Session 12 Flashcards
Describe the Ankle
- In the upright posture, the ankle is the region that bears all body weight as it is transferred to the foot.
- Centre of gravity of the body passes just in front.
- Instability of this region will lead to a fall (with a tendency to fall forwards)
- Layer of bones and muscles shifts from vertical to horizontal axes
- Injuries occur regularly either as sprains or fractures
- Arteries, motor nerves and tendons enter the foot turning forwards
- Veins, sensory nerves and lymphatics exit the foot turning upwards.
As the long tendons of muscles change direction from verticle to horizontal, what is there a risk of?
- There is a risk of bow-stringing during movement
- Various retinacula (crural fascia) strap these down to prevent bowstringing of tendons.
Why is the foot important?
It sub-serves 2 functions equally
- It supports body weight
- It is integral to the lower limb as an organ of locomotion
- The 2 functions are antagonistic to each other
What are the design requirements for a versatile foot and ankle joint?
Support body weight:
- Establishes a Broad-base for bearing body weight
- Must be robust to take all body weight
- Must be stable when weight bearing
- Absorb shocks when landing
To Underpin Movements
- Must be loose to permit displacement of the joint
- Must be stable when moving
- Must permit movements on flat, sloping and uneven surfaces.
- Must be light in weight
Capability to Generate Force
- Must be able to lift body weight during initiation of movement
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Describe the Ankle Joint
- Formed by articulation of the leg with the foot
- 3 bones are involved - 2 bones of the leg, 1 bone of the foot
- Leg bones: tibia and fibula
- Foot bone: talus
What are the articulatory surfaces of the ankle joint?
- Tibia: contributes 2 articulatory surfaces:
1) Superior articulatory surface
2) Medial articulatory surface - Fibular: contibutes 1 articulatory surface: 1) Lateral
- Talus: contributes 3 surfaces
1) Inferior
2) Infero-medial
3) Infero-lateral
What are the malleoli?
Distinguished by a pair of bony prominences in the medio-lateral plane.
These prominences are known as malleoli (pl)
Medial malleolus - distal end of tibia
Lateral malleolus - distal end of fibula
Malleoli are key landmarks in distal superficial venous drainage of lower limb
What deepens the articulatory surfaces?
The Distal Posterior Tibial :Ligament - thus further stabilising the joint.
The joint is further strengthened by a transverse tibio-fibular ligament
What type of joint is the Ankle joint?
Hinge Synovial joint
The axis of rotation in this hinge is not fixed.
It changes between extremes of plantarflexion and dorsiflexion.
It is therefore a rolling-hinge synovial joint
What is the difference between the Ankle Joint and the Sub-talar joint?
In some literature, the articulations of the talus with the calcaneus are included in the ankle joint.
To note the distinction between the ankle joint proper and sub-talar joints, sub-talar joints are formed by articulation of the talus with the calcaneus.
Describe the Division of Labour within the Ankle Joint
- Weight bearing surfaces: tibia, talus
- Joint stabilising surfaces: medial malleolus, lateral malleolus, distal tibio-fibular ligament (posteriorly) and transverse tibio-fibular ligament
last two ligaments deepen articulating surfaces tightening joint
Describe the Arches of the Foot
- A segmented structure such as the foot can hold up wieght only if built in the form of an arch
- The foot has 3 arches - present at birth
- 2 Main arches running antero-posteriorly
- 1 Transverse arch running medio-laterally
- Medial Longitudinal Arch:
- Lateral Longitudinal Arch
- Transverse Arch
Describe the Tarsal bones
- n = 7
- Markedly different in dize
- Irregular, cuboidal in shape
- Each bone has 6 surfaces
- These surfaces characterise each of the tarsals
Describe the Talus
- It is the only bone of the foot involved in the ankle joint
- It is the second largest tarsal bone
- No muscular attachments
- Yes, ligamentous attachments
- It forms the axis of rotation of the ankle joint
- It lies between the distal end of the leg and upper surface of the calcaneum
- Its long axis is directed forwards and medially
- Its long axis is in the antero-medial plane (oblique)
Describe the Dorsal Surface of Body of Talus
- It is the surface that articulates with the leg
- Its shape is reminiscent of a pulley
- Also known as the trochlear
- It is wider in front than behind (posteriorly much narrower)