What type of joint allows rotation around a single axis?

The pivot joint is specifically designed to allow rotation around a single axis, which is critical for certain movements within the human body. In a pivot joint, the end of one bone is rounded and fits into a ring formed by another bone and connective tissue. This structure enables one bone to rotate around another, facilitating movements such as the rotation of the head from side to side or the twisting motion of the forearm when turning the palm up and down.

For example, the rotation of the radius around the ulna at the elbow is made possible by the pivot joint, allowing for the actions of pronation and supination. This specialized function makes pivot joints essential for various physical activities involving rotational movements.

In contrast, the other types of joints either have different ranges of motion or do not provide the same rotational capability. Gliding joints allow for sliding movements, ball-and-socket joints provide a wide range of motion including rotation but in multiple axes, and saddle joints allow movement back and forth and side to side but not full rotation around a single axis.