Another very useful one from the archives; a BMJ article from 2015 about which issues with children’s legs don’t have to be referred to orthopaedics. Always good to know.
Possible normal lower limb variants
- Rotational: intoeing and outtoeing
- Angular: genu valgum and genu varum
- Flexible flat feet (I think this is meant to be part of the outtoeing section – article’s a little unclear at some point)
- Metatarsus adductus
- Internal tibial torsion
- Femoral anteversion
Metatarsus adductus is an internal angulation of the forefoot on a neutral or flexible hindfoot (what’s meant by ‘neutral or flexible’ isn’t clarified, but I guess it means no other deformities such as club foot?) In the normal foot, the lateral border should be straight and the heel bisector line should pass between the 2nd and 3rd toes. In metatarsus adductus, the lateral border is curved and the heel bisector falls lateral to the normal line.
Incidence is 1:1000, making it the most common congenital foot deformity.
Almost 90% will resolve spontaneously; if the foot is flexible, wait and see. Serial casting may help in cases where the foot is rigid or the adductus does not resolve by 6 – 9 months.
Internal tibial torsion:
Most common cause of intoeing overall. Feet are internally rotated while patella is in neutral position.
Check the angular difference between the transmalleolar axis of the ankle and the bicondylar axis of the knee.
Can show up as clumsiness/frequent tripping. Can be unilateral (1/3 affected children) and can be associated with metatarsus adductus (also 1/3 affected children). Usually most apparent when child begins to walk.
Resolves naturally. Occasionally needs rotational osteotomy if still present >10 years and causing significant problems with trips/falls at that point.
The angular difference between the axis of the femoral neck and the transcondylar axis of the knee (there will normally be at least some difference; an average of 16 deg in adulthood, though the average at birth is 40 deg).
Most pronounced between the ages of 4 and 6. Shows up with:
- Sitting in W position (a kind of splayed-out-sideways kneel)
- Intoeing while walking
- Tripping due to feet crossing
- Squinting patella – patellas point inwards
- Eggbeater running pattern – inward rotation of the thighs, outward rotation of the legs and feet
Spontaneously resolves in >80% by late childhood. Rarely needs treatment. Rotational osteotomy of the femur is possible, but has a high rate of complications and is rarely necessary. (Orthotics have never been shown to help.)
Normal, and usually resolves by 18 – 24 months of age. However, can also be caused by:
- Calcaneovalgus (generally responds to passive plantarflexion stretching exercises)
- Congenital vertical talus (typically needs serial casting or surgical correction)
Those two conditions can usually be differentiated by a lateral radiograph of the plantarflexed foot. Unfortunately, the article didn’t clarify how to differentiate either from normal physiological outtoeing, apart from mentioning rocker-bottom feet.
In older children:
Usually external tibial torsion and occasionally femoral retroversion. However, can also be caused by more severe conditions such as Perthes and SUFE, so these should always be considered, especially in unilateral outtoeing.
Note that external tibial torsion is associated with increased prevalence of patellofemoral instability and/or pain, so isn’t entirely harmless.
Flexible pes planus (flat feet)
Normal in infancy/toddlerhood due to fat pad. Normally resolves between 4 and 8 years.
In older children, differentiate between flexible and rigid flat feet – do this by seeing whether the arch reconstitutes when the child is on tiptoe or the foot is dependent. If so, and if the child has no symptoms, then there is now a consensus that no action is necessary and that they can be treated symptomatically. However, flexible flat feet aren’t always asymptomatic; they can sometimes be painful, though it isn’t clear how best such feet are managed. They can also be a sign of underlying disorders:
- Neurological – e.g. cerebral palsy
- Muscular – e.g. muscular dystrophy
- Connective tissue – e.g. Marfan’s, Ehler’s-Danlos
So do examine the child for underlying problems.
Rigid flat foot, which is much less common, is usually painful and can be due to:
- Tarsal coalitions
- Congenital vertical talus
- Inflammatory disorders (pes planus is a common feature of juvenile idiopathic arthritis)
Obscure interesting fact learned from a follow-up letter to the article: The names for these (varum and valgum) are the wrong way round. ‘Valgus’ was actually the Latin for ‘bow-legged’ and ‘Varus’ is the name of a famous Roman general who was in fact knock-kneed. I guess that mistake is beyond redemption at this point, as the confusion that would result from changing them over would be past bearing, but it’s good to know. Thank you, Basil Moss of Nottingham.
Intercondylar distance >6 cm when medial malleoli in contact. (I think. Article a bit fuzzy at that point.)
Physiological in growing children. (Internal tibial torsion can also make it look worse.) Pathological causes include:
- Blount’s disease
- Metabolic (rickets, renal osteodystrophy)
- Skeletal dysplasia such as achondroplasia
Causes for concern:
- Unilateral or asymmetric
- Progressive (I assume this means after age 6 months, which is when it’s typically maximal according to a study the article cited).
- Associated with short stature (I assume this is if achondroplasia is suspected)
- Seen in a child > 3 years.
Otherwise, reassure and observe – but consider possibility of Vitamin D deficiency and also role of obesity.
Intermalleolar distance >8 cm with knees in contact. Normal in young children (maximal at 4 years, typically diminishes by 11 years). Can also be idiopathic. Pathological causes include:
- Congenital (fibrous dysplasia)
- Metabolic (as for genu varum)
- Skeletal dysplasia such as pseudoachondroplasia
Causes for concern:
- Unilateral or asymmetrical
- Accompanied by short stature
- Seen in a child <2 years
Otherwise, as for genu varum above. (Note that rickets is more typically associated with bow legs, but can cause knock knees.)
Musculoskeletal examination in children
Height and weight
- Observe gait and foot progression angle (angle the child’s foot makes with the direction in which he/she is walking)
- Observe standing – squinting patella? Flat foot?
- Observe sitting – W position?
- Observe running – will accentuate any problems
- Observe lying down
- Check shape of foot – lateral edge (should be straight) + heel bisector line (should be between 2nd & 3rd toes)
- Tibial rotation – prone position, knees flexed to 90 deg, measure angle foot makes with thigh
- Femoral rotation – still in above position – check hip rotation symmetrical in internal and external rotation
- Check for hypermobility (involves something called the Beighton score, which I take it is beyond the scope of the article as wasn’t otherwise discussed).
- Distance between knees while standing and lying with ankles together (should be <6 cm)
- Distance between ankles while standing and lying with the knees together (should be <8 cm)