Something You Probably Don’t Know About Penguins - Uh, knees didn't atrophy like toes for horses or forearms for tyrannosaurs. They would have an awful time laying eggs, swimming, or walking without functional knees. Take a look at a horse some time. Know where the "knees" are? Not on the front legs. Yeah, the back. Now look up on the front of the leg, past the "heel" next to the tail. It's "knees" are not too different from a penguin in position. Usage is way different though.