Midtarsal Joint Flashcards
What does the midtarsal joint consist of?
calcaneocuboid joint + talonavicular joint
what is midtarsal joint aka?
Chopart’s joint
the midtarsal joint has a longitudinal axis and an oblique axis. what is the longitudinal axis?
(runs proximal, plantar and lateral to distal, dorsal and medial)
-is 15 degrees from transverse plane and 9 degrees from sagittal plane
what is the primary motion about the longitudinal axis of MTJ?
frontal plane motion (inversion/eversion)
describe the oblique axis of the MTJ.
(runs proximal, plantar and lateral to distal, dorsal and medial)
-is 52 degrees from transverse plane and 57 degrees from sagittal plane
what is the primary motion about the oblique axis of MTJ.
There is equal motions about the transverse plane (abduction/adduction) and sagittal plane (dorsiflexion/plantarflexion)
*PADs/DABs
what does the longitudinal axis of MTJ allow the foot to do?
allows foot to adapt to subtalar joint variations and allows foot to remain plantargrade
Ex. forefoot can:
-invert on everted rearfoot
-evert on inverted rearfoot
what is the purpose of the oblique axis of the MTJ?
“secondary ankle joint”- oblique axis can compensate for lack of ankle dorsiflexion
in which position is the “unlocked” MTJ?
STJ pronation
what happens in STJ pronation?
MTJ axes become more parallel –> unlocks MTJ –> allows foot to become mobile adaptor
what happens in STJ supination?
MTJ axes cross –> locks MTJ –> foot becomes rigid lever and decreases ROM
in which position is the “locked” MTJ and rigid lever?
STJ supination
in which position are the MTJ axes crossed? paralle?
STJ pronation = MTJ axes parallel
STJ supination = MTJ axes crossed
which position of STJ is more stable?
STJ supination (axes crossed = rigid lever)
which position of MTJ is more stable?
MTJ pronation
as STJ supinates- which is more stable, MTJ pronates
which position of MTJ is unstable?
MTJ supination
what happens to calcaneocuboid joint when MTJ pronates?
calcaneocuboid joint dorsiflexes (cuboid rotates up into dorsolateral overhang on the calcaneus)
*ligaments also tighten, preventing excessive motion
what happens to bones and ligaments when MTJ supinates?
ligaments will also tighten
bones, however, are not tightly packed (osseous locking not present)
how do you “lock” MTJ?
place STJ in neutral. then push up on 4th and 5th metatarsal heads to simulate WB.
what happens during contact period of gait? (in regards to OA, LA, STJ)?
OA- pronated (EDL and peroneus tertius activated –> allows dorsiflexion and abduction)
LA- supinated (anterior tibialis muscle contracted –> inversion)
STJ pronated to allow for shock absorption
what hapens during midstance?
STJ- supinated to prepare for propulsion
LA- pronated to help lock the MTJ to become a rigid lever
OA- pronated (dorsiflexed and abducted)
what happens during propulsion?
STJ is supinated
LA- pronated (locking still present at CC joint)
OA- supinated (windlass mechanism- big toe dorsiflexes and pulls on plantar fascia to help contract intrinsic muscles and the arch height increases)
MTJ ROM is controlled by what?
passively control by the position of STJ
STJ supination - causes decrease in MTJ ROM - “locked axes”
STJ pronation- causes increase in MTJ ROM
MTJ position is controlled by what?
GRF during stance phase of gait and by surrounding muscles during other phases
