GP-Update | Normal variants of lower limb conditions in children

How often have you encountered an anxious parent with their child with bow legs or in-toeing and wondered ‘is this normal or not?’. If you don’t feel 100% confident in knowing which child needs simple reassurance and which needs referral, you’re not alone. 25-50% of all new paediatric orthopaedic outpatient referrals are due to normal variants in the growing child! To help us a recent BMJ review nicely summarises the normal variants as well as red flags that should prompt a referral (BMJ 2015;351:h3394).

Key points in assessment

  • Normal variants should be symmetrical and painless.
  • Normal variants tend to improve over time in a predictable age-related way whereas pathological conditions worsen.
  • Consider impact of obesity and possibility of vitamin D deficiency rickets.
  • Short stature (

The table below provides a summary of different lower limb conditions.

Age range for normal variantUseful tips
Bow legs (genu varum)Present from birth. Most apparent between 10-14m age especially in early walkers. Resolves by about 2y.Measure intercondylar distance at knees whilst holding ankles together (should be <6cm). Consider vitamin D deficiency if severe/persists beyond usual age range/associated with short stature. Refer if persistent >3y as asymmetrical or worsening over time.
Knock knees (genu valgus)Part of normal development between age 3-6y before resolving.Measure intermalleolar distance at ankles whilst holding knees together (should be <8cm).Consider vitamin D deficiency if severe/persists beyond usual age range/associated with short stature.
Flat feetFoot arches do not start to develop until age 3y. Most flexible flat feet resolve by age 4-8y.Foot should be flexible and painless. Arch should appear when stands on tiptoes. No association with pain/functional problems in later life. Orthoses are unnecessary in asymptomatic children.
In-toeingThree causes: Metatarsus adductus Congential foot deformity in 1/1000 births (foot has curved border). If foot rigid or not improving by 6-9m then casting may be helpful. Internal tibial torsion – Feet internally rotated and patellae in neutral position. Femoral anteversion – Feet and knees internally rotated and child often W-sits and runs with odd egg-beater pattern.Regardless of cause most resolve by 8y without intervention (surgical intervention not considered before this age).
Out-toeingApparent from infancy as child starts to walk; resolves by 18-24m age.If persists beyond 2y or starts in older children – refer.

Referral

The following require prompt investigation +/- referral:

  • Genu varum (bow legs) in child aged >3y.
  • Genu valgum (knock knees) in child aged <2y.
    Asymmetry between limbs.
  • Knee, hip or thigh pain or progressive out-toeing in adolescents especially if overweight
  • Need urgent X-ray to look for slipped upper femoral epiphysis (needs urgent referral).
  • Knee, hip or thigh pain in school-aged children need urgent X-ray to look for
  • Perthes’ disease (needs referral).
  • Painful rigid flat feet especially in adolescents (may suggest tarsal coalition).

And, if you don’t feel very confident in examining children with musculoskeletal problems, a useful guide including videos from the Arthritis Research Council can be found here.

This article first appeared in The Sessional GP Magazine.

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