The ulna is the medial forearm bone that has several processes and surfaces for muscle and ligament attachments. The upper end has an olecranon process that projects upwards and forms the point of the elbow. It articulates with the trochlea of the humerus. The coronoid process projects forwards below the olecranon and forms part of the trochlear notch. The shaft has anterior, posterior, and interosseous borders. Multiple muscles originate from the surfaces of the ulna. The lower end has a head that articulates with the radius to form the inferior radioulnar joint. A styloid process is posterior to the rounded head.

1. ULNA (MEDIAL FOREARM BONE)
PART SUB PART SIDE
DETERMINATION
FEATURES SURFACES ATTACHMENTS OTHERS
UPPER END OLECRANON
PROCESS
Upper end is hook like
and its concavity
directed forwards.
Olecranon process
projects upwards from
shaft.
Olecranon
1) Anterior – articular, forms part of upper trochlear
notch
2) Posterior – forms triangular subcutaneous area,
its upper part forms point of elbow, separated
from skin by a bursa.
3) Medial – cont. medially with medial surface shaft.
4) Lateral – smooth, continue as post-surface shaft.
5) Superior – post part shows roughened area.
1) Triceps brachii- insertion- superior surface
of olecranon process.
2) Brachialis – inserted into anterior surface
of coronoid process.
3) Supinator – arise- supinator crest and
triangular area in front of crest.
4) Flexor digitorum superfascialis (ulnar head)
– arise- tubercle at upper end coronoid
process medial margin
5) Pronator teres (ulnar head) – arise- medial
margin of coronoid process.
6) Capsular ligament of the elbow attaches to
margins of trochlear notch which is
coronoid and olecranon process.
Most upper part
ossifies from
primary centre.
Superior part of
olecranon
ossifies from
secondary
centre.
Dislocation of
elbow- posterior
shift in olecranon
process.
Most common
fracture –
olecranon
process.
CORONOID
PROCESS
Projects forwards from
shaft just below
olecranon process.
TROCHLEAR
NOTCH
Forms articular surface
that articulates with
trochlea of humerus to
form elbow joint.
Coronoid
1) Superior – forms lower part of trochlear notch
2) Anterior – triangular and rough, its lower corner
form ulnar tuberosity.
3) Lateral – upper part marked by radial notch,
limited behind by ridge called supinator crest.
4) Medial – continues with medial surface of shaft.
RADIAL
NOTCH
Articulates with head of
humerus to form the
superior radio ulnar joint.
SHAFT Lateral border is shaft
and crest like.
Borders
1)Inter-osseous or lateral - sharpest in
middle 2/4th superiorly it continues
to supinator crest.
2)Anterior- thick and rounded, begins
above on medial side of ulnar
tuberosity, passes backwards in its
lower 1/3rd and ends at medial side
of styloid process.
3)Posterior – subcutaneous, begins-
above apex of triangular
subcutaneous area. Terminates base
of styloid process.
Surfaces
1) Anterior- btw 1&2nd border, nutrient
foramen seen on upper part.
Directed upwards.
2) Medial- btw 2&3rd border.
3) Posterior- btw 3&1st border,
subdivided into three areas by two
lines. Oblique line and vertical line.
1) Flexor digitorum profundus – arise from
upper 2/3rd of ant and medial surface of
shaft, medial surface of olecranon and
coronoid process and post border of shaft.
2) Pronator quadratus – origin- oblique ridge
on lower part anterior surface.
3) Flexor carpii ulnaris- arise post border of
shaft and medial side of olecranon process.
4) Extensor carpii ulnaris – arise from
posterior border.
5) Lateral part of posterior border gives origin
to abductor and extensor pollicis longus,
extensor indicis.
6) Interosseous membrane – attach to
interosseus border.
7)
Ossifies from
primary centre.
LOWER END HEAD Features
Articulates with ulnar notch of radius to form inferior radioulnar joint. Separated
from wrist joint by articular disc. Ulnar artery and nerve lie on its anterior aspect
Lower end
ossifies from
secondary
centre.
Madelung’s
deformity is
dorsal
subluxation of
lower end of
ulna.
STYLOID
PROCESS
Pointed styloid
process lies
posteromedial to
rounded head of ulna
at its lower end
Features
Posteriorly btw head and styloid process there is a groove for tendon of the
extensor carpi ulnaris.
1) Ulnar collateral ligament – attached to
styloid process.
2) Articular disc of inferior radio ulnar joint
attached to a small area lateral to styloid
process. Ulnar collateral ligament –
attached to styloid process.
Articular disc of inferior radio ulnar joint
attached to a small area lateral to styloid
process.