biomech final Flashcards
why is foot required to be pliable?
to absorb stress and conform to environment
why is foot required to be rigid?
to withstand large propulsive forces
what is a normal sensation that a healthy foot provides?
protection/feedback to muscles of LE
what is the ankle?
talocrural joint
articulation among tibia, fibular, talus
what is the foot?
all tarsal bones and joints distal to ankle
rearfoot/hindfoot
talus, calcaneus, subtalar joint
midfoot
remaining tarsals, transverse tarsal joint, distal intertarsal joints
forefoot
metatarsals, phalanges, tarsometatarsal joints
how much weight is transferred through fibula?
10%
describe the distal tibia
expands to load bear at ankle
twisted externally 20-30 degrees relative to proximal
~called lateral tibial torsion
3 major joints in ankle
talocrural
subtalar
transverse tarsal
talus involved with all 3
dorsiflexion/plantarflexion plane
sag
ML axis
eversion/inversion plane
frontal
AP axis
abd/add plane
horizontal
transverse axis
why are fundamental definitions inadequate at ankle?
joints have oblique axis rather than standard
they’re weird
pronation at ankle
eversion, abd, dorsiflexion
flatfoot
supination at ankle
inversion, add, plantarflexion
high arch
nickname for talocrural
mortise
concave proximal side
major natural stability to ankle
ML axis in ankle
10 degrees superior in medial side of ankle
AP axis in ankle
6 degrees anterior on the medial side on ankle
compressive force percentage through tibia vs fibula
talus and tibia - 90-95%
talus and fibula - 5-10%
width is talocrural joint articular cartilage
~3mm
can be compresses by 30-40% against peak load
if thinner, cannot support as large of a load
arthro in ankle dorsiflexion
talus rolls anterior, slides posterior
pulls achilles taut
arthro in ankle plantarflexion
talus rolls posterior, slides anterior
anterior capsule taut
factors increases mechanical stability of talocrural
increases passive tension
trochlear surface wider ant than post
ROM of right talocrural during gait cycle
plantar at heel contact
dorsiflexion during force absorption into stance
at push off, plantar flexion at toe off - propulsive force
small dorsiflexion in swing back & into plantar flexion
what is an ankle mortise injury?
extreme and violent dorsiflexion
called high ankle sprain
what is an unstable position in the ankle?
full plantarflexion
slackens most collateral ligaments of ankle
places narrower width of talus between malleoli
subtalar joint
under the talus
pronation and supination during non weight-bearing
occur al calcaneus moves relative to fixed talus
in weight-bearing pronation and supination occur as calcaneus remains relatively stationary
how much of the total articular surface does the posterior articulation of the subtalar joint occupy?
70%
subtalar axis of rotation
42 from horizontal
16 from sagittal
what motions make up pronation
eversion
abduction
what motions make up supination
inversion
adduction
by how much does inversion exceed eversion?
double
inv - 22.6 deg
ev - 12.5 deg
passive inv:ev ratio
3:1
what limits eversion?
lateral malleolus
deltoid lig on medial side
two articulations of the mid tarsal joint
talonavicular
calcaneocuboid
what is the most versatile joint in the foot?
mid tarsal
what joint allows pronation/supination of midfoot on uneven surfaces?
transverse tarsal joints
what muscle is the prime supinator of the foot?
tibialis posterior
arthro of navicular around talus in supination
spin
cave on vex
transverse tarsal joint rarely moves without:
subtalar joint
two AoR at transverse tarsal joint
long: ev/inv
oblique: abd/dorsi and add/plantar
amount of pure inv/ev of midfoot
inv - 20-25 deg
ev - 10-15 deg
what bones form the medial arch?
calc, talus, navi, cuneiforms and associated three MTs
other structures that assist medial arch in absorbing loads
plantar fat pads, sesamoid bones, superficial plantar fascia
where does weight fall when one stands normally?
near talonavicular joint
what maintains height of medial longitudinal arch during standing?
deep plantar fascia
with a fallen arch, what happens to support arch?
muscles compensate for arch
pes planus
flattening of arch
rigid pes planus
dropped arch in non weight bearing
flexible pes planus
dropped arch only when foot loaded
pes cavus
abnormally raised medial longitudinal arch
characteristics of pes planus
excessive calc eversion
increased flexibility of foot
uneven weight distribution
hallux valgus
postural symptoms
characteristics of pes cavus
limited pronation
rigidity
uneven weight distribution
digital contractures
tendency for lateral ankle instability/sprains
percent of change of height of med long arch in stance phase
60%
how pronation connects to hip
pronation of foot causes int rot, flex and add at hip
how pronation connects to knee
increased valgus stress
how pronation connects to rearfoot
lowers med long arch
consequences of rearfoot varus
over supinated at toe off
excessive use of peroneals
over stress of MT
dorsiflexion of great toe trying to force 1st MPJ down
high med arch
consequences of rearfoot valgus
over pronated at toe off
overstretching of deltoid ligaments
collapsed arch
newton’s 3rd law
equal and opposite reaction
weight is a force downwards
ground reaction force is upwards
3 other components of diagonal GRF
vertical
horizontal
ML
when does someone slow down?
