Week 3: joints and biomechanics of materials Flashcards
what shoulder movement moves in thr transverse plane
med/lateral rotation
what shoulder movement moves in the sagittal plane
flex/extend
what shoulder movement moves in the coronal plane
abduction and adduction
the axes of human movement are perpendicular to what
perpendicular to the plane in which segment rotates
x= flexion/extension axis is perpendicular to what plane
sagital
Z= abduction, adduction axis is perpendicular to what plane
to frontal plane
Y= med/lateral rot axis is perpendicular to what plane
transverse plane
what are degrees of freedom in a joint
number of planes within a joint moves
OT and PTs typically work in how many degrees of freedom/planes of movement
between 1-3 planes
what is an example of a joint that moves in only 1 plane/1 degree of freedom
PIP only flexion and extension
what is a joint in the body with 2 degrees of freedom
MCP
flex extension
abd/add
what are joints in the body with 3 degrees of freedom
hip and shoulder
human joints can be overal classed into 2 structures: what are they
synarthroses
diarthorsis
true or false: diarthroses joints have little movement
false,more movement
what are the 3 subtypes of synarthrosis
synostoses
synchondroses
syndesmoses
explain synostoses and gvie example
bone fused to bone
ex: sutures in the brain
explain synchondroses and give example
bone to bone by cartilage
ex: rib cartilage
explain syndesmosis and give example
bone to bone by fibrous connective tissue
ex: interosseous membrane
diarthorsis are aka as what types of joints
synovial
what are the 5 properties of synovial joint
articular cartilage
synovial fluid
synovial membrane
joint (articular) capsule
ligaments
articular cartilage is usually what type
hyaline
what is the function of articular cartilage in joints
at the distal aspects of bones to allow for smooth movement
joint/fibrous articular capsule contains what
contains joint receptors (mecanoreceptors) which are critical to movement (provide proprioceptive input)
what are the 4 mechanical classifications of synovial joints
uniaxial
biaxial
triaxial
no rotation
hinge and pivot joints are uni, bi or triaxial
uni
condylloid/ellipsoid are uni, bi or triaxial joints
biaxial
ball and socket joints are uni, bi or triaxial joints
tri
true or false: there is no rotation in gliding/plane joints
true
what are the chracteritics of the uniaxial/ginglymus) HINGE joint
Convex surfaces articulates with concave surface
designed for flex/extension
true or false: the hinge joint is a tight congruent joint
true
what are some examples of hinge joints
ulnohumeral, interphalangeal
what are the chracteristics of the pivot/trochoid joint
rotation of one bone on another (longitudinal axis)
what are some explains of pibot/trochoid joints
proximal radioulnar joint
atlantoaxial joint
biaxial joints have how many degrees of freedom
2
what are the characteritics of the condylloid/ellipsoid joint
convex surface fits into concave surface of similar shade
what are some examples of the condylloid/ellipsoid joint
radiocarpal joint (ellipsoid)
MCP (condyloid)
what determines if a joint is condylloid or ellipsoid
depth of the concave surface
condylloid have more shallow or deeper concave surfaces
shallow
what are the chracteritics of ball and socket joints
spherical head fits into a concave depression
what is the cost of a highly mobile joint I
increased instability
how many degrees of freedom are there in triaxial ball and socket joints
3
what are some examples of ball and socket joint
glenohumreal joint of shoulder
femoral head into acetabulum of hip
since the ball and socket joints are so mobile, they are insatable which means they rely on what
constraints by periartiuclar structures (ligaments)
what are the characteritics of saddle joints
convex and concave surfaces fit together like a sADDLE (TIGHT FIT)
what is an example of a saddle joint in the body
trapeziometacarpal joint of thumb/carpometacarpal jt of thumb
what are the chractericis of gliding synovial jjoint (plane or gliding)
articular surfaces that slide on each other. no rotation (flat surfaces)
wht are some examples of gliding synoval joints
tarsal bones, inter-carpal joints, articulr processes of the vertebra
what are the 3 types of synovial joint movement
1) spin
2) roll/rotation
3) glide (or slide)
explain spin as a synoval joint movement
rotary motion, fixed axis, no translation
true or false, in a spin movement, there is translation
false, there is rotary motion along a fixed axis but no translation
explain roll/rotation as a synoval joint movement
rotary motion, new point of contact
advances/translates forward
explain glide as a synoval joint movement
linear or translatory motion
true or false: in glide/slide, there is rotary motion
false, there is linear/translatory motion but not rotatry./rolling
in the joints of the body, it is a combo of what synoval movments
combination roll and glide
what is the instant cetner of rotation
the theoretical axis of rotation for the joint at any given position
why does COR in a joint change
changes since joint movement is rotation as well as gliding
the convex-concave rule is predicted by what
shapen of joint surface
convex-concave rule is used during rotation to determine what
the direction of intraarticular glide
according to the convex-concave rule, if the bone with the concave surface moves on the convex surface, what is the direction of intraarticular glide
the concave articular surface glides in the same direction as the bone segments roll/movement
ex: MP joint
according to the convex-concave rule, if the bone with the convex surface moves on the bone with the concave surface, what is the direction of intraarticular glide
the convex surface glides in the direction opposite to the bone rolling motion
ex: glenohum joint
joint glides are known as what types of movements
accessory movemnts
concave on convex., same or different direction of intraarticular glide
same
convex on concave, same or different direction of intraarticular glide
opposite
what is the radius of curvature
describes the amount of curvature of a joint surface
it is the length of the radius of a circle of the same curvature
what is the closed pack position (4)
point of exact congruency where:
a) joint has max area of surface contact
b) ligs are under tension
c) capsule is taut
d) joint is compressed
