Video: Talus

Hello everyone! This is Megan from Kenhub, and welcome to our tutorial on the talus. In this tutorial, we will be looking at articulations the talus is involved in as well as some bony landmarks of the talus. We'll also be looking at ligaments which are attached to the bone and then we'll finish this tutorial with some clinical notes. Before we begin, I'm just going to give a quick overview of the anatomy of the talus.

So, in this image, we can see a lateral view of the talus. It's also referred to as the ankle bone and is a snail-shaped bone which helps link the leg and the foot through the ankle joint. It's the second largest and most superior bone of the foot. As you can see in this image, it sits on top of and is supported by the calcaneus. It also articulates with the tibia and the fibula to form the ankle joint and then it projects forward to articulate with the navicular bone.

The talus bone consists of three main parts – a head, a neck and a body. I will now isolate the talus from the other bones to briefly show you these three main parts, however, I'll talk about these sections in more detail later on in this tutorial.

In this image, you can see the head of the talus. It is convex, oval and is the most distal part of the bone. Proximal to the head is the neck which is highlighted in this image. Then the most proximal part we have is referred to as the body which is highlighted in green in this image. We will come back to these bony elements in a few moments.

So, I'll now move on to talk about our first topic which is articulations that the talus is involved in. The talus is part of a group of bones in the foot which are collectively referred to as the tarsus. That talus articulates with four bones in total – the tibia, the fibula, the calcaneus, and the navicular. Within the tarsus, the talus articulates with the calcaneus below and the navicular in front to form the talocalcaneonavicular joint. Through these articulations with the calcaneus and the navicular, the talus transmits the entire weight of the body to the foot.

So let's move on to look at the articular surfaces of the talus which are involved in the talocalcaneonavicular joint. This image shows a medial view of the talus. Highlighted here is the convexly oval head of the talus which articulates with the navicular bone. This is referred to as the navicular articular surface of the talus.

We will now look at the calcaneal articular surfaces of the talus. These articular surfaces are found on the inferior aspect of the bone which is shown in this image. So here we can see the posterior articular surface then we have the middle articular surface followed by the anterior articular surface. Now, I'll go through these articular surfaces in more detail.

So the first one I'll show you is referred to as the posterior articular surface. It is located on the posterior inferior aspect of the talus and is the main articular surface for the calcaneus. Highlighted here is another articular surface known as the middle articular surface. This surface is small, oval in form, and slightly convex. It articulates with the sustentaculum tali which is a shelf-like structure located on the calcaneus. This particular articulation is known as the subtalar joint, which provides shock absorption and facilitates in the movements of inversion and eversion. And the last articular surface that we must mention is the one you see here – the anterior articular surface.

As I mentioned previously, the talus also articulates with the fibula and the tibia. These articulations form the talocrural joint which is a hinged-type synovial joint and the main joint of the ankle. Its functions are to aid stability and allow dorsiflexion and plantarflexion of the foot for locomotion. So now we'll talk about some articular surfaces of the talus which are involved in the talocrural joint.

The first articular surface is referred to as the medial malleolar surface of the talus. We can see the surface here highlighted in green on the medial view of the talus. This is dorsal pulley-like trochlear surface which articulates with the medial malleolus of the tibia. The other articular surface is known as the lateral malleolar surface and it's highlighted in green in this lateral view of the talus. This surface articulates with the lateral malleolus of the fibula. When we compare these articular surfaces in the same image, we can see that the lateral articular surface is larger and projects more inferiorly than the medial articular surface. So here we can see a medial view of the talus with the medial articular surface and here we can see a lateral view of the talus with the lateral articular surface.

So let's move on to talk about some bony landmarks which will be important to know in clinical practice. The first bony landmark we'll discuss is the head of the talus. As I've mentioned previously, the head of the talus has a convex surface and carries the articular surface of the navicular bone. In this next image, we can see an inferior view of the head of the talus.

The next bony landmark we're going to talk about is the neck of the talus which you can see highlighted here in this inferior view. The neck of the talus is a narrow region between the head and the body and it presents many surfaces for attachments of ligaments. The inferior surface of the neck of the talus contains a deep sulcus known as the sulcus tali or the talar sulcus. As we can see, the sulcus passes obliquely forward from medial to lateral and expands dramatically on the lateral side.

