Forearm/elbow Flashcards
the elbow is a ___________ joint
modified hinge
“carrying angle”
cubitus valgus
what makes up the carrying angle?
angle between long axis of humerus and long axis of forearm
normal cubitus valgus angle
15º
functional implication of cubitus valgus
ulnar nerve stretched more across medial elbow
what reinforces MCL?
prox wrist flexors and pronators
normal PROM of elbow
5-0-145
is a loss of flexion or extension more meaningful at the elbow?
flexion
elbow arthrokinematics
open chain:
concave on convex - roll and glide in same direction
what makes up the humeroradial joint?
fovea of radial head
capitulum of humerus
what makes up humeroulnar joint?
trochlear notch of ulna
trochlea of humerus
what makes up the prox radioulnar joint?
ulnar radial notch
annular ligament
radial head
what makes up the distal radioulnar joint?
ulnar notch of radius
head of ulna
articular disc
TFCC
triangular fibrocartilage complex
proximal part of TFCC articulates with _______ and distal part articulates with _________
ulnar head; carpals
primary stabilizer of distal radioulnar joint
TFCC
a pt comes in complaining of lateral wrist pain. what do you assume might be implicated?
TFCC
direction of axis of radioulnar joints
vertical
3 joints that can limit sup/pro
prox and distal radioulnar
humeroradial
normal ROM of pronation
75º
normal ROM of supination
85º
neutral position between supination and pronation
thumbs up
how many DOF of radioulnar joints?
1
how do we compensate for supination/pronation ROM limitations?
ER/IR
proximal radioulnar joint arthrokinematics
convex radial head rotates in fibro-osseous ring on concave radial notch - ring prohibits typical arthrokin
distal radioulnar joint arthrokinematics
concave radius and convex ulna - roll and glide in direction of radial head motion
pronation/supination occur closed chain as a function of…
glenohumeral ER/IR
3 elbow flexors
- biceps
- brachialis
- brachioradialis
what elbow flexor generates the most force?
brachialis
biceps is most effective with _______
supination
when is brachioradialis most effective?
during elbow flexion with neutral forearm - esp during rapid movements
in what orientation do triceps generate max force? why?
~90º bc length tension
triceps frequently act as a _________
stabilizer
elbow extension often performed with __________
shoulder flexion
in a pushup, what keeps the triceps from extending the elbow AND shoulder?
anterior delt - opposes shoulder extension torque
law of parsimony application to elbow extension
anconeus –> triceps
law of parsimony application to supination
supinator –> biceps
choose the stronger movement: supination or pronation
supination
2 primary supinators
supinator
biceps
4 secondary supinators
radial wrist extensors
EPL
ext indicis
brachioradialis (if starting from pronated position)
what angle is biceps best able to supinate at? why?
90º - LoF is perpendicular to and radius
2 primary pronators
pronator quadratus
pronator teres
law of parsimony application to pronation
quadratus –> teres
3 secondary pronators
- FCR
- palmaris longus
- brachioradialis (from supinated position)
the law of parsimony states that the nervous system tends to activated _______________ for the control of a given joint action
the fewest muscles or muscle fibers possible
why does the law of parsimony happen?
energy conservation - when bigger muscles are used, other muscles also turn on to stabilize/counteract
tasks with low-level force demands are often accompished by…
uniarticular muscles
fx of the cervical spine may result in..
C6 quadriplegia
an essential component to maximizing movement efficiency in a person with paralysis
“muscle substitution”
what is muscle substitution?
movement strategies that enable people with paraplegia to use an innervated muscle to substitute for part of the functional loss imposed by a paralyzed muscle
people with C6 quad usually can’t use their ________
elbow extensors
what muscles can “substitute” for elbow extensors?
clavicular head of pec major and/or anterior delt
explain how shoulder muscles can sub for elbow extensors
shoulder muscles adduct and/or horizontally flexes the GH joint, pulling humerus toward midline with hand firmly fixed distally