Hello everyone! This is Megan from Kenhub, and welcome to our tutorial on the calcaneus. In this tutorial, we will be looking at the bony landmarks and articular surfaces of the calcaneus as well as the tendons, muscles and ligaments that attach to it. At the end, we will briefly mention some clinical notes related to the calcaneus.
Before we begin this tutorial, just let me give you a quick introduction of this bone. The calcaneus, which is also known as the heel bone, is found at the back of the feet near the ankle. It sits just below the talus, the tibia and the fibular, which are the bones that make up the lower leg. The calcaneus is the largest bone in the foot and it projects posterior to the tibia and fibula. It acts as a short lever for the calf muscles which insert onto its posterior surface via the Achilles tendon. It plays an important role in weightbearing and stability. It articulates with two bones –the talus and the cuboid.
Now that I've given you a quick overview of the structure, let's move on to talk about the articular surfaces and bony landmarks of the calcaneus. Here, we are looking at the superior surface of the calcaneus which can be divided into three areas – the posterior, middle and anterior aspects. I will now show you these three areas in more detail.
Here, you can see the posterior aspect of the calcaneus. It is rough and concavo-convex in shape. This convexity supports the fibroadipose tissue also known as Kager's fat pad between the calcaneal tendon and the ankle joint. The middle aspect of the calcaneus is oval and convex in shape. It carries the posterior talar facet which is highlighted in green here. This facet is one of the three articular surfaces for the talus which we will talk about later. The third and final part of the superior surface of the calcaneus is the anterior aspect which is shown here.
Now, we will talk about the articular facets predominantly located on the superior surface. As I said in the beginning, the calcaneus articulates with two tarsus bones. The first of these bones is the talus which is shown here in green. The cuboid which is highlighted here in green is the other bone that the calcaneus articulates with. So, here, we can see the calcaneus and then we can see the talus, the fibula and tibia sitting above it, and the cuboid here.
So, first, we're going to talk about the talar articular facets. There are three facets, otherwise known as articular surfaces, for the talus. The first one shown here is the posterior talar articular surface of the calcaneus. This is the largest of the three and has a slightly convexed, oval surface for the body of the talus. Anteromedial to this is the medial or middle articular surface for the talus. Anterolateral to the middle talar facet is the small anterior facet for the talus which may sometimes blend with the medial facet. Both the middle and anterior surfaces are shallowly concave.
There is only one articular surface or facet for the cuboid bone. It is referred to as the cuboidal articular surface of the calcaneus. This is an obliquely-directed oval articular surface that is convex in the transverse plane and concave in the vertical plane.
Now that we have described the articular surfaces of the calcaneus, we can now talk about some of the bony landmarks. One of these landmarks is referred to as the calcaneal sulcus or sulcus calcanei. We can see that this is a rough depression between the posterior and middle talar articular surfaces.
Another bony landmark we should mention is the sustentaculum tali which is shown here in the superior view. If we switch our viewpoint and look at the medial aspect of the calcaneus, we can get a better view of this landmark. We can see that it's a horizontal shelf that arises from the anteromedial portion of the calcaneus. If we zoom in further, we may be able to see that the superior surface is concave in nature. This surface articulates with the middle calcaneal surface of the talus. The inferior surface of the sustentaculum tali has a groove for the tendon of flexor hallucis longus highlighted here in this dorsal view.
There are a few more bony landmarks we must talk about before we can move on to the calcaneal attachments. One of these landmarks is shown in this illustration here and it is referred to as the tuber calcanei or the calcaneal tuberosity. Here, you can see an image of this tuberosity when looking behind the calcaneus. This tuberosity forms the projection of the heel. The calcaneal tuberosity has two processes. The first of these is the medial process shown here in green. The second process is referred to as the lateral process. Both these processes are extremely important attachment sites for various structures in the foot.
The last bony landmark we'll talk about today is the fibular trochlea of the calcaneus. This is a small projection from the lateral aspect of the bone and we can see it here highlighted in green. Now we've covered the bony landmarks, let's move on to talk about the muscles, tendons and ligaments which attach to the calcaneus.
The calcaneus provides a large surface area for the attachment of these structures. So, let me remind you again of these bony landmark, the calcaneal sulcus. As we mentioned earlier, this sulcus is a rough depression between the posterior and middle talar articular surfaces. The calcaneal sulcus provides attachment for the interosseus ligaments which are shown here in this image as well as the talocalcaneal ligaments and the cervical ligaments.
