Knock knees (Genu Valgum)


These guidelines have been produced to guide clinical decision making for general practitioners (GPs). They are not strict protocols. Clinical common-sense should be applied at all times. These clinical guidelines should never be relied on as a substitute for proper assessment with respect to the particular circumstances of each case and the needs of each patient. Clinicians should also consider the local skill level available and their local area policies before following any guideline.



Knock knees is a condition in which the knees angle in and touch each other while the ankles remain spaced apart when the legs are straightened.

The condition is slightly more common in girls, though boys can develop it too. Knock knees are usually part of a child’s normal growth and development. Many infants have bowlegs, a condition in which both legs curve outward, up until they are about 24 months old. Knock knees usually become apparent when a child is 2 to 3 years old. The knees may tilt increasingly inward up until about age 4 or 5. Children’s legs usually become aligned by the time they are about 8 years old.

An inter-malleolar distance of between 2.5cm and 5cm is considered normal in the 3 to 7 year age group.

Rarely knock knees will have a pathological cause such as:

  • congenital bone or joint conditions
  • metabolic disorders
  • vitamin D deficiency
  • neurologic or neuromuscular conditions
  • previous trauma
  • infection.

An inter-malleolar distance of above 8cm is abnormal in any age group.

For current guidelines on assessment, management and referral guidelines on knock knees, visit HealthPathways WA

How to refer

  • Routine non-urgent referrals from a GP or a Consultant are made via the Central Referral Service
  • Routine non-urgent referrals from private hospitals are made via the PCH Referral Office
  • Urgent referrals (less than seven days) are made via the PCH Referral Office. Please call PCH Switch on 6456 2222 to discuss referral with the relevant speciality registrar.  

Reviewer/Team: Dr Kate Stannage, PCH Last reviewed: Aug 2021

Review date: Aug 2024
Endorsed by:

CPAC Date:  Aug 2021

This document can be made available in alternative formats on request for a person with a disability.

Referring service

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