Are there birds with knees instead of elbows?
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)



I also liked this diagram from a blogpost on a similar theme...


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