Hello, everyone! This is Joao from Kenhub, and welcome to another anatomy tutorial where, this time, I’m going to be talking about the bones and ligaments of the knee and lower leg.
Now, without further ado, what I’m going to be doing here on this tutorial is describing the different bones and also ligaments that comprise or are part of the this area here of your body, which is known as your knee, and also the lower leg – so the areas that you find between this. You see here partially the thigh and also your foot.
Without further ado, before I go into a lot more detail, I would like to first list the different bones that make part of the knee and also the lower leg, and these include the femur, the patella, the tibia, and the fibula – so four bones that we’re going to be discussing in a lot more detail here throughout this tutorial.
But also, if you can locate here, you see the femur, which is part of the knee as you can see, the patella, the tibia, and the fibula.
And keep in mind that we’re looking here at the lower leg from an anterior view.
Now, we’re ready to list the different ligaments that we’re going to be covering here, and we’re going to start off, then, with the collateral ligaments, the anterolateral ligament, cruciate ligaments, patellar ligament, the popliteal ligaments, and the transverse ligament of the knee.
Now, the very first one that we’re going to be talking about, the first bone that we saw on the first list is the femur, and we can clearly see it here on this image that we’re looking at the anterior view of the thigh and also a little bit of the lower leg. This is the femur right here because it’s the longest and strongest bone in the human body.
But we will only focus on the lower part of the femur, which is involved, then, in the knee joint.
The relevant structures of the femur that are involved in the knee joint are the medial and lateral epicodyles that articulate with this bone here, the tibia, and also the patella.
The epicondyles are coated with cartilage in order to provide efficient movement of the joint.
The next bone on our list was this one here that you see highlighted in green, and we’re looking at it from an anterior view on the left image. And on the right image, we’re looking at it from a lateral right view. You see a little bit of highlight here.
And this is the patella.
And the patella articulates with the femur and is part of the knee joint. It is also covered in cartilage.
Now, also important to mention or to highlight here is a function of the patella. This is a sesamoid bone that protects the knee joint and also supports extension of the knee by enlarging the lever arm of the quadriceps femoris muscle.
We are now ready to move on to the next bone that, if you see here, this is the tibia. And the tibia is right about here on this image. We’re looking at it from an anterior view. And as you can see here, this is a long bone or the second longest bone after the femur and lies between the knee and the ankle, and it is involved in both of those joints.
There are different structures of the tibia that we need to be covering, and we’re going to cover on this tutorial the different condyles, also the tibial tuberosity, and the Gerdy’s tubercle. We’re going to be looking at the medial and lateral aspect of this bone, the anterior border, and the posterior surface, and the medial meleolus.
So, without further ado, let’s continue on to the first one on the list, the condyles of the tibia. And you can see them highlighted here in green, and we’re looking at them from an anterior view. So on the image on the left side of the screen, you see the lateral condyle, while on the image on the right side, we’re looking at the medial condyle.
Now, the condyles of the tibia are the lower part of the knee joint and the top surface of the tibia. They articulate with the epicondyles of the femur, as you can clearly see here on this image.
Now, let’s take a closer look at the condyles. Right now, we’re looking at the lateral condyle. Notice that on the image on the right side, we’re looking at it from a posterior view this time. And this condyle will serve as an origin point for a muscle, the extensor digitorum longus.
Also a highlight here for the medial condyle of the tibia, seen on both anterior and posterior views to add an important point here that this will serve as an insertion point for the semimembranosus muscle through the pes anserinus profundus.
Moving on to a next structure that we’re going to be covering here, this is known (and highlighted and green) as the tibial tuberosity. And the tibial tuberosity lies at the anterior proximal end of the tibia.
What makes it so special is the fact that it’s going to serve as an insertion point for an important ligament of the knee, the patellar ligament. As you can clearly see here, the patellar ligament inserting on the tibial tuberosity. But we will be covering this ligament in a little bit more detail later on on this tutorial.
The next structure that we’re going to be seeing here, highlighted in green, is known as the Gerdy’s tubercle, which is known as the lateral tubercle of the tibia or anterolateral tubercle of this bone because we find it, then, at the lateral and anterior portion of the tibia.
