Feet and ankle

Question 1

Mechanical concept behind the arches of the foot

Answer 1

Arch can be thought of like a bridge

The keystone:
– the talus (wedge shape stone and is the most important in a bridge)

The staples (little ligaments that hold the foot together):
– small ligaments joining the tarsals and other foot bones together
—- (short plantar ligament)
—- (long plantar ligament)
—- (calcaneonavicular ligament)

The beam:
– tendon of the flexor hallucis longus
—- comes all the way down and attaches onto the medial border

The suspension:
– supplied by the peroneus longus
—- comes all the way down the lateral border underneath the foot and attached onto the medial cuneiform

The truss windlass mechanism

Question 2

Roll and slide mechanism

Answer 2

Concave on convex- they roll and slide away from each other

Concave- tibia
Convex- talus

Pivot point- mid talus

In both plantar and dorsi flexion, the tibia and the talus passively allow movement from the foot

Plantar flexion:
– talus rolls posteriorly on calcaneum
– tibia slides anteriorly on superior talus

Dorsi flexion:
– talus rolls anteriorly on calcaneum
– tibia slides posteriorly on superior talus

Question 3

The role of the arches during walking

Answer 3

The longitudinal arches (medial and lateral) act like a twisting flexible ruler

Increased twist on the medial arch leads to inversion, whilst decreased twist leads to eversion

This control on the medial arch allows small joints of the foot to be stabilised during propulsion and intrinsic muscles to produce leverage during propulsion (the act of moving or pushing an object forward)

This is supported by the long and short plantar ligaments and action of the tibias anterior and posterior

The lateral arch relies on the ‘keystone’ role of the cuboid for stability

Question 4

Role of the talus in locomotion

Answer 4

The talus acts as a torque converter, causing rotations of the leg to be converted to inversion and eversion vectors in the foot

This helps adaptation of the foot to ground reaction forces. Good for loose pack positioning after heel strike

Locking of the talus during toe off creates a stable base for weight bearing and propulsion

The tibia and fibular movements on the talus is a sliding movement which acts in the opposite movement to the talus which rolls on the calcaneum

Question 5

Neurological mechanisms involved with the foot

Answer 5

Central control- control from the brain and spinal cord (CNS)

Local control- the spinal nerves as they descend into peripheral nerves and their relationship with muscles and ligaments

Corrective measures

Feedback loops- corrective measures are apart of this, how we correct our walking.
– e.g: from ground reaction forces and different terrains how we adapt to that

Equilibrium:
– extrapyramidal system-
—- happens around the medulla oblongata
—- controls muscle tone and posture
—- they maintain postural equilibrium via active adaptation. e.g: hip shift on walking

– basal ganglia-
—- smooths out motor behaviour and inhibits unwanted movements

Central control:
– decides we want to walk from Fulton house to the library, this gets sent down and the basal ganglia will make sure that this action is smooth.

Sensory feedback:
– peripheral nerves
– via visual, vestibular and proprioceptive mechanisms
—- this is a feedback loop

Predictive or anticipatory postural control:
– feed forward loop
– this is critical for successful execution of any voluntary movement whether it is episodic or rhythmic

e.g:
– anticipatory load of putting the joints into the correct position for the desired movement

Question 5

Neurological mechanisms involved with the foot

Answer 5

Central control- control from the brain and spinal cord (CNS)

Local control- the spinal nerves as they descend into peripheral nerves and their relationship with muscles and ligaments

Corrective measures

Feedback loops- corrective measures are apart of this, how we correct our walking.
– e.g: from ground reaction forces and different terrains how we adapt to that

Equilibrium:
– extrapyramidal system-
—- happens around the medulla oblongata
—- controls muscle tone and posture
—- they maintain postural equilibrium via active adaptation. e.g: hip shift on walking

– basal ganglia-
—- smooths out motor behaviour and inhibits unwanted movements

Central control:
– decides we want to walk from Fulton house to the library, this gets sent down and the basal ganglia will make sure that this action is smooth.

Sensory feedback:
– peripheral nerves
– via visual, vestibular and proprioceptive mechanisms
—- this is a feedback loop

Predictive or anticipatory postural control:
– feed forward loop
– this is critical for successful execution of any voluntary movement whether it is episodic or rhythmic

e.g:
– anticipatory load of putting the joints into the correct position for the desired movement

Question 6

Talus

Answer 6

Has 3 facets:
– anterior, middle and posterior

Has no muscular attachments what so ever, and it responds passively to everything around it

Very important, as if your talus isn’t in the right position, then your foot and ankle mechanics will start to fail very quickly

Ligaments its dependant upon:
– cervical talocalcaneal ligament
– interosseous talocalcaneal ligament:
—- they act like ACL and PCL of the knee but in the ankle
—- they control the sheering between the talus and the calcaneus

Question 7

The truss windlass mechanism

Answer 7

Formed due to the attachments of soft tissue structures like the plantar fascia, flexor hallucis longus and peroneus longus

The way the windlass works:
– when the big toe dorsi flexes up during walking, the metatarsal will plantar flex drawing the mid foot up allowing it to stay rigid and secure during gait and running
– when the big toe is plantar flexed, the metatarsal will dorsi flex (the foot is in an unstable position in this position).