Anatomy Atlas

Ulna

Ulna
BonedraftMSK

Medial, stabilizing bone of the forearm. Its trochlear notch forms the hinge of the elbow with the humerus.

Core anatomy

Location

Medial (little finger side) of the forearm; large proximally, small distally.

Classification

Long bone.

Key features & landmarks
  • Olecranon: posterior projection, the point of the elbow; insertion of triceps brachii
  • Coronoid process: anterior projection; origin of the ulnar head of pronator teres
  • Trochlear notch: articulates with the trochlea of the humerus
  • Radial notch: articulates with the head of the radius (proximal radioulnar joint)
  • Tuberosity of the ulna: insertion of brachialis
  • Supinator crest: origin of part of supinator
  • Head (distal) and ulnar styloid process; separated from the carpals by the articular disc of the TFCC
  • Subcutaneous posterior border palpable along its whole length
Relations

The ulnar nerve runs along its medial side, deep to flexor carpi ulnaris. The interosseous membrane links it to the radius.

Muscle attachments

Joints

Mentioned in

Generated automatically from links in other entries.

Anterior view of the left radius and ulna
Left radius and ulna, anterior aspect.
Henry Vandyke Carter, Gray's Anatomy of the Human Body, 20th ed. (1918), Fig. 213. Source · Public domain (Public domain in the US: published before January 1, 1931 (per Wikimedia Commons))

Clinical correlations

Monteggia fracture-dislocation PANCE

Mechanism / lesion

Fracture of the proximal third of the ulna with dislocation of the radial head, e.g. a fall with forced pronation or a direct blow.

Classic presentation

Forearm deformity and elbow pain. The radial head dislocation is easily missed unless the elbow is imaged. The posterior interosseous nerve may be injured.

Nightstick fracture

Mechanism / lesion

Isolated fracture of the ulnar shaft from a direct blow, classically when raising the forearm to protect the face.

Classic presentation

Localized tenderness and swelling over the subcutaneous border of the ulna.

Olecranon fracture

Mechanism / lesion

A fall directly onto the point of the elbow, or avulsion by triceps.

Classic presentation

Posterior elbow pain and swelling. Displacement by triceps may prevent active extension against gravity.

Olecranon bursitis

Mechanism / lesion

Inflammation of the subcutaneous olecranon bursa from repetitive pressure ("student's elbow"), trauma, gout, or infection.

Classic presentation

Fluctuant swelling over the olecranon. Erythema, warmth and fever suggest septic bursitis, which needs aspiration.

High-yield PANCE pearls

  • MUGR: Monteggia = Ulnar fracture + radial head dislocation.
  • Forearm fractures: always image the elbow and the wrist (joint above and below).
  • Nightstick fracture = isolated ulnar shaft fracture from a direct blow.
  • Olecranon bursitis: aspirate if septic bursitis is suspected (fever, erythema, warmth).

Imaging anatomy

X-ray

Forearm AP and lateral including the elbow and wrist. In Monteggia, the radiocapitellar line does not pass through the capitellum. Elbow lateral view for olecranon fractures.

CT

Comminuted or intra-articular proximal ulna and coronoid fractures.

Ultrasound

Characterizes olecranon bursal fluid and guides aspiration.

Key views & landmarks
  • Forearm AP and lateral with the elbow and wrist included
  • Elbow lateral (olecranon, coronoid)

Physical exam

Surface landmarks

The olecranon, the entire posterior border, the ulnar head (dorsomedial wrist) and the ulnar styloid are subcutaneous and palpable.

Palpation

Run a finger along the posterior border from the olecranon to the styloid, feeling for step-off or tenderness.

Strength / function testing

Elbow flexion and extension, forearm rotation, and ulnar nerve function.

Self-quiz

Q1.

A 10-year-old boy has a displaced fracture of the proximal ulnar shaft after a fall. What associated injury must be excluded?

Show answer

B

Monteggia fracture-dislocation: proximal ulnar fracture with radial head dislocation. Check the radiocapitellar line. Galeazzi involves the DRUJ with a radial fracture.

Q2.

Which muscle inserts on the olecranon?

Show answer

C

Triceps brachii inserts on the olecranon. Brachialis inserts on the ulnar tuberosity and coronoid process; biceps inserts on the radial tuberosity.

Q3.

A police officer raised his forearm to block a baton strike and has an isolated fracture of the ulnar shaft. What is this called?

Show answer

C

An isolated ulnar shaft fracture from a direct blow is a nightstick fracture. Monteggia and Galeazzi involve a joint dislocation.

Flashcards

See also