FORCES AND FUNCTIONAL ANATOMY HIGH YIELD Flashcards
what are the ground reactive forces?
vertical forces
linear/shear forces
which of newtons laws is applicable to ground reactive forces?
newtons 3rd law
what are the two peaks of the vertical force of ground reactive forces?
1st
peak at end of contact period when BW is supported by one foot when the heel and metatarsals are loaded
2nd
midway through propulsion
what are the types of linear/shear forces?
contact (posterior shear force)
propulsion (anterior shear force)
what stance do linear/shear forces occur?
stance phase of gait
what happens during the contact portion of linear/shear forces?
heel strike causes posterior shearing when moving foot is stopped by ground friction
what happens during the propulsion portion of linear/shear forces?
when does this peak
heel lift and push off of propulsion
soft tissue slides anterior relative to the metatarsal heads
fat pad under ball of foot disperses shear of propulsion
*all help for propulsion and peaks at the moment when the opposite foot contacts the ground
when forces produce a turning effect, this is also observed as a moment and so is called?
torque
T/F, the subtalar joint is a torque converter?
T
what direction is the leg rotating during heel strike?
its internally rotating
what is the effect of subtalar joint on torque?
on external rotation of leg?
it decreases it BUT
internal torque develops between the ground and sole of foot, peaks at early contact period
starts at midstance and internal torque develops again, this peak is larger than the first peak
when does lateral shear peak?
end of contact period and peaks again during propulsion, clinically insignificant and caused bu shift in body weight
what are the two primary factors in stability?
osseous structure
muscle activity
note that muscle resists abnormal motion of bone
abnormal shear leads to what type of joint disorder? this leads too?
abnormal subtalar joint pronation
hypermobility
the foot can be referred with respect to what two columns?
medial column
lateral column
what does the medial column consist of?
the cuneiforms and metatarsals 1-3
in the medial column, what dorsiflexes?
1st ray dorsiflexes to compensate for STJ pronation and to alleviate stress on sesamoids
4-6 degree dorsiflexion
what does the lateral column consist of?
cuboid and metatarsals 4 and 5
what is the importance of the lateral column?
balance for adapting to terrain
what axis are involved in planal dominance?
vertical OMTJ axis
STJ axis
what happens when the vertical OMTJ axis is deviated so that its more vertically oriented? significance?
the axis is more perpendicular to the transverse plane
we see more abduction/adduction of forefoot on the rear foot with pronation/supination of the OMTJ
what is the affect when the STJ axis becomes more perpendicular to the transverse plane?
supination
ankle, knee, hip compensate
more transverse plane motion
what is the affect when the STJ axis is deviated more horizontally becoming more perpendicular to the frontal plane?
more frontal plane motion as a result of more angulation
increased stability, hyper mobility, and subluxation
cyma line has anterior deviation at talonavicular joint and decreased calcaneal inclination on x-ray
what is the affect of transverse deviation of the STJ?
so medial/lateral deviation leading to greater pronation and supination
what are the important lateral ankle ligaments?
ATFL, PTFL, calcaneofibular ligaments
what can result from lateral instability?
short lateral column or forefoot valgus causing calcaneus to invert to bring metatarsals to ground and inversion around the STJ
structure is made of abductor hallucis, abductor digits minimi, plantar aponeurosis
make up the medial, lateral, central bands and attach at the plantar process of the calcaneus
plantar fascia
this is associated with plantar aponeuorsis and is passive supination with no energy used?
windlass mechanism
windlass mechanism is _____?
passive supination
the oblique toe break is associated with what axis?
MPJ axis
what degrees does MPJ motion need?
MPJs need approx 62 degrees (+/- 10 degrees) of dorsiflexion of lesser digits on lesser metatarsals heads
this contributes to toebreak?
windlass mechanim
ontogenetic dysfunction is compensated or uncompensated?
abnormal STJ loading?
compensated
yes!!
what are the types of compensatory forefoot varus?
congenital
uncompensated
compensated
partially compensated
name this compensatory ontogenetic dysfunction
foot can’t dorsiflex the 10 degrees needed at midstance
will see pronation at heel contact with equines
patient walks with knee flexed
heel lift in midstance due to tight gastroc, medial or lateral hamstring
equines
name this compensatory ontogenetic dysfunction
congenital
compensates at MTJ by dorsiflexing the 1st ray or STJ supination
if MTJ we see lesions sub 2
if STJ we see lesions sub 1,5 or both
forefoot valgus
name this compensatory ontogenetic dysfunction
plane of met head 1 and 5 everted to rearfoot
1st ray plantarflexed in relation to met heads 2-5
due to contracture state of peroneus or tight medial slips of plantar fascia
compensation is STJ supination, lesions seen under 1st and 5th metatarsal heads
plantar flexed 1st ray
what are the types of abnormal STJ loading?
medial and lateral loading
can be caused by external forces
obesity
tibial valgus
medial loading
forces directed laterally due to inverted nature of calcaneus (what is this), and then so STJ pronates or supinates to get rest of foot on the ground
forefoot valgus or plantar flexed 1st ray directs forces laterally through the foot
lateral loading
name the gear
prosed by Finn bojsen Moller
transverse axis made of met heads 1 and 2 and operates at high speed like for sprinting
high gear
name the gear
oblique axis made of a line from met heads 2-5
operates for low speed power like for uphill climbing, carrying heavy loads
low gear
when is low and high gear used? like in walking
initially in propulsion we use low gear axis then shift medially to high gear for the actual propulsion
both used
what are the types of auto supports?
beams
truss
this type of auto support resists bending
ends not secure so,
- foot can elongate during contact and midstance
- foot at contact becomes beam allowing motion at joints to adapt to terrain without bending the foot abnormally
beam
this type of auto supports structure, braces it, makes it rigid
causes internal compression
ends are secured and so foot can’t elongate because of ground, osseous structure, phasic muscle activity plus windlass mechanism results in rigid lever for efficient propulsion
truss
