What type of joint is the first carpometacarpal joint?

The first carpometacarpal joint, which is located at the base of the thumb, is classified as a saddle joint. This type of joint allows for a wide range of motion, enabling the thumb to perform unique movements such as opposition, which is essential for grasping and pinching. The saddle shape of the joint surfaces permits movement in two planes, facilitating both flexion and extension as well as abduction and adduction.

In the context of the other types of joints: hinge joints allow movement primarily in one plane (like the elbow), gliding joints permit limited movement between flat surfaces (such as in the carpal bones), and pivot joints enable rotary movement around a single axis (like the atlantoaxial joint in the neck). These functionalities differ significantly from those of a saddle joint, which is specifically designed to support multidirectional movement, making it well-suited to the complex motions required by the thumb.