if the joint has max area of surface contact
b) ligs are under tension, is it in open or closed pack
closed
if the ligs are under compression, is it in open or closed back
closed
if the joint capsule is taut, is it in open or closed pack
closed
if the joint is compressed, is it in open or closed pack
closed
give an example of a joint in closed pack position
PIP joint in full extension
explain open packed position
joint surfaces are incongruent
ligs are more slack
capsule is more slack
greater easy for acessory movement
in which position is there greater ease for accessory movement: closed or open
open pack
if the ligs are more slack, is it in open or closed back
open
if the capsule is more slack, is it in open or closed back
open
if the joint surfaces are incongruent, is it open or closed pack position
open
what is joint end feel
resistance to movement at end of passive joint range of motion (pushing the joint through the arc of motion)
if there is bone on bone contact, what will the joint end feel be
hard end feel
will feel like a bony block, abrupt stop, hit a wall
if there is soft soft tissue approximation (ex bicep motion) what willthe end feel be
soft end feel (a bit of give at the end of motion)
how does joint end feel feel if you are not able to reach end point
empty end feel (ex: ligament rupture or guarding of movment)
what is the defintion of stress
force applied to deform a structure
force is perpendicular to the area
force per unit experienced by the material
in stress, the force is perpendicular to what
the area
what is the formula for stress
sigma = F/ A
F= force applied
A= area over which force is applied
what are the different types of stress forces
compression
tension
shear
what is shear stress ctreated by
by a force that is parallel (not perpendicular) to the area
what is shear stress
shear stress = shear force/ area
what is the definition of strain
resulting deformation of a material from force (perpendicular or parallel)
what is the formula for strain
strain = change in length of material / resting length of material
stress-strain curves have what 3 functions
examine how materials change with age
examine how materails react to different forces
examine how material react to every day stresses
know the stress strain curve
.
what is the toe region
initial un-crimping of fibres
what is the elastic region
material returns to the original length when load (applied force) is removed. Stress vs strain relationship is linear
what is the plastic region
structure does not return to original length when loadremoved
what is the yield point (elastic limit) in the stress strain graph
where there is the transitmitin between elastic and plastic phase
stress level at which a material begings to permanently deform
what is the failure
applied force continues beyond plasitc region
w
what is the failure point/ultimate strength
highest stress it can withstand without breaking
what is young’s (elasticity) modulus
the slope of the straight line (elastic region) of a stress strain curve is the elasticity modulus) represeted by E
what is a higher value of E (slope/elasticity modulus) indicivative of
a stifferer material
what does ductile describe
describes a material that deforms plastically before failure
what does brittle describe
describes a material that fails before plastic deformation
explain brittle failure
linear stress/strain relationshiop
failure comes before plastic deformation
explain ductile failure
failures comes after plastic deformation
material yields with continued increased in the applied force
explain ductile failure
failures comes after plastic deformation
material yields with continued increased in the applied forcew
what is poissons ratio
the ratio of lateral vs axial strain
( V= -lateral strain/axial strain)
explain poissons ratio and give example
applying a tensole force will change the length but also the width
ex: a material is pulled (tension) during testing and the diameter and length change
what does fatigue testing determine
fatigue testing determines how many loading cycles (load-unload) at a given load a material can withstand bnefore failing
what is fatigue life
number of loading cycles that a material can withstand at a given stress level
true or false: materials behave differently if they are loaded at different rates
true
most materials subjected to a higher number of loading cycles will fail at a stress lower than their ultimate strength
lower than (bending a paper clip until it breaks)
understnad the clinical example for loading cyclesi
if a material has a time dependent mechanical behaviour due to a fluid like component it is blank
viscoelastic
what is viscosity
“gooeyness” of a material. High viscocity fluid flows more slowly
High viscocity fluid flows more slowly or fast
slowly
explain viscoelasticity
material that demonstrate a time dependent behaviour due to loading
true or false: most human biological materials (ex: tendon) exhibit viscoelastic behaviour
true
what are the 2 components of viscoelastic nature of materials
creep
stress relatxiation
explain stress relaxation
the reduction of stress within a material over time as the matieral is subject to constant deformation
explain creep
the continued deformation of matieral over time as the material is subjected to a constant load
understand creep vs stress realax.
bones behave similarly to what other material with applied forced
beams
what is the neutral axis in bones
the location where a beam experiences zero stress
in bending there is stress on one side of the neutral axis is compression, what is the othr side
tension
what is torsion in beams
a twisting force can be applied to a beam instrad of bending force thus creating torsion
torsion generates what type of stress
shear stress that are distributed over the entire structure
why is understanding stress important for fractures
the type of stress impacts what type of fracture you get
tension stress causes what fracture
transverse
compression stress causes what fracture
obloque
bending stress causes what fracture
buttergly
torsion stress causes what fracture
spiral
explain isotropic material properties
they do not depend on the direction of loading
ex: glass
explain anisotropic mateiral properties
they depend on the direction of loading
ex: bones, ligs, tendons
are most structures in the body composed of isotropic or anisotropic materials
anisotropic
