digitigrade
A digitigrade is a creature that stands or walks on its digits, or toes. Digitigrades include walking birds, cats, dogs, and many other mammals. This also includes any monster girls or boys, actual monsters and alien beings. It is also common in furry artwork closer to the animalistic side of the spectrum.
Sometimes called "reverse-jointed", as digitigrade legs can look like they have a "knee" that bends the opposite way to a human knee. However this "knee" is in fact the heel; the actual knee may not be immediately apparent.