Patient Information

Knocked knees (genu valgum)

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What are knock knees?

Knock knees is a condition in which knees touch (or “knock”) one another even when the ankles are apart. It is a common condition in healthy children in early childhood and can be part of normal growth and development, usually worst at the age of 4, and ‘normalised’ by the age of 7. However, when it occurs outside of normal development or is more severe than normal, it maybe due to an underlying disease.

Diagram of lower limb alignment – Knock knees (left) vs. Normal alignment (right)

Symptoms

  • Most often this condition is asymptomatic
  • Appearance of the ankles further apart than normal when the knees are together. This usually becomes apparent from 2 - 3 years old.
  • Unusual walking pattern with outward rotated feet – hip, knee, ankle or foot pain may result from this abnormal gait.
  • Difficulty running
  • Severe cases may cause knee pain or limping

Causes

  • Physiologic – normal part of growth and development (most common)
  • Being overweight or obese
  • Trauma
  • Infection
  • Rickets
  • Skeletal dysplasia
  • Benign tumours or tumour conditions

When should parents be concerned?

  • Your child has a limp or pain in their legs
  • Difficulty in walking
  • Only one leg is affected, or one leg is significantly worse than the other
  • Knock knees are severe
  • Getting worse over the age of 5 - 6 years old
  • Persisting after the age of 10 years old
  • Your child is unusually short for their age
  • Develops later in childhood
  • Has a known underlying condition

Diagnosis

Through physical examination of the legs and gait. Measurements of the distance between both ankles may be taken and monitored over time.

Your doctor may arrange x-ray imaging for further assessment or confirmation of diagnosis.

Treatment

Treatment is rarely needed and most commonly as your child grows their legs will straighten. Majority will grow out of the condition by 7 years of age. Splints, bracing and special shoes are not recommended.

Surgery is only required if a severe deformity is present or persisting, the deformity is asymmetric, there is significant difficulty with pain or mobility which could be improved.

While your child is still growing (before the age of 13 - 14 for girls and 16 - 17 for boys), using guided growth (small metal plates or screws over the growth plate) is a small, usually day case procedure, to help correct knocked knees over time.

Case imaging: Knock Knee in Hereditary Spastic Paraparesis in 12 Year Old Girl before guided growth procedure
Case imaging: Knock Knee in Hereditary Spastic Paraparesis in 12 Year Old Girl after guided growth procedure performed by Dr Christy Graff

After your child has finished growing, realigning bones by cutting them is a much bigger operation to correct the position of the knees.

Case imaging: Asymmetric knock knee due to kidney problems through childhood in a 13-Year-Old Girl – Before surgical correction
Case imaging: Asymmetric knock knee due to kidney problems through childhood in a 13-Year-Old Girl – After surgical correction performed by Dr Christy Graff

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