Video: Regions of the lower limb

Maps are great in helping us find where we need to go. But maps aren't only useful in traveling, you know. Sometimes, mapping things out can actually be useful in learning anatomy. What? You heard me. The body can be mapped out into many different regions. Today, we're only going to focus on the regions of the lower limb. Dividing the lower limb into specific regions gives us a better idea of where each region lies, what's situated around it, and what is found within it. No more wondering what a gluteal fold or an interdigital sulcus is. It's all explained in this tutorial on the regions of the lower limb.

We'll begin our journey today by looking at the different regions within the anterior and posterior surfaces of the lower limb and explore the boundaries and contents of each. We'll finish off by taking a look at some clinical notes to help consolidate our understanding and apply our knowledge. Nice and simple.

Before we dive in, let's just take a second to outline the exact anatomical location of the lower limb.

Anteriorly, the lower limb begins just below this landmark here, which is known as the inguinal ligament. Posteriorly, the lower limb begins at the proximal aspect of the gluteal region. Needless to say, the lower limb terminates at the toes.

There are seven main regions of the lower limb that we're going to meet today. These include the gluteal region, the hip, the thigh, the knee, the leg, the ankle, and the foot. Most of these regions can be divided into anterior and posterior surfaces and are made up of smaller sub-regions which we will explore as we make our way proximal to distal along the lower limb. Let's begin with the gluteal region.

Yep, I'm talking about your beloved twerk machine – that's hardest to miss on our anatomical map. The gluteal region, also known as the buttocks, lies posterior to the bony pelvis and extends from the top of the hip bone known as the iliac crest to the gluteal fold below. If any of you are into doing squats at the gym, I'm sure you'll know that the gluteal region is made up of mostly muscles – some big and some small. The main contents include the three larger superficial gluteal muscles and the deep gluteal muscle group, also sometimes referred to as the inner hip muscles. The large nerve of the lower limb – the sciatic nerve – also travels through the gluteal region from the pelvis.

Let's stop next for a moment at the hip region. This region is located anterior and lateral to the gluteal region and extends once again from the top of the hip bone – the iliac crest – to the area just below the palpable bony part of the hip, which is formed by the greater trochanter of the femur. And that's all we're going to say about the hip region.

Next, let's meet the thigh region. This region is also known as the femoral region due to the fact that the Latin word for thigh is femur which, of course, we know is also the name of the long bone located here. The thigh is made up of the anterior and posterior thigh regions. Let's begin with taking a look at the anterior first.

The anterior thigh region, also known as the anterior femoral region, is bounded superiorly by the inguinal ligament and inferiorly by the proximal border of the knee. Let's take the skin and fascia away and take a look at what's inside the anterior thigh region. It is largely made up of the quadriceps femoris muscle group, which most of us would refer to as our quads. As its name suggests, the quadriceps femoris muscle group is made up of four muscles – the rectus femoris, the vastus lateralis, the vastus medialis, and vastus intermedius muscles.

Within the anterior thigh region, there is a small triangular sub-region known as the femoral triangle, also known as the femoral trigone. This region gets its name from its conceptual triangular shape and location within the thigh. The triangle sits on the anteromedial aspect of the thigh and is made up of the inguinal ligament superiorly, the sartorius muscle laterally, and the adductor longus muscle medially. This is not just any triangle, of course. It's important to know about as it's where we can locate a number of important anatomical structures of the thigh.

From lateral to medial, these are the femoral nerve, the femoral artery, the femoral vein, and the femoral lymph nodes, which are more commonly known as the inguinal lymph nodes. These structures are traveling to and from the lower limb passing through the femoral triangle. As the femoral artery is superficial here, this is also the site where you could palpate for a femoral pulse.

So that wraps up the anterior thigh region. Now, we're heading to the posterior thigh region, or posterior femoral region. This region begins at the gluteal fold and ends just above the popliteal region or knee pit. Like the anterior thigh, this region is made up of mostly muscle. The muscles of the posterior thigh are commonly known as the hamstrings, or in the anatomy world, the ischiocrural muscles. The hamstrings are made up of three muscles – the biceps femoris, the semitendinosus muscle, and the semimembranosus muscle. The sciatic nerve, which we mentioned earlier, continues from the gluteal region to enter the posterior thigh which we can see here in this image.

Grab your maps, we're heading south to the knee.

This region is also known as the genual region as genu is the Latin term for the knee. The knee region is largely made up of the bony condyles of the distal femur and proximal tibia as well as the patella. It also contains many tendons, ligaments, and other structures which aid in supporting the joint. Looking from an anterior perspective, we can see that this region begins at the distal border of the anterior thigh and ends at the proximal border of the anterior leg. Another, perhaps, easier way to describe the anterior knee would be the area around the kneecap, or the patella. Let's flip over to the posterior aspect of the knee, which is also known as the popliteal region.

The popliteal region is marked by the diamond-shaped popliteal fossa, which is a well-defined fat-filled space. The popliteal fossa is bounded superiorly by the tendons of the hamstring muscles of the posterior thigh. Inferiorly, it is bordered by the two tendons of the large superficial muscle of the posterior leg – the gastrocnemius muscle. The popliteal region houses some very important structures such as the appropriately named popliteal artery and vein as well as the two main nerves of the leg – the tibial and common fibular nerves.

