https://e621.net/post/show/2011968

Take this for example. There are some posts with the character like this crossing their knees in order to hide their crotch. Can there be a tag for this? I feel like this is an important position and a stark difference between merely standing.

https://e621.net/wiki/show/knock-kneed

It looks like your question has already been answered, but just so you - and anyone else who reads this - knows, there is also a "Do we have a tag for that " thread that's usually on the first page or two of the forum, under the "Tag/Wiki Projects and Questions" category.