Radius vs. Ulna — What's the Difference?
By Tayyaba Rehman — Published on August 25, 2023
The radius is the shorter, lateral forearm bone, while the ulna is the longer, medial forearm bone.
Difference Between Radius and Ulna
Table of Contents
ADVERTISEMENT
Key Differences
The radius is one of the two long bones in the forearm, located on the lateral side when in the anatomical position. The ulna, on the other hand, is the bone situated medially in the forearm. Together, these two bones play a crucial role in the movement and stability of the arm.
Both the radius and ulna articulate with the humerus at the elbow. While the ulna forms a hinge joint allowing for flexion and extension, the radius provides rotation at the wrist joint, particularly the actions of pronation and supination.
One of the distinguishing features of the radius is its radial tuberosity, which is a place of attachment for the biceps muscle. The ulna boasts the olecranon, the prominent bony point of the elbow, and the trochlear notch that interacts with the humerus.
The lower end of the radius, known as the styloid process of the radius, is distinct and can be felt on the thumb side of the wrist. Conversely, the ulna's corresponding structure, the styloid process of the ulna, is located on the pinkie finger side.
Fractures of the radius, often referred to as Colles' fractures, are common in falls onto an outstretched hand. The ulna, though sturdier, can also be fractured in various scenarios, with one type known as a nightstick fracture.
ADVERTISEMENT
Comparison Chart
Position
Lateral side of the forearm.
Medial side of the forearm.
Key Features
Radial tuberosity.
Olecranon and trochlear notch.
Articulation Point
With carpals at the wrist.
Primarily with the humerus.
Common Fractures
Colles' fracture.
Nightstick fracture.
Function
Allows wrist rotation.
Provides elbow hinge movement.
Compare with Definitions
Radius
Radius: A structural member or line from the center of a wheel or axle to its rim.
Ensure the wheel spokes connect to the rim at the right radius.
Ulna
Ulna: The inner and larger bone of the forearm, on the side opposite the thumb.
She touched the pointy end of her ulna, recognizing it as the elbow's tip.
Radius
Radius: The lateral bone of the forearm.
She fractured her radius during a skiing accident.
Ulna
Ulna: The medial bone of the forearm.
The ulna articulates with the humerus to form the elbow joint.
Radius
Radius: A specified distance around a point or location.
The restaurant is within a 5-mile radius of my house.
Ulna
Ulna: A bone that is parallel to the radius.
In anatomy class, we learned about the relationship between the ulna and the radius.
Radius
Radius: A scope or extent of activity or influence.
The topic was outside the radius of our discussion.
Ulna
Ulna: A unit of measurement in ancient Egypt.
Archaeologists discovered artifacts marked in units of ulna.
Radius
The outer and slightly shorter of the two bones of the human forearm
Ulna
Ulna: A stabilizing bone in birds corresponding to the forearm in humans.
The bird's ulna was clearly visible in the X-ray.
Radius
A circular area measured by a given radius
Every family within a radius of 25 miles of the city center.
Ulna
The ulna (pl. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm.
Radius
Radius: A straight line from the center to the circumference of a circle.
The formula to find the area of a circle is π multiplied by the square of the radius.
Ulna
The bone extending from the elbow to the wrist on the side opposite to the thumb in humans.
Radius
(anatomy) The long bone in the forearm, on the side of the thumb.
Ulna
The inner and longer of the two bones of the human forearm
Radius
A line segment that joins the center of a sphere with any point on its surface.
Ulna
The postaxial bone of the forearm, or brachium, corresponding to the fibula of the hind limb. See Radius.
Radius
A similar bone in many other vertebrates.
Ulna
A corresponding bone in the forelimb of other vertebrates.
Radius
In classical geometry, a radius of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the Latin radius, meaning ray but also the spoke of a chariot wheel.
Ulna
(anatomy) The bone of the forearm that extends from the elbow to the wrist on the side opposite to the thumb, corresponding to the fibula of the hind limb. Also, the corresponding bone in the forelimb of any vertebrate.
Radius
A line segment that joins the center of a circle with any point on its circumference.
Ulna
An ell; also, a yard.
Radius
A line segment that joins the center of a regular polygon with any of its vertices.
Radius
The length of any such line segment.
Radius
A radial part or structure, such as a mechanically pivoted arm or the spoke of a wheel.
Radius
A long, prismatic, slightly curved bone in humans, the shorter and thicker of the two forearm bones, located on the lateral side of the ulna.
Radius
(zoology) The lighter bone (or fused portion of bone) in the forelimb of an animal.
Radius
(entomology) One of the major veins of the insect wing, between the subcosta and the media; the vein running along the costal edge of the discal cell.
Radius
(geometry) A line segment between any point of a circle or sphere and its center.
Fatima claims to have visited all the bars within a five-mile radius of her Manhattan apartment.
Radius
(geometry) The length of this line segment.
Radius
Anything resembling a radius, such as the spoke of a wheel, the movable arm of a sextant, or one of the radiating lines of a spider's web.
Radius
A right line drawn or extending from the center of a circle to the periphery; the semidiameter of a circle or sphere.
Radius
The preaxial bone of the forearm, or brachium, corresponding to the tibia of the hind limb. See Illust. of Artiodactyla.
Radius
A ray, or outer floret, of the capitulum of such plants as the sunflower and the daisy. See Ray, 2.
Radius
The barbs of a perfect feather.
Radius
The movable limb of a sextant or other angular instrument.
Radius
The length of a line segment between the center and circumference of a circle or sphere
Radius
A straight line from the center to the perimeter of a circle (or from the center to the surface of a sphere)
Radius
A circular region whose area is indicated by the length of its radius;
They located it within a radius of 2 miles
Radius
Support consisting of a radial member of a wheel joining the hub to the rim
Radius
A bounded range of effective activity or influence
The operating radius of a helicopter.
Common Curiosities
What is the primary function of the radius?
The radius primarily allows for wrist rotation and works in tandem with the ulna for forearm movement.
Where is the ulna located in relation to the radius?
The ulna is located on the medial side, or inside, of the forearm, opposite the radius.
How do the radius and ulna connect to the wrist?
The radius connects directly to the wrist bones (carpals), while the ulna is separated from the wrist by a fibrocartilage disc.
Which bone is more prone to fractures, the radius or ulna?
The radius, especially near the wrist, is more commonly fractured, often due to falls on an outstretched hand.
How do the lengths of the radius and ulna compare?
The ulna is generally longer and more slender than the radius.
Is the ulna involved in wrist rotation?
While the radius plays a more prominent role in wrist rotation, the ulna contributes to the overall stability and function of the wrist and forearm.
Can you rotate your arm without the radius?
No, the radius is essential for pronation and supination, which are the rotational movements of the forearm.
Which side of the wrist does the radius end on?
The radius ends on the thumb side of the wrist.
What's the significance of the ulna's olecranon?
The olecranon is the bony prominence of the elbow and is a part of the ulna.
Do both the radius and ulna articulate with the humerus?
Yes, both bones articulate with the humerus, but in different ways: the ulna forms a hinge joint, while the radius allows for rotation.
Share Your Discovery
Previous Comparison
Degree vs. Fahrenheit
Next Comparison
Approximatly vs. ApproximatelyAuthor Spotlight
Written by
Tayyaba RehmanTayyaba Rehman is a distinguished writer, currently serving as a primary contributor to askdifference.com. As a researcher in semantics and etymology, Tayyaba's passion for the complexity of languages and their distinctions has found a perfect home on the platform. Tayyaba delves into the intricacies of language, distinguishing between commonly confused words and phrases, thereby providing clarity for readers worldwide.
