Elbow Anatomy

-- Elbow is a complex joint that allows for the flexion & extension of the arm
& pronation & supination of the forearm.

BONES
[Humerus]

-- Long bone of the upper arm.

-- Extending from the shoulder to the elbow.

-- Most important part is the distal part.

-- 2 Epicondyles: Medial & lateral epicondyles which are bony prominences

that serve as attachment points for muscles & ligaments.

-- Trochlea: Pully like structure on the medial side of the humerus that
articulates with the ulna forming the humeroulnar joint.

-- Capitulum: Rounded structure on the lateral side of the humerus that

articles with the radius forming the humeroradial joint.

-- Olecranon Fossa: Located on the posterior aspect of the distal humerus;

shallow depression that accommodates the olecranon process of the ulna.

-- Coronoid Fossa: Also known as the trochlear fossa is located on the

anterior aspect of the distal humerus above the trochlea it receives the
coronoid process of the ulna.

-- Radial Fossa: Located on the anterior aspect of the distal humerus above
the capitulum; shallow depression that accommodates the head of radius.

[Ulna]

-- Ulna  pinky which means the medial side.

-- Prominent bony tip (Olecranon process).

-- Long bone forming the medial bone of the forearm.

-- Most important part is the proximal end.

-- Olecranon Process: Prominent bony projection located at the proximal end

of the ulna; serves as the attachment point for the triceps brachii.

-- Coronoid Process: Located anteriorly & inferiorly to the trochlear notch;

triangular shaped.
-- Trochlear Notch: Deep semilunar shaped depression on the proximal end of
the ulna; articulates with trochlea of the humerus to form the humeroulnar
ligament.

-- Radial Notch: Small concave depression located at the lateral aspect of the
proximal ulna articulates with the head of the radius forming the proximal
radioulnar joint.

[Radius]

-- Radius  thumb which means the lateral side.

-- Smaller than the ulna plays a crucial role in allowing the forearm to rotate.

-- Most important part id the proximal end.

-- Head of radius: Disc shaped structure ; smooth & rounded & articulates
with humerus forming the humeroradial joint.

-- Radial tuberosity: Roughed bony prominence located in the medial aspect

of the radius; serves as the attachment site for the tendon of the biceps.

ARTICULAR SURFACE
--- Proximally  Trochlea & the capitulum of the humerus

--- Distally  Trochlear notch of ulna & head of radius

JOINTS
-- The elbow joint is comprised of three smaller joints enclosed within a single
joint capsule, enabling its movements.

[Humeroulnar joint]
-- Articulation occurs between the trochlea of the humerus & the trochlear
notch of the ulna.

-- Type: Hinge joint allowing movement in one plane

-- Planes & Axis: Sagittal plane & Frontal axis

-- Movement: Allows flexion & extension

[Humeradial joint]

-- Articulation occurs between the capitulum of the humerus & the head of
radius.

-- Type: Modified ball & socket joint because the range of motion is limited to
flexion & extension & pronation & supination only.

-- Planes & Axis:

(Flexion & Extension) Sagittal plane & Frontal axis

(Pronation & Supination) Transverse plane & Longitudinal axis

-- Movement: Allows flexion & extension + pronation & supination

[Proximal Radioulnar joint]

-- Articulation occurs between the head of radius & the radial notch of ulna.

-- Type: Pivot Joint which allows rotational movements

-- Planes & Axis: Transverse plane & Longitudinal axis

-- Movement: Allows pronation & supination

BURSAE
-- Small, fluid-filled sac that acts as a cushion between bones and other
moving parts in the body, such as muscles, tendons, or skin.

-- Bursae help reduce friction, allowing these parts to move smoothly over
each other.
-- They are lined with a synovial membrane that secretes a lubricating fluid
known as synovial fluid.

[Intratendinous Olecranon Bursa]

-- Located within the tendon of the triceps brachii.

[Subtendinous Olecranon Bursa]

-- Located between the olecranon and the tendon of the triceps brachii.

-- Reducing friction between two structures during flexion & extension.

[Subcutaneous Olecranon Bursa]

-- Located between the olecranon and the overlying connective tissue.

[Bicipitoradial Bursa]

-- Located between the biceps brachii and the radial tuberosity.

-- Reducing friction between the two structures during forearm rotation &
elbow flexion.

[Interosseous Bursa]

-- Located between the radius and the ulna.

-- Reduscing friction during forearm rotation.

FAT PAD
-- Soft tissue structures located within the joint capsule but outside the
synovial membrane of the elbow joint.

