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Ankle joint

Bones and ligaments that form the ankle joint.

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Transcript

Hello everyone! This is Joao from Kenhub, and welcome to our tutorial, and this time we're going to be talking about the ankle joint. And in this video, we will be looking at the ankle and all of its structural components, and you probably know what the ankle is – the ankle joint is where the leg meets the foot. We're looking at the right ankle from the anterior view on this image. You can see that it is actually made by more than one articulation and by that, I mean, the meeting of several bones and is held together by many ligaments. So, let's start with a quick overview of what we'll be covering today.

In this tutorial, we will first identify the bones involved in the ankle joints then we'll look at the joint itself and lastly identify the ligaments that hold these bones together. And to finish off, we'll look at some clinical correlations of the ankle joint. So first up are the bones that make up the ankle joint. We'll work from proximal to distal starting with the bones in the leg.

The leg which is the part of the lower limb between the knee joint and the ankle joint has two bones. Here we are looking at the skeleton of the lower limb from an anterior view. The larger bone which is commonly referred to as the shin bone is the tibia. The tibia is the medial of the two bones of the leg. Since we know the tibia is the medial bone of the leg, then this must be the right lower limb that we're looking at.

In this image of the foot and inferior portion of the leg, we are looking from a medial viewpoint. So, the bone we see highlighted in green is the tibia. At the distal end of the tibia, there is a bony projection on the medial side. This is called the medial malleolus. You can actually palpate and see the medial malleolus on your own ankle. You could try that now, if you would like. Are you done? Okay, let's continue on with the tutorial.

Now, we'll move across to the other bone of the leg – the lateral bone – which is the fibula. This is, of course, the lateral view of the right ankle. This bone is much more slender than the tibia. Well, the fibula is not directly involved in weight transmission though as we will see shortly, it is involved in the ankle joint. And similar to the tibia, the fibula also has a distal bony projection or malleolus. Since we're on the lateral side though, this one is called then the lateral malleolus. You can see it here in this anterior view of the ankle.

Again, you can pause this tutorial to try to palpate this structure on yourself. You'll see that it's usually much more prominent than the medial malleolus. Now, we'll move on to talk about the bones of the foot that make up the ankle joint.

The foot is made up of twenty six bones – quite a lot as you can see – but don't worry, for now, we'll just be focusing on one. And this bone is directly involved in the ankle joint and several others help to support it by providing attachment sites for ligaments that strengthen the joint. The bone directly involved in the articulation of the ankle joint is the one highlighted in this image of the skeleton, and this is the talus.

In both of these images – this one, a medial view of the foot, and this one, a lateral view – we can see the talus highlighted in green. It spans the width of the ankle joint and sits superior to the calcaneus which is this bone here.

We'll now take a closer look at the calcaneus. In this lateral image of the foot, we can see it sitting inferior to the talus. The calcaneus is the heel bone. It does not make the part of the ankle joint itself but we'll see soon that important ligaments supporting the ankle joint will be attaching to the calcaneus.

The final bone we'll identify today is this one here, the navicular bone, which you can see highlighted in green in both images. In this medial view of the foot, we can see the navicular a bit more clearly. It lies on the medial side of the foot proximal to the three cuneiform bones. We can see it articulating with the talus here as it sits directly anterior to the talus. And similar to the calcaneus, this bone is not directly involved in the ankle joint but serves as an attachment site for ligaments that support the ankle.

Alright, now let's finally get into the ankle joint itself. There are actually two bony articulations we need to discuss, the first being the ankle joint proper. We know the three bones involved in the articulation of the ankle joint proper are the tibia, fibula and talus. Together, the tibia and fibula form the ankle mortise. This arch is made up by the lateral malleolus of the fibula, the inferior portion of the tibia and the medial malleolus of the tibia. Sitting within the ankle mortise is the superior aspect of the talus. The mortise configuration of the tibia and fibula locks the talus in place making the joint very strong and stable which is essential for bearing weight of a human body.

The mortise arrangement of the tibia and fibula means the talus can only move in one axis and this means that the ankle joint is a hinge joint so it allows for only two motions to occur at it similar to a hinge of a door. The ankle can dorsiflex where the distal end of the foot moves superiorly or you can think of it as the dorsum of the foot or the superior aspect of your foot flexing towards the leg. When the ankle moves in the other direction, it is called plantarflexion.

Here the distal portion of the foot is being planted into the floor. The plantar surface of the foot which is the inferior aspect of your foot – you can say that – is being then flexed, but if the mortise of the distal leg is so strong and only permits plantarflexion and dorsiflexion then how is that we can invert and evert our ankles? Well, that movement is performed at another joint in the ankle called the subtalar joint which is the second bony articulation at the ankle. And the subtalar joint can also be called the talocalcaneal joint. Both of these names are very fitting for where the joint actually is. The two bones involved in the joint are the talus and the other one –you can guess – yes, it's the calcaneus. So naming it the talocalcaneal joint fits well. You can see, we're very creative in anatomy. In this image of the lateral view of the ankle, we can see the talus here and the calcaneus here.

Now that we've identified these bones, hopefully, you can see the joint is inferior to the talus. So, the subtalar joint name makes sense as well to you right now.

Now on this image, we are looking at the subtalar joint from an anterior and superior view. From this view, we should be able to appreciate the movements that occur at this joint. At the subtalar joint is where eversion and inversion occurs which is very different to dorsi- and plantarflexion of the ankle joint proper. Inversion is when the plantar surface of the foot moves medially and eversion is the opposite. So when the plantar surface of the foot moves laterally, the subtalar joint is what we call everting.

