Video: Tibia and fibula

Have you ever played a game of football where one of your friends misses the ball and swings their foot into your shin, making you love them a little less? Well… I have. Several times. It's extremely painful and results in swear words pouring out of my mouth like word vomit. But if you think that's bad, spare a thought for these lads who compete in the traditional English combat sport known as shin-kicking. Yep, you heard me – shin-kicking. The things I learn working for Kenhub.

Anyway, why is a kick to the shin so sore? It could be because there's no musculature cushioning the blow. If you feel your legs, you'll notice the anterior border of your shin just deep to the skin. It could also be down to the fact that your shin bone is covered by a fibrous layer called the periosteum, which is filled with pain receptors.

Today we'll be discussing your shin bone, also known as the tibia, and the other bone of the leg, the fibula.

Okay, let's have a quick overview of what we're going to talk about today. The bulk of this tutorial will be focused on the individual features of the two bones of the leg – the tibia and the fibula. We'll focus on their main bony features or landmarks and muscle attachment points. We'll also talk about the joints in which these bones participate and give you some tips on how to tell the two bones apart. Finally, we'll bring our tutorial to a close with some clinical notes about shin splints.

The tibia and fibula are the two bones of the leg. Before we go any further, let's clear up an issue that often arises when transitioning from everyday terms to anatomical terms. When we're talking to our friends and our family members, the term leg is commonly used to refer to the whole lower limb. However, this terminology is not scientifically accurate. The lower limb is further subdivided into the thigh and the leg. So, in anatomical terms, the leg is the part of the lower limb that lies between the knee and ankle joints.

The tibia and the fibula are two long bones, positioned parallel to each other. The tibia is the second largest bone in the body, after the femur, and the primary weightbearing bone of the leg. It is positioned medially to the fibula and is much thicker in appearance. In contrast, the fibula is a slender bone, located lateral to the tibia. The fibula mainly functions as an attachment site for the muscles of the leg and thigh but is also important in stabilizing the ankle joint.

Okay, now that we know where we can find the tibia and the fibula and the main differences between them, it's time to explore the main landmarks of the tibia.

The tibia is commonly referred to as the shin bone. Similar to the other long bones, the tibia can be divided into three parts – a proximal end, a body, and a distal end. The proximal end participates in the knee joint whereas the distal end contributes to the ankle joint. The tibial shaft, in turn, offers many attachment sites for the muscles of the leg and thigh.

Let's begin with exploring some of the bony features of the proximal end of the tibia, starting with two large rounded prominences known as condyles.

The tibia has a medial condyle and a lateral condyle. The medial condyle serves as a point of insertion for the semimembranosus muscle. The lateral condyle provides a point of origin for the extensor digitorum longus and the tibialis anterior muscles. The lateral condyle is also the place where the proximal tibia articulates with the proximal fibula to form the superior or proximal tibiofibular joint. So as you can see, the fibula does not contribute to the formation of the knee joint.

Together, the superior surfaces of the medial and lateral tibial condyles form the structure known as the tibial plateau. This smooth bony surface articulates with the femoral condyles via the lateral and medial menisci, forming the knee joint.

Lying between these two condyles, we find the intercondylar eminence, which is formed by the two raised edges on the medial aspect of each condyle, known as the intercondylar tubercles. In this superior view of the tibial plateau, we can also see the anterior and posterior intercondylar areas on either side of the intercondylar eminence. These areas provide attachment for the menisci and cruciate ligaments of the knee, which hold the femur and tibia together.

Moving on to the anterior surface of the lateral condyle, we can see the tubercle of the iliotibial tract, which is also known as Gerdy's tubercle, named after the French surgeon, Pierre Nicholas Gerdy. This tubercle provides a point of insertion for the iliotibial tract.

The next structure we're going to talk about is one that you can easily feel on your own leg. If you can palpate a raised area on the anterior aspect of the leg just below the kneecap, you found the tibial tuberosity. This bony prominence serves as a point of insertion for the patellar ligament.

Now onto the landmarks of the body of the tibia.