-- Anatomically positioned to act as cushions that facilitate smooth

movement and help distribute loads across the joint.

[Anterior Fat Pad]

-- Located in the anterior aspect of the elbow joint within the coranoid fossa
of the humerus.

[Posterior Fat Pad]

-- Located in the posterior aspect of the elbow joint within the olecranon
fossa of the humerus.

LIGAMENTS
-- Ligaments are tough, fibrous bands of connective tissue that connect
bones to other bones.

-- The joint capsule is strengthend by ligaments medially and laterally.

-- Provid stability to joints and preventing excessive movement.

[Medial Collateral Ligaments]

-- Also known as Ulnar Collateral Liagemnts.

-- Found in the inner side of the elbow.

-- Resist valgus stress (forces that try to push the elbow outwards)

-- Anterior Band: From the medial epicondyle of the humerus to the sublime
tubrecle of the ulna; Strongest primery stabilizer.

-- Posterior Band: From medial epiondyle of the humerus to the medial

aspect of the olecranon process; Forms the floor of the cubical tunnel
-- Transverse Band: From the proximal medial olecranon to the coroniod
process of the ulna; joins the anterior & posterior band.

[Lateral Collateral Ligaments]

-- Also known as the Radial Collateral Ligaments.

-- Found in the outer side of the elbow.

-- Resist varus stress (forces that try to push the elbow inwrads)

-- Lateral Ulnar Collateral Ligament: Thick triangular ligament; From the

lateral epicondyle of the humerus to the supinator crest of the proxiaml ulna;
Prevents posteolateral instabilty.

-- Lateral Radial Collateral Ligament: Strong fibrous band; From the lateral
epicondyle of the humerus blending with the annular ligament to the lateral
acspect of the radial neck; Primary stabilizer against varus stress.

-- Accessory Lateral Collateral Ligament: Thin band; Located anterior to the

radial collateral ligament; From the lateral epicondyle of the humerus to the
annular ligament.

[Extra Ligaments]
-- Annular ligament: Runs around the radial head attaching to the anterior
and posterior margins of the radial notch of the ulna; Strong fibrous band
forms a ring around the head of radius holding it in place against the ulna;
Allows rotation of the radial head.

-- Quadrate ligament: Strong square like shaped ligament located at the

proxiaml radioulnar joint; From the neck of radius to the ulna; Primary
function is to stabilize the head of radius within the radial notch of the ulna
during pronation & supination of the forearm.

-- Oblique Cord: Ligament that connects the antrolateral aspect of the ulna to
the posteromedial aspect of the radius inserting below the radial tubrosity.

-- Interossous Membrane: Srong fibrous sheet composed of dense connective

tissue arranged in crisscross pattern located between the radius and ulna
bones; primary function is to stabilize the radius and ulna bones and
maintain their proper alignment during forearm movements and helps in
distrbuting forces evenly between the bones and serves as attachemrnt
point for muscles.

NERVES
[Radial Nerve]

-- Origin: Arises from the posterior cord of the brachial plexus, which is
formed by nerve roots from the C5 to T1 spinal nerves.

-- Path: Travels posteriorly along the arm spiraling around the humerus in the
radial groove upon reaching the elbow the radial nerve continues its course
into the forearm; Dividing into superficial and deep branches.
-- Superficial branch: Also known as the superficial radial nerve or the radial
sensory nerve; Travels along the dorsal aspect of the forearm; Supplying
sensory innervation to the skin.

-- Deep branch: Also known as the posterior interosseous nerve (PIN); travels
along the interosseous membrane, providing motor innervation to the
muscles of the posterior compartment of the forearm.

[Ulnar Nerve]

-- Origin: Arises from the medial cord of the brachial plexus which is formed
by nerve roots from the C8 and T1 spinal nerves.

-- Path: Travels down the arm passing behind the medial epicondyle of the
humerus in the cubital tunnel (also known as the ulnar groove or cubital
sulcus) it continues distally giving off branches to muscles in the anterior and
posterior compartments of the forearm near the wrist it divides into
superfical and deep.

[Median Nerve]

-- Origin: Arises from the lateral and medial cords of the brachial plexus
which is formed by nerve roots of C5 to T1 spinal nerves.

-- Path: Descends down the arm passing through the cubital fossa anterior to
the brachial artery upon entering the forearm the median nerve travels
between the two heads of the pronator teres muscle it then continues into
the forearm giving off branches to various muscles.