Now that we have covered the bones of the ankle joint proper and the subtalar joint, it's time to get into the ligaments. Let's have a look at the structures that are helping to stabilize the ankle joint – the ligaments. There are ten ligaments that we are going to look at today. Seven more external ligaments that stabilize the ankle joint proper and the subtalar joint. The three ligaments – they are more internal and are specifically related to the subtalar joint.

It may seem like a lot to remember but there are two things that will help us organize these ligaments and therefore remember them better. One is that they are grouped nicely to either the medial a.k.a. tibial side, the lateral a.k.a. fibular side, or the talocalcaneal joint. The second thing is that they are all named for the bones they are attached to.

We'll start on the medial or tibial side. In this image, there are four different ligaments highlighted. Collectively, these ligaments make up the tibial collateral ligament also called the medial collateral ligament or deltoid ligament. Let's look at them each in turn.

The most anterior ligament is the one we can see now highlighted in green. This runs from the anterior surface of the tibia to the talus, therefore, it is named the anterior tibiotalar ligament. Remember, the ligaments are named for the bones they're attached to. Now on the posterior aspect of the joint still on the medial side, we can see another ligament running from the tibia to the talus and, yes, if you guessed, this one is therefore called the posterior tibiotalar ligament.

This next ligament now highlighted in green runs from the tibia to the navicular bone. Since there is only one of them, there is no need to add anterior or posterior. So, it is simply called the tibionavicular ligament. And, finally, the last ligament making up the tibial collateral ligament is highlighted now and this ligament is running from the tibia to the calcaneus and is therefore called the tibiocalcaneal ligament.

The second group of ligaments is on the lateral or fibular side of the ankle. It consists of three ligaments all of which are highlighted in this image – you can see here one, two and three. Together, these ligaments make up the fibular collateral ligament. We can also call it the lateral collateral ligament of the ankle, and we're going to look at each specifically.

The most anterior ligament on the lateral side is the one we can see now highlighted in green. This runs from the anterior surface of the fibula to the talus and therefore it is named the anterior talofibular ligament and this naming might seem a little bit backwards compared to the tibial collateral ligaments. When naming the tibial ligaments, the tibia portion of the name came first, for example, tibiotalar. When we're naming the lateral or fibular ligaments, the fibular portion comes then last as we can see in anterior talofibular ligament, so just keep that in mind.

Now looking at the posterior aspect of the joint, there is another ligament running again from the fibula to the talus. This one will therefore be called the posterior talofibular ligament. Finally, the last piece of the fibular collateral ligament is the one we can see highlighted now. This runs from the fibula to the calcaneus and is called the calcaneofibular ligament.

The third and final group of ligaments specific to the subtalar joint – so all run between the talus and the calcaneus. There are three of these ligaments that we'll identify. The first is seen on this medial view of the ankle. Here we can see the talus and here is the calcaneus. Since we're on the medial aspect of the ankle joint and we know the two bones the ligament connects, we can identify this ligament as the medial talocalcaneal ligament.

The other two ligaments in this group can be seen on this lateral view of the ankle joint. Again, here is the talus and here is the calcaneus. This highlighted ligament on the lateral side of the ankle is called the lateral talocalcaneal ligament. The third and final ligament of the subtalar joint is the ligament we can see now highlighted in green and this ligament is called the interosseus talocalcaneal ligament. Together, these ligaments stabilize the subtalar or talocalcaneal joint.

So we're done covering the anatomy of the ankle joint. I would like to take you through a few clinical correlations and, in terms of clinical issues with the ankle joint, a commonly experienced injury is an ankle sprain. Sprains, in general, are stretches or tears in ligaments. Although any of the ligaments involved in the ankle joint can be sprained, some are much more commonly than others.

The fibular collateral ligaments are weaker than the tibial collateral ones and are therefore more often injured. The injury usually occurs when the foot overinverts and, if you remember, inversion of the foot is when the lateral aspect of the sole of the foot moves medially, and if the foot moves too far in that direction or force is applied when the foot is inverted, the fibular collateral ligaments can sprain. This is what people often called rolling their ankle. Of the lateral collateral ligaments, the anterior talofibular ligament is most vulnerable and most often injured.

And this is the end of our tutorial but before I let you go, I would like to summarize what we've learned or what we covered throughout this tutorial.

We began by looking at the bones involved in the ankle joint. First, we saw the tibia, fibula and talus which we know are all involved in the articulation of the ankle joint. We also identified the calcaneus and navicular which serve as ligament attachment sites for the ankle joint. Next, we looked at the ankle joint proper and identified the ankle mortise formed by the lateral malleolus of the fibula, inferior surface of the tibia, and medial malleolus of the tibia. We saw how the superior aspect of the talus articulated with the ankle mortise and we then looked at the other articulation that makes up the ankle joint called the subtalar or talocalcaneal joint. This is the joint where inversion and eversion occurs between the talus and calcaneus.

Then we looked at the ligaments involved in stabilizing the ankle joint. First, we looked at the tibial collateral ligament and its four components. So, we looked at the anterior tibiofibular ligament, the posterior tibiofibular ligament then the tibionavicular ligament and the tibiocalcaneal ligament. The second group of ligaments we identified make up the fibular collateral ligament and consists of the anterior talofibular ligament, the calcaneofibular ligament, and the posterior talofibular ligament. And the final group of ligaments we identified stabilized the talocalcaneal joint, we looked at these three ligaments – the medial talocalcaneal ligament, the lateral talocalcaneal ligament, and the interosseus talocalcaneal ligament.

And at the end, we looked at a few clinical correlations. So, we looked at ankle sprains and the ligaments most commonly damaged in that injury.

And that brings us to the end of our tutorial on the ankle joint. I hope you enjoyed it and thank you for watching. I will see you on the next video.

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