Chapter 23: Biomechanics of the foot Flashcards
What is subtalar motion?
Inversion
Eversion
What is transverse tarsal motion?
Adduction
Abduction
What is ankle motion:
Plantarflexion
Dorsiflexion
What is pronation?
Dorsiflexion of the ankle
Eversion of the subtalar joint
Abduction of the transverse tarsal joint
What is supination?
Plantarflexion of the ankle
Inversion of the subralar joint
Adduction of the transverse tarsal joint.
Where is the axis of the ankle joint?
Just distal to the tip of each malleolus
What is the ROM of dorsiflexion?
20 degrees
What is the ROM of plantarflexion?
50 degrees
Where is the axis of the subtalar joint?
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.
What is the ROM of inversion?
30 degrees
What is the ROm of eversion
10 degrees
When does eversion and inversion occur in normal walking?
At initial contact until about 15% of the stance phase, after which progressive inversion occurs until the time of toe off.
For individuals with flat feet, what degree of eversion is present?
12 degrees
For individuals with cavus feet, what degree of eversion is present?
Less than 8 degrees
Which joints does the subtalar joint depend on to move correctly?
Talonavicular
Calcaneocuboid
The transverse tarsal joint consists of which joints?
Talonavicular
Calcaneocuboid joints
When the subtalar joint is in an everted position, the transverse tarsal joint axes are what?
Parallel and it is flexible
When during gait is the transverse tarsal joint flexible?
During initial contact when impact absorption is desired.
Subtalar joint inversion causes the transverse tarsal joint to do what?
The axes become noparallel and the joint becomes rigid.
What motion occurs in the metatarsophalangeal joint?
Dorsiflexion and plantarflexion
What ROM of dorsiflexion is seen at the metatarsophalangeal joint?
60 degrees
What degree of plantarflexion is seen in the metatarsophalangeal joint?
20 degrees
Where is the origin and insertion of the plantar aponeurosis?
Origin: Tubercle of the calcaneus
It passes distally to insert: Proximal phalanx of each toe.
It surrounds the sesamoid bones of the great toe.
In gait, what role does the aponeurosis play?
It helps in the transition from a supple to a rigid foot.
How does the plantar aponeurosis change the foot from flexible to rigid?
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.
Pulling the plantar aponeurosis distally does what?
Assists in inversion of the calcaneus because of the medially based origin.
At heel strike, what motion occurs in the transverse plane?
Calcaneus eversion is transmitted proximally acorss the ankle joint and results in internal rotation of the leg.
At the last half of stance phase, what motion occurs in the transverse plane?
External rotation initiated by external rotation of the pelvis as the swing leg moves forward, causing the subtalar joint to invert.
What is a steppage gait?
Increased flexion of hp an dknee provide adequate toe clearance given the lack of dorsiflexion at the ankle joint.
What are the events that occur at initial contact?
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.
What events occur at toe-off?
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
What are the sagittal plane activities that occur during gait?
Ankle joint motion Metatarsophalangeal joint motion Plantar aponeurosis function Intrinsic muscle function Configuration of the talonavicular joint.
Following initial contact, what occurs?
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.
Following foot flat, what occurs?
Progressive dorsiflexion of the ankle, controlled by eccentric contraction of the posterior calf muscles.
At 40% of the gait cycle, what occurs?
Plantarflexion of the ankle joint due to concentric contraction of the posterior calf muscles.
When does concentric contraction of the posterior calf muscles end and change to eccentric contraction again?
50% of the gait cycle
How does the stability of the talonavicular joint change during gait?
At initial contact it is unstable, but progressively increases stability as increased force is placed across the joint in the last half of stance.
What are the transverse plane mechanisms that occur?
Rotation of the lower extremity, particularly the tibia
Subtalar joint motion
Transverse tarsal joint motion
Function of the metatarsal break.
What is the suggested angle a foot should be placed in for an ankle fusion?
90 degrees at the ankle
3-5 degrees of valgus
Degree of external rotation should equal that of the opposite side.
