Developmental Milestone of Walking

Median and limit ages

 

The difference between median and limit ages is shown by considering the age range for the developmental milestone of walking unsupported.

 

The percentage of children who take their first steps unsupported is:

 

- 25% by 11 months

- 50% by 12 months

- 75% by 13 months

- 90% by 15 months

- 97.5% by 18 months.

 

The median age is 12 months and is a guide to the common pattern to expect, although the age range is wide.

 

The limit age is 18 months (2 SDs from the mean).

 

Of those not achieving the limit age, many will be normal late walkers, but a proportion will have an underlying problem, such as cerebral palsy, a primary muscle disorder or global developmental delay.

 

A few may be understimulated from social deprivation.

 

Hence, any child who is not walking by 18 months should be assessed and examined.

 

Thus, 18 months can be set as a ‘limit age’ for children not walking.

 

Setting the limit age earlier may allow earlier identification of problems, but will also increase the number of children labelled as ‘delayed’ who are in fact normal.

 

Reference: Illustrated Textbook of Paediatrics Fourth Edition