Physiological genu varum is normal in infants and maximal at 6 months of age, then progressing to excessive genu valgum followed by gradual correction to the normal adult valgus alignment by 5-6 years of age. Excessive physiological bowing is associated with early walking, and is characterised by smooth bowing of the whole limb, often with internal tibial torsion. Radiologically, the physis appears normal, and there may be equal beaking of distal femoral and proximal tibial metaphyses.
Treatment is periodic examination and reassurance of the parents.
The most common cause of pathological genu varum is tibia vara or Blount's disease. It involves an abrupt, progressive varus deformity of the proximal tibia. Infantile type occurs before 5 years old, mainly in black, obese female children who weight-bear early. The rarer adolescent type has onset after 6 years of age, mostly in black, male, obese children, in whom there is rapid progression of deformity. Histopathologically, there is disorganised physeal cartilage with islands of hypertrophic cartilage cells.