MSK 4b: elbow Flashcards
What type of synovial joint is the elbow?
Hinge
Covered in hyaline
What are the articulations of the elbow?
Humerus: trochlea (ulnar side), capitulum (radial side), olecranon fossa, coranoid fossa, radial fossa
Ulna: coranoid process, trochlear notch, olecranon process
Radius: head
When are the articulating surfaces of the elbow most in contact?
Forearm halfway between pronation and supination, and flexed at 90 deg
The joint capsule is shared with the proximal radioulnar joint. Describe its structure
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
Where is the elbow joint capsule strong/weak?
Weak anteriorly and posteriorly
Strengthened medially and laterally by collateral ligaments
Describe the ulnar collateral ligament
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
Describe the radial collateral ligament
Lateral and fan-like, extends from lateral epicondyle of humerus then blends with the anular ligament of the radius. Forms proximal radioulnar joint
Which muscles produce elbow flexion?
Brachialis, biceps brachii (main)
Brachioradialis (rapid flexion without resistance, even when main flexors paralysed)
Brachioradialis and pronator teres (with resistance assist the main muscles)
Which muscles produce elbow extension?
Triceps brachii (esp. MEDIAL HEAD) Assisted by anconeus
Why is the carrying angle greater in females?
Forearm further from trunk to allow upper limb to swing without hitting hip
What are the most clinically-relevant elbow bursae?
- Subcutaneous olecranon bursa: in subcutaneous connective tissue over olecranon
- Subtendinous olecranon bursa: between olecranon and triceps tendon [just prox. to its attachment with olecranon]
- Intratendinous olecranon bursa: sometimes present in the biceps tendon
Which nerves supply the elbow?
Radial
Musculocutaneous
Ulnar
Which arteries supply the elbow?
Anastomosis formed by collateral arteries and recurrent branches of the ulnar, radial and interosseous arteries
Bursitis?
Subcutaneous: from repeated friction and pressure or infection
Subtendinous: from repeated flexion and extension
Elbow dislocation?
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
Subluxation and dislocation of radial head-“pulled elbow”?
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
Medial epicondyle fracture?
Common in children
Tension from ligamentous structures as bones quite weak in children
If untreated can cause entrapment
Avulsion of medial epicondyle?
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
Epicondylitis?
Overuse strain of common tendon of flexor origin
Lateral epicondyle: TENNIS ELBOW
Medial epicondyle: GOLFER’S ELBOW
Supraepicondylar fracture?
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
