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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.