Bio Mechanics Of The Elbow

The Elbow Complex

Osteology • Consist of – Humerus – Ulna – Radius

Anterior aspect

Osteology

Posterior aspect

Bony Anatomy: Humerus

Osteology

Radius

Ulna

Joints of Elbow • Humeroulnar joint • Humeroradial joint • Radioulnar joint – Proximal radioulnar joint – Distal radioulnar joint

Joints of Elbow • Humeroradial joint – gliding joint in which the capitellum of the humerus articulates with the proximal end of the radius

Joints of Elbow • Humeroulnar joint – hinge joint in which the humeral trochlea articulates with the trochlear fossa of the ulna

Joints of Elbow • Radioulnar joint – the proximal and distal radioulnar joints are pivot joints

Ligaments of the Elbow

Lateral Ligamentous Structures • Lateral/radial collateral ligament – origin is near axis of elbow flexion/extension, so fibers uniformly tight throughout ROM

• Annular ligament – inserts on anterior/posterior margins of lesser (radial) semilunar notch, maintains radial head in contact with ulna (forms 4/5 of fibroosseous ring)

Ligaments of the Elbow

Medial Ligamentous Structures • Medial/Ulnar Collateral Ligament – Anterior bundle – most discrete segment – Posterior bundle – thickening of posterior capsule – Transverse bundle – spans medial border of semilunar notch, little/no contribution to elbow stability

Vascular

Vascular

Nervous Innervation

Median nerve Ulnar nerve Radial nerve

Median Nerve

Ulnar Nerve

Range of Motion • Flexion/extension – ginglymus joint (ulnohumeral articulation) • Flexion typically 0-150 degrees, stops due to soft tissue approximation • Extension typically 0-10 degrees (hyperextension, especially in females), stops due to bony opposition

Range of Motion • Forearm pronation and supination – trochoid joint (radiohumeral and proximal radioulnar articulations) • Pronation/supination typical 0-85/90 degrees each from neutral point (thumb up), stops due to tissue tensions/stretch from opposing tissue

Movements of the Elbow

Movements of the Elbow • Flexion – Brachialis – Biceps Brachii – Brachioradialis

Brachialis Biceps brachii Brachioradialis

Movements of the Elbow • Extension – Triceps Brachii – Assisted By: • Anconeus

Anconeus Triceps brachii

Movements of the Elbow • Pronation – Pronator teres – Pronator quadratus

Pronator teres

Pronator quadratus

Movements of the Elbow • Pronation – Flexor group • Pronator teres • Flexor carpi radialis • Flexor digitorum superficialis • Flexor digitorum profundus • Palmaris longus • Flexor carpi ulnaris

Flexor Digitorum Superficialis

Flexor Carpi Radialis

Flexor Carpi Ulnaris

Palmaris Longus

Flexor Digitorum Profundus

Movements of the Elbow • Supination – Supinator – Biceps brachii

Biceps brachii Supinator

Movements of the Elbow • Supination – Extensor group • Supinator • Extensor carpi radialis longus • Extensor carpi radialis brevis • Extensor carpi ulnaris • Extensor digitorum

Extensor Carpi Radialis Longus

Extensor Carpi Ulnaris

Extensor Carpi Radialis Brevis

Extensor Digitorum

Supination and Pronation

Elbow Kinematics • One of the most congruous and stable joints • In extension, anterior capsule provides most restraint, while MCL becomes primary stabilizer at 90 degrees flexion • Annular ligament encircles the head of the radius, stabilizing it in the radial notch

Elbow Kinematics • Varus stress – In extension resisted by bone structure, LCL and lateral joint capsule – In flexion, resisted primarily by bone structure

• Valgus stress – In flexion, resisted primarily by MCL – In extension equally resisted by bone structure, MCL and medial joint capsule

Load on the Elbow

Load on the Elbow

Load on the Elbow

Biomechanics of Elbow Flexors • Dominant side produces higher flexion torque, work, and power • Flexion torques are 70% higher than extension • Flexion torques are 20-25% higher in supinated versus pronated positions due to increased flexor moment arm of biceps and brachioradialis • Max torque at 90°

Biomechanics of Elbow Extensors • Generate large and dynamic extensor torques through high-velocity concentric and eccentric activities (throw, push) • Shoulder flexion with pushing activity, counteracts the tendency of elbow extensors to extend the shoulder