(gait slide 2)
when GRF is backwards
when heel hits the ground
when is GRF highest
weight fully through heel
weight fully through toes
are COG and COM the same in human body?
no
just in uniform object like a book
COG
depends on posture
COM
stays in body
eccentric contractions in gait
go with gravity
squatting down before a jump
concentric contractions in gait
against gravity
jumping up
what is flexor torque
GRF behind the joint
extensor torque
GRF in front of the joint
forces in trendelenburg
more ML force
less AP force
what are the pretibial muscles?
dorsiflexors
heel rocker
initial contact to foot flat
ankle plantarflexion
ankle rocker
foot flat to heel off
dorsiflexion
forefoot rocker
heel off to toe off
ankel PF and MTP DF
examples of when rockers may not happen correctly
knee surgery
bracing
in pain
wearing high heel
1 cycle/stride
heel strike to heel strike of the same foot
2 steps
2 phases ( stance and swing)
1 step
between right and left heel strikes
stance phase
right heel strike to right toe off
when right foot is in contact with ground
60% of gait cycle
swing phase
right toe off to next right heel contact
right foot in the air
40% of gait cycle
how long is a stride length?
144 cm
how long is a step length?
72 cm
what is foot angle?
5-7 deg externally rotated
what is step width?
8-10 cm
what happens with a larger foot angle?
larger step width
reduced step length
reduced stride length
what happens with smaller foot angle
<5 deg results in in toeing
gait velocity
3 mph
ground clearance in gait
min 1 cm
cadence of gait
133 bpm
purple haze - left up right up
how many periods of single and double limb support?
2 each
how much is first double limb support?
0-10%
weight transferred from left to right
first period of single limb support
10-50%
right in stance, left in swing
second period of DLS
50-60%
weight transferred from right to left
second period of SLS
60-100%
right in swing, left in stance
what do faster speeds do to gait?
DLS disappear and there are periods where both limbs are off the ground
what do slower speeds do to gait?
give greater stability
increase DLS
how many events in stance phase?
5
heel contact
right heel contacts the ground at 0%
foot flat
right foot flat on ground at 8%
mid stance
legs parallel at 30%
heel off
between 30-40%
the instant the right heel comes off the ground
toe off
at 60%
instant right toes come off the ground
GRF at toe off
push backward so GRF is anterior
ank- PF
knee - ex
hip - ex
how many parts to swing phase?
3
early swing
60-75%
right foot behind left
mid swing
75-85%
legs parallel
late swing
85-100%
after parallel to right heel strike
RLA gait phases
initial contact
loading response
mid stance
terminal swing
pre swing
initial swing
mid swing
terminal swing
traditional gait phases
heel strike
foot flat
mid stance
heel off
toe off
acceleration
mid swing
deceleration
sagittal plane movement in pelvis vs other LE joints
much smaller in pelvis
sagittal movement at pelvis throughout gait
at right heel contact, neutral
0-10%, small posterior tilt
just after mid stance, begins anterior tilt
2nd half of stance, posterior tilt
initial and mid swing, anterior tilt
terminal swing, posterior tilt
in double leg support, posterior pelvis tilt
what is pelvic tilt in gait caused by?
hip joint capsule
hip flexors
hip extensors
in those with hip contractures, how does their pelvis tilt in the second half of stance?
exaggerated anterior tilt
which pelvic tilt can compensate for increased lumbar lordosis?
excessive anterior pelvis tilt
compensate for lack of passive hip extension
sagittal movement of hip throughout gait
at heel contact, flexed 30 deg
before toe off, max extension of 10 deg
during pre swing, hip flexion initiated
by toe off, 0 deg flexion
during swing, continued flexion to bring LE forward
overall ROM needed at hip for walking
30 deg flexion
10 deg extension
how do individuals with limited sag hip mobility go unnoticed?
movement of pelvis and lumbar spine compensate for reduced hip motion
how is hip extension detectable through observational skills?
anterior pelvis tilt and increase in lumbar lordosis
sagittal movement of knee throughout gait
at heel contact, flexed 5 deg
during initial 15%, flex to 10-15 deg
until about heel off, approaches near full extension
by toe off, reaches about 35 deg flexion
by beginning of mid swing, reaches about 60 deg flex
what is slight knee flexion in gait controlled by?
eccentric action of quads
shock absorption and weight acceptance
what is the point of knee flexion?
toe clearance
sagittal movement at talocrural joint throughout gait
at hell contact, slight PF 0-5 deg
during the first 8%, foot is flat
during stance, 10 deg DF
after heel off, begins the PF
just after toe off, 15-20 deg PF
during swing, DF
how is plantarflexion of controlled during first 8% of gait?
eccentrically by doriflexors
average ROM in ankle for normal gait?
