Bones of The Wrist

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Introduction

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We all know that our wrist is made up of many small bones and joints, which allow our hand to perform movements, as per need, in different directions. Wrists also include the end of the arm bones. Our wrist is made up of eight small bones known as carpal bones or carpus. These bones join our hand to the two long bones which are already present in our forearm i.e radius and ulna.

The carpal bones of the wrist are in small squared, oval, and triangular shape bones. A number of carpal bones combine in the wrist, by which it becomes strong and flexible. The movement of our hand and wrist would not be the same if our wrist joint was only made up of one or two larger bones.


The Eight Carpal Bones

Eight carpal bones of the wrist are discussed below:

1. Scaphoid: This bone is present under the thumb and is long boat-shaped.

2. Lunate: This bone is present beside the scaphoid and is of a crescent-shaped. 

3. Trapezium: This bone is present above the scaphoid and the bone is of rounded-square shape.

4. Trapezoid: This bone is present beside the trapezium and the shape of the bone is like a wedge.

5. Capitate: This bone is present in the middle of the wrist and is of oval or head-shaped. 

6. Hamate: This bone is present near the pinky finger side of the hand.

7. Triquetrum: This bone is present under the hamate and the shape of the bone is pyramidal.

8. Pisiform: This bone is present at the sits on top of the triquetrum and is of round or oval shape. 

Anatomy of Wrist Joint

Three main joints are present in the wrist. These three joints maintain stability in the wrist. This provides a wide variation of movement to our wrist and hands. The wrist joints allow our wrist to move our hand up and down depending upon needs, Example: when we lift our hand to wave. Because of this joint, we can bend our wrist in both forward and backward directions, side to side movement, and rotate our hand as per need. 

1. Radiocarpal joint: This joint does the connection of radius to the thicker forearm bone which further connects with the bottom row of wrist bones: the scaphoid, lunate and triquetrum bones. Location of this joint is mainly on the thumb side of your wrist.

2. Ulnocarpal joint: This is the joint which is present between the ulna,  the thinner forearm bone and the lunate and triquetrum wrist bones. Location of this is the pinky finger side of your wrist.

3. Distal radioulnar joint: This joint is actually present in the wrist but it is excluded from the wrist bones. It acts as a connecting link between the bottom ends of the radius and ulna.

Hand Bones which are Connected from Wrist Bones are: 

The hand bones which are connected to the wrist bone are listed below:

  • Trapezium

  • Trapezoid

  • Capitate

  • Hamate

The connection point of hand bone to wrist bone is called the carpometacarpal joints.


Soft Tissue In The Wrist

Blood vessels, nerves, and skin are the major soft tissue present in the wrist. Some of the major soft tissues are discussed below:

  • Ligaments: They connect the wrist bones to each other along with hand and forearm bones also. They are like elastic bands which are helpful in keeping bones in place. They cross the wrist from each side to hold the bones together.

  • Tendons: These are also a  kind of elastic connective tissue that attaches muscles to bones. This joint allows you to move your wrist and other bones.

  • Bursae: It is a kind of wrist bone which is surrounded by fluid-filled sacs. It helps in the reduction of friction between tendons and bones.

Common Wrist Injuries

Wrist bones, ligaments, tendons, muscles and nerves can be injured or damaged because of various reasons. Some of the common wrist injuries and conditions are listed below:

  • Sprain: When you lift something heavy, in that case, you can have sprain because of stretching of the wrist. In the case of a sprain, there’s damage to a ligament. The most common place for a wrist sprain is at the ulnocarpal joint. In this kind of sprain the joint between the arm bone and wrist bone on the pinky finger side of the hand.

  • Impaction Syndrome: This syndrome is also called as an ulnocarpal abutment. This wrist condition happens when the size of the ulna arm bone is a little bit longer than the radius. This makes the ulnocarpal joint between this bone and your wrist bones less stable. Due to increased contact between the ulna and carpal bones in this syndrome, it causes pain and weakness.

  • Arthritis Pain: You can get wrist joint pain from arthritis. This can happen from normal wear and tear or an injury to the wrist. You can also get rheumatoid arthritis from an immune system imbalance. Arthritis can happen in any of the wrist joints.

  • Fracture: Fracture can happen in any of the bones in your hand because of fall or any other injury. Distal radius fracture is one of the most common types of fracture seen in the wrist. In the case of scaphoid fracture, carpal bone gets broken. This is the large bone on the thumb side of your wrist. It can fracture when you try to catch yourself in a fall or collision with an outstretched hand.

  • Repetitive Stress Injuries: Common injuries to the wrist happen from doing the same movements with your hands and wrists repeatedly for a long time. This includes typing, texting, writing, and playing tennis. They can cause swelling, numbness, and pain in the wrist and hand. Stress injuries can affect the bones, ligaments, and nerves of the wrist. 

FAQ (Frequently Asked Questions)

1. Define the Term Radiocarpal Joint.


Ans. This joint does the connection of radius to the thicker forearm bone which further connects with the bottom row of wrist bones: the scaphoid, lunate and triquetrum bones. Location of this joint is mainly on the thumb side of your wrist.


2. Explain the Term Impaction Syndrome.


Ans. This syndrome is also called as an ulnocarpal abutment. A condition of the wrist wherein the size of the ulna arm bone is a little bit longer than the radius making the ulnocarpal joint between this bone and wrist bones less stable. Owing to the increased contact between the ulna and carpal bones in this syndrome, it causes pain and weakness.


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