23: Abnormal STJ motion - Mahoney

Question 1

movement of the STJ axis occurs in what planes

Answer 1

transverse and frontal

due to anatomical position of the axis, very little normal movement occurs in sagittal plane

Question 2

normal position of STJ acis

Answer 2

16 from sagittal
42 from transverse
48 from frontal

Question 3

what planes can we find angular deviations of STJ axis?

Answer 3

sagittal plane and transverse plane (usually a pt has both)

Question 4

CKC internal rotation of the leg causes the STJ to …

Answer 4

pronate

external rotation of leg causes the STJ to supinate

Question 5

normal STJ pitch

Answer 5

pitch = location from the transverse plane

- normal pitch ranges from 35-45 degrees (42 avg)

Question 6

higher pitch/ more vertical STJ axis leads to …

Answer 6

• less STJ inversion and eversion in response to rotation of the leg
• more abduction and adduction of the foot in response to internal and external rotation of the leg
• more postural and leg complaints

Question 7

more vertical/higher pitch, more motion occurs in _______ plane

Answer 7

horizontal or transverse

The more horizontal the STJ axis (the lower the pitch), the more motion occurs in the frontal plane

Question 8

causes more inversion/eversion

Answer 8

low STJ axis/low pitch

Question 9

more adduction/abduction of foot

Answer 9

more vertical axis to the STJ

Question 10

How can we determine whether STJ axis is high or low clinically?

Answer 10

With the foot in STJ neutral, a high axis exists if the examiner can move the heel with more adduction/abduction than inversion/eversion

(very subjective and unreliable)

Question 11

patients will generally relate more medial knee pain than foot complaints

Answer 11

high pitched STJ axis

because allows more abduction/adduction it places an increased strain on the knee

Question 12

severe foot abnormalities b/c each degree of rotation of leg means more STJ inversion and eversion

Answer 12

low pitch axis (less than 35)

low pitched axis allows more frontal plane calcaneal rotation with every degree of transvers plane motion of tibia

Question 13

where do you find a keratoma with low pitch axis?

Answer 13

under 2nd and 3rd met heads

also see medial arch strain

Question 14

with a normal STJ axis, more of the WB surface of forefoot is ________ to STJ axis

Answer 14

lateral

When STJ axis is oriented within normal range (through 1st intermetatarsal space), more of the weight bearing surface of the calcaneus (rearfoot) is medial to the STJ axis and the more of the weight bearing surface of the forefoot is lateral to the STJ axis

normal transverse plane orientation is 16 degrees

Question 15

how do you measure transverse plane deviation of STJ ?

Answer 15

kirby method (pushing on foot with dots)

• Place STJ in neutral and lock MTJ by stabilizing the 5th metatarsal head
• Palpate for the axis by applying force medial and lateral to the STJ axis
• There will be no rotation when directly on the axis

Question 16

why does a medially displaced STJ axis lead to pronation?

Answer 16

STJ axis is considered medially displaced if the axis is noted to lie medial to the 1st intermetatarsal space

This is important because the foot will lose some of its supinatory torques from the calcaneus and gain additional pronatory torque from the forefoot’s longer lever arm on the lateral side of the axis

Question 17

s/s medially deviated STJ axis

Answer 17

• STJ pronates to its end ROM [i.e., if the deformity(ies) causes the calcaneus to evert past 3°, the calcaneus will continue to evert until it has used up all of its available STJ eversion]
• Forefoot symptoms
• Arch fatigue
• Medial midfoot and rearfoot ligamentous strain
• Pathologies of the lower leg, knee, pelvis and spine

Question 18

STJ axis is considered laterally displaced if …

Answer 18

the axis is noted to lie lateral to the 1st intermetatarsal space

leads to more lateral foot and ankle pain

Question 19

why does a laterally displace STJ axis lead to more supinatory foot?

Answer 19

laterally displaced STJ axis will cause loss of pronatory torque from the lateral forefoot and gain additional supinatory torque from the medial forefoot and the calcaneus

Question 20

As the STJ axis increases its distance from the transverse plane …

Answer 20

more abduction occurs AND more transverse plane movement occurs

Question 21

A patient exhibits a flatfoot with a transverse plane dominance. Which of the following is /are true?
A: The axis of motion lies in the frontal and sagittal planes
B: The axis of motion lies in the transverse and sagittal planes
C: The STJ is more horizontal
D: Forefoot abduction will predominate
E: Calcaneal eversion will predominate

Answer 21

A and D

Question 22

when is position of calcaneus most critical?

Answer 22

stance phase of gait

Question 23

how are positional displacement of calcaneus and STJ axis related?

Answer 23

calcaneal position changes the applied force to STJ axis

Question 24

A line that bisects the longitudinal axis of the tibia will pass through …

Answer 24

the middle of the talus which is locked in the ankle mortise (tibio-talar unit)

A line that bisects the middle of the calcaneus will almost always lie lateral to the tibio-talar bisection (called the calcaneal translational displacement)

Question 25

what x ray do you order to assess calcaneal position?

Answer 25

long leg axial

Question 26

“calcaneal translational displacement”

Answer 26

A line that bisects the middle of the calcaneus will almost always lie lateral to the tibio-talar bisection

5-10 mm is the normal amount of lateral displacement

Question 27

if calcaneal translational displacement is greater than 10 mm lateral to bisection of tibia …

Answer 27

then ground force causes the heel to evert (body of the heel is lateral to the STJ axis)

If medial to the bisection of the tibia, then ground force causes heel to invert (body of the heel is medial to the STJ axis)

Question 28

what is a koutsogiannis osteotomy?

Answer 28

One of the options to correct a flatfoot is to transpose the body of the calcaneus more medially in order to create a supinatory moment of the STJ

Question 29

what happens if you remove a wedge of bone with the base lateral (dwyer osteotomy) ?

Answer 29

One of the options to correct a cavus foot is to move the body of the calcaneus more laterally in order to create a pronatory moment of the STJ

In these cases, the calcaneus is also inverted and is determined by measuring the calcaneal tibial angle

Question 30

normal calcaneal tibial angle

Answer 30

between 2 degrees varus and 4 degrees valgus

pes cavus will have greater than 2 degrees varus typically

Question 31

If the STJ axis lies closer to the horizontal (transverse) and sagittal planes, the deformity …

If the STJ axis lies closer to the vertical (frontal) and sagittal planes, the deformity is …

If the STJ axis lies closer to the frontal and horizontal planes, the deformity …

Answer 31

If the STJ axis lies closer to the horizontal (transverse) and sagittal planes, the deformity is frontal plane dominant and there is more inversion-eversion

If the STJ axis lies closer to the vertical (frontal) and sagittal planes, the deformity is transverse plane dominant and there is more adduction-abduction

If the STJ axis lies closer to the frontal and horizontal planes, the deformity is sagittal plane dominant and there is more dorsiflexion-plantarflexion

Question 32

A foot that is pronated will have the body of the calcaneus positioned:

Answer 32

greater than 10 mm lateral to tibiotalar bisection