10 deg DF
20 deg PF
what happens at ankle to allow toes to clear the ground?
DF
what causes premature heel off?
lack of ankle DF form tight achilles
what is toeing out?
compensation for limited DF
rolls off medial foot in second half of stance
increased pronation as compensation for DF
greater stresses to soft tissue of foot
how would someone compensate for DF during toe clearance?
increased knee and/or hip flexion
what can cause limited DF in swing?
PF tightness
calf spasticity
joint dysfunction
DF weakness
are frontal or sagittal plane movements bigger?
sagittal movements larger
frontal movement at pelvis throughout gait
downward motion as result by gravity and controlled by eccentric activation of right hip abductors
how is frontal movement at pelvis best observed?
in front or behind
total pelvis ROM in gait through PonF add and abd
10-15 deg
frontal movement at hip throughout gait
elevation and depression
during stance, primarily PonF
3 reasons why excessive movement at pelvis and hip in frontal plane are observed
weak hip abductors
reduced shortening of swing limb
discrepancy in limb length
what is the drop of contralateral iliac crest during stance controlled by?
eccentric activation of hip abductors
frontal movement at knee throughout gait
in the last 20% of gait, 5 deg adduction
frontal movement at ankle throughout gait
very small
frontal movement at foot and subtalar joint throughout gait
at heel contact, inverted 2-3 deg
until midstance, rapid eversion to 2 deg
after midstance, starts to invert
between heel and toe off, reaches 6 deg inversion
during swing, slightly inverted
what is rapid pronation of foot good for?
provides a flexible and adaptable foot structure for making contact with ground
what is inversion of foot good for?
more rigid foot structure, which helps propel the body forward
horizontal movement at pelvis throughout gait
0-15% - int rot
15-60% - ext rot
60-100% - int rot
horizontal movement at femur throughout gait
0-18% - int rot
18-60% - ext rot
60-100% - int rot
horizontal movement at tibia throughout gait
0-20% - int rot
20-60% - ext rot
60-100% - int rot
horizontal movement at subtalar joint throughout gait
0-30% - everting
30-55% - inverting
55-100% - everting
horizontal movement at midfoot throughout gait
0-30% - increasing pliability
30-55% - increasing stability
55-100% - increasing pliability
ROM at hip during gait
IC - 20 flexion
IC-LR - 20 flexion
LR-MS - 0
MS-TS - 20 extension
TS-PS - 10 extension
PS-IS - 15 flexion
IS-MS - 25 flexion
MS-TS - 20 flexion
ROM at knee during gait
IC - 0
IC-LR - 20 flexion
LR-MS - 5 flexion
MS-TS - 0
TS-PS - 40 flexion
PS-IS - 60 flexion
IS-MS - 25 flexion
MS-TS - 0
ROM at ankle during gait
IC - 0
IC-LR - 5 PF
LR-MS - 5 DF
MS-TS - 10 DF
TS-PS - 15 PF
PS-IS - 5 PF
IS-MS - 0
MS-TS - 0
muscles at hip during gait
IC - E hams
IC-LR - C glutes, hams
LR-MS - C glutes, E glute med
MS-TS -
TS-PS - E iliopsoas, adductors
PS-IS - C iliopsoas
IS-MS - C iliopsoas
MS-TS -
muscles at knee during gait
IC - C quads
IC-LR - E quads
LR-MS - C quads
MS-TS -
TS-PS - E quads
PS-IS - C hams
IS-MS - C hams
MS-TS - C quads, E hams
muscles at ankle during gait
IC - pretibs
IC-LR - E pretibs
LR-MS - E gastroc, soleus
MS-TS - E soleus
TS-PS - C gastroc, soleus
PS-IS - C pretibs
IS-MS - C pretibs
MS-TS - pretibs
subtalar open chain pronation
calc - evert
talus - stable
forefoot - abs, DF
subtalar closed chain pronation
calc - everts
talus - add, PF
forefoot - stable
subtalar open chain supination
calc - inverts
talus - stable
forefoot - add, PF
subtalar closed chain supination
calc- inverts
talus - abd, DF
forefoot - stable
