Elbow (bones, muscles, and applied)

3 bones in the forearm

• humerus

• radius

• ulna

4 joints in the forearm

• humerulna joint

• humeroradial joint

• proximal radioulnar joint

• distal radioulnar joint

lateral epicondyles

common origin for wrist extensors

medial epicondyles

common origin for wrist flexors

lateral and medial supra-epicondylar ridges

between shaft and epicondyle, where bone starts to widen

coronoid fossa

on the anterior surface of humerus

• during elbow flexion coronoid process of ulna lodges in this fossa

radial fossa

on the anterior surface of humerus

• during elbow flexion head of radius lodges into this fossa

olecranon fossa

on the posterior surface of humerus

• olecranon process of ulna lodges in this fossa during extension

humeroulnar joint

true elbow joint

• articulation of humeral medial condyle (trochlea) and ulnar trochlear notch

• synovial hinge joint

• 1 degree of freedom: flexion/extension

humeroradial joint

articulation of humeral lateral condyle (capitulum) and radial head

• no true motion

• flexion/extension occurs due to humeroulnar joint motion

proximal radioulnar joint

articulation of radial head and radial notch of ulna

• synovial joint - pivot

• movements: supination and pronation

distal radioulnar joint

between ulnar head and ulnar notch of radius

type of synovial joint: pivot

movements:

• supination/pronation

• mechanically coupled with proximal radioulnar joint

elbow complex stability structures

elbow joint

• medial collateral ligamentous complex (MCLC)

• lateral collateral ligamentous complex (LCLC)

radioulnar joint

• oblique cord

• interosseous membrane

• TFCC

capsular ligament

surrounds all three proximal joints

UCLC/MCLC

valgus stabilizer of the elbow

3 components

• anterior

• posterior

• oblique or transverse

anterior UCLC/MCLC

primary valgus stabilizer

• medial epicondyle to medial aspect of coronoid process of ulna

posterior UCLC/MCLC

medial epicondyle to medial border of olecranon process of ulna

oblique or transverse UCLC/MCLC

between coronoid process and olecranon process

lateral collateral ligamentous complex (LCLC)

varus stabilizer of the elbow

3 components

• annular ligament

• radial collateral ligament

• lateral ulnar collateral ligament

annular ligament

two ends of radial notch (ulna) and incircles radius

radial collateral ligament (RCL)

primary varus stabilizer

runs between lateral epicondyle to annular ligament

lateral ulnar collateral ligament (LUCL)

from the lateral epicondyle, blending with fibers from the annular ligament (superficially) and attached at supinator crestxfr

radio-ulnar joint

• oblique cord

• interosseous membrane

distal radioulnar joints ligament

triangular fibrocartilage complex (TFCC)

• fibro-cartilagenous articular disc

• radioulnar ligaments (dorsal and palmar)

• ulnocarpal collateral ligament

function of triangular fibrocartilage complex (TFCC)

• function as meniscus of wrist

• load transmission across the ulnocarpal joint and partially load absorbing

• stabilize the distal radio ulnar joint during rotation

movements and muscles of elbow joint (humero-ulnar joint)

flexion and extension caused by 5 muscles grouped in anterior and posterior compartments

• anterior (flexor): brachialis, brachioradialis, biceps brachii

• posterior (extensor: triceps brachii, and anconeus

movement and muscles of forearm (radioulnar joint)

supination and pronation caused by 4 muscles

• 2 for supination: biceps brachii, and supinator

• 2 for pronation: pronator quadratus, pronator teres