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 variant Useful 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 feet Foot 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-toeing Three 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-toeing Apparent 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.

Aimee Lettis

Aimee Lettis from the GP Update team gives us short, sharp nuggets of clinical information for sessional GPs. The GP Update team run one-day courses, bringing GPs up to date with all the latest evidence and guidelines.

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