Wrist Anatomy: Ultimate Guide to Parts, Names & Diagram

Overview of Wrist Anatomy

The wrist joint, or the radiocarpal joint, is a crucial connection between the forearm and hand. It allows various movements like bending, straightening, side-to-side, and twisting. This joint is like a modified ball and socket, allowing flexibility while maintaining stability. The wrist anatomy (joint) is made up of bones that form two surfaces: one is like a cup (formed by the end of the radius bone and a cartilage disk), and the other is like a ball (formed by the scaphoid, lunate, and triquetrum bones). These bones allow movement in two main directions: up and down (like when you wave your hand) and side to side (like when you move your hand towards your thumb or pinky finger). The wrist joint helps us do everyday tasks with our hands, like writing, typing, or picking things up.

It is important to note that the ulna bone isn’t part of this joint; it connects to the wrist differently. In this article, we will see the details of wrist anatomy with their parts, functions & diagrams.

Wrist Anatomy Diagram

Parts of a Wrist

Bones

Carpal Bone Names

Proximal row (closest to the forearm)
- Scaphoid
- Lunate
- Triquetrum
- Pisiform
Distal row (closest to the hand)
- Trapezium
- Trapezoid
- Capitate
- Hamate

Joints

Radiocarpal Joint
Intercarpal Joints
Midcarpal Joint
Carpometacarpal Joints
Intercarpometacarpal Joints
Distal Radioulnar Joint

Muscles

Flexor carpi radialis
Palmaris longus
Flexor carpi ulnaris
Extensor carpi radialis longus
Extensor carpi radialis brevis
Extensor carpi ulnaris

Ligaments

Radial collateral ligament
Ulnar collateral ligament
Palmar radiocarpal ligament
Dorsal radiocarpal ligament
Scapholunate ligament
Triangular fibrocartilage complex (TFCC)

Tendons

Flexor pollicis longus tendon
Flexor digitorum superficialis tendons
Flexor digitorum profundus tendons
Extensor pollicis longus tendon
Extensor digitorum tendons
Extensor digiti minimi tendon

Wrist Anatomy: Bones

The carpal bones are eight tiny bones in your wrist that link it to your forearm. They are essential for wrist mobility. They connect with the bones in your forearm to facilitate smooth motion.

These bones also support your hand muscles, such as those in your thumb and little finger. It helps them to function properly and boosts their capacity to understand things.

They also form the carpal tunnel, which allows nerves and tendons to travel from your forearm to your hand. It ensures everything works properly and you can feel things correctly.

Proximal Row (closest to the forearm)

The proximal row of carpal bones is situated closest to the forearm. These are the 4 bones contribute to wrist movement, stability, and overall hand function.

1. Scaphoid

The scaphoid bone in your wrist is a boat shape, the biggest one in the row closest to your forearm.

It is called “scaphoid” because it looks like a boat (“scaphos” in Greek means boat). You can find it just below a spot on your wrist called the anatomical snuffbox.

This bone connects to the radius on one end and the trapezium and trapezoid bones on the other. It also links up with the lunate and capitate bones nearby.

If you feel the palm of your hand, you might notice a bony bump – that’s the scaphoid tubercle.

2. Lunate

The lunate is a moon-shaped bone in your wrist that sits in the middle of the wrist bones. It connects with the radius on one side, the scaphoid bone on another, the triquetral bone on the other, and the capitate bone below. Its name comes from Latin, meaning “moon-shaped.”

This bone helps your wrist move smoothly and supports your joints. It works together with the two bones in your forearm, the radius and ulna.

Sometimes, “lunate” refers to a small stone tool with a straight, sharp edge and a curved back. It is called that because of its crescent shape, similar to the moon.

3. Triquetrum

The triquetrum is a bone in your wrist that looks like a pyramid with three corners. It sits on the inner side of your wrist.

It connects to the lunate bone on one side and the hamate bone on the other. Also, it has a small oval spot on its lower front side, connecting to the pisiform bone.

4. Pisiform

The pisiform is a small bone shaped like a pea. It sits on the bottom of your wrist near a triquetrum bone. The pisiform bone has a smooth area on top where it connects to the triquetrum bone.

It is special because a tendon surrounds it like a seed in a fruit. This tendon is from a muscle called the flexor carpi ulnaris. You can feel the pisiform easily on the palm side of your hand.

Distal Row (closest to the hand)

1. Trapezium

The trapezium bone is an important part of your wrist. It is on the outer side and is part of the lower row of wrist bones. It connects with other bones and helps make your wrist strong and stable.

It has bumps and grooves where tendons and ligaments attach, which help with movement. Also, it is close to an artery that brings blood to your hand and fingers, keeping them healthy.