The body, or shaft of the tibia, is triangular in cross-section. Consequently, it consists of three borders and three surfaces where the borders form the corners of the triangle. Here, we can see the anterior border. This is the most prominent border and can be easily palpated as it lies just underneath your skin. As we saw earlier, this is often the site of those all too painful shin kicks.

Now let's look at the medial border, which is also palpable underneath the skin. The medial border of the tibia begins just posterior to the medial condyle and ends just proximal to the medial malleolus at the distal end of the tibia.

The final border of the tibia is the interosseous border, which is the attachment site of the interosseous membrane. The interosseous border is also sometimes known as the lateral border of the tibia.

Now for the surfaces. The medial surface lies between the anterior border and the medial border. You can feel the surface on yourself as it is located just deep to the skin. The semitendinosus, gracilis, and sartorius muscles insert onto the proximal aspect of the surface via the pes anserinus.

Next, we see the lateral surface which lies between the anterior border and the interosseous border. This surface serves as a point of origin for the tibialis anterior muscle.

Finally, let's have a look at the posterior surface of the tibia. The posterior surface lies between the medial border and the interosseous border. This surface is slightly rounded and provides a point of origin for the flexor digitorum longus and the tibialis posterior muscles as well as an insertion point for the popliteus muscle.

While we're looking at the posterior aspect of the tibia, let's talk about a short, oblique raised ridge known as the soleal line. As the name suggests, this bony landmark serves as a point of origin for the soleus muscle.

Moving to the distal end of the tibia, we can see that it has a rectangular shape and an inferior bony projection on the medial side known as the medial malleolus. The medial malleolus is used as a landmark when palpating the posterior tibial pulse as the posterior tibial artery runs behind it. This pulse is examined by physicians when assessing the peripheral vascular disease.

On the posterior surface of the distal end of the tibia, there is a vertical groove which continues inferiorly and medially onto the posterior surface of the medial malleolus. This groove is known as the malleolar groove and allows for the passage of the tendon of the tibialis posterior muscle.

On the lateral aspect of the distal tibia, we can see a triangular indentation known as the fibular notch of the tibia. The anterior and posterior edges of this notch project and converge proximally to the interosseous border of the tibia. The tibia and the distal end of the fibula articulate here, forming the inferior or distal tibiofibular joint.

The lower surface of the distal end of the tibia and the lateral surface of the medial malleolus contain distal articular surfaces which articulate with the talus of the foot, contributing to the formation of the ankle joint.

That wraps up the bony landmarks of the tibia. Now let's talk about the other bone of the leg, which is the fibula.

In this illustration, we can see the fibula from an anterior view. This bone also has a proximal end, a body, and a distal end. Again, let's look at some bony features of the fibula, starting with the proximal end of the fibula.

The proximal end is mainly formed by an irregularly-shaped enlargement known as the head of the fibula. This portion of the bone has a circular articular facet on its superomedial surface that articulates with the lateral condyle of the tibia at the proximal tibiofibular joint. The head of the fibula is a point of origin for the extensor digitorum longus, the fibularis longus, and the soleus muscles. This bony landmark can be palpated at the lateral aspect of the leg, just distal to the knee joint.

On the posterolateral aspect of the head of the fibula is a small bony projection known as the apex. Sometimes the apex is also referred to as the styloid process. Let's take a look at the fibula from a posterior view to get a better look at the apex. The apex of the fibula serves as an insertion point for the biceps femoris muscle, which we can see here in this image.

The next structure that we're going to talk about is known as the neck of the fibula. This structure connects the head with the body, or shaft of the fibula. One important structure passes around the neck of the fibula, the common fibular nerve, also known as the common peroneal nerve. This nerve travels around the posterolateral aspect of the fibular neck, providing innervation to structures of the lower limb. The location of this nerve is clinically significant as trauma to this part of the bone can lead to neurological deficits of the lower limb.

Similar to the tibia, the body or shaft of the fibula is kind of triangular in cross-section; therefore, it also consists of three borders and three surfaces. The structure of the fibula can vary slightly amongst individuals with its surfaces and borders being a little bit harder to decipher when compared to the tibia. Here we can see the anterior border of the fibula, which runs from the anterior aspect of the head in an inferolateral direction, descending along the shaft of this bone. The border provides a point of origin for the extensor digitorum longus muscle.

