Elbow Joint and Forearm Anatomy

The Elbow and Joints of the Forearm

• The elbow joint is a hinge type synovial joint that allows for flexion and extension movements.
• At full extension, the ulna makes an angle of 170º with the humerus (long axis), and the forearm is angled further away from the trunk in females.
• The muscles involved in producing hinge movements at the elbow are:
  • Biceps brachii
  • Triceps brachii
  • Brachioradialis

Capsule and Ligaments of the Elbow

• The elbow joint capsule is weak anteriorly and posteriorly, but strengthened by collateral ligaments medially and laterally.
• The ulnar collateral ligament has three bands: anterior (strongest), posterior, and oblique (deepens the socket for the trochlea).
• The radial collateral ligament is fan-like and blends with the annular ligament.

Bursae of the Elbow

• There are several bursae associated with the elbow joint, including:
  • Subcutaneous olecranon bursa
  • Subtendinous olecranon bursa

Neurovascular Supply of the Elbow

• The radial nerve passes anterior to the lateral epicondyle, while the ulnar nerve passes posterior to the medial epicondyle.
• Hilton's law states that the neurovascular supply of the elbow involves arterial anastomoses formed by collateral arteries and recurrent branches of the ulnar, radial, and interosseous arteries.

Radioulnar Joints

• The radioulnar joints consist of:
  • Proximal radioulnar joint (pivot joint)
  • Interosseous membrane (fibrous joint)
  • Distal radioulnar joint (pivot joint)
• The proximal radioulnar joint involves movement of the head of the radius on the capitulum of the humerus.
• The annular ligament is a ligamentous collar attached to the ulna, anterior and posterior to its radial notch.

Pronation and Supination

• Pronation and supination involve movement at the elbow and forearm joints (proximal and distal).
• The head of the radius pivots on the capitulum of the humerus.
• The supinator, biceps brachii, pronator quadratus, and pronator teres are muscles involved in pronation and supination.

Distal Radioulnar Joint

• The distal radioulnar joint involves the articulation of the rounded head of the ulna with the ulnar notch on the medial border of the radius.
• The articular disk is the main structure affording joint integrity and separates the cavity of the distal radioulnar joint from the wrist cavity.

Wrist

• The wrist joint consists of:
  • Radiocarpal joint (articulation of distal radius and articular disk with proximal carpal bones)
  • Osteology of the radius and carpus (distal radius and proximal row of carpal bones)