Biomechanics Ankle

Question 1

when the talocrural joint or subtalar joint are described to have a tri-plane axis, what does that mean?

Answer 1

movement “cuts through” each cardinal plane, but the joints do not have 3 degrees of freedom
there is 1 degree of freedom

Question 2

subtalar joint pronation

-what motion is occurring in each plane?

Answer 2

transverse
-adduction of talus
sagittal
-plantarflexion of talus
frontal
-eversion of calcaneus

Question 3

subtalar joint supination

-what motion is occurring in each plane

Answer 3

transverse
-abduction of talus
sagittal
-dorsiflexion of talus
frontal
-inversion of calcaneus

Question 4

suffixes

• what suffix do you use to describe static posture of the foot
• to describe foot motion

Answer 4

posture
-“-ed”
-patient is standing in a pronated position
motion
-“ion”
-patient is undergoing pronation while walking

Question 5

ankle joint complex consists of the upper and lower ankle joint
-what is the joint at each of these areas?

Answer 5

upper
-talocrural (ankle) joint
lower
-subtalar joint

Question 6

talocrural joint

-joint type

Answer 6

diarthrodial or synovial joint

classified as a hinge or ginglymus type

Question 7

talocrural joint

• loose pack position
• closed pack position

Answer 7

loose pack
-position in which joint capsule and surrounding tissues are most relaxed
-20 degrees of plantar flexion
closed pack
-maximum dorsiflexion

Question 8

talocrural joint

-arthrokinematic rule (open chain)

Answer 8

convex on concave

Question 9

talocrural joint mortise

• formed by…
• function

Answer 9

formed by
-distal tibia (medial malleolus and plafond)
-fibula
act as a wrench on the talus
-adjustable wrench

Question 10

proximal tib-fib joint

-static structures

Answer 10

anterior and posterior tib-fib ligaments

Question 11

distal tib-fib joint

-static structures

Answer 11

anterior and posterior tib-fib ligaments

interosseous membrane

Question 12

talocrural joint talus articular surfaces

Answer 12

superior
medial
lateral

Question 13

talocrural joint talus

• what is it’s shape?
• consequence

Answer 13

cone shaped (not a cylinder)
body of talus is wider anteriorly than posteriorly
result
-mortise needs to be an adjustable wrench to accept talus during max DF
-this is why max DF is closed pack position

Question 14

as mortise widens to accept talus in max DF, what occurs at the proximal tib-fib joint?

Answer 14

fibula glides laterally and superiorly

superior movement is transferred proximally to proximal tib-fib joint

Question 15

talocrural joint capsule

• thickness
• where is it weakest
• stability highly dependent on…

Answer 15

very thin
weakest anteriorly and posteriorly
stability highly dependent on collateral ligaments
-lateral and medial collateral ligaments

Question 16

lateral collateral ligaments

-names

Answer 16

anterior talofibular ligaments
calcaneofibular ligaments
posterior talofibular ligaments

Question 17

medial ligament of the ankle (broad name)

Answer 17

deltoid ligament

Question 18

talocrural joint axis

• where does the axis run (from a clinical standpoint)
• primary motions

Answer 18

axis runs beneath the distal tips of the malleoli
primary motions
-dorsiflexion (normal ROM 10-20)
-plantarflexion (normal ROM 20-50)

Question 19

talocrural joint functions

Answer 19

provides “rocker” action during stance phase
-permits smooth progression of the body over the stance limb
talocrural coupling

Question 20

what is talocrural coupling

Answer 20

transfer point of transverse plane rotation of the lower extremity into frontal plane motion of the foot
serves as the body’s “U” joint

Question 21

functional phases of walking

Answer 21

contact phase
midstance phase
terminal stance

Question 22

during dynamic activities (such as walking), femoral and lower leg rotation are caused by…

Answer 22

pelvic rotation in the transverse plane

Question 23

lower leg rotation and talocrural coupling in standing (remember the example where we stood up)
what motions occur at the lower leg, talus, and foot during
-posteiror pelvic movement
-anterior pelvic movement

Answer 23

posterior pelvic movement
-tibial ER
-upward gliding of talus
-foot supination
anterior pelvic movement
-tibial IR
-inward gliding of talus
-foot pronation

Question 24

action of plantarflexors during terminal stance in walking

• which muscles do what?
• result

Answer 24

calf muscles, tibialis posterior, FDL
-plantarflexion with hindfoot inversion
fibularis longus and brevis
-plantarflexion with hindfoot eversion
result
-enhances talocrural joint stability

Question 25

fibularis longus unique action during terminal stance

Answer 25

stabilizes first metatarsal as forefoot loaded medially in terminal stance