Another important landmark that is related to the neck of the talus is this one you can see here which is the sinus tarsi or the tarsal sinus. This is a small cavity located on the outside of the ankle between the neck of the talus and the anterior superior aspect of the calcaneus. This funnel-shaped canal contains numerous anatomical structures including blood vessels, nerves and a ligamentous complex which is comprised of the interosseus talocalcaneal and cervical ligaments and roots of the inferior extensor retinaculum.

Another bony landmark we will look at is the body of the talus which we can see here from a superior view. The body of the talus is cuboidal in shape and it articulates with the distal end of the tibia. It's covered dorsally by a trochlear surface which also articulates with the distal end of the tibia. In this next image, we can see an inferior view of the body. So on the left hand side, we can see the lateral surface of the talus. It is triangular, smooth and concave for the articulation with the lateral malleolus. On the right hand side, we can see the medial surface. It is covered by comma-shaped facets for articulation with the medial malleolus and, distally, the surface contains numerous vascular foramina.

Another bony landmark I'll mention is the posterior process of the talus, which is seen here in an inferior view. It's formed by the lower part of the medial surface of the body of the talus. The posterior process consists of both a medial and lateral tubercle. We can see the medial tubercle here and the lateral tubercle here. So, let's look at these tubercles in more detail.

Highlighted on the left is the lateral tubercle which is the larger of the two tubercles and articulates with the sustentaculum tali. This tubercle provides an attachment for the posterior talofibular ligament which we will talk about later on in this tutorial. The medial tubercle is highlighted in this image on the right. Many ligaments attach near this tubercle. The medial talocalcaneal ligament is attached below the medial tubercle whereas the most posterior superficial fibers of the deltoid ligament attach above the tubercle. The deep fibers of the deltoid ligament attach slightly higher. Again, these ligaments will be discussed later on in this tutorial.

These two tubercles have a groove between them which is shown here highlighted in green. This is a groove for the tendon of flexor hallucis longus as it passes from the leg to the foot. So here we have the lateral tubercle of the posterior process, the medial tubercle of the posterior process and, running between them, the groove for tendon of flexor hallucis longus. We will now go on to talk about the ligaments which attach to the talus.

There are a large number of ligaments attached to the talus since it's the centerpiece for three joints – the ankle, the subtalar and the talocalcaneonavicular joints. This makes the talus an important bone in the stability of the ankle. The ligaments of the ankle joint ensure that the talus cannot rock from side to side or move backwards or forwards relative to the tibia and fibula. So on the medial side, the ankle is held together by a massive ligament referred to as the deltoid ligament. This ligament is also known as the medial collateral ligament. This ligament originates from the tibia and inserts on a broad area of the talus as well as the adjoining bones in front and below.

Another ligament which holds the ankle together is the lateral collateral ligament and as you can see in this image, the ligament consists of three different components. Two of these components are attached to the talar bone and one to the calcaneus. Now, we'll look at these components individually.

So here we can see one of the components of the lateral collateral ligament and is referred to as the anterior talofibular ligament. As the name suggests, it connects the talus to the fibula anteriorly. Here is another component of the lateral collateral ligament. It's referred to as the posterior talofibular ligament. Again, as the name suggests, it connects the talus to the fibula but in a posterior direction. The final ligament involved in the lateral collateral ligament is referred to as the calcaneofibular ligament. As the name implies, it attaches the calcaneus to the fibular bone.

So to wrap up this tutorial, let's talk about some clinical notes on the talus. Talar fractures can be displaced or undisplaced and displaced fractures can cause vessel rupture. Displaced fractures of the neck of the talus where two segments of the talar neck become incorrectly aligned can cause interruption to the blood supply of the talar body. This can result in avascular necrosis and nonunion. There are few arteries which are particularly vulnerable to rupture. They include branches of the posterior tibial artery as well as dorsalis pedis and the peroneal artery. These arteries are connected through a sling of vessels that lie within the sinus tarsi. Undisplaced fractures of the talus can also occur but tend not to be associated with vessel rupture.

And that brings us to the end of this tutorial. Thanks for listening.

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Now, good luck everyone, and I will see you next time.