Chapter 23: Biomechanics of the foot

Question 1

What is subtalar motion?

Answer 1

Inversion

Eversion

Question 2

What is transverse tarsal motion?

Answer 2

Adduction

Abduction

Question 3

What is ankle motion:

Answer 3

Plantarflexion

Dorsiflexion

Question 4

What is pronation?

Answer 4

Dorsiflexion of the ankle
Eversion of the subtalar joint
Abduction of the transverse tarsal joint

Question 5

What is supination?

Answer 5

Plantarflexion of the ankle
Inversion of the subralar joint
Adduction of the transverse tarsal joint.

Question 6

Where is the axis of the ankle joint?

Answer 6

Just distal to the tip of each malleolus

Question 7

What is the ROM of dorsiflexion?

Answer 7

20 degrees

Question 8

What is the ROM of plantarflexion?

Answer 8

50 degrees

Question 9

Where is the axis of the subtalar joint?

Answer 9

In the transverse plane, it deviates 23 degrees medially from the long axis of the foot.
In the sagittal plane, it deviates 40 degrees superiorly to the horizontal plane.

Question 10

What is the ROM of inversion?

Answer 10

30 degrees

Question 11

What is the ROm of eversion

Answer 11

10 degrees

Question 12

When does eversion and inversion occur in normal walking?

Answer 12

At initial contact until about 15% of the stance phase, after which progressive inversion occurs until the time of toe off.

Question 13

For individuals with flat feet, what degree of eversion is present?

Answer 13

12 degrees

Question 14

For individuals with cavus feet, what degree of eversion is present?

Answer 14

Less than 8 degrees

Question 15

Which joints does the subtalar joint depend on to move correctly?

Answer 15

Talonavicular

Calcaneocuboid

Question 16

The transverse tarsal joint consists of which joints?

Answer 16

Talonavicular

Calcaneocuboid joints

Question 17

When the subtalar joint is in an everted position, the transverse tarsal joint axes are what?

Answer 17

Parallel and it is flexible

Question 18

When during gait is the transverse tarsal joint flexible?

Answer 18

During initial contact when impact absorption is desired.

Question 19

Subtalar joint inversion causes the transverse tarsal joint to do what?

Answer 19

The axes become noparallel and the joint becomes rigid.

Question 20

What motion occurs in the metatarsophalangeal joint?

Answer 20

Dorsiflexion and plantarflexion

Question 21

What ROM of dorsiflexion is seen at the metatarsophalangeal joint?

Answer 21

60 degrees

Question 22

What degree of plantarflexion is seen in the metatarsophalangeal joint?

Answer 22

20 degrees

Question 23

Where is the origin and insertion of the plantar aponeurosis?

Answer 23

Origin: Tubercle of the calcaneus
It passes distally to insert: Proximal phalanx of each toe.
It surrounds the sesamoid bones of the great toe.

Question 24

In gait, what role does the aponeurosis play?

Answer 24

It helps in the transition from a supple to a rigid foot.

Question 25

How does the plantar aponeurosis change the foot from flexible to rigid?

Answer 25

As the body passes forwar across the foot, the metatarsophalangeal joints are passibely dorsiflexed. The aponeurosis is drawn forward over the metatarsal heads and at the same time depresses them. This results in elevation of the longitudinal arch and provides considerable stability to the arch structure.

Question 26

Pulling the plantar aponeurosis distally does what?

Answer 26

Assists in inversion of the calcaneus because of the medially based origin.

Question 27

At heel strike, what motion occurs in the transverse plane?

Answer 27

Calcaneus eversion is transmitted proximally acorss the ankle joint and results in internal rotation of the leg.

Question 28

At the last half of stance phase, what motion occurs in the transverse plane?

Answer 28

External rotation initiated by external rotation of the pelvis as the swing leg moves forward, causing the subtalar joint to invert.

Question 29

What is a steppage gait?

Answer 29

Increased flexion of hp an dknee provide adequate toe clearance given the lack of dorsiflexion at the ankle joint.

Question 30

What are the events that occur at initial contact?

Answer 30

Heel pad striking the ground Controlled ankle plantarflexion Eversion of the calcaneus, which results distally in parallel axes of the tranverse tarsal joint, thereby making the joint flexible, and proximally in enhancement of internal rotation of the lower extremity.

Question 31

What events occur at toe-off?

Answer 31

Progressive external rotation of the tibia Subtalar joint inversion Transverse tarsal joint axes made nonparallel, resulting in locking of the joint. Dorsiflexion of the metatarsophalangeal joint, resulting in the plantar aponeurosis elevating the longitudinal arch. Seating of the talonavicular joint

Question 32

What are the sagittal plane activities that occur during gait?

Answer 32

``` Ankle joint motion Metatarsophalangeal joint motion Plantar aponeurosis function Intrinsic muscle function Configuration of the talonavicular joint. ```

Question 33

Following initial contact, what occurs?

Answer 33

Rapid plantarflexion of the ankle joint mediated by eccentric contraction of the anterior compartment muscles. This also help to advance the tibia forward over the fixed foot.

Question 34

Following foot flat, what occurs?

Answer 34

Progressive dorsiflexion of the ankle, controlled by eccentric contraction of the posterior calf muscles.

Question 35

At 40% of the gait cycle, what occurs?

Answer 35

Plantarflexion of the ankle joint due to concentric contraction of the posterior calf muscles.

Question 36

When does concentric contraction of the posterior calf muscles end and change to eccentric contraction again?

Answer 36

50% of the gait cycle

Question 37

How does the stability of the talonavicular joint change during gait?

Answer 37

At initial contact it is unstable, but progressively increases stability as increased force is placed across the joint in the last half of stance.

Question 38

What are the transverse plane mechanisms that occur?

Answer 38

Rotation of the lower extremity, particularly the tibia Subtalar joint motion Transverse tarsal joint motion Function of the metatarsal break.

Question 39

What is the suggested angle a foot should be placed in for an ankle fusion?

Answer 39

90 degrees at the ankle 3-5 degrees of valgus Degree of external rotation should equal that of the opposite side.