subtalar joint Flashcards
articulation
formed by 3 separate plane articulations
b/w the talus superiorly and the calcaneus inferiorly
together they will provide triplaner movement around a single joint axis
what is normal ROM and fxining of this joint critical for
dampening the rotational forces imposed by the body weight while maintaining contact of the foot with the supporting surface
what does the talocalcaneal joint prevent
unwanted movements
3 articular facets
posterior
anterior and medial
posterior facet
concave on convex
largest of the 3 facets
concave talus articulating w/ a convex facet on the body of the calcaneus
has its own joint capsule
anterior and medial facet
convex facets on the inferior body and neck of the talus and 2 concave facets on the calcaneus
2 articulations will share a joint capsule w/ the talonavicular joint
subtalar joint ligaments
very stable joint with strong ligamentous support
4 major ligaments
4 major ligs of the subtalar joint
interosseous talocalcaneal lig
ligamentum cervicis
posterior talocalcaneal ligaments
lateral talocalcaneal ligaments
arthrokinematics
complex twisting or screw like motion
can continue only until the posterior and anterior and middle facets can no longer accommodate the simultaneous and opposite motions
posterior facet –> glide is in the same direction
anterior and middle facets –> glide is in the opposite directions
arthrokinematics motion
rotation
_d/t the different shapes of the articular facets
result of complex arthrokinematics
triplanar motion of the talus around a single oblique joint axis
subtalar joint is a
uni-axial joint w/ 1 degree of freedom
allows for supination and pronation
supination and pronation
component motions w/ movement in each of the 3 planes
component motions DO NOT OCCUR INDEPENDENTLY
subtalar joint can
ABD/ADD
invert/evert
PF/DF
but will always happen together
OKC movements
talus is fixed and the calcaneus and the more distal segments of the foot move on it
OKC supination
combination of
ADD (around a vertical axis)
inversion (around an A-P axis)
PF (around a frontal axis)
what bone moves in OKC supination
calcaneus and distal segments of the foot
calcaneus is in what position during OKC supination
varus
OKC pronation
combo of
ABD (around a vertical axis)
eversion (around an A-P axis)
DF (around a frontal axis)
what bone is moving during OKC pronation
calcaneus and the distal segments of the foot
what position is the calcaneus in during OKC pronation
valgus
pronation was once called
eversion
supination was once called
inversion
axis of motion OKC
orientation of the axis is inclined
42 degrees upward and anterior from the transverse plane
inclined medially 16 degrees from the sagittal plane
subtalar neutral OKC
point in which the calcaneus will invert twice as many degrees as it will evert
CKC arthro
calcaneus is fixed
but is capable of some inversion and eversion with the foot on the group
cannot DF/PF or ABD/ADD (Completed by the talus)
CKC supination
calcaneus will invert
talus will ABD (ER) and DF
CKC pronation
calcaneus will every
talus will ADD (IR) and PF
talar ABD/ADD is sometimes referred to as
IR (ADD), medial rotation
ER (ABD), lateral rotation
d/t occurring on the vertical axis
if the mortise moves (CKC)
the talus moves
most congruent joint in the body
in WB positions…
the lower leg and the subtalar joint are mechanically linked
motion of the lower leg will influence the subtalar joint
motions of the subtalar joint will influence movement at the lower leg
lateral rotary force is imposed on the leg
lateral motion of the tibia carries the ankle mortise and the trochlea of the talus laterally
if the talus laterally rotates (ABD), then the other component motions must occur
when the talus ABDs, it will also DF and the calcaneus will invert (occur simultaneously)
what if the subtalar joint is forced into pronation by uneven terrain
talar PF and ADD
calcaneal eversion
the ankle mortise is carried with the subtalar joint and will result in medial rotation of the tibia
what can the subtalar joint do d/t the mechanical link
absorb lateral and medial rotary forces/movements with pronation and supination
does the mechanical link exist in OKC
no
calcaneal movement
easily measured
10 degrees of eversion
20 degrees of inversion
supination ROM
limited by the ligamentum cervicis
considered the closed packed position
lig tension is the greatest
draws articulating surfaces together
pronation ROM
limited by interosseous talocalcaneal ligament
position of mobility for the foot
