MSK 4b: elbow

Question 1

What type of synovial joint is the elbow?

Answer 1

Hinge

Covered in hyaline

Question 2

What are the articulations of the elbow?

Answer 2

Humerus: trochlea (ulnar side), capitulum (radial side), olecranon fossa, coranoid fossa, radial fossa

Ulna: coranoid process, trochlear notch, olecranon process

Radius: head

Question 3

When are the articulating surfaces of the elbow most in contact?

Answer 3

Forearm halfway between pronation and supination, and flexed at 90 deg

Question 4

The joint capsule is shared with the proximal radioulnar joint. Describe its structure

Answer 4

Fibrous layer: attaches to humerus at the margins of the lateral and medial ends of articular surfaces of the capitulum and trochlea
Synovial membrane: lines internal surface of fibrous layer of capsule and the intracapsular non-articular parts of humerus

Question 5

Where is the elbow joint capsule strong/weak?

Answer 5

Weak anteriorly and posteriorly

Strengthened medially and laterally by collateral ligaments

Question 6

Describe the ulnar collateral ligament

Answer 6

Medial and triangular shaped, extending from medial epicondyle to coronoid process and olecranon
Anterior band: strongest, limits dislocation
Posterior band: fan-like, weakest, helps distribute forces as joint moves
Oblique band: thin, deepens the socket for the trochlea

Question 7

Describe the radial collateral ligament

Answer 7

Lateral and fan-like, extends from lateral epicondyle of humerus then blends with the anular ligament of the radius. Forms proximal radioulnar joint

Question 8

Which muscles produce elbow flexion?

Answer 8

Brachialis, biceps brachii (main)
Brachioradialis (rapid flexion without resistance, even when main flexors paralysed)
Brachioradialis and pronator teres (with resistance assist the main muscles)

Question 9

Which muscles produce elbow extension?

Answer 9

Triceps brachii (esp. MEDIAL HEAD)
Assisted by anconeus

Question 10

Why is the carrying angle greater in females?

Answer 10

Forearm further from trunk to allow upper limb to swing without hitting hip

Question 11

What are the most clinically-relevant elbow bursae?

Answer 11

1. Subcutaneous olecranon bursa: in subcutaneous connective tissue over olecranon
2. Subtendinous olecranon bursa: between olecranon and triceps tendon [just prox. to its attachment with olecranon]
3. Intratendinous olecranon bursa: sometimes present in the biceps tendon

Question 12

Which nerves supply the elbow?

Answer 12

Radial
Musculocutaneous
Ulnar

Question 13

Which arteries supply the elbow?

Answer 13

Anastomosis formed by collateral arteries and recurrent branches of the ulnar, radial and interosseous arteries

Question 14

Bursitis?

Answer 14

Subcutaneous: from repeated friction and pressure or infection
Subtendinous: from repeated flexion and extension

Question 15

Elbow dislocation?

Answer 15

Posterior-when fall onto hands with elbow flexed, or hyperextension, or force on the ulna making it move posteriorly

Distal end of humerus goes through the weak anterior part of the fibrous layer of capsule, radius and ulna dislocate posteriorly

Ulnar collateral ligament often torn

Associated fracture to radius, coronoid process or olecranon may occur

Ulnar nerve may be damaged–>numbness of little finger, weak flexion and ADduction of wrist

Question 16

Subluxation and dislocation of radial head-“pulled elbow”?

Answer 16

Subluxation=incomplete dislocation
Small children esp. vulnerable: child suddenly lifted by upper limb while forearm is pronated, anular ligament not formed properly in children so partly tears causing radial head to move distally
Proximal part of torn ligament may become trapped between head of radius and capitulum of humerus
Pain=pinched anular ligament
Treated by supinating the forearm with elbow flexed, then heals in about 2 weeks

Question 17

Medial epicondyle fracture?

Answer 17

Common in children
Tension from ligamentous structures as bones quite weak in children
If untreated can cause entrapment

Question 18

Avulsion of medial epicondyle?

Answer 18

Forced separation of ME due to a fall that causes severe abduction of extended elbow. Traction on UCL pulls ME distally
Commonly leads to traction injury of ulnar nerve

Question 19

Epicondylitis?

Answer 19

Overuse strain of common tendon of flexor origin
Lateral epicondyle: TENNIS ELBOW
Medial epicondyle: GOLFER’S ELBOW

Question 20

Supraepicondylar fracture?

Answer 20

Fall on a flexed elbow. Transverse fracture spanning between the two epicondyles
Swelling can interfere with brachial artery supply to forearm–>may cause Volkmann’s ischaemic contracture
Can also damage radial, median or ulnar nerves