Kinesiology The Elbow Joint

Introduction

The elbow joint is a hinge-type synovial joint that connects the upper arm to the forearm. It plays a crucial role in daily activities, allowing movements like bending, extending, and rotating the forearm. The elbow is designed for both strength and precision, providing stability while enabling dynamic arm movements.

Bones of the Elbow Joint

The elbow is formed by the articulation of three bones:

Humerus (Upper Arm Bone)

  • The distal end of the humerus features two major articular surfaces:
    • Trochlea: Articulates with the ulna.
    • Capitulum: Articulates with the radius.
  • The medial and lateral epicondyles serve as attachment points for muscles and ligaments.

Ulna (Inner Forearm Bone)

  • The olecranon (bony prominence at the back of the elbow) fits into the olecranon fossa of the humerus, allowing elbow extension.
  • The trochlear notch articulates with the trochlea of the humerus.

Radius (Outer Forearm Bone)

  • The head of the radius articulates with the capitulum of the humerus, allowing rotation of the forearm.
  • The radial tuberosity serves as an attachment point for the biceps brachii.

Articulations of the Elbow

The elbow consists of three joints enclosed within a single joint capsule:

Humeroulnar Joint

  • Type: Hinge joint.
  • Function: Allows flexion and extension.

Humeroradial Joint

  • Type: Modified hinge joint.
  • Function: Facilitates forearm flexion and extension, and contributes to rotation during pronation and supination.

Proximal Radioulnar Joint

  • Type: Pivot joint.
  • Function: Allows pronation and supination of the forearm.

Ligaments of the Elbow Joint

Ligaments provide stability to the elbow, preventing excessive movements that could lead to injury.

Ulnar Collateral Ligament (Medial Collateral Ligament)

  • Located on the inner side of the elbow.
  • Prevents excessive lateral movement (valgus stress).

Radial Collateral Ligament (Lateral Collateral Ligament)

  • Located on the outer side of the elbow.
  • Prevents excessive medial movement (varus stress).

Annular Ligament

  • Encircles the head of the radius.
  • Stabilizes the proximal radioulnar joint and allows rotation of the forearm.

Joints of the Forearm

The forearm contains additional joints that facilitate rotation and movement.

Proximal Radioulnar Joint

  • Located near the elbow.
  • Allows rotation of the radius around the ulna.

Distal Radioulnar Joint

  • Located near the wrist.
  • Works with the proximal radioulnar joint to allow supination and pronation.

Anatomical Axis of the Elbow

The elbow joint follows a biomechanical axis that influences movement patterns:

  • The flexion-extension axis runs through the trochlea and capitulum.
  • The pronation-supination axis runs through the radial and ulnar articulations.

Movements of the Elbow Joint

The elbow is primarily responsible for two major types of movement: flexion-extension and pronation-supination.

Flexion

  • Bending the elbow to decrease the angle between the humerus and forearm.
  • Example: Bringing the hand toward the shoulder.
  • Primary muscles involved: Biceps brachii, brachialis, brachioradialis.

Extension

  • Straightening the elbow to increase the angle between the humerus and forearm.
  • Example: Pushing an object away.
  • Primary muscles involved: Triceps brachii, anconeus.

Pronation

  • Rotating the forearm so the palm faces downward.
  • Example: Turning a doorknob counterclockwise.
  • Primary muscles involved: Pronator teres, pronator quadratus.

Supination

  • Rotating the forearm so the palm faces upward.
  • Example: Holding a bowl of soup.
  • Primary muscles involved: Biceps brachii, supinator.

Muscles Involved in Elbow Movement

Various muscles control the elbow’s movements, contributing to both stability and force generation.

Flexor Muscles

  • Biceps Brachii: Main flexor, also assists in supination.
  • Brachialis: Primary elbow flexor, strongest in neutral grip.
  • Brachioradialis: Assists in flexion, particularly in a semi-pronated position.

Extensor Muscles

  • Triceps Brachii: Primary elbow extensor.
  • Anconeus: Assists the triceps in extension.

Pronator Muscles

  • Pronator Teres: Helps rotate the forearm downward.
  • Pronator Quadratus: Stabilizes the distal radioulnar joint during pronation.

Supinator Muscles

  • Biceps Brachii: Strongest supinator when the elbow is flexed.
  • Supinator: Assists in rotating the forearm upward.

Conclusion

The elbow joint is a highly functional structure that allows for critical upper limb movements. Its combination of hinge and pivot mechanisms enables both stability and flexibility. Understanding the anatomy and biomechanics of the elbow is essential for optimizing performance, preventing injuries, and enhancing rehabilitation strategies.

Previous Lesson
Back to Course
Next Lesson