Upper Extremity - Elbow & Humerus Anatomy

Upper Extremity - Elbow & Humerus Anatomy

Overview

  • This study guide focuses on the anatomy of the elbow and humerus as taught in the Anatomy & Physiology 1 course (ANAT 1015) at Loyalist College of Applied Arts & Technology.

Review of Key Concepts

  • Anatomical Structure of the Proximal Forearm: The study of the bones and structures including joints in the proximal forearm.
  • Movements of the Proximal Forearm: Understanding the dynamics of movement in the proximal forearm region.

Anatomical Structures of the Proximal Forearm

  • Trochlear Notch: A concave surface on the ulna that articulates with the humerus.
  • Coronoid Process: A bony prominence on the ulna that forms part of the elbow joint.
  • Radial Notch (Lateral): The location on the ulna where the radial head articulates.
  • Olecranon Process: The bony prominence of the ulna, forming the elbow's posterior aspect.
  • Ulnar Structures:
    • Head: Distal end of the ulna.
    • Neck: Narrow part of the ulna below the head.
    • Ulnar Styloid Process: Prominence on the distal end of the ulna.
  • Radial Structures:
    • Body: The shaft of the radius.
    • Head: The proximal end of the radius, which articulates with the humerus.
    • Radial Tuberosity: A bony prominence for muscle attachment.
    • Radial Styloid Process: The distal end of the radius.

Positions of the Hand

  • Supinated (AP Hand): The palm is facing up.
  • Pronated (PA Hand): The palm is facing down.

Required Readings

  • Anatomy & Physiology, Openstax College, Rice University
    • Chapter 8, Section 8.2 "Humerus".
  • Merrill’s Atlas of Radiographic Positioning and Procedures
    • Chapter 5, pages 146-150.

Learning Objectives

  • Identify and Describe the bones of the elbow and humerus along with their key features.
  • Explain the articulations of the elbow joint.
  • Describe the rotational movement of the elbow.

Key Terms

  • Effusion: Abnormal fluid collection in a joint space.
  • In Profile: Optimal visualization of a specific anatomical landmark.
  • Fat Pad: Accumulation of adipose cells surrounded by fibrous tissue septa, commonly found in synovial joints.

Elbow Anatomy

  • The elbow is a joint located between the upper and lower arm, comprised of:
    • Ulna
    • Radius
    • Humerus
  • The elbow is classified as a synovial hinge joint.

Elbow Joint Articulations

  • Proximal Radioulnar Articulation:
    • The radial head articulates with the radial notch on the ulna.
  • Humeroulnar Joint:
    • The trochlea of the humerus articulates with the ulna at the trochlear notch.
  • Humeroradial Joint:
    • The capitulum of the humerus articulates with the radial head.
  • Both Humeroulnar and Humeroradial articulations allow for flexion and extension and are classified as synovial hinge joints.

Elbow Fat Pads

  • The elbow contains three distinct fat pads visualized on lateral projection:
    • Posterior Fat Pad: Located within the olecranon fossa (posterior aspect of humerus).
    • Anterior Fat Pad: Comprised of the superimposed coronoid and radial fat pads, located within the coronoid and radial fossa (anterior aspect of humerus).
    • Supinator Fat Pad: Lies anterior and parallel with the anterior aspect of the proximal radius.
  • When the elbow is flexed at 90 degrees, only the anterior and superior fat pads are visible.
  • Clinical Note: Elbow injuries may lead to effusions that can displace the fat pads or alter their shape, with visualization of the posterior fat pad indicating potential pathology on radiographs.

Elbow Rotational Movements

  • Supination:
    • The arm is in anatomical position (palm up).
    • Medial and lateral humeral epicondyles are visible in profile.
    • 1/8th of the radial head superimposes the ulna.
    • The radial tuberosity is in medial profile.
    • Radius and ulna are parallel.
  • Pronation:
    • The hand is positioned palm down.
    • 3/4th of the radial head is superimposed by the ulna.
    • The coronoid process, trochlear notch, and the medial aspect of the trochlea are clearly visible in profile.
    • Radius crosses over the ulna.

Humerus Anatomy

  • General Overview: The humerus is the largest and longest bone of the upper extremity. It consists of a shaft and two articular ends:
    • Proximal End: Articulates with the shoulder girdle.
    • Distal End: Articulates with the radius and ulna.
Proximal Humerus Features
  • Head: A large, smooth, rounded articular surface located in an oblique plane on the superomedial side.
  • Anatomic Neck: The constricted area just below the head.
  • Surgical Neck: Located immediately below the tuberosities, this region is a common site of fractures.
  • Lesser Tubercle: Positioned on the anterior aspect of the humerus just below the anatomical neck.
  • Greater Tubercle: Located on the lateral surface and responsible for the rounded appearance of the shoulder.
  • Intertubercular Groove (Bicipital Groove): A deep depression situated between the lesser and greater tubercles.
Humeral Shaft (Body)
  • The shaft is cylindrical in shape but becomes flattened and widened at its distal end.
Distal Humerus Anatomy
  • The entire distal end is known as the Humeral Condyle:
    • Trochlea: The medial aspect of the condyle, larger in size, articulating with the ulna at the trochlear notch.
    • Capitulum: The lateral aspect, which articulates with the head of the radius.
    • Epicondyles (Medial/Lateral): Palpable structures superior to the humeral condyles.
Distal Humerus Features
  • Coronoid Fossa: A shallow depression on the anterior surface, positioned superior to the trochlea; this fossa receives the coronoid process when the elbow is flexed.
  • Radial Fossa: A depression found on the anterior surface, lateral to the coronoid fossa, which accommodates the radial head when the elbow is flexed.
  • Olecranon Fossa: A deep posterior depression, accommodating the olecranon process when the elbow is extended.

Knowledge Check

  • Activities and discussion points that assess understanding of the elbow joint anatomy and functionalities.

Key Takeaways

  • The elbow consists of the humerus, radius, and ulna, which collectively permit flexion and extension motion of the upper extremity.
  • Three fat pads in the elbow can indicate radiographic pathologies and injuries.
  • During pronation, the radial shaft crosses over the ulna, with a greater portion of the radial head being obscured.
  • The humerus comprises important anatomical regions including the head, anatomical neck, surgical neck, tubercles, trochlea, capitulum, and epicondyles.

Questions?

  • Inquiry opportunities and engagement prompts for better exploration of elbow and humerus anatomy concepts.

References

  • Betts, J. G., Young, K. A., Wise, J. A., Johnson, E., Poe, B., Kruse, D. H., Korol, O., Johnson, J. E., Womble, M., & DeSaix, P. (2022). Anatomical Terminology - Anatomy and Physiology 2E. OpenStax.
  • Patton, K. T., Thibodeau, G. A., & Douglas, M. M. (2012). Essentials of Anatomy and Physiology - Text and Anatomy and Physiology Online Course. Mosby.
  • Rollins, J. H., & Curtis, T. (2025). Merrill’s Atlas of Radiographic Positioning and Procedures - Volume 1. Elsevier.