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Bow legs and knock knees in children

6-minute read

Key facts

  • A child has bow legs if their ankles touch but their knees are wide apart.
  • A child has knock knees if their knees touch but not their ankles when they are standing.
  • Knock knees and bow legs are usually physiological, which means they are a normal part of a child’s growth and development.
  • Sometimes knock knees and bow legs can be caused by an underlying medical condition.
  • Usually knock knees and bow legs don’t need any treatment and improve over time.

What are bow legs and knock knees?

Very young children often have knees and legs that look a bit awkward. Two types of bone-related conditions that can become obvious in young children are bow legs and knock knees. Both of these conditions are fairly common, and usually disappear as a child grows and matures.

What are bow legs?

When a child has bow legs, their ankles touch but their knees are wide apart — this is the opposite of knock knees. The medical term for bow legs is genu varum. Many babies have bow legs at birth. The condition may become more obvious once they start crawling or walking. However, most children will go on to outgrow the condition by 3 years of age.

What are knock knees?

A child has knock knees if their knees touch but not their ankles when they are standing. The medical term for knock knees is genu valgum. Parents often first notice their child has knock knees around 3 years of age.

A child will usually outgrow knock knees at 7 or 8 years of age. Most adults still have slight knock knees.

Illustration of a child with bow legs standing next to an older child with knock knees.
Bow legs are when a child’s ankles touch but their knees are wide apart. In knock knees, their knees touch but ankles are far apart.

What are the causes of bow legs and knock knees?

Knock knees and bow legs are usually physiological, which means that they are just a normal part of your child’s growth and development. Many children are born with bow legs, their knees then straighten out at around 2 years of age. They may then they develop knock knees at around age 4. Most children’s legs then straighten out again between ages 6 and 11 years of age. This is a normal process.

Knock knees can also be pathological rather than physiological. This means that there is a medical condition causing the knock knees. When knock knees are pathological, the knock knee angle is large, it worsens after age 8 rather than improving, occurs on only one leg, and may cause pain or a limp.

Some medical conditions that cause knock knees include:

Like knock knees, bow legs are usually physiological. If your child’s bow leg is only one sided, is severe, is getting progressively worse, doesn’t resolved by age 3, or your child is particularly short, a pathological cause may need to be considered.

Some medical conditions that cause knock knees include:

When should I seek help?

In most cases, children outgrow these conditions without needing any special treatments.

See your doctor if:

  • the condition is severe
  • your child still has bow legs after 3 years of age
  • knock knees worsen after 8 years of age
  • one leg is worse than the other
  • your child is in pain or limping
  • your child is short for their age

If your child has one of these conditions, and you are worried they may need help, see your doctor for advice.

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How are bowlegs and knock knees treated?

Children with physiological bowlegs and knock knees do not need any particular treatments, as they will simply grow out of these conditions with time.

Some children with pathological knock knees may need surgery to help correct their knee alignment, especially if they are in pain or have difficulty walking.

If your child’s knock knees or bow legs are due to an underlying medical problem, that medical problem may need to be treated.

Resources and support

The Royal Children’s Hospital website has a fact sheet on bow legs and knock knees in children.

Speak to a maternal child health nurse

Call Pregnancy, Birth and Baby to speak to a maternal child health nurse on 1800 882 436 or video call. Available 7am to midnight (AET), 7 days a week.

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Last reviewed: June 2023

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