Flashcards in M: The foot and ankle Deck (56)
The ankle joint is formed by articulations between what 3 bones?
1) Distal tibia
2) Distal fibula
What kind of joint is the ankle joint?
Synovial hinge joint
What is the trochlear of the tallus?
The articular surface which articulates with the malleoli
What is the malleolar mortice?
The bony arch formed by the tibial plafond and the 2 malleoli
What are the 2 main reasons for the high stability of the ankle?
1) Good congruity between malleolar mortice and the trochlea of the talus - the malleoli grip the tallus
2) Very strong ligaments between the bones of the ankle join including the distal part of the interosseous membrane and the anterior and posterior tibiofibular ligaments
What is the most stable position of the ankle joint?
Why is dorsiflexion the most stable position of the ankle joint?
1) The trochlear of the talus is wider anteriorly than posteriorly
2) During dorsiflexion the anterior part of the trochlea moves between the malleoli
3) The spreads the tibia and fibula slightly, increasing their grip on the talus
What are the 3 most important lateral ligaments of the ankle joint?
1) Anterior talofibular ligament (fibular to talus)
2) Posterior talofibular ligament (fibular to talus)
3) Calcaneofibular ligament (fibular to calcaneus)
Which is the weakest of the 3 lateral ligaments of the ankle?
Anterior talofibular ligament
What is the alternative name for the medial ligament of the ankle joint?
The deltoid ligament of the ankle is made up of what 4 parts?
1) Posterior tibiotalar part
2) Tibiocalcaneal part
3) Tibionavicular part
4) Anterior tibiotalar part
What is the shape and attachments of the deltoid ligament?
Attached to the medial malleolus and fans out to attach to the talus, navicular and calcaneus
What are the 4 movements possible at the ankle joint?
1) Dorsiflexion (toes to ceiling)
2) Plantarflexion (toes to floor)
3) Eversion (sole laterally) - very little
4) Inversion (sole medially) - very little
Dorsiflexion generally occurs due to muscles located where?
In the anterior compartment of the leg
Plantarflexion generally occurs due to muscles located where?
In the posterior compartment of the leg (except popliteus)
At what joint does eversion and inversion of the foot primarily occur, what other joint contributes slightly?
The subtalar joint between the talus and underlying calcaneus with some movement in the transverse tarsal joint
Most ankle sprains are what kind of injury?
Inversion injuries with twisting of a plantar flexed foot
What ligament is most at risk of damage in an ankle sprain caused by and inversion injury?
Anterior talofibular joint
Which ligament is weaker, the medial or lateral ligament of the ankle?
The lateral ligament - particularly the anterior talofibular joint
What are the possible 3 complications of/difficulties with an ankle sprain with a torn ligament?
1) Ligaments are relatively avascular so heal slowly
2) If a ligament is detached from bone the fibres do not grow back into bone cortex as extensively so a healed ligament is usually weaker
3) Torn ligaments destabilise the joint - predispose to dislocation
What is important about the joint space in a normal ankle XR?
Joint space all around should be the same width
What does a difference in joint space indicate in an ankle XR?
Talar shift (talus moving in one direction) - suggests something is wrong, dislocation or damage to ligaments
What is the most common fracture in the ankle (resulting from an inversion injury)?
Lateral malleolar fracture - fracture of the distal fibula
What term is used to describe fracture of the lateral and medial malleolus?
Eversion injuries are less common than inversion injuries - when severe what damage can they cause to the ankle joint?
Eversion injury pulls the strong medial ligament causing avulsion of the medial malleolus
The talus rotates laterally fracturing the fibula too
What are the 4 main functions of the foot?
1) Support and transmit body weight
2) Act as a lever to propel body forward during motion
3) Act as a resilient spring to absorb shock
4) If the foot was rigid each impact with the ground would generate large forces, instead foot is a series of bones and ligaments which can deform to absorb shock and adapt to uneven surfaces
What 3 groups can the tarsal bones be divided into?
1) Proximal tarsal bones
2) Intermediate tarsal bones
3) Distal tarsal bones
Which 2 bones make up the distal tarsal bones?
Which bone is the intermediate tarsal bone?