Now let's also take a look at the medial border. The medial border, as its name implies, faces medially. It begins just below the medial aspect of the head and ends inferiorly. At the lower fourth of the fibula, the medial border becomes continuous with the interosseous crest. This border is sharp and well-marked at the upper and middle parts of the bone. A layer of deep fascia that separates muscles of the posterior leg compartment is attached to the medial border.

The last border we're going to talk about is the posterior border. We have to flip the fibula over to clearly see this border. The posterior border runs from the posterior aspect of the head of the fibula descending along its shaft in an inferomedial direction. The distal end of the posterior border has a sharp prominent spine while its proximal end is slightly rounded and harder to decipher. The posterior border serves as a point of origin for the soleus muscle.

As mentioned earlier, the fibula has three surfaces. The medial surface lies between the medial border and anterior border of the fibula as we can see here in the cross-section of the fibula. The medial surface can be further divided into anteromedial and posteromedial surfaces by a raised line known as the interosseous crest. The interosseous membrane of the leg attaches to this crest. As the interosseous crest extends distally along the medial surface of the fibula, its lower border curves medially, blending with the medial border of the fibula at the lower fourth of the bone.

The lateral surface lies between the anterior and posterior borders of the fibula. This surface faces the lateral compartment of the leg and provides a point of origin for the fibularis longus and the fibularis brevis muscles.

Lastly, we have the posterior surface of the fibula. The posterior surface is located between the medial border and the posterior border of the fibula. The posterior surface serves as a point of origin for the flexor hallucis longus and tibialis posterior muscles.

As mentioned previously, the surfaces and borders of the fibula can be quite tricky to decipher, leaving room for differing opinions. Bibliographic sources provide distinct definitions of the medial and posterior surfaces of the fibula. Some sources describe the medial surface as being located between the anterior border and the interosseous crest which they name the interosseous border and the posterior surface as being located between the interosseous crest and the posterior border. In these sources, the medial border is named medial crest and is located on the posterior surface. This notation is handy because this way each surface corresponds to the muscular compartments of the leg of the same name.

In the nomenclature we used in this tutorial, the anterior muscular compartment corresponds to the anteromedial surface of the fibula, the posterior muscular compartment to the posteromedial and posterior surfaces of the fibula, and the lateral muscular compartment to the lateral surface of the fibula.

Now that we left the most confusing part of this tutorial behind, it's time to move on to the distal end of the fibula. If we look at the distal end of this bone, we can see the last feature of the fibula that we're going to talk about today, which is an inferoposterior projection known as the lateral malleolus. The small articular facet located on its medial aspect articulates with the talus as part of the ankle joint.

Now let's quickly review the joints in which these two bones participate.

The tibia and the fibula articulate with each other in three different places, forming the three tibiofibular joints. We've talked a little bit about these joints already, but now let's piece them together and take a closer look.

The small superior tibiofibular joint is a synovial plane joint which allows very little movement. The articular surfaces located on the inferior aspect of the lateral condyle of the tibia and on the superomedial aspect of the head of the fibula are flat and circular. The capsule is strengthened by anterior and posterior ligaments.

The interosseous membrane is a thin sheet of fibrous connective tissue, linking the interosseous border of the tibia to the interosseous crest and distal part of the medial border of the fibula. This membrane forms the middle tibiofibular joint. Besides linking these bones together, the interosseous membrane also serves as a point of attachment for the muscles of the leg. There are two openings in the membrane, one proximally and the other distally, for the passage of vessels between the anterior and posterior compartments of the leg.

The distal ends of the tibia and fibula are maintained together by the tibiofibular syndesmosis, also known as the inferior or distal tibiofibular joint. This joint is formed by the rough medial convex surface on the distal end of the fibula and the rough concave surface of the fibular notch of the tibia. It is reinforced by the anterior and posterior tibiofibular ligaments, but the strongest bond between the bones is the interosseous ligament located between the bones and therefore not visible in this image. To be able to see this important ligament, we have to look at this longitudinal section of the distal ends of the tibia and fibula.

