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Are there any birds whose legs fold the same way human legs do, in a knee, instead of an elbow which is what all the birds I know have?

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The joint you are thinking of is not a knee, nor is it an elbow, instead it is an ankle which is bending the same way as us humans. You can see from the below diagram that the knee - the joint between the femur and tibia - is just further up the leg normally hidden by feathers.

Birds have a comparatively elongated metatarsus which gives the impression that the knee bends backwards more like an elbow, but it's just the ankle. (Image from here)

enter image description here

I also liked this diagram from a blogpost on a similar theme... enter image description here

To follow up there appears to be no animals whose ankles bend the "wrong" way.

http://www.answers.com/Q/Which_animal_has_backward_knees

http://qi.com/infocloud/knees

http://www.ehow.com/info_12317202_birds-knees-backwards.html#page=1

Though these are far from conclusive resources. I'd guess the way knee is defined (it means something to humans but not to nature (a bit like the species being a concept which has weak biological bounds)) has something to do with that

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  • $\begingroup$ Good point, thank you! It didn't occur to me. However, the joint I'm talking about is between Tibia and Metatarsus (ankle, right)? Are there any birds whose ankles bend backwards? $\endgroup$ – Violet Giraffe Oct 21 '14 at 16:12
  • $\begingroup$ according to the blogpost mentioned above no, no tetrapods do this $\endgroup$ – rg255 Oct 21 '14 at 16:14
  • $\begingroup$ @violetgirraffe edits made $\endgroup$ – rg255 Oct 21 '14 at 18:54
  • $\begingroup$ +1 Nice answer. You should add a reference to the first figure thought. $\endgroup$ – fileunderwater Oct 22 '14 at 10:51
  • $\begingroup$ Did you replace the first illustration? You shouldn't have, the other one was much larger and clearer; I can hardly read anything on this one. $\endgroup$ – Violet Giraffe Oct 22 '14 at 15:06

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