Knock Knees and Flat Feet in Children

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Knock Knees and Flat Feet in Children

• Dr Gillian Wilson

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Knock Knees / Genu Valgum

• Legs are bowed inwards in the standing position.
  Bowing occurs at or around the knee. On standing
  with knees together, the feet are far apart.

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Normal Development

• Most children are bowlegged from birth until
  around 3 years old, then become knock kneed
  until age 4 to 5, and straighten towards adult
  alignment by age 6 to 7.

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Investigations 1

• Measurement of intermalleolar distance. i.e
  Distance between two malleoli when the knees are
  gently touching with legs in adduction.
• Up to 3 and a half inches (9 centimeters) with
  child lying down is acceptable.
• 75 of children aged 2 - 4 years have some degree
  of intermalleolar separation.

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Investigations2

• Intermalleolar separation under 3 inches is
  normal at any age.
• Periodic observation and measurement if less than
  3.5 inches.
• If gt 3.5 inches, need AP X-Ray with both legs on
  same film for knee deformity, hip and ankle
  joints and view of both long bones.

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Indicators of Serious Disease

• Pronounced asymmetry
• Short stature
• Other skeletal abnormalities
• Intermalleolar separation greater than 3.5 inches

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Aetiology

• Developmental
• Miscellaneous syndromes e.g Rickets (Alk Phos
  raised, with x-ray changes)
• Rare Genetic disorders e.g Cohen Syndrome
• Nutritional conditions e.g Vitamin C deficiency
• Autoimmune e.g RA
• Degenerative e.g OA

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When to refer

• Age gt 7 with knock knee
• Unilateral problem i.e Asymmetry of legs
• Intermalleolar distance gt 3.5 inches (9 cms)
• Associated symptoms e.g Pain, Limp

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Treatment

• No evidence that shoe modification, splints, or
  exercises affect condition
• No evidence to justify surgical intervention
  under 6 inches of intermalleolar separation.
• Surgical options
• Medial epiphyseal stapling at 10 to 11 years
• Corrective osteotomy at maturity.

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Flat Feet / Pes Planus

• Arch of the foot is low. Medial arch is lost.
  There may be some valgus and eversion deformity
  of the foot.

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Normal Development

• Flat feet are normal when learning to walk.
• Medial arch does not develop until 2nd / 3rd year
  of life.
• Normal arch functions as a shock absorber.

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Investigation

• Ask patient to stand on tiptoes.
• If medial arch restores itself when standing on
  tiptoe or when foot is unloaded, no action is
  needed.

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Presentations

• 2 Groups
• Pain free feet with normal mobility and muscle
  power.
• Painful, stiff, hypermobile feet with abnormal
  muscle power i.e weak or spastic feet.

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Causes of Flat Feet

• Loose - ligamented flat foot
• Commonest type.
• Always bilateral.
• Arch looks normal when non weight bearing /
  standing on tip toe.
• Laxity can often be demonstrated in other joints.

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Rare Causes of Flat Feet

• Rocker bottom foot Congenital vertical talus.
• Coalition Syndrome Peroneal spastic flat foot.
• In both, subtalar joint movement is limited.
• In peroneal spastic flat foot, attempting to
  invert hind foot produces painful spasm of
  peroneal muscles.

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Rare Causes of Flat Feet

• May be part of a more generalized condition
• Severe joint laxity
• Cerebral Palsy
• Peroneal spastic flat foot
• Downs Syndrome

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Treatment

• No proven benefit from insoles, shoe
  modification, foot exercises.
• Spasmodic type
• Hindfoot fusion for pain relief.
• Subtalar arthrodesis corrects deformity.

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Summary

• Knock Knees
• less than 3 inches intermalleolar separation is
  normal at any age.
• Refer if age gt7. Asymmetry, intermalleolar
  distance gt 3.5 inches, short stature, pain or
  limp.
• Remember normal developmental stages.

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Summary

• Flat Feet
• Test by standing patient on tip toes.
• Refer if painful, stiff, hypermobile with
  abnormal muscle power.
• Waiting time for Orthopaedic OPA at Birmingham
  Childrens Hospital is less than 4 weeks, but gt 13
  weeks for physiotherapy.