Normal development

• Children at birth normally have varus knees (bow legs) which become neutrally aligned at around 14 months, progressing to 10 to 15° valgus (knock knees) at age 3 and then gradually regress to the physiologic valgus of 6° by around the age of 7‐9
• Parents may often be concerned at the appearance however the vast majority develop normal alignment and most cases need reassurance only
• Some people develop minor degrees of varus or valgus alignment which often can be familial

Variation in development

• Considerable variation exists and the normal range varies by around
• Pathological varus or valgus is where alignment is considered outside the normal range (+/‐ 6° from mean value for age)
• Measurements can be taken on x-rays and charted against normal reference ranges
• A valgus deformity at the knee will result in a more of a knock knee appearance with a larger gap than normal between the feet/ankles
• A varus deformity will result in a larger gap between the knees
• The majority of cases of bow legs or knock knees will resolve by the age of 10 but genu varum or excessive genu valgum after the age of 10 may require surgery
• Many cases are idiopathic, whilst some are familial
• Some cases may be due to an underlying skeletal disorder (skeletal dysplasia, Blount’s disease), physeal injury with growth arrest (usually unilateral) or biochemical disorder (rickets)