Elbow Anatomy and Kinesiology

Rajat Mathur M.D.October 2013

PGY2

Elbow Overview● Hinge joint made up of

humerus, ulna and the radius bones

● Function: properly place hand in space by shortening and lengthening the upper limb

● Most upper extremity movements involve the elbow and radioulnar joints

Bones● Ulna is much larger

proximally than radius● Radius is much larger

distally than ulna● Scapula and humerus

serve as proximal attachments for muscles that flex and extend the elbow.

● Ulna and radius serve as distal attachments for these same muscles

Bones● Scapula, humerus, and ulna

serve as proximal attachments for muscles that pronate and supinate the radioulnar joints.

● Distal attachments of the radioulnar joint muscles are located on radius

● Bony Landmarks○ Lateral and medial

epicondyle○ Olecranon process○ Radial head

Joints● 3 joints enveloped by common capsule

Joint From To Description

Humeroulnar joint

trochlear notch of the ulna

trochlea of humerus

- simple hinge joint- allows movement of flexion & extension only

Humeroradial joint

head of the radius

capitulum of the humerus

- synovial ball and socket hinge type joint- allows flexion, extension, pronation and supination

Proximal radioulnar joint

head of the radius

radial notch of the ulna

- tochoid (pivot) joint- flexion or extension- pronation and supination

Ligaments● Ulnar collateral ligament

○ medial side of the elbow○ extends from medial

epicondyle of humerus to proximal portion of ulna

○ function is to prevent excessive abduction of elbow joint

● Radial collateral ligament○ lateral side of the elbow○ extends from lateral epicondyle

of humerus to head of radius○ function is to prevent excessive

adduction of elbow joint

Ligaments● Ulnar collateral ligament

is critical in providing medial support to prevent the elbow from abducting when stressed in physical activity.○ Many contact sports and

throwing activities place stress on the medial aspect of the joint, resulting in injury.

Ligaments● Radial collateral

ligament provides lateral stability and is rarely injured

● Annular ligament provides stability for radial head during pronation and supination○ commonly injured in children

when arm pulled forcefully

Interosseous MembraneThe joint between shafts of radius & ulna held tightly together between proximal and distal articulations by an interosseous membrane

Kinesiology of the elbow● The elbow moves from

0 degrees of extension to 145-150 degrees of flexion.

Elbow motions● Primarily involve movement

between articular surfaces of humerus and ulna

● The humeral trochlea fits into the ulna trochlea notch

● Radial head has a relatively small amount of contact with humerus

● As the elbow reaches full extension, the olecranon process fits into the olecranon fossa○ allows increased joint

stability when fully extended

Elbow motions● As the elbow flexes 20

degrees or more, its bony stability is unlocked, allowing for more side to side laxity.

● Stability in flexion is more dependent on the lateral (radial collateral ligament) and the medial (ulnar collateral ligament).

Movements● Flexion

○ movement of forearm to shoulder by bending the elbow to decrease its angle

● Extension○ movement of

forearm away from shoulder by straightening the elbow to increase its angle

Movements● Pronation

○ internal rotary movement of radius on ulna that results in hand moving from palm-up to palm-down position

● Supination○ external rotary

movement of radius on ulna that results in hand moving from palm-down to palm-up position

Pronation/Supination● Radioulnar joint

○ trochoid or pivot joint○ radial head rotates

around proximal ulna○ distal radius rotates

around distal ulna○ annular ligament

maintains radial head in its joint

○ Supinate: 80-90 degrees from neutral

○ Pronate 70-90 degrees from neutral

Nerves● All elbow and radioulnar joints muscles are

innervated from median, musculocutaneous, and radial nerves of brachial plexus

Radial Nerve● Radial nerve:

originates from C5, C6, C7, & C8○ Triceps brachii○ Brachioradialis○ Supinator (posterior

interosseous nerve)○ Anconeus○ Sensation to

posterolateral arm, forearm, & hand

Median Nerve● Median nerve -

originates from C6 & C7○ Pronator teres○ Pronator

quadratus (anterior interosseus nerve)

○ Sensation to palmar aspect of hand & first three phalanges, palmar aspect of radial side of fourth finger, dorsal aspect of index & long fingers

Musculocutaneous Nerve● Musculocutaneous

nerve - Originates from C5 & C6○ Biceps brachii○ Brachialis

Muscles overview● Elbow flexors

○ Biceps brachii○ Brachialis○ Brachioradialis○ Weak assistance from

pronator teres● Elbow Extensor

○ Triceps brachii○ Anconeus provides

assistance

● Radioulnar pronators○ Pronator teres○ Pronator quadratus○ Brachioradialis

● Radioulnar supinators○ Biceps brachii○ Supinator muscle○ Brachioradialis

Muscles● Anteriorly

○ Primarily flexion and pronation■ Biceps brachii■ Brachialis■ Brachioradialis■ Pronator teres■ Pronator

quadratus

Muscles● Posterior

○ Primarily extension & supination■ Triceps brachii■ Anconeus■ Supinator

Biceps Brachii ● Flexion of elbow● Supination of

forearm● Weak flexion of

shoulder joint ● Weak abduction of

shoulder joint when externally rotated

Brachialis● True flexion of the

elbow

Brachioradialis Muscle● Flexion of elbow● Pronation from

supinated position to neutral

● Supination from pronated position to neutral

Triceps Brachii● All heads: extension

of elbow● Long head:

extension of shoulder joint; adduction of shoulder joint, horizontal abduction

Anconeus● Small contribution

towards extension of elbow

Pronator Teres ● Pronation of

forearm● Weak flexion of

elbow

Pronator Quadratus● Pronation of

forearm

Supinator● Supination of

forearm

MRI Anatomy of the Elbowhttp://gme.bridgeporthospital.com/portals/7/cchip_client/anatomywiz/awiz.aspx?TID=1

Thank you

http://www.youtube.com/watch?v=3l3-5Ij3JZ8