When you need to talk to another rehabilitator or veterinarian, you have to make make sure you talk about the same thing.
A common error is that you call a bird’s ankle a knee, because it sits in the place where you expect a knee to sit. It becomes easier to remember if you think that a bird’s knee is angled in the same direction as a human knee. A bird’s knee usually sits directly below the body, embedded in feathers, so you do not see it when you take a picture of a bird.

Here are a number of pictures, so you can find and use the right name!