Unit Three: Elbow & Forearm Complex


Definitions

  • Elbow

    • Joint separating arm from forearm

    • Distal Humerus

    • Proximal Ulna

  • Forearm

    • Bones between elbow and wrist joints

    • Radius

    • Ulna

Bones of the Elbow and Forearm

Humerus

  • Arm

    • Major bone of the upper arm

  • Landmarks:

    • Lateral & Medial Epicondyle

    • Lateral & Medial Supracondylar Ridge

    • Capitulum

    • Trochlea (true elbow)

    • Coronoid Fossa

    • Olecranon Fossa

    • Spiral Groove

Radius

  • Function

    • Lateral bone of forearm

  • Landmarks:

    • Head

    • Neck

    • Tuberosity

    • Styloid Process

Ulna

  • Function

    • Medial bone of forearm

  • Landmarks:

    • Olecranon

    • Coronoid Process

    • Trochlear Notch

    • Ulnar Tuberosity

    • Styloid Process

    • Head

Joints of the Elbow and Forearm

Articulations

  • Humero-ulnar Joint

    • Known as the "elbow"

    • Type: Synovial hinge

    • Motions: Flexion/extension

    • Characteristics:

    • Stable joint

    • Bone congruity

    • Ligament capsule

  • Humero-radial Joint

    • Type: Synovial hinge joint

    • Articulation: Capitulum of humerus articulates with head of the radius

    • Motions: Flexion/extension

    • Arthrokinematics: Spin of radial head as forearm pronates & supinates

  • Radial-ulnar Joint

    • Type: Synovial, pivot

    • Distal & Proximal Joints

    • Motions: Pronation & supination

  • Radial-ulnar Joint (Fibrous)

    • Type: Fibrous joint created by interosseous membrane along shaft

    • Motions: Supportive

Motions of the Elbow and Forearm

  • Elbow Motions:

    • Flexion

    • Extension

  • Forearm Motions:

    • Pronation

    • Supination

Concept Check

  • Planes & Axes?

Supination/Pronation

  • Mechanics: Radius moves around ulna

  • Action: Radial head spins on capitulum (in annular ligament)

  • Static Motion: Ulna does not move for this motion – try it!

Anterior View of Supination/Pronation

  • Key components include:

    • Olecranon

    • Trochlear Notch

    • Coronoid Process

    • Radial Tuberosity

    • Interosseous Membrane

    • Ulnar Tuberosity

Ligaments of the Elbow and Forearm

Ulnar Collateral Ligament

  • Also known as medial collateral

  • Attachments:

    • From medial epicondyle to coronoid process

  • Features:

    • Most stable/strong joint of elbow

    • Resists valgus stress

Radial Collateral Ligament

  • Also known as lateral collateral

  • Attachments:

    • From lateral epicondyle to radial head

  • Features:

    • Smaller, less stable

    • Helps resist varus stress

Annular Ligament

  • Function:

    • Wraps around head of radius from ulna

    • Helps radius maintain position during pronation/supination

    • Keeps radial head “spinning” on capitulum of humerus

Interosseous Membrane

  • Description:

    • Broad, flat, fibrous membrane located between radius and ulna

  • Function:

    • Keeps bones from separating

    • Provides surface area for attachment

Olecranon Bursa

  • Location:

    • Over olecranon process

  • Condition:

    • Olecranon bursitis, known as “student’s elbow”

    • Often occurs from excessive leaning, driving, or sitting

Landmarks of the Elbow and Forearm

Cubital Fossa

  • Description:

    • Shallow, triangular depression on anterior elbow

  • Borders:

    • Lateral: Brachioradialis

    • Medial: Pronator teres

    • Superior: Imaginary line between medial & lateral epicondyles

  • Floor:

    • Brachialis and supinator

  • Contents:

    • Biceps tendon

    • Brachial artery

    • Median nerve

Other Landmarks

  • Olecranon Process

  • Head of Radius

  • Radial Styloid

  • Ulnar Styloid

Compartments of the Elbow and Forearm

Volar Compartment (Flexors)

