“according to the jewish law a ladys (sic) knees are not allowed to show at all.”
This is the problem I have with the common understanding of tznius. Nowhere does it say in the Torah that a woman is required to keep her knees, elbows, and collarbone covered. Obviously, men and women must both ensure that we dress modestly and do not attract attention to our bodies, but the standards that I see used today by some go so far beyond what is really necessary. I don’t see a problem with either skirt in the example above, and outside of certain communities where men are used to seeing women completely covered up, I don’t think the average man would get excited by the sight of an uncovered knee.