Ulna and Radius Elbow Complex

what is the function of the brachialis

elbow flexion: regardless of the position of the forearm

where is the medial/ulnar collateral ligament

extends from medial epicondyle of humerus to the coronoid process and olecranon of the ulna

what does the proximal radioulnar joint allow

rotation to occur: supination and pronation

what muscles are activated first until more torque is needed

shorter muscles or muscles that cross only one joint

where does compression injury occur

occurs at the elbow joint during a fall on our hand with elbow in closed-packed position

olecranon process

posterior surface: bursa anterior surface: part of trochlear notch

what are the two types of pronators

pronator teres pronator quadratus

what is the function of the humeroulnar joint

provides majority of structural stability to the elbow

what is the function of the medial/ulnar collateral ligament

provides the most significant resistance against a valgus force at the elbow

what are the additional joints of the forearm

proximal radioulnar joint distal radioulnar joint

what percent of compression force is through the ulna

20%

what percent of compression force is through the radius

80%

what happens when the pectorals major acts as elbow extensor

GH jt adducts, horizontally flexes, pull the humerus towards the midline

what is the humeroulnar joint enclosed by

a joint capsule

what is the smaller extensor muscle

anconeus

which fibers are the strongest and stiffest of the medial/ulnar collateral ligament

anterior

what does the medial/ ulnar collateral ligament consist of

anterior, posterior, and transverse fiber bundles

supinator notch

between supinator crest and the distal part of the coronoid process

what is a powerful supinator

biceps brachii

what are the different types of elbow flexors

biceps brachii brachioradialis brachialis

what is known as the work horse of elbow flexion

brachialis

what muscle usually generates the greatest force of any muscle crossing the elbow

brachialis

what is an example of the biceps as a flexor

bringing spoon to mouth

what does the brachioradialis do

can be readily palpated during resisted elbow flexion with forearm in neutral

what is elbow dislocation

caused by a distraction force exerted on the radius

who is most susceptible for elbow dislocation

children: nursemaid's elbow

where does the humeroulnar joint articulate

concave, trochlear notch (ulna) around the convex trochlea (humerus)

what does the distal radioulnar joint consist of

convex head of ulna fitting into a shallow concavity on the radius (ulnar notch)

what is the carrying angle of the elbow called

cubitus valgus

where does the humeroradial joint articulate

cuplike fovea of radial head and the rounded capitulum (humerus)

where is the ulnar notch of the radius

distal end of radius which accommodates the head of the ulna

what happens during pronation at the proximal radioulnar joint

distal segment of the radius rotates and crosses over a fixed ulna

where does the shaft of radius enlarge

distally whereas ulna shaft decreases distally

what does the anconeus do

first to initiate and maintain low level of elbow extensor force due to law of parsimony

what is the function of the annular ligament

fits snugly around the head of radius and holds against the ulna

______ are 2x as strong as ______ in all positions

flexors, extensors

what doe the interosseous membrane allow

for transmission of forces through the upper limb

what is compression injury

force from the fall transmits force through either the radius or ulna

what is triceps paralysis

fracture of cervical spine may result in C6 quadriplegia

what is a valgus injury

fully extended elbow receives a violent valgus force

where is the lateral/radial collateral ligament seen

goes from the lateral epicondyle and blends into the annular ligament and supinator crest of the ulna

what is excessive cubits valgus

greater than 20 degrees

what does the pronator teres do

has 2 heads: humeral and ulnar primary forearm pronator

what is part of the radius

head of radius shaft of radius distal end of radius

what does the interosseous membrane do

holds the radius and ulna together

what are the different joints at the elbow

humeroulnar humeroradial

what does the proximal radioulnar joint share the same joint capsule with

humeroulnar joint and humeroradial joint

when is a valgus injury commonly seen?

in a fall or when pitching a baseball, results in overstitching of the medial collateral ligament

what happens at rest with the humeroradial joint

in full extension, little if any physical contact exists at the humeroradial joint

ulnar tuberosity

inferior side of coronoid process

supinator crest

inferior to radial notch on lateral surface of ulna

what is the brachioradialis

longest elbow muscle

what does the triceps function as in elbow extensor

large and powerful provides stability at elbow produces majority of total extensor torque at elbow during maximal extensor effort

where is the radial styloid process

lateral aspect of radius

radial notch of ulna

lateral side of coronoid process, receives head of radius

head of ulna

lateral surface articulates with ulnar notch of radius styloid process of ulna

what is cubits varus

less than 5 degrees

where is the brachialis

lies deep under biceps muscle

what is the posterior surface of the radial shaft called

lister's tubercle which forms tunnels for extensor tendons

where is the annular ligament and what is composed of

located a proximal radioulnar joint thick circular band of connective tissue

what is a supinator

located deep on the dorsal side of the forearm relentless forearm supinator during elbow flexion

how many heads are in the triceps and what are they

long, medial, lateral

biceps brachii: flexor- what does it do

may be palpated when elbow is flexed and forearm is supinated simultaneously performs elbow flexion and supination for the forearm

what happens if the ulna is fallen on in a compression injury?

may cause fracture of coronoid or olecranon process

what happens if the radius is fallen on in a compression injury?

may cause fracture of the radial head

what is the humeroulnar joint stabilized by

medial collateral ligament

what does the pronator quadratus do

most active and consistently used pronator- regardless of power demands

what about the fibers of the interosseous membrane?

most are directed away from the radius to the ulna

what is the law of parsimony

nervous system tends to activate the fewest muscles or muscle fibers possible for the control of a given joint

what is cubitus valgus do

normal carrying angle of the elbow approximately 10-20 degrees abduction keeps carried items away from the side of the thigh while walking

what does the biceps brachii do as a supinator

normally recruited during high power supination activities, especially those associated with elbow flexion

what type of joint capsule is the elbow joint

one joint capsule

what can act as elbow extensor in a closed kinematic chain

pectoralis major

what does the distal radioulnar joint do during pronation and supination

stabilizes the distal forearm

what is the function of the lateral/radial collateral ligament

stabilizes the elbow against a vagus-directed force

coronoid process

superior surface- forms a part of the trochlear notch

what is part of the head of radius

superior surface: articulates with capitiulum of humerus circumference radial neck: distal to head radial tuberosity: distal to medial part of neck

what is the first muscle to initiate supination at low to moderate intensity supination activities

supinator

what happens to the ulna and radius when the forearm is fully supinated at the forearm

the radius and ulna are parallel

what does the distraction cause

the radius to slip out of the annular ligament

what would be paralyzed in triceps paralysis

triceps (C7) and other shoulder muscles such as pectorals major (C5-C6) would remain innervated

what are the elbow extensors

triceps brachii anconeus

what is consisted of the ulna

trochlear notch olecranon coronoid process shaft of ulna head of ulna ulnar tuberosity radial notch of ulna supinator crest supinator fossa

some the force through the radius is transferred to what via the membrane

ulna

what is the differences between men and women in carrying angle

women is greater due to different angle in pelvis for childbirth enables women to fit their upper arms in close to waist when carrying items

example: getting into bed (triceps paralysis)

wrist fixed to bend, the muscles rotate elbow into extension once locked into extension, the stable elbow allows the entire limb to accept weight without buckling