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Bow legs and knock knees

What are bow legs?

This happens when there’s a gap between your childā€™s knees and ankles when they stand with their feet together. It’s normal in children aged under 2 years old.

Your childā€™s legs should gradually straighten once they start to walk, typically around 12 to 18 months old.

What are knock knees?

This happens when your child stands with their knees together and their ankles are at least an inch apart. It’s normal to have a gap of 2.5 inches (6 to 7cm) between 2 and 4 years old.

When your child grows, their legs usually becomeĀ increasingly straight and fully resolved at around 7 to 10 years old.

Causes of bow legs and knock knees

It’s rare that disease causes bow legs or knock knees but in some cases there may be an underlying cause.


Most children with bow legs or knock knees do not need treatment unless there’s a rare underlying cause which needs medical attention.

We recommend that children stay physically active to help their physical development and gross motor skills.

When to get further advice

Get advice from your GP when:

  • the appearance of your child’s legs is prominent
  • their condition persists for longer than the expected age range
  • your child experiences pain or it impacts on their normal function.