2. Trapezoid

The trapezoid bone is like a small wedge in your wrist. Even though it looks tiny from the front, it is wider when you look at it from the back.

It connects to other bones: the scaphoid on one side, the trapezium on another, and the capitate on another. Plus, it touches the second metacarpal bone at the bottom.

3. Capitate

The capitate bone, the os magnum, is the biggest of the eight wrist bones. It sits in the middle of the wrist and acts like a keystone. It has a round head, a narrow neck, and a body.

The capitate bone connects with almost all other wrist bones except one. It also links to several ligaments in the wrist.

You can usually feel the capitate bone on the back of your wrist, close to the bone in the middle of your hand. It starts to harden into bone about two months after a baby is born.

4. Hamate

The hamate bone is triangle-shaped in your wrist, near your pinky and ring fingers. It is one of the bones in the lower row of wrist bones.

This bone has six sides, facing your palm, toward the middle of your body, and towards the outside. The palm-facing side has a little curved hook called the hamulus.

Wrist Anatomy – Joint

Wrist anatomy consists of a Radiocarpal Joint, Intercarpal Joint, Midcarpal Joint, Carpometacarpal Joints, Inter Carpometacarpal Joints, and Distal Radioulnar Joint.

1. Radiocarpal Joint

The wrist joint is where your forearm meets your hand. It is special because it lets you move your hand in many directions.

This joint allows you to bend your hand up and down, move it from side to side, and even twist it. It is made by the end of your forearm bone connecting with a few small bones in your hand.

2. Intercarpal Joints

The intercarpal joints in your wrist connect the small bones. They are flexible, allowing smooth movements without a fixed pivot point. These joints work closely with the muscles in your wrist.

When you bend your wrist forward (flexion), it mainly happens at the wrist joint itself. But when you straighten your wrist (extension), it mostly involves these intercarpal joints.

They also help your wrist move sideways (abduction and adduction) and in circular motions (circumduction).

3. Midcarpal Joint

The midcarpal joint is a pivot point between the carpal bones in your wrist. It is made up of two special joints: one involving the capitate, hamate, and scaphoid bones and the other involving the trapezium, trapezoid, and scaphoid bones. These joints are shaped like saddles.

Your wrist can bend and move because of these joints. They absorb force when you do things like grip or lift objects.

These bones also play a role in forming the arches of your hand, which are important for securely gripping objects.

4. Carpometacarpal Joints

The carpometacarpal (CMC) joints connect the base of the metacarpal bones to the carpal bones in the hand. They are found at the top part of the hand.

These joints allow for a little sliding motion and are most flexible in the little finger. Ligaments, like the anterior oblique ligament, help stabilize them.

The thumb’s CMC joint allows various movements and adds strength for gripping things. Cartilage covers and cushions the bones in these joints.

5. Inter Carpometacarpal Joints

The wrist has intercarpal joints connecting the wrist bones to the bases of the finger bones. The wrist bones (carpals) link with the bases of the finger bones (metacarpals) through five joints called carpometacarpal joints.

These joints have ligaments that provide strength. They help optimize hand grip by allowing the finger bases to move smoothly.

Among these joints, the thumb joint is the most flexible. It can move in different directions, allowing the thumb to grasp objects effectively.

While some CMC joints are relatively fixed, others are more mobile. This mobility helps with gripping, particularly when the fourth and fifth finger bones move slightly toward the thumb.

6. Distal Radioulnar Joint

The distal radioulnar joint is a pivot joint in your forearm, connecting the radius and ulna bones. It allows you to turn your palm up (supinate) or palm down (pronate).

It is crucial to your forearm’s movement, working alongside the proximal radioulnar joint, forearm bones, and interosseous membrane.

The distal radioulnar joint also helps your wrist handle weight by spreading forces across your forearm bones. Plus, it is closely linked to the wrist’s ulnocarpal joint.

Wrist Anatomy – Muscle

The wrist anatomy consists of a Flexor Carpi Radialis, Palmaris Longus, Flexor Carpi Ulnaris, Extensor Carpi Radialis Longus, Extensor Carpi Radialis Brevis, and Extensor Carpi Ulnaris.

1. Flexor Carpi Radialis

The flexor carpi radialis is a thin muscle in the forearm that helps bend the wrist and move the hand sideways.

It is located on the palm side of the forearm and runs from the inner part of the upper arm bone to the base of the second metacarpal bone. The flexor carpi radialis is part of the muscles at the front of the forearm and sits just below the skin.

Its main jobs are to bend the wrist, aid in sideways hand movement, and support the scaphoid bone. It starts from a bump on the inner side of the upper arm bone and attaches to the bases of the second and third metacarpal bones.

