My daughter is 4yrs and her legs pans only at night Is there reason?

A. There can be two reasons associated with this first of all is growth pain which is common to be seen between the age of 3 1/2 years to 13 years of age and second could be when the kids start going to school they do a lot of running walking and playing around with which they use maximum of their legs it could be associated with that also as of now massaging with warm mustard oil would be good and check with the doctor if you need to start with calcium and vitamin D for the child