The elbow is a complex joint made up of the humerus articulating with the ulna (ulnohumeral joint) and the radius (radiohumeral joint)
Typical synovial, hinge joint allowing only uniaxial movement and reinforced by strong set of collateral ligaments
Note carrying angle: 10-15° in males, 20-25° in females
Articular Surfaces
Articular surfaces on the humerus are the trochlea (anterior and posterior) and capitulum (anterior only)
Ulnar - trochlea notch formed by the coronoid and olecranon processes
Radius - biconcave superior aspect of head of radius
All covered with hyaline cartilage
Capsule
Covered by a fibrous capsule that encloses the superior radio-ulnar joint
Attaches superiorly above the olecranon, radial and coronoid fossae and inferiorly blends with the annular ligament, to the neck of the radius and margins of the coronoid process
Medially and laterally is thickest and reinforced by the radial and ulnar collateral ligaments
Synovial Membrane
Very extensive - extends from the margin of the articular surface of the humerus, lines the coronoid, radial and olecranon fossæ (prone to impingement)
Lines deep surface of capsule
Attaches to articular margins of the ulna, annular ligament and radius
Fat pads within fossae protect bony elements in extension
Radial Collateral Ligament
Supported by a strong set of collateral ligaments
Lateral (radial) collateral ligament - smaller of the 2
From lateral epicondyle
To annular ligament
Limits adduction of forearm and extension
Ulnar Collateral Ligament
Stronger - formed from 3 (occasionally 4) bands
Anterior band - from medial epicondyle to medial coronoid process
Posterior band - from medial epicondyle to medial olecranon
Transverse (oblique) band - unites the distal attachments of the anterior and posterior bands
Movements & Surface Markings of the Elbow Joint
Physiological movements possible at the elbow are flexion/extension
Abduction / Adduction are limited by the collateral ligaments
Surface makings can be identified by drawing a line from a point 2 cm below the medial epicondyle to a point 1cm below the lateral epicondyle
Function & Stability
The joint is very stable due to:
Good congruence between the joint surfaces
Collateral ligaments
Muscles surrounding the joints at certain angles
Max stability at 90 flexion due to muscle activation and maximum bony contact
Cubital fossa - area in the anterior elbow for venopuncture median nerve - brachial artery - radial nerve
Injuries
Dislocation in children predominantly
Supracondylar, olecranon and radial head fractures most common
Medial joint damage due to a traumatic abduction force or repetitive strain
Superior Radioulnar Joint
Classified as a synovial pivot joint
Between the circumference of the head of the radius and the radial notch on the ulna (covered in hyaline cartilage)
The inner surface of the annular ligament - attaches to anterior and posterior margins of radial notch - lined with fibrocartilage
Superior Radioulnar Joint
Common joint cavity and capsule with elbow
Stability is via the annular ligament, the quadrate ligament (from neck of radius to below radial notch) and the interosseous membrane
Inferior Radioulnar Joint
Also classified as a synovial pivot joint
Between head of ulna and ulnar notch on lower end of radius - both covered with hyaline cartilage
United by a loose capsule
Stabilised by anterior and posterior thickenings in the capsule, interosseous membrane and the articulardisc (from base of ulnar styloid to distal edge of ulnar notch)
Interosseous Membrane
Very strong fibrous membrane that passes from the interosseous border on the ulna to the interosseous border on the radius
Fibres pass obliquely downwards and medially
Note oblique cord
Functions
Stabilises 2 bones of forearm/limits movement
Allow transmission of force from large lower end of radius to large upper end of ulna
Compartmentalises
Provides openings for passage of vessels and nerve from anterior to posterior
Provides increased surface area for attachment of muscle
Radioulnar Articulations
Superior and inferior RU joints are palpable beneath the skin
All 3 articulations allow the movements of supination and pronation