The Elbow & Radioulnar Joints

• Describe the humeroulnar and humeroradial joints including joint structure, and factors influencing stability.

• Describe the ligaments supporting the humeroulnar, humeroradial and radioulnar joints.

• Describe the carrying angle and how it is formed.

• Describe the movements of the humeroulnar, humeroradial and radioulnar joints including the muscles involved in these movements.

• Describe the cubital fossa and the structures that are located within this fossa Source: www.fysioweb.nl/.../ elleboog/page_01.htm

Distal Humerus• Trochlea

– Resembles rounded empty spool of thread– Almost complete circle, seperated by thin wall of bone– The groove runs as a spiral around the bone– Articulates with the trochlear notch of the ulna

• Capitulum– Hemisphere of bone on anterior inferior surface of distal

humerus– Medial border is truncated to form the capitulotrochlear

groove– Radial fossa located proximal to capitulum

Distal Humerus

Anterior View Posterior View

Source: mywebpages.comcast.net/ wnor/lesson4bonesofarm...

Proximal Radius/Ulna• Proximal Ulna

– Olecranon process forms the point of the elbow– Coronoid process projects sharply from anterior proximal ulna– Trochlear notch articulates with the trochlea of the humerus. It

contains a curved longitudinal ridge that fits into the groove of the trochlea.

– Radial notch – depression lateral to inferior edge of trochlear notch• Proximal Radius

– Concave superior surface to articulate with capitulum – Cup like depression called the fovea– Distally to the head is the bicipital tuberosity, it acts as attachment

point for biceps

The Carrying Angle

There is a lateral va’L’gus angle between the upper arm and forearm.This L shaped angle allows the elbow to fit into the depression above the iliac crest (waistline) and aids in carrying heavy loads.Usually 5° in Men / 10-15° in WomenIt is due to the trochlea of the humerus (medial edge) projecting more distally and anteriorly than the lateral edge.

Joint Capsule & Ligaments

A fibrous capsule encloses the elbow joint as well as the superior radioulnar joint.It is strengthened at the sides by the radial (medial) and ulnar (lateral) collateral ligaments Its is relatively weak anteriorly and posteriorly

Elbow and R/U Ligaments

Adapted from: www.orthogastonia.com/.../ elbow_anatomy.html

Ligaments of the elbow jointMedial collateral Lig

• Anterior, posterior and intermediate

• Anterior is strongest and associated with common extensor tendon

• Triangular Shaped• Protect against valgus

stress

Lateral Collateral Lig• Less defined than medial

ligament• Divided into bundles

– one binds with annular ligament

– the other attaches to the superior crest of the ulna.

• Protects against vargus stress

Both are continuous with the joint capsule, are tense in flexion and extension, and strictly limit any abduction, adduction, axial rotation

Ligaments of the Radioulnar JtAnnular Ligament• Encircles 4/5’s of the radial head• Attached to the anterior and posterior margins of the radial notch.• Flexible – allows the head to rotate i.e. pronate/supinate• Strong – holds the radial head into the radial notch.• Upper fibres strengthened by the radial collateral ligament.

Interoseous Membrane• Strong fibrous sheet which stretches between the the inner surfaces of radius

and ulna• Runs from proximal to distal• Helps to absorb forces transmitted from the hands,• Prevent displacement of the radius from the ulna and,• Provides a large surface for muscle attachments.• Also found between the tibia and fibula.

Interosseous Membrane

Source: web.sc.itc.keio.ac.jp/.../ A03506001-003.html

MusculatureFlexion:• Biceps Brachii• Brachialis• Brachioradialis• Pronator Teres

Extension:• Triceps brachii• Anconeus

Pronation:• Pronator Teres• Pronator Quadratus• Brachioradialis

Supination:• Supinator• Biceps brachii• Brachioradialis

Movements of the Humeroradial joint

Movements of the Humeroradial joint

Distal Radioulnar Joint• Head of ulna sits into ulnar

notch on radius• Closed inferiorly by

triangular articular disc• Stability due to articular disc,

interosseous membrane and pronator quatratus which overlies.

• Main movement is supination 85° /pronation 75 °

• Describe process of supination…

Cubital Fossa

Triangular shaped space, bounded laterally by brachioradialis and medially by pronator teres.

Main contents include:• Brachial artery• Cephalic and Median cubital veins• Median, radial and lateral cutaneous nerves• Biceps tendon