We're traveling to the next part of the lower limb, which is the leg.

Although this might be a word you learned when you were about two and got a boo-boo on your leg, the term leg actually causes quite a bit of confusion for lots of adults when learning anatomy. That's because to anatomists, your leg is confined only to the region between your knee and your ankle and not your entire lower limb. Good to know! So let's begin with the anterior part of the leg, also known as the anterior crural region, which begins at the distal border of the knee and ends at an imaginary line above the knobbly parts of your ankle, which are known as the medial and lateral malleoli.

The anterior leg is mostly defined by the sharp anterior border of the tibia, or shin bone, to you and me. The outside, or lateral anterior leg, is defined by some anterior and lateral leg muscles known as the tibialis anterior and fibularis longus, while the inner or medial side of the anterior leg is mostly formed by the medial part or the head of the gastrocnemius muscle.

Quickly moving on to the posterior region of the leg, or the posterior crural region, which lies on the posterior surface of the leg between the popliteal fossa and the ankle region. This region contains the large calf muscles – the gastrocnemius and soleus – as well as several deeper muscles of the posterior leg. It also contains the posterior tibial artery and veins as well as the tibial nerve. Feel free to check out the video on the muscles of the leg when you're ready to learn more about this area.

Moving on to the anatomical bridge between the leg and the foot, we're now looking at the ankle region. This region is also known as the talocrural region. Looking from an anterior perspective, we can see this region is bounded superiorly by the distal border of the anterior leg and inferiorly by the proximal border of the dorsal region of the foot. The anterior talocrural region is defined by the distal ends of the tibia and fibula which form the bony protrusions of the ankle region known as the medial and lateral malleoli, respectively. Between them is the most proximal bone of the foot – the talus. This region also contains the distal tendons of the anterolateral leg muscles which act in the foot as well as many vessels and nerves of the leg which pass over the ankle joint.

Just around the corner from the anterior talocrural region, we meet the posterior region of the ankle. This region is bounded superiorly by the distal border of the posterior leg and inferiorly by the proximal border of the heel of the foot, which is known as the calcaneal region. Once again, the posterior talocrural region is marked by the medial and lateral malleoli, which are separated by a large tendon of the calf muscles – the calcaneal tendon – which is commonly referred to as the Achilles tendon. Between the calcaneal tendon and both malleoli are two small sub-regions known as the medial and lateral retromalleolar regions.

Both of these regions give passage to tendons of some of the posterior and lateral leg muscles as they travel distally to insert on the foot. The medial retromalleolar region also gives passage to the posterior tibial artery, and therefore, this region is where you can check for the posterior tibial pulse.

Right down at the distal end of the lower limb, we have now reached the foot. The foot, or the pedal region, is made up of a number of smaller regions which we are about to explore. Working proximal to distal, the first region that we meet is the calcaneal region. Calcaneal is derived from the Latin word calx, which means the heel. The proximal region of the foot is made up of a number of bones known as the tarsal bones and the calcaneal region is marked by a posterior protrusion of the largest of these known as the calcaneus as well as the large calcaneal fat pad which provides cushioning.

Moving distally, we meet the dorsal and plantar region of the foot. Let's begin with the dorsum of the foot. Dorsum, or dorsal in Latin, translates to back. But why would the front of the foot be called the back of the foot? During the early days of the developing fetus, the sole of the foot faces upwards while the dorsum of the foot lies inferiorly, or facing back, as their name suggests. However, during development, the limbs begin to rotate, which essentially flips everything around. The dorsum of the foot, which was originally located on the inferior aspect, now faces superiorly, while the plantar aspect faces inferiorly.

The dorsum of the foot contains several structures including the dorsal surfaces of bones at the foot namely the tarsal bones, the metatarsals, and the phalanges of the foot. It also contains the extensor muscles of the foot, the neurovascular structures of the dorsal aspect of the foot, as well as the tendons of the anterior muscles of the leg.

The dorsal region of the foot can be broken down into several smaller regions such as the metatarsal region as we can see here lying in this image. This is the region overlying the metatarsal bones. Distal to the metatarsal bones, we meet the toes, or the digits. The digits can be numbered from one to five with the great toe, or hallux, being the first digit, and the little toe, the fifth digit. In between the digits, we meet the interdigital spaces, which are highlighted in this image.

On the medial and lateral sides of the foot, we find the medial and lateral border of the foot. The medial side is also known as the tibial border of the foot as the tibial bone of the leg sits on the medial aspect. The lateral aspect of the foot is therefore known as the fibular border as the fibula lies on the lateral aspect.

