allows back-and-forth and side-to-side movement, permitting a wide range of motion; found in thumb

A saddle joint allows movement back and forth and from side to side, giving the thumb a wide range of motion. The joint at the base of the thumb is a saddle joint, which also enables opposition—the movement of the thumb across the palm. Therefore, the correct choice is “saddle joint.”

AI-written and checked against the verified answer.