The Sole and Arches of The Foot

Question 1

Draw a simple diagram illustrating the cutaneous innervation of the sole of the foot.

Answer 1

[Diagram]

Question 2

Briefly describe the deep fascia of the foot. (Parts, orientation of the collagen fibers …)

Answer 2

1. The deep fascia of the foot consists of 3 parts: central, medial and lateral.
2. The central part is very thick and termed plantar aponeurosis. The medial and lateral parts are thin and termed the medial and lateral plantar fasciae respectively.
3. The collagen fibres are arranged longitudinally in the plantar aponeurosis and transversely in the medial and lateral plantar fasciae.
4. [Diagram]

Question 3

The medial and lateral plantar nerves are terminal branches of the ________ nerve.

Answer 3

tibial nerve
[Diagram]

Question 4

Name the three muscles of the first layer of the foot from medial to lateral. State their innervation and functions.

Answer 4

1. Abductor hallucis; medial plantar nerve; abduction and flexion of the great toe
2. Flexor digitorum brevis; medial plantar nerve; toe flexion at metatarsophalangeal joints of the lateral four digits
3. Abductor digiti minimi; lateral plantar nerve; abduct 5th toe and hence support lateral longitudinal arch during walking/running
4. [Diagram]

Question 5

Name the muscles and tendons of the second layer of the foot. State the innervation and function of the muscles.

Answer 5

Muscles:
Quadratus plantae (lateral plantar nerve; flex the toes)
Lumbricals (first lumbrical is innervated by the medial plantar nerve and the other three are innervated by the lateral plantar nerve; flexion and adduction of the toes)
Tendons: (of) flexor hallucis longus and flexor digitorum longus
[Diagram]

Question 6

Name the muscles of the third layer of the foot. State their innervation and actions.

Answer 6

1. Flexor digiti minimi brevis: superficial branch of the lateral plantar nerve, flexion of small toe at metatarsophalangeal joint and supports lateral longitudinal arch
2. Adductor hallucis: lateral plantar nerve, adduction and flexion of the great toe and supports the medial longitudinal arch
3. Flexor hallucis brevis: medial plantar nerve, flexes great toe at metatarsophalangeal joint and supports medial longitudinal arch
4. [Diagram]

Question 7

Name 2 intrinsic muscles in the deepest layer of foot and state their innervation. (2 marks)

Answer 7

Dorsal and plantar interossei
Innervation: Lateral plantar nerve
[Diagram]

Question 8

State the pillars, summit and joints of the medial longitudinal arch.

Answer 8

Pillars
a) The medial half of the calcaneum forms the posterior pillar of the medial longitudinal arch.
b) The heads of the medial three metatarsals form the anterior pillar of the medial longitudinal arch.
Summit
superior articular surface of talus (keystone is talus)
Joints
talocalcaneonavicular and subtalar joints

Question 9

State the pillars, summit and joints of the lateral longitudinal arch.

Answer 9

Pillars
The posterior pillar of the lateral longitudinal arch is formed by the lateral tubercle of the calcaneum and the anterior pillar is formed by the heads of the lateral two metatarsals.
Summit
calcaneus; superior surface (keystone is cuboid)
Joints
Calcaneocuboid joint

Question 10

Why is the medial longitudinal arch of the foot higher than the lateral longitudinal arch of the foot?

Answer 10

The medial arch is formed by the calcaneus, talus, navicular, three cuneiforms, and the first three metatarsal bones. The shape and arrangement of these bones create a higher arch compared to the lateral side.

Question 11

Name the factors maintaining the medial longitudinal arch. (Hint: bones, intersegmental ties, sling, tie beams)

Answer 11

[Diagram: supports of a stone bridge]

Bones
✓ The wedge shape of the bones
✓ The talus is the keystone of the arch

Intersegmental ties
✓ Plantar calcaneonavicular ligament (Spring ligament)
✓ Interosseous ligaments

Sling
✓ Tibialis anterior
✓ Tibialis posterior
✓ Flexor hallucis longus
[Diagram]

Tie beams
✓ plantar aponeurosis (medial half)
✓ abductor hallucis
✓ flexor hallucis brevis

Question 12

Name the factors maintaining the lateral longitudinal arch. (Hint: bones, intersegmental ties, sling, tie beams)

Answer 12

[Diagram: supports of a stone bridge]

Bones
✓ Wedge-shape of the bones
✓ Cuboid is the keystone of the arch

Intersegmental ties
✓ short plantar ligament
✓ long plantar ligament
✓ interosseous ligaments
[Diagram]

Sling
✓ fibularis longus
✓ fibularis brevis
✓ fibularis tertius
[Diagram 1] [Diagram 2]

Tie beams
✓ plantar aponeurosis (lateral half)
✓ abductor digiti minimi
✓ flexor digiti minimi brevis

Question 13

State the functions of the arches of the foot.

Answer 13

1. Distribute the body weight to the weight-bearing points of the sole (e.g., heel; balls of the toes, mainly those of first and fifth toes and lateral border of the sole).
2. Act as shock absorber during jumping by their spring like action.
3. The medial longitudinal arch provides propulsive force during locomotion.
4. The lateral longitudinal arch functions as a static organ of support and weight transmission.
5. The concavity of the arches protects the nerves and vessels of the sole.

Question 14

Identify the deformity and state its effects: [Click here].

Answer 14

Identification: pes planus (flat foot) [collapse of the medial longitudinal arch]
Effects:
1. clumsy/shuffling gait due to loss of spring in the foot
2. the foot becomes more liable to trauma due to loss of the shock absorbing function
3. there may be compression of the nerves and vessels of the sole due to loss of its concavity

Question 15

Identify the deformity: [Click here].

Answer 15

pes cavus (high-arched foot) [exaggeration of the longitudinal arch]

Question 16

Identify and briefly describe the deformity: [Click here].

Answer 16

talipes equinovarus: the most common deformity of the foot; the foot is adducted, inverted and plantar flexed

Question 17

Identify and briefly describe the deformity: [Click here].

Answer 17

talipes equinovalgus: the foot is abducted, everted and plantar flexed. The weight of the patient rests on the medial border of the foot and the medial arch is absent.

Question 18

Name and briefly describe the four phases of walking.

Answer 18

1. Heel strike
   ✓ This is the initial stage where the foot hits the ground, heel first.
   ✓ The gluteus maximus decelerates the forward motion of the lower limb.
   ✓ The quadriceps femoris keeps the leg extended at the knee joint and the thigh flexed at the hip.
   ✓ The anterior compartment of the leg maintains the ankle dorsiflexion, positioning the heel for the strike.
2. Support
   ✓ After the heel strike, the rest of the leading foot hits the ground.
   ✓ The foot inverters and evertors contract in a balanced manner to stabilize the foot.
   ✓ Gluteus minimus, medius and tensor fascia lata contract, keeping the pelvis level by counteracting the imbalance created from having most of the body weight on one leg.
3. Toe-Off
   ✓ In this phase, the foot prepares to leave the ground - heel first, toes last.
   ✓ The hamstring muscles extend the thigh at the hip.
   ✓ The quadriceps femoris maintains the extended position of the knee.
   ✓ The posterior compartment of the leg plantarflexes the ankle.
4. Swing
   ✓ This is the final phase where the raised leg is propelled forward.
   ✓ The iliopsoas and rectus femoris flex the thigh at the hip.
   ✓ Quadriceps femoris extends the leg at the knee, positioning the foot for landing.
   ✓ The anterior compartment of the leg maintains ankle dorsiflexion so that the heel is in place for landing.
5. [Video: 1 min]