My DD (almost 8) has a very pronounced vein above the back of her knee. I've noticed it for a while and its definitely not getting lots worse BUT it is gradually getting more noticeable. I'm sure it never used to be there.
You can feel it through the skin as it's slightly raised all along but it isn't knotty or lumpy. It doesn't seem to hurt her.
Pic attached. The pock marks are molloscum scars (weirdly the molloscum seemed to follow the vein line).
I have emailed our doctors (great service - every GP should do this!) and they said it doesn't sound worrying but to get it checked next time she's in for something.
Has anyone seen veins like this in a child?