Its gotta be the cheeks!

[Scav]

Except from the DRF Plus article on Juan Carlos Guerrero:

"Most trainers touch the horse's knees with their hands to feel for heat, but your cheeks are more sensitive, so I get down and put my face next to the horse's knees to see if there is any slight difference in temperature," Guerrero said. "I also check the feet for a pulse to see if there might be the start of any kind of abscess."

LOL