student_kn 261_elbow(2) copy

Applied Musculoskeletal Anatomy

KN 261

Unit 3: Upper Extremity

  • Focus of Discussion: Elbow & Radioulnar Joints

  • Text Reference: Chapter 6

Learning Objectives

  • By the End of Discussion 2, You Will Be Able To:

    • Understand the following aspects of the radioulnar and elbow joints:

      • Bones & bony landmarks

      • Ligaments

      • Muscles

      • Identify the agonists during various exercises

Elbow & Radioulnar Joints

Bones & Bony Landmarks

  1. Key Bones: Humerus, Radius, Ulna

  • Ulna: Much larger proximally compared to radius

  • Radius: Much larger distally than ulna

Distal Humerus

  • Articulates with Radius

  • Important Landmarks:

    • Lateral supracondylar ridge

    • Radial fossa

    • Lateral epicondyle

    • Capitellum

    • Medial supracondylar ridge

    • Coronoid fossa

    • Medial epicondyle

    • Trochlea

    • Neck of radius

    • Radial tuberosity

    • Ulnar tuberosity

Joints

  • Joint Capsule:

    • Surrounds all three articulations of the elbow, consistent with synovial joints

  • Elbow Joints:

    1. Humeroulnar Joint

    2. Radioulnar Joints

    • Proximal

    • Distal

Humeroulnar Joint

  • Type: Hinge Joint

  • Spool-like trochlea of humerus articulates with the semilunar notch of ulna

Ligaments of Humeroulnar Joint

  • Ulnar Collateral Ligament (UCL or MCL):

    • Resists valgus forces

  • Radial Collateral Ligament (RCL or LCL):

    • Provides lateral stability

Proximal and Distal Radioulnar Joints

  • Proximal Radioulnar Joint:

    • Type: Pivot joint

    • Articulating Surfaces: Radial notch of ulna, capitulum of humerus, head of radius

    • Annular Ligament: Holds radius to ulna allowing for rotation during forearm pronation and supination

  • Distal Radioulnar Joint:

    • Type: Pivot joint

    • Articulating Surfaces: Ulnar notch of radius, articular disk, head of ulna

    • Ligaments: Anterior & posterior radioulnar

Movement Characteristics

  • Humeroulnar Joint:

    • Range of Motion: 0° of extension to 145-150° of flexion

    • Movements occur in the sagittal plane around a lateral axis

  • Radioulnar Joint:

    • Supination: 80-90° from neutral

    • Pronation: 70-90° from neutral

    • Movements occur in the transverse plane around a vertical axis

Muscles (AOII)

Elbow & Radioulnar Joint Muscles

  • Anterior (Primarily Flexors &/or Pronators):

    • Biceps Brachii (long & short heads)

    • Brachialis

    • Brachioradialis

    • Pronator Teres

    • Pronator Quadratus

  • Posterior (Primarily Extensors &/or Supinators):

    • Triceps Brachii (long, lateral, medial heads)

    • Supinator

    • Anconeus

Biceps Brachii

Long Head:

  • Origin: Supraglenoid tubercle above the superior lip of the glenoid fossa

  • Insertion: Tuberosity of radius & bicipital aponeurosis

  • Innervation: Musculocutaneous nerve (C5, C6)

Short Head:

  • Origin: Coracoid process & upper lip of glenoid fossa

  • Insertion: Tuberosity of radius & bicipital aponeurosis

  • Innervation: Musculocutaneous nerve (C5, C6)

Biceps Brachii Functions

  • Isolated Functions:

    • Supination, elbow flexion, weak glenohumeral flexion & abduction

  • Integrated Functions:

    • Eccentrically decelerates elbow extension, radioulnar pronation, shoulder extension & adduction

    • Stabilizes elbow & shoulder girdle isometrically

Brachialis

  • Origin: Distal half of anterior humerus

  • Insertion: Coronoid process of ulna

  • Innervation: Musculocutaneous nerve (C5, C6)

  • Isolated Function: Elbow flexion, effective when flexing while pronated

  • Integrated Function:

    • Eccentrically decelerates elbow extension

    • Isometrically stabilizes elbow

Brachioradialis

  • Origin: Distal two-thirds of lateral condyloid ridge of humerus

  • Insertion: Lateral surface of distal end of radius at the styloid process

  • Innervation: Radial nerve (C5, C6)

  • Isolated Function: Elbow flexion in neutral position

  • Integrated Function:

    • Eccentrically decelerates elbow extension

    • Isometrically stabilizes elbow

Pronator Teres

  • Origin: Distal medial condyloid ridge of humerus & medial side of proximal ulna

  • Insertion: Middle one-third of lateral surface of radius

  • Innervation: Median nerve (C6, C7)

  • Isolated Function: Pronation, weak elbow flexion

  • Integrated Function:

    • Eccentrically decelerates forearm supination

    • Isometrically stabilizes proximal radioulnar joint & elbow

Pronator Quadratus

  • Origin: Distal quarter of anterior ulna

  • Insertion: Distal quarter of anterior radius

  • Innervation: Median nerve (C6, C7)

  • Isolated Function: Pronation

  • Integrated Function:

    • Eccentrically decelerates forearm supination

    • Isometrically stabilizes radioulnar joint

Triceps Brachii

Long Head

  • Origin: Infraglenoid tubercle below inferior lip of glenoid fossa

  • Insertion: Olecranon of ulna

  • Innervation: Radial nerve (C7, C8)

  • Isolated Functions: Elbow extension, glenohumeral extension & adduction

Medial Head

  • Origin: Distal two-thirds of posterior humerus

  • Insertion: Olecranon of ulna

  • Innervation: Radial nerve (C7, C8)

  • Isolated Functions: Elbow extension

Lateral Head

  • Origin: Upper half of posterior humerus

  • Insertion: Olecranon of ulna

  • Innervation: Radial nerve (C7, C8)

  • Isolated Functions: Elbow extension

Triceps Brachii Integrated Function

  • Eccentrically decelerates shoulder flexion (long head), elbow flexion

  • Isometrically stabilizes shoulder girdle (long head) & elbow

Supinator

  • Origin: Lateral epicondyle of humerus & posterior part of ulna

  • Insertion: Lateral surface of proximal radius just below the head

  • Innervation: Radial nerve (C6)

  • Isolated Function: Supination

  • Integrated Function:

    • Eccentrically decelerates forearm pronation

    • Isometrically stabilizes radioulnar joint & elbow

Anconeus

  • Origin: Posterior surface of lateral condyle of humerus

  • Insertion: Posterior surface of lateral olecranon & proximal quarter of ulna

  • Innervation: Radial nerve (C7, C8)

  • Isolated Function: Elbow extension

  • Integrated Function:

    • Eccentrically decelerates elbow flexion

    • Isometrically stabilizes elbow

Educational Approach

  • Emphasis on fostering curiosity, problem-solving, self-direction, and metacognition

Case Studies and Exercises

  • Engagement in practical examples to identify agonists and apply knowledge

  • Exercises and activities highlighting discussions of muscle actions and rehabilitative approaches

Review and Application

  • Questions related to the unit and discussions on muscle functions and roles in rehabilitation

Quotes and Reflections

  • "Education is the kindling of a flame, not the filling of a vessel." - Socrates

  • Encouragement for students to reflect on their learning processes.