Ankle and lower leg intro and arthrology (wk4)

Question 1

Intro of the bones of the lower leg and foot:

Answer 1

-Structure -> relatively long lower leg, shortened but more adaptable foot, 33 joints, large extrinsic muscles for power and short intrinsic muscles for control
-Foot -> Tarsal bones, metatarsals, phalanges (3 for everything but the big toe – which has 2)
>Tiger cubs need MILC (Talus, Calcaneus, Navicular, cuneiforms (Medial, Intermediate Lateral), Cuboid
-One shin bone> -> Movement of the fibula allows greater adaptability whilst keeping flexibility. Includes the superior tibiofibular joint (synovial plane joint) and the inferior tibiofibular joint (syndesmosis)

Question 2

Describe ankle foot function and movement:

Answer 2

-When standing -> weightbearing, stability, adaptability to surface and maintain centre of gravity over base of support
-When moving -> produce force (propulsion), absorb force (deceleration), adaptability to surface and direction, move centre of gravity as base of support changes
-Ankle and foot movements -> Dorsiflexion/plantarflexion, inversion/eversion, toe flexion/extension, toe abduction/adduction (mostly multi-joint movements with muscles acting over multiple joints)

Question 3

Types of joint in the ankle and foot:

Answer 3

-Talocrural joint (hinge joint but has 3 bones which are more cupped over each other) -> synovial hinge joint, dorsiflexion and plantarflexion, mortice and tenon, 3 articular surfaces (trochlea/medial/lateral)
-Lower leg muscles -> Four compartments; superficial posterior, deep posterior, lateral and anterior

Question 4

Describe the structure of the foot (arches):

Answer 4

-Needs to act as a base of support -> flexibility and stress absorption
-Adapt to uneven surfaces -> flexibility and stress absorption
-Shock absorber -> flexibility and stress absorption
-Provide propulsion -> rigidity and stress transmission
-Fulfils both roles (flexibility and stress absorption + rigidity and stress transmission) via an arch system

Question 5

Explain how the arches are stabilised:

Answer 5

-Lateral, medial and transverse arches form the plantar vault ->
* Three main arches – medial (inside of foot), lateral (outside of foot), anterior (across the front of the foot)
* Plantar vault supported by the 3 arches in a shape of a triangle
* Plantar vault contacts ground at 3 points -> A) Head metatarsal 1, B) Head metatarsal 5, C) Calcaneal Tuberosity (knobbly section of heel)
-Shape and bones that comprise each of the lateral, medial and transverse arches ->
* Medial arch -> highest arch, no contact with ground and extremely flexible. Made up of 5 bones; calcaneus, talus, navicular, medial cuneiform, calcaneus.
* Lateral arch -> Flatter than medial arch, in contact with ground and more rigid than medial arch. Made up of 3 bones; calcaneus, cuboid and metatarsal 5.
* Anterior transverse arch -> Relatively flat and contacts ground. Formed by the heads of the 5 metatarsals.

Question 6

Describe keystone arches in the foot:

Answer 6

• Shape of bones -> Example of medial arch. The talus acts as the keystone for the medial longitudinal arch.
• Arches can be supported by the shape of the bones and short ligaments (staples), long soft tissues (tie beam) and muscles pulling on the arch (sling)

Question 7

Explain which type of support (staple, tie beam and sling) provides stability for the 3 main arches of the foot:

Answer 7

• Staple -> Stones are bound together underneath to prevent them being separated by weight. Example: Anterior arch -> The metatarsal heads are connected by deep transverse ligaments
• Tie beam -> Connects the 2 ends of the arch and prevents them separating when weightbearing due to the tie beam. The tie beam of the medial and lateral arches of the foot is the plantar fascia. Plantar fascia is a strong layer of thick, fibrous tissue that spans the length of the foot.
• Sling -> Arch supported from above my ‘cable’. The sling of the lateral arch is the peroneus longus and the contraction of this raises the lateral arch.

Question 8

Describe the movements of the foot during the stance phase of gait:

Answer 8

• Heel strike -> weight is through the calcaneus and arches are raised
• Stance phase -> Vault is flattened – shock absorption. Muscle contract to stop further flattening, known as ‘plantar tighteners’
• Heel off -> Plantar tighteners contract further and foot now is a rigid lever – caught between 2 forces. The plantar flexors are moving up, while the body weight is going down.
• Toe off -> As the big toe extends, plantar fascia tightens, reinforcing medial arch, known as the ‘windlass mechanism’. The toe flexes to help you push off the ground.
• The foot can move off the floor and on the floor

Question 9

Why does the foot need to be flexible to absorb force and when it needs to be rigid to transmit force during gait:

Answer 9

• During walking, the foot can be:
  Flexible -> To act as a shock absorber
  Rigid -> To act as a propulsive lever

Question 10

Describe how the tri-planar movements of inversion and eversion are compromised of other movements:

Answer 10

• Inversion -> Sole of the foot faces inwards
• Eversion -> Sole of the foot faces outwards
• Dorsiflexion -> Foot faces upwards + Plantarflexion -> Foot faces downwards
• Abduction -> Movement away from midline + Adduction -> Movement towards midline
• Pronation -> Foot rolls towards midline + Supination -> Foot rolls away from the midline
• Inversion -> Plantarflexion, Adduction, Supination
• Eversion -> Dorsiflexion, Abduction, Pronation

Question 11

-Describe the bones and articulations of the subtalar and midtarsal joints:

Answer 11

• Foot is split up into 3 sections -> Hindfoot, Forefoot and Midfoot
• Hindfoot -> Movement is at the Subtalar joint.
• Forefoot -> Movement is at the midtarsal joint (transverse joint)

Question 12

Explain how the range of movements and joints allow the foot to adapt to the floor surface:

Answer 12

• Foot on the floor -> Tri-planar motion. Weight transfers medially: ‘pronation’. Wright transfers laterally: ‘supination’.
• Eversion/inversion – the foot/sole actually comes off the floor, whereas with pronation/supination the sole of foot is staying on the floor
• Inversion/eversion -> The forefoot and hindfoot are moving in the same direction ad both doing the same thing/action. In pronation/supination, when the hindfoot rolls in, the forefoot rolls out (relatively)
• Pronation:
  Hindfoot (back) -> Adducts, pronates, plantar flexion
  Forefoot (front) -> Abducts, supinates, dorsiflexion
  +Medial arch flattens
• Supination :
  Hindfoot -> Abducts, dorsiflexion, supinates
  Forefoot -> Adducts, plantar flexion, pronates
  + Medial arch rises