MSK - The Ankle Joint Flashcards
What type of joint is the ankle joint?
Synovial hinge type joint
What bones form the ankle joint?
Tibia
Fibula
Talus
What actions does the ankle joint permit?
Dorsiflexion and planterflexion
What are the tibia and fibula bound together by?
What type of socket does this produce?
What is this socket called?
Strong tibiofibular ligaments
Bracket type socket
Mortise
What shape is the articulating part of the talus?
Where is it largest and where is it thinnest?
Wedge Shapes
Thicket posteriorly and thinnest anteriorly
During dorsiflexion, what part of the talus is held by the mortise?
Is the joint more stable in dorsiflexion or plantarflexion?
Anterior part
Dorsiflexion
During planterflexion, what part of the talus is held in the mortise?
Posterior
What colour is the talus?
Yellow
How many sets of ligaments are there at the ankle joint?
Where do they originate?
Two
Originate from each malleolus
Where does the medial ligament originate from?
How many ligaments make up the medial ligament?
What is its main function?
Medial Malleolus
4
Resist over-eversion of the foot
Where does the lateral ligament originate from?
What is its main function?
How many ligaments make up the medial ligament?
Lateral malleolus
Resists over-inversion of the foot
3
What are the three ligaments that make up the lateral ligament?
Where do they span between?
Anterior talofibular - Spans between the lateral malleolus and lateral aspect of the talus
Posterior talofibular - Spans between the lateral malleolus and the posterior aspect of the talus
Calcaneofibular - Spans between the lateral malleolus and the calcaneum
Label the ligaments that make up the lateral ligament of the ankle joint
The ankle joint and associated ligaments can be visualised as a ring in the coronal plane
What forms the upper part of the ring?
Upper Part - Formed by the articular surfaces of the tibia and fibula
The ankle joint and associated ligaments can be visualised as a ring in the coronal plane
What forms the lower part of the ring?
Lower part - Formed by the subtalar joint (between the talus and the calcaneus)
The ankle joint and associated ligaments can be visualised as a ring in the coronal plane
What forms the sides of the ring?
Sides - Formed by the medial and lateral ligaments
What must you bear in mind when dealing with an injury to the ankle joint?
Why?
A fracture of the ankle joint may occur in association with ligament damage – which would not show up on x-ray
A ring, when broken, usually breaks in two places
What muscles are involved in Plantarflexion of the foot?
Produced by the muscles in the posterior compartment of the leg; gastrocnemius, soleus, plantaris and posterior tibialis
What muscles are involved in dorsiflexion of the foot?
Produced by the muscles in the anterior compartment of the leg; tibialis anterior, extensor hallucis longus and extensor digitorum longus
What does an ankle sprain refer to?
Partial or complete tears in the ligaments of the ankle joint
When does ankle sprain usually occur?
In a plantarflexed weight-bearing foot, which is excessively inverted
Why is the lateral ligament more likely to be damaged in an ankle sprain?
The lateral ligament is weaker than the medial ligament
The lateral ligament resists inversion
What ligament making up the lateral ligament is most at risk of irreversible damage?
Anterior talofibular
What has happened in this picture?
Pott’s fracture (bimalleolar) of the ankle joint
Pott’s fracture is used to describe what?
Any bimalleolar fracture (i.e. a fracture of both the medial and lateral malleoli)
How does a bimalleolar fracture occur?
This type of injury occurs via forced eversion, in a series of stages:
1 - Forced eversion pulls on the medial ligaments, producing an avulsion fracture of the medial malleolus
2 - The talus moves laterally, breaking off the lateral malleolus
3 - The tibia is then forced anteriorly, shearing off its distal, proximal portion against the talus
