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Knock Knees


Knock kneed alignment, or genu valgum, is an abnormal curvature of the lower legs which result in a large gap between the feet and ankles when the knees are touching. Knock kneed alignment is usually noticeable by ages 4 or 5 but the legs begin to straighten and align normally without treatment by the time the child is 6 or 7. In some cases, knock kneed alignment persists for unknown causes. Bone conditions such as rickets or scurvy, as well as inherited bone deformities, can also cause knock knees.


In most cases of knock kneed alignment the cause is unknown, although childhood conditions that can be responsible include:

  • Rickets – a rare condition that affects a child's bone development and is usually caused by a vitamin D deficiency (sunlight is a source of vitamin D and is also found in oily fish, eggs and fortified spreads and breakfast cereals.
  • Nutritional conditions – such as scurvy (a vitamin C deficiency), which can adversely affect the development of bones and joints (although this is rare)
  • Rare genetic conditions – examples include Cohen syndrome, which causes a number of problems, such as moderate to severe learning difficulties, progressive visual problems and unusually bendy joints

A family history of skeletal abnormality can also be an underlying cause of knock knee in children.


If a child with knock knee stands with their knees together, their lower legs will be spread out so that their feet and ankles are further apart than normal.

A small distance between the feet and ankles is considered normal. In children up to four years old, a gap of up to 10cm (around four inches) is not a cause for concern.

However, you should have your child examined by a doctor if:

  • the gap between their ankles is greater than 10cm
  • there is a big difference between the angle of their lower legs when standing straight
  • there is an excessive inward or outward knee angle
  • they have knee pain as a result of the angle of their knee
  • they are having difficulty walking or they walk awkwardly


In addition to measuring the distance between your child’s ankles, your doctor may also assess your child’s:
  • height
  • knee symmetry (how even the knees are)
  • leg, hip and feet alignment
  • gait when they walk (to check whether they can walk normally)

Your child may need to have an X-ray to help identify any underlying problems that are causing knock kneed alignment.


In most cases, knock kneed alignment does not need to be treated, because the abnormal curvature of the lower legs corrects itself as a child grows. In young children (up to four years old), a gap between the ankles of 10cm (around four inches) or less is not usually a cause for concern. It will often correct itself by the time the child is six or seven years old.

If your child’s knock knee is caused by an underlying condition, such as rickets or scurvy, the condition will need to be treated.

In rare cases, corrective surgery is used to treat severe cases of knock knee. It is usually only recommended when the gap between a child’s ankles is greater than 10cm and their lower legs are severely curved, resulting in knee pain or difficulty walking.

After surgery, the knee has to be kept still and straight using a splint (support), which will usually need to be worn for about five to six weeks. Crutches will also need to be used during this time to keep the weight off the leg that has been operated on. It will usually take about three months for the leg to fully heal. During this time, physiotherapy may be recommended to help improve the mobility of the knee and aid recovery.