S5) The Ankle

Question 1

What is the ankle joint?

Answer 1

The ankle joint (talocrural joint) is a hinge-type synovial joint located in the lower limb, formed by the bones of the leg and the foot – the tibia, fibula and talus

Question 2

What is the mortise?

Answer 2

• The mortise is the hyaline cartilage-covered socket formed by the binding of the tibia and fibula together by strong tibiofibular ligaments
• The body of the talus fits snugly into the mortise

Question 3

Describe the location and function of the medial ligament (deltoid ligament) of the malleolus

Answer 3

• Location: attached to the medial malleolus and consists of 4 ligaments which fan out and attach to the talus, calcaneus and navicular bones
• Function: resist over-eversion of the foot

Question 4

Identify the different ligaments composing the medial ligament of the malleolus

Answer 4

Question 5

Describe the location and function of the lateral ligament of the malleolus

Answer 5

• Location: attached the lateral malleolus and consists of three ligaments which fan out and attach to the talus and calcaneus bones
• Function: resists over-inversion of the foot

Question 6

Identify the different ligaments composing the lateral ligament of the malleolus

Answer 6

Question 7

Identify the possible movements of the ankle joint and the muscles involved

Answer 7

• Plantarflexion – gastrocnemius, soleus, plantaris and posterior tibialis (posterior compartment of leg)
• Dorsiflexion – tibialis anterior, extensor hallucis longus and extensor digitorum longus (anterior compartment of leg)

Question 8

Describe the arterial supply of the ankle

Answer 8

Arterial supply via malleolar branches of the anterior tibial, posterior tibial and fibular arteries

Question 9

Describe the innervation of the ankle joint

Answer 9

Innervation by tibial and deep fibular nerves

Question 10

What is the subtalar joint?

Answer 10

The subtalar joint is a planar synovial joint formed from the articulation between two of the talus and calcaneus bones of the foot

Question 11

Identify the articulating surfaces of the subtalar joint

Answer 11

• Inferior surface of the body of the talus
• Superior surface of the calcaneus

Question 12

Identify the 3 ligaments which stabilise the subtalar joint

Answer 12

• Posterior talocalcaneal ligament
• Medial talocalcaneal ligament
• Lateral talocalcaneal ligament

Question 13

An additional ligament is also found in the subtalar joint – the interosseous talocalcaneal ligament.

Describe its location and function

Answer 13

• Function: binds the talus and calcaneus together
• Location: lies within the sinus tarsi (a small cavity between the talus and calcaneus)

Question 14

Identify the possible movements of the subtalar joint and the muscles involved

Answer 14

• Eversion — muscles of the lateral compartment of the leg
• Inversion – tibialis anterior muscle respectively

Question 15

Describe the arterial supply of the subtalar joint

Answer 15

Arterial supply via posterior tibial and fibular arteries

Question 16

Describe the innervation of the subtalar joint

Answer 16

• Plantar innervation – medial or lateral plantar nerve
• Dorsal innervation – deep fibular nerve

Question 17

Identify the Ottawa Rules of when to X-ray an ankle fracture

Answer 17

• Tenderness over the medial malleolus
• Tenderness over the lateral malleolus
• Tenderness over navicular
• Tenderness over base of metatarsal
• Inability to bear weight

Question 18

The ankle joint and the associated ligaments can be visualised as a ring in the coronal plane.

Identify and describe the borders of this ring

Answer 18

• Upper part – formed by articular surfaces of tibia & fibula
• Lower part – formed by subtalar joint
• Sides – formed by medial and lateral ligaments

Question 19

In light of the ankle ring, discuss what is meant by stable and unstable ankle fractures

Answer 19

Question 20

What is an ankle sprain?

Answer 20

• An ankle sprain is the partial/complete tear in the ligament of the ankle joint, occuring in a plantar-flexed weight bearing foot which is excessively inverted
• The lateral ligament is damaged as its weaker and resists inversion

Question 21

What is a Pott’s Fracture-Dislocation?

Answer 21

A Pott’s fracture is a term used to describe a bimalleolar (medial & lateral malleoli) or trimalleolar (medial & lateral malleoli, distal tibia) fracture which occurs due to the force eversion of the foot