The flexor carpi radialis is controlled by the median nerve (C6-C7) and gets blood supply from arteries around the forearm.

2. Palmaris Longus

The palmaris longus (PL) muscle is a thin forearm muscle that helps to bend the wrist and smaller hand joints. It begins in the inner elbow and extends to the flexor retinaculum, which joins the palmar fascia.

Despite its heterogeneity across people, it promotes hand stability by constricting palmar aponeurosis. Surgeons sometimes use their tendons in surgeries for the hand and arm.

3. Flexor Carpi Ulnaris

The flexor carpi ulnaris is a powerful muscle in your forearm that bends and pulls your hand closer to the body. It is unique because only the ulnar nerve controls it entirely.

This muscle is divided into two parts: the humeral head, which originates on the inside of your elbow, and the ulnar head, which begins on the bony hump at the elbow. They adhere to the tiny bones of your hand.

The flexor carpi ulnaris bends your wrist and slides it sideways toward your little finger.

4. Extensor Carpi Radialis Longus

The extensor carpi radialis longus is a forearm muscle important for moving the wrist and hand. It works with other muscles to extend the wrist, move it sideways (radial deviation), bend the elbow, and make a fist. You can feel it easily just below and behind the elbow.

The extensor carpi radialis longus starts from specific points on the humerus bone and grabs onto some fibers from the elbow’s outer bump. It then runs down to attach at the base of the second metacarpal bone in the hand.

The radial nerve from the neck’s C6 and C7 roots tells the extensor carpi radialis longus when to contract. It gets blood from the radial artery.

5. Extensor Carpi Radialis Brevis

The extensor carpi radialis brevis is a forearm muscle that helps straighten and move the wrist to the side.

It is found at the back of the forearm and starts from a bony bump on the outer side of the upper arm called the lateral epicondyle.

The extensor carpi radialis brevis tendon travels through a passage in the wrist and attaches to the base of the third finger bone on the backside of the hand.

The extensor carpi radialis brevis muscle is shorter and thicker compared to another muscle nearby called the extensor carpi radialis longus. They both share a protective covering around their tendons.

6. Extensor Carpi Ulnaris

The Extensor Carpi Ulnaris muscle is found along the outer edge of the forearm. It stretches from the elbow down to the base of the little finger.

Its main job is to straighten and pull the wrist towards the pinky side. Keeping the wrist steady and aid movement towards the ulnar side is crucial.

It originates from a bony bump on the outer part of the elbow called the lateral epicondyle. It ends by attaching to the base of the fifth metacarpal bone in the hand.

The radial nerve supplies signals to the Extensor Carpi Ulnaris muscle. In contrast, its blood supply comes from the ulnar artery.

Wrist Anatomy – Ligament

The wrist anatomy consists of a Radial Collateral Ligament, Ulnar Collateral Ligament, Palmar Radiocarpal Ligament, Dorsal Radiocarpal Ligament, and Scapholunate Ligament.

1. Radial Collateral Ligament

The radial collateral ligament is a strong band that connects the upper arm bone (humerus) with the forearm bone (radius).

It is a tough ligament that starts from the outer edge of the radius bone at the wrist and attaches to a wrist bone called the scaphoid.

Its main job is to prevent too much wrist bending towards the thumb. Additionally, it helps keep the elbow joint stable by resisting forces that might push the joint inward.

2. Ulnar Collateral Ligament

The ulnar collateral ligament is a strong band inside your elbow that connects your upper arm to your forearm bone. It helps keep your elbow stable when you move your arm around.

It is made up of three parts. The main part of the ulnar collateral ligament, the anterior band, is important for keeping your elbow steady and supporting your arm.

3. Palmar Radiocarpal Ligament

The palmar radiocarpal ligament connects the lower arm bone (radius) to the bones in your wrist. It is made up of different strands of fibers that crisscross each other.

It allows your hand to move smoothly as your forearm twists. This ligament also helps to keep your wrist stable.

It is positioned on the front side of your wrist, right where you can feel your pulse. This ligament sits in front of certain hand muscle tendons.

4. Dorsal Radiocarpal Ligament

The dorsal radiocarpal ligament is an extrinsic ligament in your wrist that connects the back of your hand bones.

It starts from the back of the long bone in your forearm (radius) and stretches downwards towards the outer side of your wrist.

It attaches to two small bones in your wrist (lunate and triquetral) and ends at a bony bump on the triquetral bone.

The dorsal radiocarpal ligament and other tissues, like cartilage and tendons, help keep your wrist steady from the back.

5. Scapholunate Ligament

The scapholunate ligament is a key ligament in the wrist that connects two bones, the scaphoid and the lunate. It is frequently injured and crucial for stable wrist movement.