My anthros are mostly an engineered race, a somewhat stereotypical blending of humans and animals. Naturally the alien bioengineer who designed the setup intended a more useful system while producing the more bestial look a digigrade of an animal. This ended up as the "double knee."

This looks like the legs of many animals, with the back bones of the foot drawn up into the main limb to form the "shin" while the ankle joint is right next to the knee. The "foot" is slightly more limited in movement than a human foot, but the design allows the job to be done from several approaches, so it balances out. The shin and calf bones are drawn up to very short segments in the double knee, providing the connection between the stronger knee joint and the ankle joint. Almost all of the shock absorbtion is done in the knee, leading to an alien gait. Rarely seen, this does allow the knee to bend forward, useful sometimes in certain kicks and such.

The appearance would be somewhat like Renamon, with an unexagerated digigrade appearance and longer, thin lower legs. Plantigrade animals have an different ankle setup. The "normal" setup is perserved, with a more normal knee and the two joints in the ankle as it appears. Hooves do seem abnormally large as they're scaled up some to reduce ground pressure. Odd foot setups would tend towards one or the other--an elephant for example would end up more like a plantigrade mod than a digigrade one.

reptilians are plantigrade, their creators weren't as imaginative, and dragons are a more traditional digigrade.