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Bow Legged Knee (Genu Varum)

  • What is bow legged knee?

    Bow legged knee

    Bow legs is a condition where the legs curve outward at the knees so that, when standing, the knees do not touch. Its appearance is most obvious between the ages of 12 – 18 months and can occur in 1 or both knees.

    It is rarely serious and usually does not require treatment as it does not cause pain and does not affect a child’s ability to crawl, walk or run. In most cases, bow legs go away by the time the child is 3 or 4 years old.

    However, if it persists into a child’s teenage years or adulthood, bow legs may cause discomfort in the ankles, knees and hips and require treatment for correction.

  • Bow legs in infants can be caused when a baby’s legs are slightly twisted in the tight confines of the womb.

    Other causes of bow legs include:

    • Blount’s disease

      This condition causes abnormal development of a child’s shins. The shins curve below the knees and, once the child starts walking, worsens the bow legs. Over time, this may lead to knee joint problems as well.
    • Bone dysplasia

      Bone dysplasia is a general term for many conditions that affect bone and cartilage growth, leading to abnormalities in bone size or shape.
    • Dwarfism

      The most common form of dwarfism is caused by a condition known as achondroplasia, which is a bone growth disorder that can lead to bow legs.
    • Infection or injury

      Prior infection, injury or a poorly healed bone fracture may prevent normal growth and development of the leg bones.
    • Paget’s disease

      Paget’s disease is a metabolic disease, more common in older people, which affects the way bones break down and rebuild. It causes the rebuilt bones to be weaker than usual, which can cause the legs to become bowed.
    • Rickets

      Rickets is caused by prolonged deficiency of vitamin D, which is essential for the healthy growth and development of bones. This condition causes the bones to become soft and weak, causing the legs to bow.

    Risk factors for bow legs include:

    • Being overweight

      Childhood obesity can place excessive weight or pressure on the joints, contributing to Blount’s disease and arthritis, among other conditions.
    • Starting to walk at an early age

      Children normally start walking between 11 and 14 months. Starting to walk too early increases their risk for Blount’s disease.
    • Having a family member who had bow legs

      Some causes of bow legs have a genetic link. This includes degenerative conditions such as osteoarthritis.

    There is no known way to prevent bow legs but it may be possible to reduce your risk for some conditions that may cause the condition. This includes:

    • Ensuring sufficient intake of vitamin D

      Rickets is caused by long-term deficiency of vitamin D, which can be prevented by consuming sufficient amounts in dietary intake and safe exposure to sunlight.
    • Protecting knee joints

      Maintaining a healthy body weight prevents unnecessary pressure on the knees, staying active helps to strengthen the muscles that stabilise the knees, and proper technique while lifting can also prevent injury to the knee joint.
  • While bow legs usually do not cause discomfort or pain in young children, this may change if the condition does not correct itself. Bow legs that persist can lead to symptoms such as:

    • An obvious gap between the knees when standing with the feet together
    • A gap that persists or worsens past the age of 3
    • Reduced range of motion in the hips
    • Difficulty walking or running
    • Knee or hip pain that is not related to injury
    • Instability of the knee
  • Bow legs can be diagnosed through:

    • Physical examination

      Your doctor will observe how your child walks and check if the bowing is symmetrical or if one leg is more severely bowed than the other. For children below 2 years of age, symmetrical bowed legs may not require further testing.
    • X-ray

      An X-ray may be recommended if one leg is more severely bowed than the other, or if the child is above 2 years of age. The X-ray can reveal if the bowed legs are caused by rickets, or any other bone abnormalities.
    • EOS imaging

      An alternative to conventional X-rays, EOS imaging is a low-dose, weight-bearing technology that uses less radiation. It simultaneously takes 2-dimensional and 3-dimensional full-body images of the skeleton from front and side view.
    • Blood tests

      A blood test will help to determine if the bow legs are caused by deficiencies in calcium or vitamin D, or if it is caused by Paget’s disease.
  • Bow legs may be treated using non-surgical or surgical methods, depending on its cause. Surgery is usually recommended if non-surgical options such as bracing and medication is insufficient to correct the bowing, or for teenaged and adult patients who are no longer growing.

    Non-surgical options for bow legs include:

    • Bracing and other orthopaedic devices can help younger children to correct the bowing. However, it is not effective for teenagers.
    • Guided growth, which involves using a temporary tether of the normal outer growth plate at the knee in a younger child or a permanent tether in an older child.
    • Supplements and medication can help to treat rickets.

    Surgical options for bow legs include:

    • Osteotomy may be performed to realign or straighten the leg. For moderate cases, it may also be stabilised by inserting a plate or rod. For severe cases, an external fixator may be needed, in which pins are used to connect the bone to an external device.
    • Limb-lengthening surgery can help to correct situations where bow legs has caused one leg to be shorter than the other.

    Treatment for bow legs is usually deferred if the child is below 2 years of age. However, if it appears to persist past the age of 3, it is best to see your paediatrician.

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  • Complications of untreated bow legs include:

    • Deformities such as difference in leg lengths if only one leg is bowed
    • Difficulty walking and running
    • Knee damage
    • Higher risk of arthritis later in life
    • Knee instability

    Complications occasionally seen after surgery for bow legs include:

    • Compartment syndrome (increased pressure in a muscle compartment)
    • Growth disturbance
    • Infection
    • Recurrence of deformity
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