Elbow and Forearm Anatomy Quiz

Elbow and Forearm Anatomy

• The elbow joint is a hinge type synovial joint
• At full extension, the ulna makes a 170° angle with the humerus (long axis)
• In females, the forearm is angled further away from the trunk (carrying angle)

Joint Considerations

• Articulations: The bones forming the joint (humerus, radius, ulna)
• Capsule: Connective tissue sac surrounding the joint
• Ligaments: Strong bands of tissue reinforcing the joint
• Movements: Actions possible at the joint (flexion, extension, etc.)
• Muscles: Muscles produce the movements
• Neurovascular supply: Nerves and blood vessels supplying the joint
• Bursae: Small fluid-filled sacs reducing friction

Elbow Articulations (Osteology)

• Humerus:

  • Trochlea
  • Capitulum
  • Olecranon fossa
  • Coronoid fossa
  • Radial fossa

• Ulna:

  • Coronoid process
  • Trochlear notch
  • Olecranon process

• Radius:

  • Head

Elbow Movements

• Flexion: Bending the elbow
• Extension: Straightening the elbow
• Carrying angle: Forearm angled further away from the trunk in females

Muscles

• Biceps brachii: Flexor of the elbow
• Triceps brachii: Extensor of the elbow
• Branchioradialis: Flexor, innervated by the radial nerve

Elbow Capsule

• Weak anteriorly and posteriorly
• Strengthened by collateral ligaments (medially and laterally)
• Elbow and proximal radioulnar joints share a capsule
• Synovial membrane lines the fibrous capsule and humerus

Elbow Ligaments (Ulnar Collateral Ligament)

• Three bands:
  • Anterior (strongest)
  • Posterior
  • Oblique (deepens the socket for the trochlea)
• Radial collateral ligament: Fan-like, blends with annular ligament

Elbow Bursae

• Many bursa (fluid-filled sacs)
• Problems are rare except some:
  • Subcutaneous olecranon bursa
  • Subtendinous olecranon bursa

Nerves

• Radial nerve passes anterior to the lateral epicondyle
• Ulnar nerve passes posterior to the medial epicondyle

Neurovascular Supply

• Hilton's law: nerves and vessels supplying a joint also innervate the muscles moving the joint.
• Anastomoses formed by collateral arteries (and recurrent branches) of ulnar, radial, and interosseous arteries

Radioulnar Joints

• Proximal: Pivot joint, osteology of the radius head and ulna's radial notch
• Interosseous membrane: Fibrous joint, allows force distribution to the ulna
• Distal: Osteology of the ulna head, rounded head of radius, ulnar notch on medial border, articular disk.
• The articular disk is important for maintaining joint integrity and separating the distal radioulnar joint cavity from the wrist cavity.

Radioulnar Movements

• Pronation/Supination: Rotation of the forearm
• The head of the radius pivots on the capitulum of the humerus

Proximal Radioulnar Joint

• Pivot joint
• Osteology: radius head, ulna's radial notch

Annular Ligament

• Ligamentous collar and attached to the ulna, anterior and posterior to its radial notch

Pulled Elbow (Children)

• Dislocation of the radial head from the annular ligament

Dislocation/Subluxation

• Dislocation: Complete loss of joint contact of joint surfaces.
• Subluxation: Partial dislocation (misalignment) but bone ends remain in contact

Interosseous Membrane

• Fibrous joint
• Fibers run inferomedially
• Allows force distribution from radius to ulna

Distal Radioulnar Joint

• Osteology: rounded head of radius, ulnar notch on medial border
• Articular disk
• Maintains joint integrity, separating distal radioulnar joint cavity from wrist cavity

Distal Radioulnar Joint in Pronation/Supination

• Articular disk ensures maintenance of joint integrity
• Sacciform recess is a superior expansion of the synovial capsule that allows twisting of the capsule

Movements of Radioulnar Joints

• Supinator: Muscle assisting in supination
• Biceps brachii: Muscle assisting in supination
• Pronator teres: Muscle assisting in pronation
• Pronator quadratus: Muscle assisting in pronation

Wrist

• Radiocarpal joint: Articulation of distal radius and articular disk with proximal carpal bones
• Osteology: Radius (distal), carpus (proximal row excluding pisiform)
• Ligaments: Collateral, palmar radiocarpal, and dorsal radiocarpal ligaments
• Movements: Flexion/extension, abduction/adduction (radial/ulnar deviation), limited by the radial styloid process

Wrist Fractures

• Colles fracture: Posterior displacement of the distal radius fragment
• Scaphoid fracture: Fall onto outstretched hand causes tenderness over the anatomical snuffbox. Complications can include avascular necrosis.

Self-Study

• Review upper limb osteology, joint classifications (synovial and fibrous joints), and clinically relevant sections from anatomy texts.