Radius

Radius and ulna are two bones of the forearm. By rotating around the longitudinal axis, the radius is essential for the pronation and supination motions. It has a thicker distal end with a large contact area for the wrist joint.

Download JPG image — Forearm bones in situ.
When two forearm bones from one subject are compared, the radius appears shorter and thicker than the ulna.

Download JPG image — Anterior aspect of the right radius
Both forearm bones have tuberosities near their proximal ends. However, the radial tuberosity is generally more prominent as it is caused by the attachment of the primary flexor of the forearm – the biceps brachii muscle.
The list of terms:
Caput radii – Head of radius
Circumferentia articularis – Articular circumference
Collum radii – Neck of radius
Tuberositas radii – Radial tuberosity
Corpus radii – Body of radius
Margo interosseus – Interosseous margin
Margo anterior – Anterior margin
Facies anterior – Anterior surface
Facies lateralis – Lateral surface
Processus styloideus – Styloid process

Download JPG image — Posterior aspect of the right radius
The two joints between radius and ulna are in their epiphyses. They have organized similarly: one bone has a rim-like surface called articular circumference, and the second has the congruent notch. The only tricky point is to remember that the corresponding incisure of the radius is called ulnar notch, and the one on the ulna is called the radial notch.
The list of terms:
Caput radii – Head of radius
Circumferentia articularis – Articular circumference
Collum radii – Neck of radius
Tuberositas radii – Radial tuberosity
Corpus radii – Body of radius
Margo interosseus – IInterossious margin
Margo posterior – Posterior margin
Facies posterior – Posterioir surface
Facies lateralis – Lateral surface
Processus styloideus – Styloid process
Incisura ulnaris – Ulnar notch
Tuberculum dorsale – Dorsal tubercle

Download JPG image — The distal epiphyses of the right radius and ulna. Anterior oblique view
On the distal end, the radius has a large concave-shaped articular surface for the joint with the carpal bones (facies articularis carpalis). Note that the distal end of the ulna is separated from the wrist bones by the articular disc. This is why the distance between ulna and carpal bones is much larger than the one on the radial side, and the shape of the ulna's head is not congruent to the carpal bones.
The list of terms:
Facies articularis carpalis – Articular carpal surface
Processus styloideus (radii) – Styloid process (of radius)
Tuberculum dorsale – Dorsal tubercle
Incisura ulnaris – Ulnar notch
Circumferentia articularis (ulnae) – Articular circumference (of ulna)
Processus styloideus (ulnae) – Styloid process (of ulna)

Forearm bones articulating with the condyle of the humerus — The proximal epiphyses of the radius and ulna. Anterior oblique view
Both forearm bones articulate with the condyle of the humerus. The shape of the articular fovea on the head of radius corresponds to the convexity of capitulum humeri, and the trochlear notch of ulna corresponds to the trochlea humeri.
The list of terms:
Fovea articularis – Articular fovea
Circumferentia articularis – Articular circumference
Incisura radialis – Radial notch
Collum radii – Neck of radius
Tuberositas radii – Radial tuberosity
Tuberositas ulnae – Ulnar tuberosity
Processus coronoideus – Coronoid process
Incisura trochlearis – Trochlear notch
olecranon

360° rotation of the radius. All views are synchronized.

First published: 2/Jul/2020
Last update: 28/Nov/2020