Study Notes for Chapter 6: Elbow and Radial Ulnar Joint

Chapter 6: Elbow and Radial Ulnar Joint

Overview of Elbow Joint

  • Functionality: The elbow is primarily involved in flexion and extension.

  • Bone Involvement: The main bones involved are:

    • Humerus (distal end)

    • Ulna

    • Radius (less involved in the true elbow biomechanics)

Key Movements

  • Primary Movements: Flexion and extension only; no rotation occurs at the elbow joint.

Anatomy of the Elbow

  • Bones: Interaction mainly between the humerus and ulna.

  • Important Landmarks:

    • Medial Epicondyle: Easily palpable on the inner elbow; important for wrist flexors.

    • Lateral Epicondyle: Palpable on the outer elbow; important for wrist extensors.

    • Olecranon Process: Located at the top of the ulna.

    • Olecranon Fossa: Concave surface on the humerus; it accommodates the olecranon process during extension.

    • Coronoid Process: The anterior projection on ulna, fits into the coronoid fossa of the humerus during flexion.

    • Trochlea: The part of the humerus that articulates with the trochlear notch of the ulna.

Elbow Flexion and Extension

  • Hard Endpoints vs. Soft Endpoints:

    • Hard Endpoints: Bone-to-bone contact (e.g., olecranon fitting into olecranon fossa during full extension, 180°).

    • Soft Endpoints: Muscle-to-muscle/lifting tension (e.g. when flexing the elbow). Active flexion can go to approximately 145°, while passive flexion might reach 160°.

  • "Double Jointed" Concept: Refers to hypermobility where the elbow extends beyond 180°.

Musculature of the Elbow Joint

Flexors of the Elbow

  1. Biceps Brachii

    • Heads: Two heads—long head (originates from supraglenoid tubercle) and short head (originates from coracoid process).

    • Insertion: Radial tuberosity.

    • Functionality: Primarily elbow flexion; also assists in supination.

    • Active Insufficiency: The muscle cannot exert maximum force across multiple joints.

  2. Brachialis

    • Characteristics: Considered the prime mover for elbow flexion, originates from the distal half of the anterior humerus.

    • Insertion: Coronoid process of ulna. This muscle only crosses the elbow joint and can exert maximum force for that action.

  3. Brachioradialis

    • Location: Runs from the distal two-thirds of the lateral condylar ridge of the humerus to the styloid process of the radius.

    • Functionality: Flexes the elbow and assists in both pronation and supination.

    • Palpable: Easy to feel during flexion.

Extensors of the Elbow

  1. Triceps Brachii

    • Heads: Three heads (long, lateral, and medial).

    • Insertion: Olecranon process.

    • Functionality: Predominately responsible for elbow extension.

  2. Anconius

    • Characteristics: A small muscle that assists in elbow extension. Originates from the posterior surface of the lateral condyle of the humerus.

Radial Ulnar Joint

  • Joints Involved: Includes the proximal and distal radioulnar joints.

  • Functionality: Pronation and supination movements.

Key Muscles at the Radial Ulnar Joint

  1. Pronator Teres

    • Origin: Medial condyle of the humerus and medial aspect of the ulna.

    • Insertion: Middle third of the radius.

    • Functionality: Medially rotates (pronation).

  2. Pronator Quadratus

    • Origin/Insertion: Originates from the distal ulna, inserting on the distal radius, facilitating pronation.

  3. Supinator

    • Origin: Lateral epicondyle of the humerus. Inserts below the radial head and ulna.

    • Functionality: Responsible for supination.

Joint Stability

  • Types of Joints:

    • Elbow as a hinge joint (flexion and extension).

    • Radial ulnar as a pivot joint (pronation/supination).

  • Stabilizing Ligaments:

    • Radial Collateral Ligament (RCL) - on the lateral aspect.

    • Ulnar Collateral Ligament (UCL) - on the medial aspect; can have injuries requiring Tommy John surgery.

    • Annular Ligament - holds radius against the ulna.

    • Interosseous Membrane - holds both bones together, providing stability.

Carrying Angle and Cubitus Position

  • Carrying Angle: Typical angle of deviation at the elbow, 10°-25° laterally, influenced by anatomy of the humerus and ulna.\

    • The angle helps with functional carrying of objects without interference.

  • Cubitus Valgus: Angle greater than normal indicating lateral deviation.

  • Cubitus Varus: Angle lesser than normal; less common.

Summary of Movements and Roles

  • Flexion: Primary flexors include biceps brachii, brachialis, and brachioradialis.

  • Extension: Triceps brachii and anconius.

  • Pronation: Pronator teres, pronator quadratus, and brachioradialis.

  • Supination: Biceps brachii, supinator, and brachioradialis (having dual roles).

Closing Remarks

  • Focus on maintaining proper joint angles to ensure effective function during activities, as well as addressing any anatomical variances in patient evaluations and treatment plans.

  • Emphasized importance of both flexor and extensor muscle functions in daily arm movements, particularly in occupational therapy and rehabilitation contexts.