Radius

The radius is one of the two long bones present in the forearm. It is located laterally in the supinated anatomic position. It has a smaller proximal end and enlarges to a larger distal end (opposite to the ulna). 

The proximal radius comprises the radial head and immediately distally is the radial neck, and tuberosity.

The radial shaft is thicker than the ulna and becomes thicker distally.  It has a triangular cross section, with a lateral convexity, and a sharp medial (interosseous) border.

The distal radial shaft flares out to form the distal radius with a facet for articulation with most of the proximal carpal row. Laterally, there is the radial styloid and medially the ulnar notch. On the dorsal margin of the distal radius, Lister's tubercle (dorsal tubercle) separates the 2nd (ECRB and ECRL)  and 3rd (EPL) extensor compartments.

  • proximal
    • radial head: capitellum of the humerus (elbow flexion and extension)
    • radial head: radial notch of the proximal ulna (site of supination and pronation)
  • distal
    • distal radius facet: scaphoid and lunate fossae separated by a small ridge
    • ulnar notch: ulna head (site of supination and pronation)
  • Musculotendinous
  • Ligamentous
    • annular ligament: ulnar notch of radius to supinator crest of ulna
    • volar/palmar radiocarpal ligament: non-articular volar surface of distal radius to scaphoid, lunate, triquetrum
    • dorsal radiocarpal ligament: non-articular dorsal surface of the distal radius to scaphoid, lunate, triquetrum
    • radial collateral ligament of wrist joint: apex of the radial styloid process to scaphoid, trapezium
    • radial collateral ligament of elbow joint: anterior aspect of lateral epicondyle of humerus to annular ligament and supinator fascia
    • interosseous membrane: forms syndesmotic joint with ulna along medial border of radius

Ossifies from 3 centers:

  • body: appears in 8th week of fetal life
  • proximal extremity: appears around 5 years of age and fuses with body around 17-18 years of age
  • distal extremity: appears around 9-26 months of life and fuses with body around 20 years of age

See also:

Anatomy: Upper limb
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Article information

rID: 29037
Section: Anatomy
Synonyms or Alternate Spellings:
  • Radius bone
  • Radius anatomy
  • Radial anatomy

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