Knock Knees | Testing and Diagnosis

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How are knock knees diagnosed?

Knock knees become apparent when a child stands with legs straight and toes pointed forward. Your child’s doctor can determine the severity of the knock knees by observing the position of the legs, knees and ankles and by measuring the distance between the inner ankle bones. The condition is considered more severe the wider the distance between the ankles.

The doctor’s exam for diagnosing knock knees may include:

  • measurements of your child’s length and height 
  • measurements of weight and body mass index (BMI) 
  • measurements taken of knee extensions and rotations 
  • assessment of leg-lengths and leg symmetry 
  • observation and assessment of gait

What tests are needed?

If your child is within the normal age for knock knees, has a normal exam with a typical appearance and no functional problems, Boston Children’s doctors don’t usually take x-rays, preferring to avoid unnecessary radiation. If your child is older than the usual age range or if the legs aren’t symmetrical, your doctor will usually opt for standing x-rays.

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- Sandra L. Fenwick, President and CEO

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