Elbow Anatomy: Distal Humerus, Bony Landmarks, and Related Conditions

What is the Upper Part of Your Elbow Called?

The "upper part" of your elbow primarily refers to the distal (lower) end of the humerus, the long bone of your upper arm, which forms the superior component of the elbow joint and features several distinct bony landmarks crucial for its function.

Anatomy of the Elbow Joint

The elbow is a complex hinge joint that permits flexion and extension, as well as pronation and supination of the forearm. It is formed by the articulation of three bones:

• Humerus: The single bone of the upper arm. Its distal end contributes to the "upper part" of the elbow.
• Ulna: The longer of the two forearm bones, located on the medial side (pinky finger side).
• Radius: The shorter of the two forearm bones, located on the lateral side (thumb side).

These bones articulate at three distinct joints within the elbow capsule:

• Humeroulnar joint: Between the trochlea of the humerus and the trochlear notch of the ulna. This is the primary hinge joint for flexion and extension.
• Humeroradial joint: Between the capitulum of the humerus and the head of the radius. This joint also contributes to flexion/extension and allows for rotation of the radius during pronation/supination.
• Proximal Radioulnar joint: Between the head of the radius and the radial notch of the ulna. This joint is essential for forearm rotation (pronation and supination).

Key Bony Landmarks of the Distal Humerus

When discussing the "upper part" of the elbow, the focus is typically on the anatomical features of the distal humerus. These landmarks serve as attachment sites for muscles and ligaments, and articulate with the forearm bones:

• Medial Epicondyle: This prominent, bony protrusion is located on the inner (medial) side of the distal humerus. It is a common attachment site for the forearm flexor muscles (e.g., pronator teres, flexor carpi radialis) and the ulnar collateral ligament. It's often referred to as the "funny bone" due to the superficial ulnar nerve passing behind it.
• Lateral Epicondyle: Located on the outer (lateral) side of the distal humerus, this less prominent projection serves as an attachment point for the forearm extensor muscles (e.g., extensor carpi radialis brevis, supinator) and the radial collateral ligament.
• Trochlea: A spool-shaped articular surface located medially on the distal humerus. It articulates with the trochlear notch of the ulna, forming the humeroulnar joint.
• Capitulum: A rounded, knob-like articular surface located laterally to the trochlea on the distal humerus. It articulates with the concave head of the radius, forming the humeroradial joint.
• Olecranon Fossa: A large, deep depression on the posterior surface of the distal humerus, superior to the trochlea. During full elbow extension, the olecranon process of the ulna fits into this fossa, preventing hyperextension.
• Coronoid Fossa: A smaller depression on the anterior surface of the distal humerus, superior to the trochlea. It accommodates the coronoid process of the ulna during elbow flexion.
• Radial Fossa: A shallow depression on the anterior surface of the distal humerus, superior to the capitulum. It accommodates the head of the radius during elbow flexion.

Beyond Bone: Soft Tissues of the Elbow

While the bones form the structural basis of the "upper part" of the elbow, it's crucial to acknowledge the vital role of the surrounding soft tissues:

• Ligaments: Provide stability to the joint, including the ulnar collateral ligament (medial), radial collateral ligament (lateral), and annular ligament (surrounding the radial head).
• Muscles: Numerous muscles cross the elbow joint, originating from the distal humerus and inserting onto the forearm or hand, facilitating movement (e.g., biceps brachii, triceps brachii, forearm flexors and extensors).
• Nerves: Major nerves (ulnar, median, radial) pass through or around the elbow, supplying sensation and motor control to the forearm and hand.
• Bursae: Fluid-filled sacs (e.g., olecranon bursa) reduce friction between bones, tendons, and skin.

Clinical Significance and Common Issues

Understanding the anatomy of the "upper part" of the elbow is vital for diagnosing and treating common conditions:

• Epicondylitis: Inflammation or degeneration of the tendons attaching to the epicondyles.
  • Medial Epicondylitis (Golfer's Elbow): Affects the flexor-pronator muscles originating from the medial epicondyle, often due to repetitive wrist flexion and pronation.
  • Lateral Epicondylitis (Tennis Elbow): Affects the extensor-supinator muscles originating from the lateral epicondyle, typically due to repetitive wrist extension and supination.
• Fractures: Fractures of the distal humerus, particularly supracondylar fractures, are common, especially in children, and can affect the stability and function of the elbow.
• Ulnar Nerve Entrapment (Cubital Tunnel Syndrome): The ulnar nerve can become compressed as it passes behind the medial epicondyle, leading to numbness, tingling, or weakness in the hand.

Conclusion

The "upper part" of your elbow is precisely defined by the distal end of your humerus, featuring critical bony landmarks like the medial and lateral epicondyles, trochlea, and capitulum, along with associated fossae. These structures are not merely anatomical points but are integral to the elbow's complex mechanics, serving as crucial sites for muscle and ligament attachment, and facilitating the wide range of movements essential for daily function and athletic performance. A comprehensive understanding of this region is fundamental for anyone involved in exercise science, kinesiology, or health.