by Laura Murphy, M.D.
Published on Jun. 23, 2003
A common question we hear in the office at toddler well checks is, “Why are his legs so bowed?”, which leads to “How can he walk like that?”, and “Is that normal?”
Bowlegs, or genu varum, is relatively common in children, and is normally present to some degree in toddlers. In the vast majority of cases it is completely normal. Most cases can be attributed to physiologic bowing, with “physiologic” essentially meaning “normal”. All infants show genu varum, which peaks at six months of age. Correction to normal alignment often occurs by 18 months of age, but can sometimes take longer. There is a predictable pattern in which the very bowlegged infant begins to walk and slowly develops straighter alignment by about age two. After this point, over-correction usually occurs, which leads to “knock knees”, or genu valgum, by age four. This is then followed by eventual straightening by about five or six years of age. The normal progression then is bowlegs-to-straight, to-knock-knees-to-straight once more. In general, children’s legs are more or less in line by the time they go to school.
The answer to this in no, as the term “physiologic” implies a normal part of development. This would not cause any later deformity or abnormality.
No. If an X-ray was done, it would simply show an even bowing of the entire limb with no sharp or acute angles. This would not change the prognosis or management.
Just reassurance and observation—the condition usually corrects by about two years of age, though occasionally may take longer.
In the overwhelming majority of cases the answer is yes. Rarely, toddlers may have a condition called Blount’s disease, or tibia vara. In this condition, one sees a more abrupt deformity at the top of the lower leg, or the upper end of the tibia. It can occur in two forms, infantile and adolescent. In its infantile form, the onset is before age five, is progressive and does not self resolve. It seems to occur more often in black, obese, and female children, and also in those who walk earlier. It can be difficult to distinguish physiologic genu varum from infantile Blount’s. But again, with Blount’s the condition tends to be progressive and is more severe than typical bowing. Even less common causes of bowlegs are rickets, severe kidney disease, or even a certain type of dwarfism. These children, however, would present also with poor growth and a very different picture than an otherwise healthy child with bowed legs.
The deformity of Blount’s disease involves abnormal growth of the proximal part of the tibia (a bone in the lower leg). It is unclear exactly why this occurs, but it may have an underlying mechanical cause as it seems to happen more in obese children who are early walkers.
Bowlegs might be more than just a physiologic occurrence when associated with poor growth (short stature). Another signal for concern would be a progressive deformity or one that is not resolving even as the child reaches age two. In the majority of children, however, it is a normal part of their development that corrects all on its own.