Overview
This lecture covers the anatomy, movements, muscles, ligaments, and common pathologies of the elbow joint, emphasizing key structures and clinical concepts.
Elbow Joint Structure
- The elbow joint consists of three joints within a single capsule: humeroulnar, humeroradial, and proximal radioulnar.
- Humeroulnar joint is a synovial hinge joint allowing only flexion and extension.
- Humeroradial joint is a gliding joint, allowing flexion, extension, pronation, and supination.
- Proximal radioulnar joint is a pivot joint, enabling rotation (pronation and supination) of the forearm.
- The carrying angle (cubital angle) is the lateral deviation of the forearm due to the trochlea extending further distally than the capitulum.
Movements of the Elbow
- Flexion: Decreasing the angle at the elbow.
- Extension: Increasing the angle at the elbow.
- Pronation: Turning the palm downward (radius crosses over ulna).
- Supination: Turning the palm upward (radius and ulna parallel).
Ligaments of the Elbow
- Annular ligament encircles the head of the radius, securing it to the ulna.
- Lateral (radial) collateral ligament stabilizes the lateral side.
- Medial (ulnar) collateral ligament stabilizes the medial side.
- Interosseous ligament connects the interosseous borders of the radius and ulna.
- Oblique cord is a short ligament near the proximal forearm connecting the two bones.
Muscles Acting on the Elbow
- Flexors: Biceps brachii (also supinates), brachialis (primary flexor), brachioradialis (moves to neutral/handshake position), pronator teres (also pronates).
- Pronators: Pronator teres (proximal) and pronator quadratus (distal).
- Supinators: Biceps brachii and supinator.
- Extensors: Triceps brachii (main extensor, three heads) and anconeus (minor helper).
Muscle Actions and Types of Contractions
- Agonist: Prime mover for an action.
- Antagonist: Opposes the agonist.
- Synergist: Assists the agonist in the same action.
- Isotonic contraction: Muscle changes length (concentric = shortens, eccentric = lengthens).
- Isometric contraction: Tension without length change.
Common Elbow Pathologies
- Dislocation (complete) and subluxation (partial) often involve the radial head, especially in children (nursemaid's elbow).
- Tendinitis (inflammation of a tendon), often affects distal biceps tendon.
- Strain: Injury to muscle or tendon (brachialis muscle common).
- Sprain: Injury to ligament or joint capsule.
- Bursitis: Inflammation of the olecranon bursa (student’s elbow).
- Medial epicondylitis (golfer’s elbow): Involves flexor tendons.
- Lateral epicondylitis (tennis elbow): Involves extensor tendons, especially from eccentric overload.
- Hyperextension injury occurs with forced extension, common in sports.
Key Terms & Definitions
- Articulation — the technical term for a joint where bones meet.
- Carrying angle (cubital angle) — lateral deviation of the forearm when the arm is extended.
- Pronation — turning the palm downward.
- Supination — turning the palm upward.
- Bursa — fluid-filled sac reducing friction between tissues.
- Tendinitis — inflammation of a tendon.
- Strain — injury to muscle or tendon.
- Sprain — injury to a ligament.
- Valgus/Varus — distal segment angled away/toward the midline.
Action Items / Next Steps
- Review anatomical diagrams of the elbow and associated muscles.
- Memorize muscle origins, insertions, and primary actions.
- Practice identifying types of joint movement and contraction.
- Study the differences between strain, sprain, and bursitis for exam preparation.