The inferior extensor retinaculum highlighted in this image also attaches to the calcaneal sulcus. Here, we can see the posterior talar facet we talked about earlier. There's also a non-articular area distal to this facet which provides an attachment surface for some ligaments and muscles. The extensor digitorum brevis muscle, which is highlighted in green here, is one of the structures that attaches to the non-articular area distal to the facet. Here, we can see the extensor digitorum brevis originating from the calcaneus and extending towards the phalanges.
Another structure that attaches to this point is the main band of the inferior extensor retinaculum, shown in this image. The bifurcate ligament also attaches to this non-articular area. Another bony landmark which provides an attachment surface is the medial process of the calcaneal tuberosity. The superficial part of the flexor retinaculum, which is shown in this image, attaches to this tuberosity as well as the plantar aponeurosis also known as the plantar fascia.
Some muscles also attach to the medial process of the calcaneal tuberosity such as the abductor hallucis muscle which is shown here in green. So, here, we can see this muscle extending from the calcaneus towards the proximal phalanx of the hallux or the big toe. Another muscle which attaches to the medial process of the tuberosity is the flexor digitorum brevis muscle. Here, we can see the flexor digitorum brevis muscle extending from the calcaneus to the phalanges. A small part of abductor digiti minimi also attaches on to the medial process.
The lateral process of the calcaneal tuberosity also provides an attachment surface for muscles. Although part of abductor digiti minimi attaches to the medial process, the majority of the muscle attaches to the lateral process of the calcaneal tuberosity. There are a few more muscles, tendons and ligaments that we should mention which attach to the posterior aspect of the calcaneus. One of these is the long plantar ligament which is shown in this image highlighted in green. The flexor accessorius? (8:24) muscle, otherwise known as the quadratus plantae muscle, is another structure which attaches to the posterior calcaneus. Specifically, the head of this muscle is involved in this attachment. The short plantar ligament also attaches here. The plantaris muscle highlighted in green in this image also attaches to the posterior calcaneus. The calcaneal tendon, otherwise known as the Achilles tendon, is another structure which attaches here.
Here is an image of the fibular trochlea we talked about earlier. Just proximal to this trochlea, a ligament referred to as the calcaneofibular ligament attaches here.
The last bony landmark involved in muscle and ligament attachments is the sustentaculum tali. Here, we can see the flexor retinaculum, which is one of the structures that attaches close to the sustentaculum tali. The plantar calcaneonavicular ligament also attaches in this area. The tendon of tibialis posterior, shown here, also attaches to the sustentaculum tali. The superficial fibers of the deltoid ligament and the medial talocalcaneal ligaments also attach to the calcaneus in this area. The tendon of flexor digitorum longus is another structure which attaches around the sustentaculum tali.
Quadratus plantae attaches around the sustentaculum tali as well as to the posterior calcaneus. Specifically, the large medial head of flexor accessorius is the point of attachment in this area. So, finally, to round off this tutorial, we will briefly discuss some pathological conditions related to the calcaneus.
The calcaneus is the most commonly fractured tarsal bone and accounts for about two percent of all fractures in the body and sixty percent of all tarsal fractures. Calcaneal fractures can be divided broadly into two types – extra-articular fractures and intra-articular fractures. Extra-articular fractures account for twenty-five to thirty percent of cases and could be either calcaneal tuberosity avulsion fractures or extra-articular Lover's fractures, otherwise known as Casanova fractures. The other main type – intra-articular fractures – account for about seventy to seventy-five percent of cases. They are also known as intra-articular Lover's fractures.
Plantar fasciitis, a condition which indirectly affects the calcaneus, is the pain caused by degenerative irritation at the insertion of the plantar fascia. The plantar fascia inserts on the medial process of the calcaneal tuberosity which is highlighted here in green. It is the most common cause of heel pain and the typical presentation is sharp pain localized at the anterior aspect of the calcaneus.
Now that you just completed this video tutorial, then it’s time for you to continue your learning experience by testing and also applying your knowledge. There are three ways you can do so here at Kenhub. The first one is by clicking on our “start training” button, the second one is by browsing through our related articles library, and the third one is by checking out our atlas.
Now, good luck everyone, and I will see you next time.