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What Are Knock Knees?

Knock knees, also known as genu valgum, are a deformity in the legs characterized by close distance between the knees and a large gap between the feet. This inward turning (valgus) of the knees is developmentally normal between the ages of two and five, but the alignment should return to neutral after about age 7. When it does not, it is considered genu valgum.


Slightly knocked knees may cause no symptoms. More severe cases of knock knees can cause:

  • Abnormal gait
  • Balance issues
  • Knee, foot, ankle or hip pain
  • Stiff joints

Causes and Risk Factors

Knock knees are a developmental condition, meaning they develop as a child grows. At birth, a child has bowed legs due to his or her position in the womb. When the child begins to walk, usually between 12 and 18 months, the legs straighten out to neutral.

By age two or three, the legs have shifted to a knock knee position, where the knees are close together and the ankles are far apart. This too is normal, and the legs should return to neutral by about age 7.

If the condition appears later than toddlerhood—about age 6—it could be a sign of an underlying neurological or orthopedic condition such as:

  • Cerebral palsy
  • Dysplasia
  • Metabolic bone disease
  • Rickets
  • Spina bifida

Obesity is thought to increase the severity of knock knees.


Diagnosing knock knees is usually a simple process. For severe cases of knock knees, often a visual inspection is all that is required. Doctors can also measure the distance between the knees or the ankles. Imaging studies are rarely necessary to diagnose knock knees.


Slight cases of knock knees, as well as cases involving very young children, do not need to be treated. These are usually observed and monitored to make sure the knock knees either normalize on their own or do not get any worse.

More severe cases—such as those that interfere with balance or gait, cause knee pain or are the result of an underlying condition—can be treated. Treatment for any underlying conditions may also be necessary.

Conservative, nonsurgical treatment is usually sufficient and can involve:

  • Exercise and physical therapy
  • Leg braces or splints
  • Lifestyle modifications such as weight loss
  • Orthotics (custom shoe inserts)

Surgery, when it is necessary, can take a number of forms. One of these is called hemiepiphysiodesis, aimed at making the legs grow straighter and eventually return to a neutral position. This is accomplished by placing staples or a plate on the side of the knee closest to the other knee so that side stops growing but the outside continues to grow.

Another form of knock knees surgery is a wedge osteotomy. This is where a small chunk at the top of the tibia (shin bone) or bottom of the femur (thigh bone) is removed, which will correct knocked knee alignment.

If your child has knock knees that have not returned to neutral and you are interested in getting the condition corrected, schedule an appointment with our pediatric orthopedics department. We will discuss your child’s treatment options and help you make the best decision for your family.

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