Complete ulnar bone
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ulna bone anatomy
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ulna bone labeled anatomy diagram anterior posterior
Complete ulna (ulnar bone): key anatomy
The ulna is the medial long bone of the forearm (little-finger side in anatomical position). It runs parallel to the radius.
Main parts
-
Proximal end (largest)
- Olecranon process: posterior projection, forms the tip of the elbow
- Coronoid process: anterior projection
- Trochlear (semilunar) notch: between olecranon and coronoid, articulates with humeral trochlea
- Radial notch: lateral facet for radial head (proximal radioulnar joint)
- Ulnar tuberosity: distal to coronoid, insertion of brachialis
-
Shaft
- Triangular in cross-section through much of its length
- 3 borders: anterior, posterior, interosseous (lateral)
- 3 surfaces: anterior, posterior, medial
- Interosseous border gives attachment to interosseous membrane between radius and ulna
-
Distal end (smaller)
- Head of ulna: articulates with ulnar notch of radius
- Styloid process: pointed medial/posterior projection
- Distal ulna is separated from carpal bones by TFCC (articular disc), so it has limited direct carpal contact
Articulations
- Humeroulnar joint: trochlear notch with humeral trochlea (elbow hinge)
- Proximal radioulnar joint: radial notch with radial head
- Distal radioulnar joint: ulnar head with ulnar notch of radius
Important muscle/ligament attachments (high yield)
- Triceps tendon to olecranon
- Brachialis to ulnar tuberosity/coronoid region
- Flexor digitorum profundus from anterior/medial ulna
- Pronator quadratus from distal anterior ulna
- Supinator near proximal lateral/interosseous region
- Ulnar collateral ligament complex attaches around sublime tubercle/coronoid and olecranon region
Clinical relevance
- Olecranon fractures (direct trauma/fall)
- Nightstick fracture: isolated ulnar shaft fracture
- Distal ulna/styloid fractures often with distal radius injuries
- Positive ulnar variance can increase ulnocarpal load (ulnar impaction)
Reference: Imaging anatomy text and atlas Volume 3, Bones, joints, Vessels and Nerves, p. 96-97.
Complete ulnar bone
The complete ulna is described in 3 parts:
- Proximal end
- Olecranon process (forms tip of elbow)
- Coronoid process
- Trochlear (semilunar) notch between them (articulates with humerus)
- Radial notch (articulates with head of radius)
- Ulnar tuberosity
- Shaft (body)
- Long triangular shaft
- 3 borders: anterior, posterior, interosseous
- 3 surfaces: anterior, posterior, medial
- Distal end
- Head of ulna
- Styloid process
So if asked to “complete ulna bone,” include all named landmarks above from proximal end to distal end.
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