Final answer:
The only saddle joint in the human body is the first carpometacarpal joint, located between the trapezium and the first metacarpal bone at the base of the thumb.
Step-by-step explanation:
The saddle joint in the body is a unique type of synovial joint in which the articulating ends of two bones resemble a saddle, each one being concave in one direction and convex in another. This structure allows for biaxial movement, which means movement along two different planes. The only saddle joint in the human body is the first carpometacarpal joint, which is located between the trapezium, one of the carpal bones, and the first metacarpal bone at the base of the thumb. This joint is vital for the opposable movement of the thumb, a key characteristic of human dexterity.