What is the anatomical term for a two jointed leg?

Question

Allow me to apologize in advance for the layman's terminology. I'm wondering what the anatomical term for a cat- or a goat-style hind leg is. Cats, goats, t-rexes, and many many other animals don't have human hind legs (i.e., with one knee / one pivot point). They have two pivot points, with one bone going down, then another going back-ish, then another going down again. I've googled and googled for the answer, but I'm completely at a loss as to what this is called! *Is* there any name for that style of leg? I'm sure there's a lot of variation inside the category, but there *is* a category, correct?

Answer 1

There are three anatomical postures typically associated with mammal locomotion styles: digitigrade, plantigrade, and unguligrade posture!

1. Plantigrade: feet and 'metatarsals' flat on the ground - the closest thing to a second pivot point is the heel/ankle (can be remembered because feet are planted on the ground)
2. humans, bears, rodents, etc.
3. Digitigrade: stands and walks on its toes, causing the ankle to be elevated and act not unlike a second knee facing backwards to aid locomotion (they rend to be faster!)
4. walking birds, cats, dogs, etc.
5. Unguligrade: similar to digitigrade in that the ankle creates a second pivot point, but they have hooves rather than digits
6. horses, cows, pigs, deer, etc.

Fun Fact: We are actually able to use our knowledge of locomotion in other species to further the biological sciences for humans - for example, a rotationplasty is a medical procedure that can rotate the ankle and move it upwards to create a pseudo-knee in the case of someone needing their knee removed!