The ankle- Palastange Flashcards
Classification
Synovial hinge
What is regulated at the ankle joint
The line of gravity
Where does the line of gravity fall during normal standing
In front of the ankle joint
How does the axis of the ankle joint lie and why is this significant
(think looking from the head down at the foot)
Axis is horizontal but oblique to the frontal plane by some 20-25degrees
The axis of the foot runs perpendicular to this
Means simultaneous movement of the knee and ankle can only occur when combined with movement at the subtalar joint
What are the articular surfaces
Distal ends of the tibia and fibula and the body of the talus
(only the trochlear surfaces of the tibia and talus bear weight)
Describe the features of the talus
Slightly broader in front that behind
Central longitudinal groove
When is the ankle most stable and why
In extension (dorsiflexion) Due the the wide talus being forced into the relatively narrower malleolar mortise and then tightly gripped by the malleoli and their ligaments
When is the ankle least stable and why
In flexion (plantarflexion) Narrower posterior talus is less tightly gripped by the malleolar mortise allowing some side to side movement
Describe the joint capsule
Completely surrounds the joint
Is weak in front and behind to accommodate movementt
Strengthened laterally and medially by collateral ligaments
Features of the medial collateral (deltoid) ligament
Strong triangular composed of several bands of fibres fused together
Deep parts- anterior and posterior tibiotalar bands
Superficial parts- tibionavicular band, tibiocalcaneal band
What makes up the lateral collateral ligament
3 bands
- anterior and posterior talofibular ligaments
- calcaneofibular ligament lying in between the 2 above
Weaker than the deltoid
What supports the ankle anteriorly and posteriorly
Anterior and posterior ligaments which are just really thickenings of the joint capsule
Sectioning the lateral ligaments is associated with an increase in range of which movement of the ankle
Dorsiflexion
but not plantarflexion
Blood supply
Malleolar branches from anterior tibial, fibular and posterior tibial branches
Transverse stability of the joint depends on
Interlocking of articular surfaces
When may transverse movement occur and what sequence of events must happen to allow this
When the foot is forcibly moved laterally (trauma)
Rupture of inferior TF ligaments- widening of mortise (diastasis)- talus can move from side to side- lateral malleoli may fracture
(All made worse if deltoid is sprained)
If the fibula does not fracture at the lateral malleolus where else may a fracture occur and why is this important
Fracture may occur at the level of the fibular neck
Is important as not usually within the limits of an ankle x-ray so separate higher views must be taken to exclude
What is the maximum range of movement at the ankle
Dorsi- and plantar-flexion may approach 90degrees
What is the range of dorsiflexion
30 degrees
What is the range of plantarflexion
50 degrees
Limits to dorsiflexion
Tension in gastrocnemius and soleus as well as post part of deltoid ligament, calcaneofibular ligament and post joint capsule
Also wedging of the talus between the malleoli
What is talipes equinus
Foot permanently fixed in plantarflexion due to shortening of gastrocnemius and soleus (cannot dorsiflex)
Limits to plantarflexion
Tension in ant compartment muscles
Anterior part of deltoid, anterior talofibular ligament and ant joint capsule
What happens to the range of motion used by the ankle with an increase in walking speed
ROM decreases, being mainly a decrease in plantarflexion
do not use full ROM during gait anyway
Plantarflexors of the ankle
Superficial
-gastrocnemius, plantaris, soleus
Deep
-tibialis posterior, flexor digitorum longus, flexor hallucis longus
fibularis longus and brevis assist
Muscles that dorsiflex the ankle
Tibialis anterior
Extensor digitorum longus
Extensor hallucis longus
Fibularis tertius
Muscles inverting the foot
Tibialis posterior and anterior
Muscles everting the foot
Fibularis longus, brevis and tertius
