Dear 100 Hour Board,
My roommate said that he has calf muscles of a stallion, but I didn't think that horses had calf muscles. When I tried to research it, I got very confused at the not only whether horses have muscles between their "knee joint" and their hoof, but also what is defined as a "calf muscle" (and then I wondered if "calf muscle" has any reference to baby cows). Please help!
The skeletal and muscular systems of horses are pretty different from us, although they are analogues. They have (pretty much) all the same bones, but they are shaped differently.
The lower leg of humans are made from the tibia and fibula, and the calf muscles are gastrocnemius, soleus, and plantaris.
Here is what the back leg off a horse looks like (these bones are pictured as if the horse is facing to the left):
The box surrounds the horse's "gaskin", which is analogous to the human calf (both are formed by the tibia and fibula). The teeny tiny bones below that are the tarsals, which is analogous to the human ankle (the "knee joint" you are probably thinking about, which is called the "hock"). Below that are the metatarsals, which are analogous to the human foot bones. Below that are the phalanges, which are analogous to human toes.
From what I can tell from this handy dandy Wikipedia article and from puttering around the internet, there are no muscles below the tarsals - only tendons. It seems that the muscle bodies are in the gaskin and the tendons extend below and attach to the bones, which is how horses can move their lower legs - all of the force is coming from above the hock.