The interosseous ligament is an inferior extension of the interosseous membrane and spans the narrow space between the adjacent articular surfaces. This strong connection between the distal ends of the tibia and fibula is fundamental to produce the skeletal framework for articulation with the foot at the ankle joint. Besides articulating with each other, the tibia and fibula participate in two other important joints that we've already mentioned during this tutorial – the knee and the ankle. The tibia and fibula articulate with the talus to form the ankle joint, while only the tibia articulates with the femur and participates in the formation of the knee joint.

The knee joint is one of the largest joints of the body being responsible for bearing a considerable amount of biomechanical stress every time you stand or walk. It is a complex synovial joint because it connects three bones. Besides the condyles of the femur and the tibial plateau, an articular surface from a third bone, the patella, takes part in this joint.

The ankle joint, also known as the talocrural joint, is also a complex synovial joint. It is formed by the articular surfaces of the malleoli of the tibia and fibula and the body of the talus. This joint allows for movements of the foot and it supports our body weight against the ground while we're standing.

Now that we're familiar with the bones of the leg, let's get clinical.

In today's clinical notes, we're going to talk about shin splints, which refers to pain in the shins typically caused by exercise or overuse. Medically known as medial tibial stress syndrome, shin splints often occur in individuals who have recently intensified or modified their exercise routine. For example, it can occur in runners who increase their speed or the distance they run. This leads to inflammation of the periosteal tissue surrounding the tibia and causes pain. Pain is usually dull to begin with but it can become increasingly sharp and severe to the point where exercise is no longer possible. Treatment involves taking a break from the exercise that caused the shin splints and switching to low impact sports like yoga and swimming. Ice packs are recommended to reduce pain and swelling and pain medication can be taken when required. Patients usually recover and get back to their normal activities within a few weeks.

Before we bring our tutorial to a close, let's quickly summarize what we've learned today. We started off by introducing the bones of the leg – the tibia and the fibula – which are positioned parallel to each other. The tibia which is located on the medial side is the weightbearing bone of the leg and is, for that reason, much bigger than the fibula. The fibula is a slender bone located on the lateral side of the leg.

Next, we talked about each of these bones in more detail, starting with the tibia. On the proximal end of the tibia, we found several landmarks – the lateral and medial condyle, the tibial plateau, the tubercle of the iliotibial tract, and the tibial tuberosity. The body of the tibia is triangular in cross-section and has anterior, interosseous, and medial borders as well as medial, lateral, and posterior surfaces. On the posterior surface, we find the soleal line.

The distal end of the tibia has a bony protuberance on the medial side, the medial malleolus, and the lateral side is occupied by the fibular notch to which the distal end of the fibula is anchored. We also identified a small groove on the posterior surface of the distal tibia known as the malleolar groove. This little groove lodges the tibialis anterior tendon. Finally, on the lower surface of the distal tibia and lateral surface of the medial malleolus are the distal articular surfaces that articulate with the talus, contributing to the formation of the ankle joint.

We then moved on to talk about the fibula, and on its proximal end, we have the head, with the apex or styloid process, and the neck of the fibula. The body of the fibula is also triangular in cross-section and has anterior, medial, and posterior borders as well as medial, lateral, and posterior surfaces. The interosseous crest is found on the medial surface. The distal end of the fibula expands to form the lateral malleolus.

The tibia and fibula articulate with each other in three places – the superior or proximal tibiofibular joint between the head of the fibula and the lateral condyle of the tibia; the middle tibiofibular joint which is the interosseous membrane of the leg; and the tibiofibular syndesmosis or inferior tibiofibular joint between the fibular notch on the distal end of the tibia and the corresponding surface on the distal end of the fibula. Additionally, the tibia and fibula articulate with the talus to form the ankle joint, while only the tibia articulates with the femur and participates in the formation of the knee joint.

Finally, we concluded our tutorial with some clinical notes about shin splints.

So that brings us to the end of our tutorial on the tibia and fibula.

We hope you enjoyed it. Thanks for watching. See you next time, and happy studying.