  • Innervation:

    • Median and ulnar nerve innervates superficial flexors

    • Median nerve innervates deep flexors

Dorsal Compartment (Extensors)

  • Innervation:

    • Radial nerve innervates extensors

    • Mobile wad of 3: (flexors often)

    • Radial nerve

Posture

  • Carrying Angle

    • Angle of elbow in anatomical position

  • Abnormal Postures:

    • Cubital Valgum - carrying angle above 5-15 degrees

    • Cubital Varum - Known as “gunstock deformity”

Muscles of the Elbow and Forearm

Muscles of Elbow Flexion

  • Brachialis

    • Origin: Distal half of anterior humerus

    • Insertion: Coronoid process & ulnar tuberosity

    • Strong flexor, known as “workhorse of the elbow”

    • Not involved in supination/pronation because it doesn’t attach to the radius

  • Biceps Brachii

    • Two heads: Long head from supraglenoid and short head from coracoid to radial tuberosity

    • Innervation: Musculocutaneous nerve

  • Brachioradialis

    • Origin: Lateral supracondylar ridge of humerus

    • Insertion: Styloid process of radius

    • Does not assist in pronation/supination due to anatomical position

    • Innervation: Radial nerve

  • Pronator Teres

    • Assists flexion (small, diagonal muscle)

Muscles of Elbow Extension

  • Triceps Brachii

    • Heads: Long head from infraglenoid tubercle, lateral and medial heads from posterior humerus

    • Insertion on olecranon process

  • Anconeus

    • Origin: Lateral epicondyle of humerus

    • Insertion: Lateral & inferior of olecranon process

    • Small muscle that rolls with annular ligament

    • Innervation: Radial nerve

Muscles of Forearm Supination

  • Supinator

    • Origin: Posterior lateral epicondyle

    • Insertion: Anterior proximal radius (deep)

    • Innervation: Radial nerve

  • Biceps Brachii

    • Also contributes to supination

    • Innervation: Musculocutaneous nerve

Muscles of Forearm Pronation

  • Pronator Teres

    • Origin: Medial epicondyle of humerus

    • Insertion: Lateral radius

  • Pronator Quadratus

    • Origin: Distal quarter of ulna

    • Insertion: Distal quarter of radius

    • Assists in pronation (small muscle)

    • Innervation: Median nerve

Pathologies of the Elbow and Forearm

Common Pathologies

  • Lateral Epicondylitis

    • Known as “tennis elbow”

  • Medial Epicondylitis

    • Known as “golfer’s elbow”

  • Little League Elbow

  • Epicondylitis

  • Bone Chips

  • UCL Stretching

  • Growth Plate Injuries

  • Early Onset Arthritis

Innervation of the Elbow and Forearm

Overview of Brachial Plexus

  • Nerve Formation:

    • Nerves from cervical spinal cord merge, blend, and then split into major nerves that innervate upper extremity (UE)

  • Spinal Nerves Involved:

    • C5, C6, C7, C8, T1

Innervation of Anterior Arm

  • Musculocutaneous Nerve

    • Innervates: Brachialis, Biceps Brachii, Coracobrachialis

Innervation of Posterior Arm & Forearm

  • Radial Nerve

    • Innervates: Triceps Brachii, Anconeus, Brachioradialis, Supinator

Innervation of Anterior Forearm

  • Median Nerve

    • Innervates: Pronator Teres, Flexor Carpi Radialis, Palmaris Longus, Flexor Digitorum Superficialis, Flexor Digitorum Profundus, Flexor Pollicis Longus, Pronator Quadratus, Abductor Pollicis Brevis, Opponens Pollicis, Flexor Pollicis Brevis (superficial head), and 1st and 2nd lumbricals

Lab Components

  • Focus:

    • Identification and palpation of bones & landmarks

    • Review of muscles (Origin, Insertion, Action)

Questions?

  • SALTO

Additional References

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