First carpometacarpal joint

A pivotal joint located at the base of the thumb, facilitating a wide range of thumb movements.

The first carpometacarpal joint, commonly known as the CMC joint of the thumb, is where the first metacarpal bone (the bone of the thumb) meets the trapezium bone of the wrist. This unique saddle joint allows for multidirectional movement, making it essential for intricate hand functions.

Terminologia Anatomica

articulatio carpometacarpalis primi

System

Skeletal system

Function

The primary function of the first carpometacarpal joint is to enable the opposability of the thumb, which is crucial for grasping, pinching, and performing a variety of fine motor tasks. This joint is highly mobile, allowing for a range of movements, including flexion, extension, abduction, adduction, and opposition, providing humans with the ability to hold and manipulate objects with precision. The opposition of the thumb, in particular, is vital for forming a pinching grip, which is essential for tasks such as writing, threading a needle, or grasping a small object. Its unique structure allows for both stability and flexibility, making it one of the most important joints in the hand, integral to many daily functions.

Location

The first carpometacarpal joint is located at the base of the thumb, at the wrist level, where the trapezium bone of the carpal bones articulates with the first metacarpal bone. It is situated on the radial side of the hand, just proximal to the thumb. This joint is positioned in such a way that it allows the thumb to move freely around the palm, enabling efficient interaction with the fingers and other areas of the hand. Its anatomical location, combined with its unique shape, allows for a large range of motion, which is essential for the thumb's role in human hand function.

Did You Know?

The first carpometacarpal joint is the most mobile joint in the hand, allowing for a range of motion that is unique among the carpometacarpal joints.
Injuries or arthritis affecting this joint can significantly impair hand functionality.
The ability to oppose the thumb is considered one of the key features that distinguish human hands from those of other primates.