Bow legs/Leg deformities in children

ANGULAR KNEE DEFORMITIES:

Bow legs (Inward bowing of legs, genu varum) and knock knees (outward bowing of legs, genu valgum) are common deformities in children. In genu varum, in a standing child the knees remain divergent with ankle touching each other, while in genu valgum when the knees are touching each other, the ankles tend to remain divergent apart.

Know the alignment of lower limbs at different ages: From birth to 1 year limb are naturally bent inward at knees to 10-15 degrees. This is called physiological (natural) varum. After 1 year of age, this inward bending gradually reduces and by 18–24 months, a neutral relationship is attained. After 2 years limbs start bending to outwards(valgus) which peaks at 3–4 years of age (may go up to 15–20°). Thereafter, the outward bending gradually reduces to 5-7 degrees by 5–6 years of age, which persists into adult life.

Common causes of leg deformities in children:

Vitamin D deficiency (rickets) is most common cause of bow legs (genu varum) in India. Other common cause is Blount’s disease. Cause of knock knees (genu valgum) remains unknown in most of the cases. Vitamin D deficiency is 2^nd most common cause of knock knees.

Blount’s disease:

This disease is also a common cause of bow legs in children and it is common in early walker and overweight. Early weight bearing in overweight children may cause mechanical disruption of growth plate. Diagnosis is made on X rays which shows deformed growth plate.

Management:

Parents need not worry for bow legs up to two years as bowing is normal (physiological) during this period. Parents may also notice intoing (toes point inward instead of pointing straight during walk) during this period which is also normal in toddlers. Both of these conditions correct as child grows older. Bowing after two years needs to be evaluated by a doctor. Most of the cases of abnormal bowing correct with vitamin D repletion. Persistant cases need surgical intervention. Braces are required for Blount’s disease for upto 2-3 years after that surgical intervention is required.

Knock knees (legs curve outward) are normal up to 7 years. However excessive curvature (doctor will assess on X rays) even during this age needs intervention. Persistent outward curvature beyond even years may require surgical intervention.