usually games dont need to worry about this knee bending behavior cuz they jump so low the time needed to bend the knee is negligible. but in tes where you can jump 10 feet high, things start to be different
They can have a neutral animation, with some knee bending, and you decide how much you jump (bound by the maximum the character is supposed to jump) by releasing the jump button while jumping or something. It doesn't get in the way of the gameplay, gives control over the jump, it doesn't look weird, and it solves the problem of jumping while running, where you don't need the same preperation as a static jump.