paediatric orthopaedic specialist.