I think Adams referring to the ankle joints, in digitagrade legs the ankles are usually very pronounced and sharply visable, in reality this is due to all digitagrade animals being quadrapedal. People might be expecting that highly pronounced ankle to carry over into a bipedal being as well, but since such a creature doesnt exist in reality, you are of course free to do your own take on it and not be any more right or wrong than anyone else. I personally quite like it since it produces a very graceful arch from knee to foot.