We are independent & ad-supported. We may earn a commission for purchases made through our links.

Advertiser Disclosure

Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.

How We Make Money

We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently from our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

What Are the Carpometacarpal Joints?

By Shelby Miller
Updated May 17, 2024
Our promise to you
WiseGeek is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At WiseGeek, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

The carpometacarpal (CMC) joints are found between the bones of the hand and those of the wrist. Specifically, these are the articulations between the clustered carpal bones in the base of the hand and the metacarpals, the five long bones stretching across the hand to the base of each finger. The carpometacarpal joints below the four fingers are known as arthrodial or gliding joints, a synovial, or movable, joint type that allows the bones to slide against one another. The joint at the base of the thumb is another type of synovial joint called a saddle joint, and it allows a much greater range of motion than the other four joints.

While the carpals are arranged in a sort of cluster like a small pile of irregularly shaped rocks, they can be divided into two rows. The proximal row articulates with one of the long bones of the forearm, the radius, to form the radiocarpal or wrist joint. Beyond the proximal row, the distal row of carpals meets with the proximal or near ends of the five metacarpals to form the five carpometacarpal joints. Four carpals are found in the distal row, with the hamate on the pinky finger side, the capitate next to it, then the trapezoid, and finally the trapezium on the thumb side.

The fifth or pinky-finger metacarpal aligns with the hamate. The fourth or ring-finger metacarpal articulates with the hamate and the near corner of the capitate. The third or middle-finger metacarpal meets mostly with the capitate. The second or index-finger metacarpal links to the trapezoid, though it touches the capitate and trapezium on either side, and the first or thumb metacarpal forms a joint with the trapezium bone.

As the second through fifth carpometacarpal joints do not permit a wide range of motion at the joints themselves. Instead, they make the wrist joint more flexible by allowing the metacarpal and carpal bones to move past each other in several directions as the hand moves about on the end of the radius bone. In addition, these four carpometacarpal joints allow movement about the palmar arch. This is the concave curve at the base of the palm formed when the hand curls around an object like a baseball and created by an inward rotation of the fifth metacarpal. It makes grasping small objects possible.

The first CMC joint is situated at the base of the thumb. It differs from the last four carpometacarpal joints in that it permits a wide range of motion, which distinguishes the human thumb as opposable or able to grasp and hold things. As a sellar, or saddle, joint, which gets its name because the ends of the two adjoining bones resemble a pair of saddles arranged perpendicular to and curved about each other, the first CMC joint allows front-to-back and side-to-side movements. It also allows circumduction, a circling motion, and opposition, which is the drawing inward of the thumb to touch it to the tips of the other fingers.

WiseGeek is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.

Discussion Comments

WiseGeek, in your inbox

Our latest articles, guides, and more, delivered daily.

WiseGeek, in your inbox

Our latest articles, guides, and more, delivered daily.