Genu varum and valgum is physiologic (normal) at certain points in a child's development. Infants and children up to approximately 2 years of age frequently exhibit genu varum. Internal tibial torsion often co-exists with genu varum and may to accentuate the 'bow-legged' appearance. Children with other abnormalities such as short stature should be investigated with x-rays to determine if this is part of a generalized skeletal abnormality (or skeletal dysplasia). Radiographs are otherwise deferred unless the deformity is extreme or progressive. Non-physiologic genu varum may be the result of abnormalities of bone mineralization (rickets), skeletal dysplasia or "Blount's disease", a condition of unknown etiology where the medial tibial growth plate becomes disturbed and does not grow normally. Between the ages of 2 and 3 years, most children develop genu valgum. This may exceed the normal 5-7 degrees seen in adults and usually peaks at about 36 months of age.

This graph demonstrates the normal transition from genu varum (birth to age 2) to excess genu valgum (peaks at age 3) and eventual normalization to an adult pattern (5 to 7 degrees valgum) - from Salenius P, Vankka E: The development of the tibiofemoral angle in children. JBJS 1975;57:259 (Copyright Journal of Bone and Joint Surgery; used with permission)