Animal leg anatomy cheat sheet

We've spoken before about that oh-so common artist's mistake of believing that some animals have "backwards knees." But in that original post, we only discussed "digitigrades." Digitigrades are animals that walk on their toes, with the "sole" of their feet off the ground, like cats and dogs -- this leads to the common myth that they have "backwards knees," as their ankles are easily mistaken for knees by humans who don't walk on their toes all of the time!

A drawing of a dog's back leg bones, demonstrating that what people commonly mistake for the knee is actually the ankle.

Diagram of a dog's back leg

But take care, not all four legged animals are digitigrade. Today, we'll look deeper into this topic and explore some other animal leg styles.  

A drawing of a monkey's skeleton, demonstrating the positioning of the knee and ankle joints.

A diagram of a monkey

Plantigrades are animals that walk on the soles of their feet. The animal in this category that you know best are humans, but bears, mice, raccoons, weasels, and monkeys are also plantigrades. It's typically much easier for artists breaking into drawing animals to learn to draw plantigrade critters, because their back legs are configured in a familiar way; unless, of course, they've been told about digitigrades! Then some artists will attempt to apply that knowledge even to plantigrade animals, leading to some unintentional tip-toeing bear drawings.  

A drawing of a horse's skeleton, demonstrating the positioning of the knee and ankle joints.

A diagram of a horse

Horses, donkeys, pigs, gazelles and most other animals with hooves are ungulates. Ungulates are animals that walk on their nails (hooves are just big nails!) rather than their toes. Picture these critters as the en pointe ballerinas of the animal kingdom.  

A drawing of a bird's skeleton, demonstrating the positioning of the knee and ankle joints.

A diagram of a bird

Birds are among the most difficult to recognize anatomically, as their upper legs are actually inside of their body, hiding some of the points you'd normally recognize in a leg. However, most birds are digitigrades, and again, what most people assume is a backward knee is actually their ankle!

A drawing of an ostrich's skeleton, demonstrating the positioning of the knee and ankle joints.

Diagram of an ostrich



Thanks for this its really helpful :)

Kim - Site admin

So glad to hear that! :)

Laura (unregistered visitor)

Oh my gosh, This was eye-opening. Thank you!

Olivier Renken (unregistered visitor)

So informative! Epic.


This is really great content. Thanks :)

Kim - Site admin

So glad you approve! :)

Shai (unregistered visitor)

Wow... finally understood my animals' anatomy!

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Fascinating. Your site was recommended by YouTuber, Brad Colbow. Don’t know who he is but I’m glad I followed through. I especially enjoyed the information on bird leg anatomy since they are one of my favorite subjects. Looking forward to the benefits of full membership.

Maya (unregistered visitor)

These informations are great! I've got another bird-tip, which many people have some problems: most birds have on each toe another number of bones and therefore joints. the first toe has 1 bone + claw (2 joints), the second toe has 2 bones + claw (3 joints), and so forth, till you got 4 toes (not 5 toes). The counting depends on the species. on "normal" birds like crows, with 3 toes forwards and 1 backwards, you start counting with the backwards toe and then the frontside toe on the inner side. by birds with "climbing feet", like parrots you count diffrent, because they have on the front, and backside each 2 toes. if anyone wants more information it's german, but the pictures are better to understand ;o)
and by the way, the ostrich picture has a little mistake: the ostrich is the only bird with just 2 toes (both forwards) ;o)

Sanne - Site moderator

That is super useful information, thank you so much!

Mia Is Cool

This is really cool, Thanks!

Cat Jupiter

Awesome, thank you!


Great! I love this

Paul (unregistered visitor)

I was so surprised by this, and all the animals I thought had backward knees?
Are there any animals that do have backward knees or is it always the case that we are mistaking ankles for knees?

Thank you.

Sanne - Site moderator

I don't think there are any animals with legitimate backwards knees, while being actual knees. In the case of digitrades, any mammal walking on their toes is being mistaken as having backwards knees to my knowledge. :)

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