Intoe-ing or “Pigeon-toed” is a reasonably common condition. Intoe-ing can cause clumsiness, tripping and falling. It can also cause leg and foot pain often dismissed as “growing pains.”
In our first 6 years of life, our leg bones undergo a series of rotational changes.
We start off with our legs rotated inwards making it look like this:

Normal infant leg rotation
Our legs then continue to de-rotate as we pass developmental milestones such as crawling and progressing to standing and walking. By the time we reach 2 and a half the leg should look something like this – reasonably straight with a mild flat arch:

Normal leg rotation
At the age of six the legs resemble the child’s adult legs and not much rotational changes occur after that.
There are cases in which the de-rotation of the leg bones are delayed and this results in intoeing.
Treatment
Fortunately, most cases are treatable but the treatment needs to be customised per child depending on severity.