Session 12 - The ankle Flashcards
What makes the ankle joint unstable?
- Centre of gravity passes just in front
- Gravitational pull makes it unstable
What are the two main types of injuries which occur at the ankle?
- Sprains
- Fracture
Why are the tendons of the foot susceptible to bow-stringing during movement? What prevents this?
- The change in direction from the leg to the foot
- Flexor and extensor retinaculum (Crural fascia)
How is the ankle designed to support body weight?
- Broad base
- Robust
- Stable when weight-bearing
- Absorbs shock
How is the ankle designed to allow locomotion?
- Loose to permit displacement of joint for walking (opposes robust)
- Stable when moving
- Light weight
What 3 bones make the ankle joint?
- Tibia
- Fibula
- Talus
What articulations are made in the ankle joint?
- Superior between tibia and talus
- Medial between medial malleolus and talus
- Lateral between lateral malleolus and talus
Where do the long and short saphenous veins run in relation to malleoli?
- Long runs anteriorly to medial malleolus
- Short runs posteriorly to lateral malleolus
What ligaments support the distal tibio-fibular syndesmosis?
-Anterior and posterior tiobiofibular ligaments
What are the main functions of the ankle?
- Transfer weight to the foot and bears all the body weight
- Integral to locomotion
What deepens the articulating surfaces of the ankle joint?
-Posterior tiobiofibular ligament
What type of joint is the ankle joint?
-Synovial hinge joint
What is the classical name for a synovial hinge joint?
-Ginglymus
Why is the ankle described as a mortise and tenon joint?
- Distally the tibia and fibular form a concavity/box called a mortise
- The talus inserts into the concavity and is the tenon
Why is the hinge-joint of the ankle different from other hinge joints?
-It is a rolling hinge joint as the superior surface of talus is rounded and allows axis rotation of the hinge, changing during dorsiflexion and plantar flexion
What bones make the ankle proper? What other bones are a pssibility of being involved in the ankle joint?
- Tibia, fibular and talus
- Calcaneous
What are the stabilising features of the ankle joint proper?
- Malleioli
- Posterior tibiofibular ligament
- Transverse tibiofibular ligament
Which bones in the ankle are weightbearing?
-Talus and tibia
What are the three arches present in the foot?
- Medial longitudinal arch
- Lateral longitudinal arch
- Transverse arch
What makes the medial longitudinal arch?
- Calcaneous
- Talus
- Navicular
- 3 cuniforms
- 1st, 2nd and 3rd metatarsals
What makes the lateral longitudinal arch?
- Calcaneous
- Cuboid
- 4th and 5th metatarsals
What forms the transverse arch?
-Articulations between tarsals and metatarsals
What type of bones are the tarsals of the foot?
-Short bones
How many surfaces does each tarsal bone have?
-6
What type of attachments does talus have?
-Ligamentous only
In what direction is the long axis of talus lie?
-Antero-medial plane (oblique)
Describe the superior surface of talus
-Rounded with convex medial and lateral edges and the central being concave
What is another name for the superior surface of talus?
-Trochlear
What is the main difference between the anterior and posterior surfaces of talus?
-Anterior is wider than posterior
What bones does talus articulate with?
-Tibia, fibular and calcaneous
What is the subtalar joint?
-The talo-calcaneal joint between talus and calcaneous
What typf of joint is the subtalar joint?
-Uniaxial hinge joint
What are the articulations between talus and calcaneous?
- One anteriorly between a convex area of talus and a concave area of calcaneous
- One posteriorly between the concave surface of talus and convex surface of calcaneous
What is the tarsal canal?
-A deep groove which rune between the two articulations of the subtalar joint (also called sinus tarsi)
What type of movement does ankle proper allow?
-Plantarflexion and dorsiflexion
What type of movement does the subtalar joint allow?
-Inversion and eversion (Side to side motion of foot)
What is the purpose of inversion and eversion?
-Allow walking on uneven ground
What are the normal degrees of inversion and eversion?
- Inversion = 30
- Eversion = 15
What is dorsiflexion?
-Narrowing of the angle between the anterior surface of the leg and the dorsal surface of the foot
What is plantarflexion?
-Widening of the angle between the anterior surface of the leg and the dorsal surface of the foot
What happens to the articulations of ankle proper on dorsiflexion?
-Broad anterior portion of talus occupies and almost completely fills the mortise
Why id dorsiflexion more stable than plantar flexion?
-Wide anterior portion fits tightly with the tibio-fibular syndesmosis contributing stability in extreme dorsiflexion
What happens to the articulations of ankle proper in plantar flexion?
-Narrow posterior segment of talus occupies mortise
Why is there some adduction and abduction in plantarflexion and not dorsiflexion?
-On plantarflexion, narrow talus in mortise allows some rotational movement
When is the ankle proper least stable?
-Plantarflexion
What nerve and corresponding roots enables dorsiflexion?
-Deep fibular nerve from roots L4-S3 (sciatic)
What muscles are responsible for dorsiflexion?
- Tibilis anterior
- Extensor digitorum longus
- Extensor hallucis longus
What nerve and roots allows plantarflexion?
- Tibial division of sciatic nerve
- L4-S3 (sciatic)
What muscles are responsible for plantarflexion?
-Triceps surae (gastronemius and soleus)
Assisted by tibialis posterior, flexor hallucis longus and flexor digitorum longus
Describe the medial ligament of the ankle
- Also known as deltoid ligament
- Strongest ankle ligament which re-enforces medial malleolus
- Fan-shape, combined by 4 segments running inferiorly from medial malleolus
- Has superficial and deep fibres
Describe the superficial fibres of the medial ligament
- Anterior tibia-navicular ligament
- Middle calcaneo-tibial ligament
- Posterior talo-tibial ligament
Describe the deep fibres of the medial ankle ligament
-Anterior talo-tibial ligament
medial malleolus to medial talus
What tendons cross the medial ankle ligament?
- Tibialis posterior
- Flexor digitorum longus
Describe the lateral ankle ligament
- 3 separate bands radiating from lateral malleolus
- Anterior and posterior attach to talus
- Intermediate pass to calcaneus
Name the ligaments of the ankle joint
- Medial ligament (deltoid)
- Lateral ligament
- Syndesmosis
Which bones are normally involved in a fractures ankle?
-Malleoli
Why is it rare to break the ankle only on one side?
-The ankle joint forms a ring of bones and ligaments;
medial malleolus to talus via deltiod
talus to lateral malleolus via lateral ligament
fibula to tibia via syndesmosis
-So injuries commonly effect both the lateral and medial aspects of the joint
What is potts fracture?
-A term applied loosely to a variety of bimalleolar ankle fractures
What causes potts fracture?
- Excessive eversion results in combined ABduction an lateral rotation which pulls on the strong medial ligament tearing off the medial malleolus
- Talus then moves laterally and shears off the lateral malleolus and more commonly the tibio-fibular syndesmosis
