Elbow Applied Biomechanics

elbow proper joint

humeroulnar joint

flexion/extension elbow joints

humeroulnar and humeroradial

pronation/supination elbow joints

proximal and distal radioulnar joints

what are the sources of ROM restriction for elbow flexion/extension?

biceps, olecranon fossa, coronoid process

what are the sources of ROM restriction for pronation/supination?

interosseous membrane, ligaments

open chain pronation

distal segment moves, radius, palmar

open chain supination

distal segment moves, radius, dorsal

closed chain prontation

proximal segment moves, ulna + humerus, palmar/int rot

closed chain supination

proximal segment moves, ulna + humerus, dorsal/ext rot

open chain proximal radioulnar pronation

screw home mechanism with radial compression

open chain proximal radioulnar supination

radial head spinning

what limits open chain proximal radioulnar supination?

pronators, interosseous membrane, annular ligament, flexor carpi radialis, finger flexors

open chain distal radioulnar joint supination

concave ulnar notch of radius slides/rolls in similar directions of convex ulnar head

what limits open chain distal radioulnar joint supination?

articular disc, palmar capsular ligament

closed chain pronation/supination

humerus/ulna rotate relative to fixed radius + hand

closed chain pronation

humerus and ulna externally rotate

closed chain supination

humerus and ulna internally rotate

open chain humeroulnar flexion/extension

concave trochlear notch of ulna rolls/slides in same direction on convex trochlea of humerus

closed chain humeroulnar flexion/extension

convex trochlea of humerus rolls/slides in opposite directions on concave trochlear notch of ulna

what factors limit humeroulnar extension?

olecranon, coronoid

what factors limit humeroulnar flexion?

ligaments, anterior/posterior capsule

what boney processes stabilize elbow flexion?

coronoid process and coronoid fossa

what boney processes stabilize elbow extension?

olecranon process and olecranon fossa

primary elbow varus stabilizers

lateral ulnar collateral ligament (also resists flexion and ext rot of proximal forearm relative to humerus)

secondary elbow varus stabilizers

radial collateral ligament

primary elbow valgus stabilizers

anterior fibers of MCL (strongest, taut in full ext)

secondary elbow valgus stabilizers

posterior fibers of MCL (may get taut in full flexion) and transverse fibers of MCL

carrying angle

normal cubital valgus=15 degrees

annular ligament

holds proximal radius against ulna

interosseous membrane

fibers run distal-medial from radius to ulna, disperses compressive forces at radiocarpal joint, prevents proximal migration of radius, slack during distraction

primary elbow flexors

attach proximally: brachialis, biceps, brachioradialis

secondary elbow flexors

attach distally: pronator teres, flexor carpi radialis/ulnaris, flexor digitorum superficialis, palmaris longus

primary elbow extensors

triceps, anconeus

secondary elbow extensors

ECRL, ECRB, extensor digitorum, extensor carpi ulnaris, extensor digiti minimi

agonist

muscle that causes the movement/joint action

antagonist

muscle that does the opposite action of the agonist

synergist

helps agonist

neutralizer

cancels out unwanted motions of agonist

stabilizer

stabilizes joints around the movement

agonist in using a screwdriver

biceps

antagonist in using a screwdriver

pronator teres

synergist in using a screwdriver

supinator

neutralizer in using a screwdriver

triceps

stabilizer in using a screwdriver

serratus anterior (scapula stabilizer)

agonist in cable curl

brachialis

antagonist in cable curl

triceps

synergist in cable curl

biceps, brachioradialis

neutralizer in cable curl

pronator teres

stabilizer in cable curl

posterior deltoid (shoulder stabilizer)

concentric contraction

muscle shortens

eccentric contraction

muscle lengthens