zoology - What is the anatomical term for a two jointed leg?

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

Welcome to Biology.SE!

I think you are talking about plantigrade, digitigrade and unguligrade.

Please note that the number of joints in mammals does NOT vary, but only the relative length (and shape) of the different parts of the leg.

• A Plantigrade walks on the sole of the foot. 'Sole' translates to 'planta' in Latin hence the name.
  
  
  
  • Examples: Human, squirrel, raccoons, ...
  
  
  • Below is a chimpanzee skeleton
  
  
  
  

• A Digitigrade walks on the digits (the toes).
  
  
  
  • Examples: dog, cat, hyena, ...
  
  
  • Below is a cat skeleton
  
  
  
  

• An Unguligrade walks on the nails. 'nail' translates to 'ungula' in Latin hence the name.
  
  
  
  • Examples: cow, reindeer, goat, ...
  
  
  • Below is a cow skeleton