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The word radius is Latin for "ray". In the context of the radius bone, a ray can be thought of rotating around an axis line extending diagonally [clarification needed] from center of capitulum to the center of distal ulna. While the ulna is the major contributor to the elbow joint, the radius primarily contributes to the wrist joint. [5]
The head of the radius has a cylindrical form, and on its upper surface is a shallow cup or fovea for articulation with the capitulum of the humerus. The circumference of the head is smooth; it is broad medially where it articulates with the radial notch of the ulna , narrow in the rest of its extent, which is embraced by the annular ligament .
De Quervain syndrome causes pain over the styloid process of the radius. [3] [4] This is due to the passage of the inflamed extensor pollicis brevis tendon and abductor pollicis longus tendon around it. [4] [5] The styloid process of the radius is a useful landmark during arthroscopic resection of the scaphoid bone. [6]
Beneath the neck of the radius, on the medial side, is an eminence, the radial tuberosity; its surface is divided into: . a posterior, rough portion, for the insertion of the tendon of the biceps brachii.
It is composed of 270 bones at the time of birth, [2] but later decreases to 206: 80 bones in the axial skeleton and 126 bones in the appendicular skeleton. 172 of 206 bones are part of a pair and the remaining 34 are unpaired. [3] Many small accessory bones, such as sesamoid bones, are not included in this.
The articular surface for the ulna is called the ulnar notch (sigmoid cavity) of the radius; it is in the distal radius, and is narrow, concave, smooth, and articulates with the head of the ulna forming the distal radioulnar joint.
Lister's tubercle or dorsal tubercle of radius is a bony prominence located at the distal end of the radius. It is palpable on the dorsum of the wrist. Structure
The scaphoid is situated between the proximal and distal rows of carpal bones. It is located on the radial side of the wrist, [1]: 176 adjacent to the styloid process of the radius. [2] It articulates with the radius, lunate, trapezoid, trapezium, and capitate. [1]: 176 Over 80% of the bone is covered in articular cartilage. [3]