Joints of the ankle and foot

Transcript

Some of us can agree that we love rock and roll.

However, most of us can also agree that we don't love it when we step on a rock, and roll our ankles.

How is that for a segway into talking about the ankle?

Alright, enough of the bad opening lines, let’s discuss the joints of the ankle and the foot!

The ankle joint or tibiotalar joint, is a hinge-type synovial joint located between the distal ends of the tibia and the fibula and the superior part of the talus, which are the three main bones of this joint.

The main articular components of this joint are the trochlea and body of the talus, which articulates medially with the medial malleolus of the tibia and laterally with the lateral malleolus of the fibula.

In a nutshell, the tibia and fibula are bound together by the strong tibiofibular ligaments, and, together, their respective malleoli form a bracket shaped socket, which is covered in hyaline cartilage.

This socket is known as a malleolar mortise and is where the pulley-shaped trochlea of the talus fits.

The malleolar mortise is bounded posteriorly by the inferior part of the posterior tibiofibular ligament, superiorly by the articular surface of the tibia, with the medial and lateral walls being the medial malleolus and lateral malleolus respectively.

The joint capsule of the ankle joint is thin anteriorly and posteriorly but is supported on each side by a series of strong ligaments.

Its fibrous layer is attached superiorly to the borders of the articular surfaces of the tibia and the malleoli and inferiorly to the talus.

By contrast, its synovial layer is loose and lines the fibrous layer of the capsule.

Now, the supportive ligaments reinforce the ankle joint.

Laterally, there’s the lateral ligament of the ankle consisting of three completely separate ligaments which help prevent inversion of the ankle.

First, there’s the anterior talofibular ligament that extends anteromedially from the lateral malleolus to the neck of the talus.

Second, there’s the posterior talofibular ligament, which runs horizontally, medially and posteriorly from the malleolar fossa to the lateral tubercle of the talus.

And third, there’s the calcaneofibular ligament, which passes posteroinferiorly from the tip of the lateral malleolus to the lateral surface of the calcaneus.

And medially, you guessed it!

There’s the medial ligament of the ankle, also known as the deltoid ligament, which stabilizes the ankle joint during eversion and prevents subluxation of the joint.

This ligament attaches proximally to the medial malleolus, from where it fans out, attaching distally to the talus, calcaneus, and navicular via four adjacent and continuous parts: the tibionavicular part, the tibiocalcaneal part, and the anterior and posterior tibiotalar parts.

The main movements of the ankle joint are dorsiflexion, and plantarflexion.

Dorsiflexion of the ankle is produced by the muscles in the anterior compartment of the leg, namely tibialis anterior extensor digitorum longus, and extensor hallucis longus.

Plantarflexion of the ankle is produced by the muscles in the posterior compartment of the leg, including the gastrocnemius, and soleus in the superficial subcompartment, as well as the muscles of the deep subcompartment such as tibialis posterior, flexor digitorum longus, and flexor hallucis longus.

Now, because the thicker anterior part of the talus is held in the mortise during dorsiflexion, the joint is more stable in dorsiflexion, and less stable during plantarflexion because it's the narrow, posterior part of the talus that is held more loosely in the mortise.

Finally, the arterial supply of the ankle joint is derived from the malleolar branches of the fibular and anterior and posterior tibial arteries.

And nerve supply of the ankle joint derives from the tibial nerve and deep fibular nerve.

Before the joints of the foot kick in, you know the drill; let’s take a break and review the main components of the ankle joint!

Ok, so some of the main joints of the foot include the subtalar joint, transverse tarsal joint, other intertarsal joints, tarsometatarsal joints, metatarsophalangeal joints, and interphalangeal joints.

Let’s start out with the subtalar joint, which can be defined in two ways.

First, the anatomical subtalar joint.

This joint is a single synovial joint between the slightly concave posterior calcaneal articular surface of the talus and the convex posterior articular facet of the calcaneus.

The clinical subtalar joint includes the anatomical subtalar joint, plus the talocalcaneal part of the talocalcaneonavicular joint, which are separated by the strong interosseous talocalcaneal ligament that lies in the tarsal sinus.

The clinical subtalar joint is used instead of the anatomical subtalar joint description alone to describe the functionality of this joint, because both the subtalar joint and the talocalcaneal part of the talocalcaneonavicular joint act together, forming a single functional unit.

The subtalar joint undergoes inversion, primarily thanks to the tibialis anterior and tibialis posterior muscles, as well as eversion primarily carried out by fibularis brevis and fibularis longus.

Next, the transverse tarsal joint is a compound joint formed by two separate joints aligned transversely: the talonavicular part of the talocalcaneonavicular joint and the calcaneocuboid joint.