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?
Which 4 bones make up the distal tarsal bones?
Medial, intermediate and lateral cuneiforms
Cuboid (most laterally)
What are the 5 main types of joint in the foot?
1) Interphalangeal joints (distal and proximal - only one in great toe as only 2 phalanges)
2) Metatarsophalangeal joint
3) Tarsometatarsal joints
4) Naviculo-cuneiform joints
5) Transverse tarsal joint
What 2 joints is the transverse tarsal joint made up of?
1) Talonavicular joint
2) Calcaneocuboid joint
What disease typically effects the 1st metatarsophalangeal joint (great toe)?
What disease typically affects the hands but is also common in the small joints of the feet too?
What is the function of the arches of the foot? 3
1) Help to distribute the weight acting as shock absorbers
2) Increase flexibility of the foot
3) Act as spring boards for propulsion during walking, running and jumping
What are the 3 arches of the foot?
1) Medial longitudinal (MLA)
2) Lateral longitudinal (LLA)
3) Transverse (TA)
Which is the highest and most important longitudinal arch in the foot?
The medial longitudinal arch
The medial longitudinal arch comprises which 9 bones?
4) 3 cuneiforms
5) Medial 3 metatarsals
Medial longitudinal arch causes weight to be transmitted how?
Weight is transmitted through the talus to the calcaneus and metatarsal heads
The lateral longitudinal arch comprises which 4 bones?
3) Lateral 2 metatarsals
The transverse arch of the foot comprises which 9 bones?
2) 3 cuneiforms
3) Bases of the 5 metatarsals
What are the 2 mechanisms to support the arches of the foot?
1) Passive support includes ligaments and the shape of the bones
2) Dynamic support includes intrinsic and extrinsic muscles of the foot
What is pes planus?
Seen in adolescents or adults, flat foot with no arches, can be flexible or rigid (ie. fusion of tarsal bones)
What is flexible pes planus?
Arch is present with the foot is not weight bearing but the arches flatten out when weight bearing
Which type of pes planus is more common?
What is pes planus usually caused by and what can exacerbate it?
Usually caused by loose or degenerating ligaments
Can be exacerbated by gaining weight and/or spending a long time standing
What are the clinical features/symptoms of pes planus?
- May be asymptomatic
- Can result in displacement of the talus infero-medially
- This causes misalignment of the ankle and knee causing pain in these areas
- Can also decrease shock absorption by the foot leading to lower back pain
How is pes planus treated?
With orthotics (specialised insoles) that support the arches of the foot
What are the 4 movements possible in the joint of the foot?
- Flexion and extension at the metatarsophalangeal joints and the proximal and distal interphalangeal joints
- Limited abduction and adduction occurs at the metatarsophalangeal joints
What is the medical term for bunions?
What defines a convoluted fracture?
Fracture resulting in more than 2 pieces of bone
Why do fractures which affect the articular surfaces of joints have to be treated?
Have to be fixed as can affect the function of the joint afterwards
Why are fractures at the base of the 5th metatarsal common?
Because the tendon of fibularis brevis (in the lateral compartment of the leg) runs down the lateral side of the foot and inserts into the base of the 5th metatarsal so when eversion injuries occur the tendon of fibularis brevis is stretched and pulls off the bone
What is a Lisfranc injury in the foot?
Damage or fracture to the joints between the metartarsals distal tarsal bone (cuneiforms and cuboid)
What is a Lisfranc injury in the foot commonly caused by?
When the foot is thrown forward - eg. fall from a horse with body thrown forwards and foot still in stirrup