Foot and Ankle Flashcards
Describe the key features of the ankle joint
The ankle joint (or talocrural joint) is a synovial joint located in the lower limb. It is formed by the bones of the leg and the foot – the tibia, fibula and talus.
Functionally, it is a hinge type joint, permitting dorsiflexion and plantarflexion of the foot.
How are the tibia and fibula bound at the ankle joint?
The tibia and fibula are bound together by strong tibiofibular ligaments, producing a bracket shaped socket, which is covered in hyaline cartilage. This socket is known as a mortise.
The body of the talus fits snugly into the mortise formed by the bones of the leg. The articulating part of the talus is wedge shaped. It is wider anteriorly, and thinner posteriorly. During dorsiflexion, the anterior part of the bone is held in the mortise, and the joint is more stable (vice versa for plantarflexion).
Describe the ligaments within the ankle joint
There are two sets of ligaments, which originate from each malleolus. The medial ligament (or deltoid ligament) is attached to the medial malleolus. It consists of four separate ligaments, which fan out from the malleolus, attaching to the talus, calcaneus and navicular bones. The primary action of the medial ligament is to resist over-eversion of the foot.
Where does the lateral ligament originate?
The lateral ligament originates from the lateral malleolus
What are the components of the lateral ligament?
It resists over-inversion of the foot. It is comprised of three distinct and separate ligaments:
Anterior talofibular: Spans between the lateral malleolus and lateral aspect of the talus.
Posterior talofibular: Spans between the lateral malleolus and the posterior aspect of the talus.
Calcaneofibular: Spans between the lateral malleolus and the calcaneus.
Which movements are made in the ankle joint
The ankle joint is a hinge type joint, with movement only possible in one plane. Thus, plantarflexion and dorsiflexion are the only movements that occur at the ankle joint. Eversion and inversion are produced at the other joints of the foot, such as the subtalar joint.
Which muscles are responsible for plantar flexion of the ankle?
Plantarflexion – Produced by the muscles in the posterior compartment of the leg; gastrocnemius, soleus, plantaris and posterior tibialis.
Which muscles are responsible for dorsiflexion of the ankle?
Dorsiflexion – Produced by the muscles in the anterior compartment of the leg; tibialis anterior, extensor hallucis longus and extensor digitorum longus.
How is blood supplied to the ankle joint?
The arterial supply is derived from the malleolar branches of the anterior tibial, posterior tibial and fibular arteries. Innervation is provided by tibial and deep fibular nerves.
Describe how the arches of the foot facilitate functions such as walking and running.
The foot has three arches: two longitudinal (medial and lateral) arches and one anterior transverse arch. They are formed by the tarsal and metatarsal bones, and supported by ligaments and tendons in the foot.
Their shape allows them to act in the same way as a spring, bearing the weight of the body and absorbing the shock produced during locomotion.
Describe the key features of the medial arch of the foot
The medial arch is the higher of the two longitudinal arches. It is formed by the calcaneus, talus, navicular, three cuneiforms and first three metatarsal bones. It is supported by:
Muscular support: Tibialis anterior and posterior, fibularis longus, flexor digitorum longus, flexor hallucis, and the intrinsic foot muscles
Ligamentous support: Plantar ligaments (in particular the long plantar, short plantar and plantar calcaneonavicular ligaments), medial ligament of the ankle joint.
Bony support: Shape of the bones of the arch.
Other: Plantar aponeurosis.
What is the subtalar joint?
The subtalar joint is an articulation between two of the tarsal bones in the foot – the talus and calcaneus. The joint is classed structurally as a synovial joint, and functionally as a plane synovial joint.
Describe the articulating surfaces of the subtalar joint
The subtalar joint is formed between two of the tarsal bones:
Inferior surface of the body of the talus – the posterior talar articular surface.
Superior surface of the calcaneus – the posterior calcaneal articular facet.
Describe how the subtalar joint retains stability
The subtalar joint is enclosed by a joint capsule, which is lined internally by synovial membrane and strengthened externally by a fibrous layer. The capsule is also supported by three ligaments:
Posterior talocalcaneal ligament
Medial talocalcaneal ligament
Lateral talocalcaneal ligament
An additional ligament – the interosseous talocalcaneal ligament – acts to bind the talus and calcaneus together. It lies within the sinus tarsi (a small cavity between the talus and calcaneus), and is particularly strong; providing the majority of the ligamentous stability to the joint.
Describe the movements of the subtalar joints
The subtalar joint is formed on an oblique axis and is therefore the chief site within the foot for generation of eversion and inversion movements. This movement is produced by the muscles of the lateral compartment of the leg. and tibialis anterior muscle respectively.
The nature of the articulating surface means that the subtalar joint has no role in plantar or dorsiflexion of the foot.
