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Knock knees

Knock knees is a condition in which the knees touch, but the ankles do not touch. The legs turn inward.

Alternative Names

Genu valgum

Causes, incidence, and risk factors

Infants start out with bowlegs because of their folded position while in their mother's womb. The legs begin to straighten once the child starts to walk (at about 12 to 18 months). By age 3, the child becomes knock-kneed. When the child stands, the knees touch but the ankles are apart.

By puberty, the legs straighten out and most children can stand with the knees and ankles touching (without forcing the position).

Knock knees can also develop as a result of a medical problem or disease, such as:

  • Injury of the shinbone (only one leg will be knock-kneed)
  • Osteomyelitis (bone infection)
  • Overweight or obesity
  • Rickets (a disease caused by a lack of vitamin D)

Signs and tests

A doctor or nurse will examine your child. If there are signs that knock knees are not a part of normal development, tests will be done.

Treatment

Knock knees are usually not treated.

If the problem continues after age 7, the child may use a night brace. This brace is attached to a shoe.

Surgery may be considered for knock knees that are severe and continue beyond late childhood.

Expectations (prognosis)

Children normally outgrow knock knees without treatment, unless it is caused by a disease.

If surgery is needed, the results are usually good.

Complications

  • Difficulty walking (very rare)
  • Self-esteem changes related to cosmetic appearance of knock knees
  • If left untreated, knock knees can lead to early arthritis of the knee

Calling your health care provider

Call your health care provider for an appointment if you think your child has knock knees.

Prevention

There is no known prevention for normal knock knees.

References

Wells L, Sehgal K. Normal Limb Development. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 667.1.

Updated: 11/12/2012

Neil K. Kaneshiro, MD, MHA, Clinical Assistant Professor of Pediatrics, University of Washington School of Medicine. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, David R. Eltz, Stephanie Slon, and Nissi Wang.


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