– Ulna bone is a medial bone of forearm

-The ulna is one of two bones of forearm, and the other one is radius.

-It forms the elbow joint with the humerus and also proximally and distally it articulates with the radius .

– In the anatomical position of hand It is located in the medial forearm .

-It is the larger of the two forearm bones.

– It is homologous to fibula of lower limb.

– It has : Upper end

Lower end




• Side determination

1) Upper end


– Hook like

– Concavity directs forward


2) Shaft

– Lateral border is crest like and sharp.


3) Styloid process lies posteromedial to rounded head of ulnar bone at its lower end.




• Upper end of ulna bone

– It has,

√ the olecranon and the Coronoid processes

√  the Trochlear and radial notches


1) The olecranon process

– Projects upwards from shaft.

– It has ,

√ Superior surface

√ Anterior surface

√ Posterior surface

√ medial surface

√ Lateral surface


* The anterior surface :

– Articular

– It forms upper part of Trochlear notch.


* The posterior surface :

– It forms a triangular subcutaneous area and is separated from skin by the bursa.

– It continuous with posterior border of the shaft  of ulna inferiorly.

– It’s upper part forms a point of eblow.


* The medial surface :

– Continuous with medial surface of the shaft inferiorly.


* The lateral surface :

– Smooth

– Continues as posterior surface of shaft.


* The superior surface :

– Posterior part shows a roughened area.


2) The Coronoid process


– It projects forwards from shaft just below the olecranon process.

– It has ,

√ Superior surface

√ Anterior surface

√ Medial surface.

√ Lateral surface


* Superior surface

– Forms lower part of Trochlear notch.


* Anterior surface :

– Triangular and rough

– Lower corner forms the ulnar tuberosity.


* Lateral surface  :

– Upper part :

It is marked by radial notch for head of radius.

Annular ligament is attached to anterior and posterior margins of the notch.


– Lower part :

Forms a depressed area for accomodation of  radial tuberosity .

Behind it has a supinator crest.


* Medial surface :

– Continuous with medial surface of shaft.


3) The Triangular notch

– Forms a articular surface which Articulates with Trochlea of humerus to form elbow joint.


4) The radial notch

– Articulates with radial head to form Superior radioulnar joint.



• Shaft of ulna bone


– It has 2 borders and 3 surfaces.

* Borders

1) The lateral or interosseous border

– Sharpest in middle 2/4 th

– Inferiorly : traced to lateral side of head.

– Superiorly : Continuous with supinator crest.


2) The anterior border

– Thick and rounded.

– It begins on medial side of ulnar tuberosity above , then passes backwards in its lower 1/3 rd.

– It terminates at styloid process ( medial side ).


3) The posterior border

– It is subcutaneous

– It begins at the apex of the triangular subcutaneous area at the back of olecranon

– Terminates at base of styloid process.



* Surfaces


1) The anterior surface :

– It lies between anterior and lateral border.

– A nutrient foramen is present on its upper part.

– It is directed upwards.

– Nutrient artery is derived from anterior interosseous artery .


2) The medial surface :

– Lies between anterior and posterior border.


3) The posterior surface :

– It lies between Posterior and lateral border.

– It is subdivided into 3 areas by the 2 lines.

– It is divided into upper and lower parts by an oblique line .

– Lower part is further divided into medial and lateral area by a vertical line.


 Lower end of ulna bone


– It is made up of head and styloid process.

– The head articulates with ulnar notch of radius and forms inferior radioulnar joint.

– It is separated from the wrist joint by articular disc .

– Ulnar artery and nerve lies on the anterior aspect of ulnar head.

– Styloid process projects downwards posteromedial side of lower end of Ulna.

– Posteriorly, between the head and styloid process , there is a groove for the extensor carpi ulnaris tendon.





1) The Triceps brachii

– Inserted into superior surface of olecraolecranon.

– Anterior part of this surface is covered by a bursa.

2) The Brachialis

– Inserted into anterior surface of Coronoid process including ulnar tuberosity

3) The Supinator

– Arises from supinator crest and from triangular area in front of the supinator crest.

4) Flexor digitorum superficialis ( ulnar head )

– Arises from tubercle at the upper end of medial margin of Coronoid process.

5) Pronator teres ( Ulnar head )

– Arises from Coronoid process ( medial margin ).

6) Flexor digitorum profundus

– Arises from,

√ Upper 3/4 th of anterior and medial surface of shaft.

√ The Coronoid and olecranon process ( medial surface )

√ Posterior border of shaft through an aponeurosis which also gives origin to flexor carpi ulnaris and extensor carpi ulnaris.

7) The Pronator quadratus

– Originates from oblique ridge on lower part of anterior surface.

8) Flexor carpi ulnaris ( ulnar head )

– Arises from medial side of olecranon process and from posterior border.

9) Extensor carpi ulnaris

– Arises from Posterior border.

10) The Anconeus

– Inserted into olecronon process ( lateral aspect ).

– And upper 1/4 th of shaft ( posterior surface).

11) The lateral part of posterior surface gives origin from above downwards to adductor pollicis longus, the extensor pollicis longus and the extensor indicis.

12) The interosseous membrane

– Attached to interosseous border.

13) The oblique cord

– Attached to ulnar tuberosity.

14) Capsular ligament of elbow joint

– Attached to margin of Trochlear notch

i.e., to the Coronoid and olecranon processes.

15) The annular ligament of superior radioulnar joint

– Attached to two margins of radial notch of ulna.

16) The ulnar collateral ligament of wrist

– Attached to styloid process.

17) The articular disc of inferior radioulnar joint

– Attached by its apex to small rough area just lateral to styloid process.






* Primary centre

– The shaft and most of upper end ossifies from primary centre which appears during 8 th week of development.

* Secondary centre

– Superior part of olecranon process ossify from secondary centre .

– This appears during 10 th year.

– It forms a scale like epiphysis which joins the rest of bone by 16 th year.

– The lower end ossifies from a secondary centre appears during 5 th year and joins with shaft by 18 th year

– This is growing end of bone.




√ The ulna is a stabilising bone of forearm , with its Trochlear notch gripping the lower end of humerus.

On this foundation, the radius can pronate and supinate for efficient working of the upperlimb.


√ The shaft of ulna may fracture either alone or along with that of radius .

Cross union between radius and ulna must be prevented to preserve pronation and supination of hand.

√ Dislocation of elbow

– Produced by fall on outstretched hand with elbow slightly flexed.

– Olecranon shifts Posteriorly and elbow is flexed in slight flexion.

– Normally , in an extended elbow , the tip of the olecranon lies in a horizontal line with 2 epicondyles of the humerus and in the flexed elbow , the three bony points form an equilateral triangle .


These relations are disturbed in elbow dislocation.


√ Fracture of olecranon

– It is common and is caused by fall on point of elbow.

√ Fracture of Coronoid process

– It is uncommon and us usually accompanies with elbow dislocation.

√ Madelung’s deformity

-It is dorsal displacement of lower end of Ulna , due to growth retardation of the lower end of radius.







Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top