Foot and Ankle Biomechanics Flashcards
What happens to foot during weight acceptance?
foot pronates to absorb shock
What happens to the foot during mid stance
pronation ends
What happens to the foot during terminal stance?
foot moves into supination
ROM necessary for gait? DF, EV, INV? how much does the foot need to pronate and supinate from neutral position?
10 degrees DF
4-6 degrees EV
8-12 degrees INV
pronate and supinate 6-8 degrees from neutral position
What happens during gait of the STJ is stiff?
There is excessive pronation –> excessive mobility–> can’t go into rigid lever (axes can’t cross) –> get propulsion from 1st ray OR by rotating LE and compensating with hip and knee.
What’s Dutton’s definition of SINGLE PLANE?
single plane: leg, foot, and ankle
FRONTAL PLANE
HORIZONTAL PLANE
SAGITTAL PLANE
What is in and happens in the FRONTAL PLANE?
Motion of the foot- anterior/posterior axis
inversion and eversion
What is in and happens in the HORIZONTAL PLANE?
Motion of the forefoot- superior/inferior axis
abduction and adduction
What is in and happens in the SAGITTAL PLANE?
movements at the ankle and midtarsal joint- medio-lateral axis
plantar flexion and dorsiflexion
What is TRIPLANE movement and where does it occur in the foot/ankle?
movement about an obliquely oriented axis through all three body planes
talocrural, subtalar, midtarsal joints, 1st ray, 5th ray
Describe OKC and CKC motions at the subtalar joint.
Triplanar Motion
OKC
- pronation = calcaneal eversion/abduction and dorsiflexion
- supination= calcaneal inversion/adduction and plantarflexion
CKC
- pronation= calcaneal eversion with adduction and plantar flexion of the talus
- supination= calcaleal inversion, abduction and dorsiflexion of the talus
Sub-Talar Neutral (STJN)
mid position of the sub-talar joint = range at which STJ should act to prevent dysfunction
Measured as an angle between the bisection of the distal portion of lower leg and line that bisects calcaneus
Should be 0-3 degrees or mathematically position of 2:1 inversion to eversion.
What should you see in a posterior view of the foot/ankle during normal gait?
Heel strike: rear foot inverted
Midstance: rearfoot perpendicular
Heel rise: rearfoot inverted
What would you see in a posterior view of an excessively pronated foot during gait?
Heel strike: inverted
Midstance: everted
Heel rise: everted
What would you see in a posterior view of an excessively supinated foot during gait?
Heel strike: inverted
Midstance: Inverted
Heel rise: inverted (maybe everted)
What are some intrinsic causes of excessive supination? are they compensated or uncompensated?
plantar flexed first met (compensated)
forefoot valgus (compensated)
uncompensated rearfoot and forefoot varus
What are some extrinsic causes of excessive supination? are they compensated or uncompensated?
femoral retroversion (compensated)
uncompensated tibial varum
neurological disorders
leg length discrepency
What are some intrinsic causes of excessive pronation? are they compensated or uncompensated?
forefoot varus (compensated)
rearfoot varus (compensated)
What are some extrinsic causes of excessive STJ pronation? are they compensated or uncompensated?
compensation for limited DF during gait
compensation for excessive tibial varus
achilles tightness
weak peroneus longus or ankle/STJ invertors (posterior tibialis, FDL, FHL; anterior tibialis, EHL) arch laxity
compensation for increased LE IR secondary to femoral anteversion or muscle strength imbalance of hip internal: external rotators
At the STJ, what would you expect to see at the in the gait cycle in a foot with forefoot valgus?
supination when forefoot becomes plantargrade ( need enough mobility in forefoot in order to do this)
According to Dutton, how much rearfoot varus is normal?
3 degrees rearfoot varus
At the STJ, what would you expect to see in the gait cycle of a foot with rearfoot varus?
early and prolonged pronation of mobile adapter
At the STJ, what would you expect to see in the gait cycle of a foot with forefoot varus?
excessive pronation in stance
pt can’t push off and will probably compensate (i.e. push off with knee –> patella femoral symptoms)
Genu vara can cause excessive ____________ at the foot/ankle.
supination
