The timeline, from the source

The American Academy of Pediatrics gives the whole arc in one paragraph, and it is longer than most parents expect: "Toddlers' legs often have a bowed appearance. In fact, many children have bowing of the legs until they are about two years old, then they'll look knock-kneed until they are about six years of age. At times, children may not have straight lower legs until they are nine or ten years old."

And the conclusion: "Bowlegs and knock-knees usually are variations of normal, and require no treatment. Typically, a child's legs will straighten naturally by the teen years."

So a newborn with curved legs is at the very start of a normal sequence that runs for years. There is no milestone in the first months at which the legs are supposed to be straight.

Why newborn legs look the way they do

Two things are happening at once. The first is position. The AAP describes a newborn as keeping their arms and legs bent up close to the body, just as they did in the womb, with the feet naturally curving inward, and says "it may take several weeks for their body to unfold from this preferred fetal position." Months of being folded up leave the legs bowed and the hips reluctant to straighten.

The second is genuine bone shape. The lower leg bones of infants and toddlers really do curve outwards, and they remodel gradually as a child grows and starts to bear weight. That is the process the AAP's timeline describes.

The NHS's version

The NHS covers the same territory in its guidance on children's legs and feet, and its framing is useful because it puts all the variations in one place: "It's also common for young children to appear bow-legged or knock-kneed, or walk with their toes turned in or out", and "most minor foot problems in children correct themselves".

Its specific note on bow legs: "Before the age of 18 months, it is very common for children to have a small gap between their knees and ankles when they stand. If the gap is pronounced or does not correct itself, check with your GP or health visitor."

For the stage that follows, the NHS says knock knees — standing with the knees together and a gap between the ankles — usually correct themselves by the age of seven. In-toeing usually corrects by around eight, out-toeing by around four, and flat feet by around six.

The five signs that need checking

The AAP publishes a short list of features suggesting bowlegs or knock-knees may be caused by a serious problem rather than being a normal variation:

The curvature is extreme.
Only one side is affected.
The bowlegs get worse after age two.
The knock-knees persist after age seven.
Your child is unusually short for their age.

The AAP names the conditions this is screening for: arthritis, injury to the growth plate around the knee, infection, tumour, Blount's disease — a growth disorder of the shinbone — and rickets. All are rare, and all are reasons the asymmetry item on that list matters most. Normal bowing is symmetrical. One leg noticeably different from the other is not normal bowing.

What does not help

The AAP is unusually direct about interventions: "Bracing, corrective shoes, and exercise are rarely helpful, and may hinder a child's physical development and cause unnecessary emotional stress."

That covers most of what is sold to parents on this topic. There is no published evidence that special shoes, inserts, leg wraps, massage regimes or particular carrying positions change the curvature of a healthy child's legs. The NHS's own advice for the same age group is that children do not need proper shoes until they are walking on their own, and that the priority is shoes and socks that are the right size, because the bones in a baby's toes are soft and cannot straighten if they are cramped.

The things that do get checked

Legs, hips and spine are examined together as part of routine newborn care. NICE's postnatal care guideline NG194 specifies that the complete examination within 72 hours of birth, and again at six to eight weeks, includes the limbs, hands, feet and digits, assessing proportions and symmetry, and separately the hips using Barlow and Ortolani's manoeuvres.

That hip check is worth knowing about here, because hip dysplasia is the condition most often confused with leg shape. The NHS's signs are asymmetry rather than curvature: one leg moving differently to the other during play and nappy changes, legs of different lengths, a clicking or popping in the hips, and later dragging one leg when crawling or limping when walking. If what you are noticing is a difference between the two legs rather than a curve in both, that is the question to ask about.

When to call

Speak to your midwife, health visitor, public health nurse or GP if:

Only one leg is bowed, or one leg looks shorter than the other.
The curve is extreme, or the gap between the knees is pronounced.
The bowing is getting worse rather than gradually improving.
The thigh or buttock skin creases are not symmetrical, or one hip does not open as widely during a nappy change.
Your baby seems to be in pain when a leg is moved, or will not move a leg.
Your baby is not meeting movement milestones, or is unusually small for their age.

Call your local emergency number (999 in the UK and Ireland, 911 in the US and Canada, 000 in Australia, 111 in New Zealand) if your baby: will not move a limb at all after a fall or knock; has a temperature of 38C (100.4F) or above or below 36C (96.8F); looks pale, ashen, mottled or blue; is unresponsive or unrousable; has a weak, abnormally high-pitched or continuous cry; is grunting or breathing over 60 breaths a minute; has a bulging fontanelle, neck stiffness or a seizure; or has a rash that does not fade under a pressed glass. Those are NICE's red flags for serious illness in young babies, from NG194.

What to let go of

Nothing about a newborn's leg shape predicts how they will walk, and nothing you do in the first year will change it. The AAP's timeline — bowed to about two, knock-kneed to about six, straight by the teens — is the normal path, and it runs on its own. The only things worth your attention are asymmetry, pain, and a curve that is getting worse rather than better.

Newborn Bowed Legs