As you know, our feet don't sit completely flat on the ground. Along the tarsal and metatarsal parts of the foot is a prominent arch commonly referred to as the bridge of the foot. Although it may seem like there's only one arch, there are actually three. The first two are the transverse arches. The transverse arches, as the name suggests, are orientated transversely across the foot. The proximal transverse arch is the larger of the two and is formed by four of the tarsal bones – the three cuneiform bones and the cuboid bone laterally. The distal transverse arch lies more distal near the digits and is formed by the heads of the five metatarsal bones. Because of the distal transverse arch, only the heads of the first and fifth metatarsal heads make contact with the ground. Many muscles of the leg and foot, in addition to surrounding ligaments, help to support these arches and cause them to adapt to movements of the foot helping us as we walk and run.

The third arch of the foot is the longitudinal arch. This arch is composed of both medial and lateral parts which lie on either side of the transverse arch. The medial part is formed by the medial tarsal and metatarsal bones which is once again heavily supported by surrounding ligaments, muscles, and tendons. The lateral part of the longitudinal arch is less prominent than the medial aspect and is supported by the lateral tarsal bones and fourth and fifth metatarsal bones.

We have now reached our final destination. As you can see on your map, we are headed in a southerly direction to reach the sole of the foot. The sole of the foot is also known as the plantar region of the foot. This region is found on the inferior aspect of the foot and is the part of the foot that makes contact with the ground. This region contains the intrinsic muscles of the sole of the foot as well as the tendons of the posterior compartment of the leg. It also contains the arteries and veins of the sole of the foot. Just like we had the dorsal surface of digits one to five, we also meet the plantar surfaces of digits one to five here too.

Towards the distal aspect of the sole of the foot, we meet the hallucial eminence. This eminence is part of the ball of the foot. The protrusion at this region is caused by the bulky articulation between the proximal phalanx of the hallux, two small sesamoid bones, and the head of the first metatarsal bone as well as a well-defined fat pad for cushioning.

We've traveled all over the lower limb and located each region and its contents. Before we finish, I want us to just quickly travel back up north to the femoral triangle where we're going to take a look at some clinical notes.

The femoral artery is one of the largest arteries in the thigh, and therefore, is vitally important in delivering oxygen-rich blood to the lower limb. As we mentioned earlier, the femoral artery is easily palpated within the femoral triangle. The pulse can be located on the medial aspect of the proximal thigh at the mid-inguinal point. As with any artery in the body, narrowing or blockages in the lower limb arteries due to plaque and atherosclerosis may develop. When this occurs, it is extremely important to remove this blockage surgically to restore normal blood flow to the limb. This can be done using a procedure known as a balloon angioplasty. An angioplasty is a medical procedure in which a stent and/or a balloon is inserted into the artery to alleviate the blockage and allow for placement of a stent to keep the artery open. Understanding the exact location of the femoral artery within the femoral triangle helps surgeons to easily find the artery and remove the blockage quickly and accurately.

That completes our tutorial on the regions of the lower limb. We now know where to find all the regions and what is contained in each region. Well done for keeping up and not getting lost. Before you put that map away, I'm just going to quickly summarize what we learnt.

In today's tutorial, we created a map of the regions of the lower limb and their associated contents. The first region that we met was the gluteal region. Just lateral to the gluteal region on either side, we identified the hip region, which was defined around a large bony prominence of the femur known as the greater trochanter. Just below the gluteal region, we identified the thigh, or the femoral region. This region is divided into the anterior and posterior thigh. At the anteromedial aspect of the anterior thigh, we identified a small sub-region – the femoral triangle.

Moving distally, we came to the knee. The anterior region of the knee can also be known as the patellar region due to the presence of the bony patella. The posterior region of the knee is known as the popliteal region and is marked by the popliteal fossa.

Moving on to the leg, we identified the anterior and posterior leg. These are also known as the anterior and posterior crural region. This is the region between the knee and ankle anteriorly and posteriorly. Distal to the leg, we came to the ankle. This region is also split into anterior and posterior surfaces. The posterior ankle region contains two sub-regions known as the lateral and medial retromalleolar regions. These regions sit tucked behind both malleoli.

The foot is divided into a number of smaller regions with the first being the calcaneal region, or the heel region. This region is marked by the protrusion of the large tarsal bone – the calcaneus. Next, we meet the dorsal region of the foot located on the superior aspect of the foot. Just over the metatarsal bones, we identified a sub-region of the dorsal surface – the metatarsal region of the foot. Distal to the five metatarsals, we also met the five digits and interdigital spaces. On the medial and lateral aspects of the feet, we found the medial, or tibial, border and lateral, or fibular, borders of the foot.

Moving on, we came to the three arches of the foot. We identified the proximal and distal transverse arches centrally and the longitudinal arch. The medial and lateral aspects of the longitudinal arch support the transverse arch. We identified the sole of the foot as the plantar region of the foot, and on the distal aspect of the sole of the foot, we met the hallucial eminence, or protrusion of the joint of the hallux.

For the final portion of this tutorial, we had a look at some clinical notes on the femoral artery within the femoral triangle. We identified the correct point to palpate the femoral pulse. We also explored atherosclerotic complications of the femoral artery and how these blockages can be cleared by a procedure known as femoral angioplasty.

That brings us to the end of this tutorial. I hope you enjoyed learning and mapping out the different regions of the lower limb. Happy studying!