Anatomy of the Elbow

Bony Anatomy

• Bones:
  • Humerus
    • Lower end has two epicondyles: lateral and medial
    • Capitellum (lateral) and trochlea (medial)
  • Ulna
    • Proximal ulna: olecranon process, trochlear notch, coronoid process
    • Bursa located on top of the olecranon process
  • Radius
    • Composed of radial head, neck, and radial tuberosity

Joint Stability

• Primary Stabilizer: Unhumeral joint
• Coronoid Process:
  • Anterior buttress of the olecranon
  • Prevents posterior dislocation of the elbow
  • Fractures >50% height lead to instability

Medial Side Structures

• Medial Elbow Ligaments:
  • Ulnar Collateral Ligament (MCL)
    • Three bands: anterior, posterior, transverse
      • Anterior Band: Strongest, stabilizes valgus stress at 90° flexion
      • Posterior Bundle: Tight in elbow flexion; release for more flexion in stiff elbow
    • Originates at posterior medial epicondyle of distal humerus
    • Inserts into sublime tubercle of medial coronoid process
    • Valgus/moving valgus stress test for deficiency
    • MRI best for diagnosing MCL tears
• Muscles:
  • Pronator teres and flexor muscles (attached to medial epicondyle)
  • Ulnar nerve in cubital tunnel

Posterior Elbow

• Muscles:
  • Triceps muscle and tendon
• Bursa:
  • Ulnar bursitis

Lateral Side Structures

• Lateral Collateral Ligament:
  • Important parts: lateral ulnar collateral ligament, lateral radial collateral ligament, accessory lateral collateral ligament, annular ligament
  • Lateral Ulnar Collateral Ligament:
    • Prevents post-trilateral instability
    • Acts as a sling for radial head
    • Arises from lateral humeral epicondyle, inserts into crista subinators of proximal ulna
  • Issues:
    • Postrolateral rotatory instability diagnosed via pivot shift test (axial load, spination, valgus)
    • Intermedial coronoid facet fracture associated with lateral collateral ligament tear

Lateral Side Muscles

• Common extensor tendon muscles:
  • Extensor carpi radialis longus and brevis
  • Extensor digitorum
  • Extensor carpi ulnaris

Anterior Elbow

• Cubital Fossa:
  • Contains pronator teres and brachioradialis
  • Biceps muscle
    • Radial nerve lateral to biceps
    • Brachial artery and median nerve medial to biceps
    • Biceps inserted into radial tuberosity
    • Radial recurrent arteries above biceps
    • Lateral antebrachial cutaneous nerve (branch of musculocutaneous nerve) prone to injury in distal bicep surgery

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