Huh?
https://en.wikipedia.org/wiki/Genu_valgum
Don't think this has anything to do with being skinny unless you had malnutrition. Looks like if you have it as a kid, it's normal enough and you tend to grow out of it. If it's severe or you don't grow out of it, it's due to malnutrition or other disease processes.
So I'd wager most people on Lemmy do not have this. I'm fairly thin and I have never had that.