29. The elbow

Question 1

What are the two articulations of the elbow joint?

Answer 1

 The humeroulnar joint between the trochlea of the humerus and the trochlear notch (or sigmoid notch) of the ulna
 The humeroradial joint between the capitellum of the humerus and the radial head

Question 2

What is the proximal radio-ulnar an articulation between?

Answer 2

Between the side of the head of the radius and the radial notch of the ulna (not part of the elbow joint)

Question 3

What do the two condyles of the distal humerus support?

Answer 3

The distal humerus has two condyles (medial and lateral) that support the articular elements: the trochlea and capitellum

Question 4

What do the epicondyles of the distal humerus provide attachment for?

Answer 4

Lateral: extensor group in the posterior forearm
Medial: flexor-pronator group of muscles in the anterior forearm

Question 5

Which structures accommodate the the radial head and the coronoid process of the ulna in flexion?

Answer 5

radial and coronoid fossae of the humerus

Question 6

What structure accommodates the olecronon in extension?

Answer 6

Olecronon fossa on posterior distal humerus

Question 7

What part of the ulna does the radial head articulate with?

Answer 7

The radial head articulates with the capitellum of the ulna.

Question 8

Describe the radial kneck

Answer 8

Inferior to the radial head is the radial neck; this is thin and consequently vulnerable to fracture

Question 9

What inserts into the radial tuberosity?

Answer 9

biceps brachii tendon

Question 10

How dos the ulna and distal humerus articulate?

Answer 10

The ulna has a sigmoid notch that articulates with the trochlea of the distal humerus

Question 11

What inserts into the olecronon?

Answer 11

triceps brachii muscle

Question 12

What originates from the supinator crest (on the ulnar)?

Answer 12

ulnar head of the supinator muscle

Question 13

Which ligaments strengthen the Joint capsule of the elbow joint medially and laterally?

Answer 13

Radial (lateral) collateral ligament

Ulnar (medial) collateral ligament

Question 14

What are the attachments of the lateral collateral ligament and what is its function?

Answer 14

This fan-shaped structure attaches between the lateral epicondyle of the humerus and annular ligament of the radius with which it blends.
It keeps the head of the radius and the capitellum in close association during pronation and supination of the forearm

Question 15

What are the attachments of the ulnar (medial) collateral ligament and what are the 3 bands?

Answer 15

This triangular ligament stretches between the medial epicondyle of the humerus and the coronoid process and olecranon of the ulna.

It consists of three bands: the ‘anterior band’, which is the strongest component; the fan like ‘posterior band’, which is weak; and the slender oblique (inferior) band which deepens the socket for the trochlea of the humerus

Question 16

What is the proximal radioulnar joint stabilised by?

Answer 16

annular ligament

Question 17

What is the annular ligament?

Answer 17

forms a collar around the radial head within which the radial head can rotate whilst maintaining its contact with the radial notch of the ulna

Question 18

What movements is the elbow joint capable of?

Answer 18

Flexion and extension

Question 19

WHat angle does the ulna make in full extension?

Answer 19

a valgus angle (Remember: vaLgus = Lateral angulation) with the long axis of the humerus

Question 20

What is the carrying angle and what are the normal values?

Answer 20

Angle between long axis of the humerus and the ulnar - VALGUS ANGLE

• men: 5-10°
• women: 10-15°

Question 21

Why is the carrying angle important?

Answer 21

Permits the forearm to clear the hips in swinging movements of the arm during walking

Question 22

What is an excessive carrying angle called

Answer 22

cubitus valgus

Question 23

What is a carrying angle that deviates towards the body called?

Answer 23

cubitus varus

Question 24

What provides dynamic stability to the elbow joint?

Answer 24

Whilst the structure of the bones and ligaments makes the elbow a relatively stable joint, additional dynamic stability is provided by surrounding muscles.

Question 25

What are the flexors of the elbow joint?

Answer 25

• Brachialis, Biceps brachii, Brachioradialis
• The muscles originating from the common flexor origin on the medial humeral epicondyle are also weak flexors of the elbow

Question 26

What are the extensors of the elbow joint?

Answer 26

• The major extensor of the elbow joint is triceps brachii.
• Anconeus is a relatively weak extensor.
• The muscles originating from the common extensor origin on the lateral humeral epicondyle are also weak extensors of the elbow.

Question 27

Which muscles are responsible for pronation at the proximal and distal radio-ulnar joints?

Answer 27

pronator quadratus and pronator teres

Question 28

Which muscles are responsible for supination at the proximal and distal radio-ulnar joints?

Answer 28

• absence of resistance to movement, is performed by supinator
• when there is resistance, supination is performed by biceps brachi

Question 29

at the proximal and distal radio-ulnar joints

Answer 29

olecranon bursa: subcutaneous olecranon bursa lies in the subcutaneous connective tissue overlying the olecranon

subtendinous bursa: lies between the triceps tendon and the tip of the olecranon

Question 30

What is the function of the olecranon and subtendinous bursa?

Answer 30

The role of these bursae is to reduce friction between
bone and skin / subcutaneous tissue (e.g. olecranon bursa), or between tendon and bone (e.g. subtendinous bursa), during movements of the elbow joint

Question 31

Where is the distal radio-ulnar joint (DRUJ) located? What type of joint is it?

Answer 31

located immediately proximal to the wrist joint. It is a pivot joint in which the ulnar notch of the radius rotates anteriorly around the head of the ulna

Question 32

Where is the axis of rotation in the forearm?

Answer 32

axis of rotation passes longitudinally though the head of the radius proximally and through the styloid process of the ulna distally

Question 33

What binds the radius and ulnar together at the distal end?

Answer 33

fibrocartilaginous articular disc called the triangular fibrocartilage complex (TFCC) binds the radius and ulnar together and also separates the distal radioulnar joint from the wrist joint

Question 34

What connects the shaft of the radius and ulnar?

Answer 34

Interosseous membrane

Question 35

How do the fibres of the interosseous membrane run and what is its function?

Answer 35

interosseous membraneforms a fibrous joint between the radius and ulna.
The fibres run diagonally, from the radius proximally to the ulna more distally.
This membrane keeps the bones together during the movements of pronation and supination, and also prevents proximal displacement of the radius a force is applied to the outstretched hand