ankle and foot pt 2 Flashcards
what is the biomechanically optimal position of the rearfoot compared to what is actual common?
biomechanically- should be in neutral
actually- varus approx 3-4º of subtalar joint
from neutral how much supination can a person typically get at the rearfoot?
20º
the amount of supination a person can get at the rearfoot from neutral is makes up how much of total motion?
2/3
the amount of pronation a person can get at the rearfoot from neutral is makes up how much of total motion?
1/3
from neutral how much pronation can a person typically get at the rearfoot?
10º
how do we calculate rearfoot neutral position?
add the amount of inversion and amount of eversion. then divide that total by 3.
then subtract the total (1/3) from the valgus position
if the value is negative then its varus is positive its valgus
how is the subtalar joint like a mitered hinge between distal leg and the foot?
split 45º and 45º if supinate pulls into lateral rotation
what 2 joints make up the transverse tarsal joint?
the talocalcaneonavicular joint and the calcaneocuboid joint
the TCN joint is known as what kind of joint?
“ball and socket”
what makes up the TCN joint?
convex talar head and concave posterior navicular
which ligament deepens the navicular cavity?
the spring ligament (plantar calcaneonavicular ligament)
in closed chain at the TCN what is moving on what?
talus moving on relatively fixed calcaneonavicular “unit”
what does weightbearing do to navicular movement?
“locks” it
what do ligaments do to the calcaneus and navicular?
bind them
why is the TCN key to foot function?
the foot distal to the TCN form a single elastic unit that will move in response to and in compensation for subtalar motion
what motion occurs at the TCN?
triplanar supination/pronation
what motions occur largely at the transverse tarsal joint?
compensatory
how far is the TCN joint from the vertical axis?
approx 45º
how far is the TCN joint from the longitudinal axis?
approx 45º
how far is the TCN joint from the M-L axis?
60º
what motions is the TCN joint good at?
good at all motions. pretty good at ev/inv and abd/add. good at pf/df
is the calcaneocuboid joint more or less restrictive than the talonavicular joint?
still a lot of mobility but it is more restrictive
how is the calcaneocuboid joint?
sellar surfacereciprocallly concave/convex
what are the ligaments of the transverse tarsal joint?
lateral band of the bifurcate ligament
dorsal cancalcneocuboid ligament
short plantar ligament
long plantar ligament
what os the lateral band of the bifurcate ligament a check rein to?
plantarflexion
what is the dorsal calcaneocuboid ligament a check rein to?
inversion and plantarflexion
what are the short plantar and long plantar ligaments for?
they support the longitudinal arch for stability of the foot
what are both the short plantar and long plantar ligaments together called?
plantar calcaneocuboid ligament
how far from the A-P axis is the longitudinal axis of the transverse tarsal joint?
15º
how far from the vertical axis is the longitudinal axis of the transverse tarsal joint?
75º
how far from the M-L axis is the longitudinal axis of the transverse tarsal joint?
81º
what movements is the transverse tarsal joint very good at about the longitudinal axis?
very good at inversion eversion (better than the subtalar joint that is 42º away still)
what movements is the transverse tarsal joint not good at about the longitudinal axis?
abd/add
df/pf
how far from the M-L axis is the oblique axis of the transverse tarsal joint?
33º
how far from the A-P axis is the oblique axis of the transverse tarsal joint?
57º
How far from the vertical axis is the oblique axis of the transverse tarsal joint?
38º
what motions is the transverse tarsal joint good at about the oblique axis?
DF/PF
abd/add
what motions is the transverse tarsal joint not as good at about the oblique axis?
inversion/eversion
So overall what motions is the transverse tarsal joint good at?
All of them:
in the longitudinal axis: inversion/eversion
in the oblique axis: df/pf and abd/add
can we quantify and separate motions between the longitudinal and oblique axes of the transverse tarsal joint?
no it is very difficult
both axes of the transverse tarsal joint together provide how much total range of supination and pronation of the talus and calcaneus?
1/3-1/2 of that which is available at the subtalar joint
which joints are linked mechanically?
the subtalar joint and the transverse tarsal joint
in closed chain the subtalar joint (talar) causes motion at the talonavicular joint with what motions?
abd/add and df/pf
in closed chain the subtalar joint (calcanael) causes motion at the calcaneocuboid joint with what motions?
iv/ev
what occurs with subtalar joint supination?
transverse tarsal joint supination (which is the locking/closed pack position)
what occurs with subtalar joint pronation?
transverse tarsal joint pronation (which is the mobile/loose pack position)
what are the two functions of the transverse tarsal joint?
add to supination/pronation range of the subtalar joint
compensate the forefoot for hindfoot position (ability of the forefoot to remain on the ground while subtalar joint pronates and supinates)
according to inman and manns’s mechanical model when medial rotary forces are imposed on the leg it acts through the oblique axis of the subtalar joint and the transverse tarsal joint to do what in normal mechanics?
the subtalar joint will pronate and the transverse tarsal joint will maintain the forefoot in a relatively fixed position
according to inman and manns’s mechanical model when medial rotary forces are imposed on the leg it acts through the oblique axis of the subtalar joint and the transverse tarsal joint to do what if the subtalar joint pronation is a little limited?
if subtalar joint is a little limited the transverse tarsal joint can help bc the axes are parallel
according to inman and manns’s mechanical model when medial rotary forces are imposed on the leg it acts through the oblique axis of the subtalar joint and the transverse tarsal joint to do if there is excessive pronation of the subtalar joint?
then the transverse tarsal joint can compensate and excessively pronate to try and make up for the subtalar joint and keep the forefoot down on the ground still
according to inman and manns’s mechanical model when lateral rotary forces are imposed on the leg it acts through the oblique axis of the subtalar joint and the transverse tarsal joint to do what in normal mechanics?
supination of the subtalar joint creates lateral rotation of the leg and the transverse tarsal joint allows it and will maintain the foot flat on the ground
according to inman and manns’s mechanical model when lateral rotary forces are imposed on the leg it acts through the oblique axis of the subtalar joint and the transverse tarsal joint to do if the subtalar joint excessively starts to supinate?
because it is the closed pack position the axes are crossed the transverse tarsal joint cant act on its own and now so the transverse tarsal joint is forced to supinate with the subtalar lifting the medial part of the foot off the ground
according to inman and manns’s mechanical model when lateral rotary forces are imposed on the leg it acts through the oblique axis of the subtalar joint and the transverse tarsal joint to do if the subtalar joint has a restriction or is limited?
then the transverse tarsal joint can supinate to get to normal supination that we would see