And this is an important structure because another important one will be inserting here, and the (as you can see here around this image) the iliotibial tract, seen here highlighted in green, will then insert on the Gerdy’s tubercle.
We’re ready to move on to another structure, another highlight on the tibia. This is the medial aspect of this one. And the top portion of the medial aspect of the tibia serves as an insertion point for the tibial collateral ligament, and also, there are three muscles that will insert at the pes anserinus superficialis: the sartorius, semitendinosus, and the gracilis.
If the tibia has a medial aspect, then we should have another one, this one that you see now, highlighted in green: the lateral aspect of the tibia. This is also an origin point for a muscle, the tibialis anterior, which performs dorsal extension of the foot.
The lateral aspect of the tibia will also serve as an attachment point for an important structure, the interosseous membrane of the leg, which is a fibrous structure connecting the two bones, the tibia with the fibula.
And we’re now ready to move on to the last one on the list when it comes to the different structures of the tibia, this one seen here highlighted in green. On the left side, we’re looking at it on the anterior view, and on the right image, we’re looking at it from a posterior view. And this is the medial malleolus, and this is a prominence, a distal prominence on the medial side of the tibia.
And together with the lateral malleolus of the fibula that you find right about here, they form the upper part of the ankle joint.
An important point to make about the medial malleolus is that this structure that you see here, highlighted in green, the posterior tibial artery runs next to the medial malleolus which, then, enables you to palpate the pulse of the foot dorsally from the medial malleolus.
We’re now ready to move on to the next bone, the fibula, which you find on the lateral side of the tibia – this one, this thin bone right here.
And together with the tibia, the fibula, then, forms the base of… the bony base of the lower leg.
The fibula is connected to the tibia and shapes the upper part of the ankle joint with it, as you can see right here, distally.
And just like the tibia, there are a few structures that we’re going to be seeing on the fibula as well that are worth listing before we go into more detail. We’re going to look at the head, neck, and the body or shaft of the fibula. We’re going to also see a medial and lateral aspects of this bone and one structure that I already mentioned, the lateral malleolus.
Without further ado, let’s start off with the first one that you see here highlighted in green. This is known as the head of the fibula. This is the top portion of this bone and can be easily palpated at the lateral side of the knee.
The head of the fibula articulates with the lateral condyle of the tibia, forming then a joint known as the superior tibiofibular joint.
This structure will serve as an insertion point for one muscle, the biceps femoris, which you can see here highlighted in green on this image, and you notice here that, distally, this muscle is inserting at the head of the fibula.
We’re looking at it from a posterior view.
The next structure that we’re going to be highlighting is known as the neck of the fibula, and this structure connects the head with this structure here that we will be talking about next, the body or shaft of the fibula.
Now, the next one, as I already mentioned, highlighted in green, this is known as the body of the fibula and can be divided into a lateral aspect and also a medial aspect.
We’re going to start off with the first one on the list, seen now highlighted in green. This is the medial aspect of the body of the fibula. It serves as an origin point for the interosseous membrane and the origin of the extensor hallucis longus.
We’re also going to see, then, now highlighted in green, the other aspect, the lateral aspect of the fibula, which works as an origin point for the fibular longus and the fibularis brevis – two muscles which will originate from the lateral aspect of the fibula.
The other structure that we saw on the list that is now seen here highlighted in green, this is the lateral malleolus, and this is the distal end of the fibula that forms the upper part of the ankle joint together with the medial malleolus of the tibia.
Now, before we move on to the different ligaments of the lower leg and knee, we’re going to do a quick review of the bones that we just talked about, the main bones that we saw on the lower leg and knee. So if you remember well, this one here is the, yes, femur.
We have this bone here which is, then, the patella. This one that is found medially, the tibia. And laterally, you see this thin bone. If you remember well, the fibula.
And you can notice here the interosseous membrane between the tibia and the fibula.
We’re now ready to talk about the different ligaments of the knee and lower leg, and I just have here the list again so you can remember the order that we’re going to be covering them.
Now, starting off with the very first one here on the list: the collateral ligaments, and you need to know that there are two collateral ligaments, starting off with this one here, the fibular collateral ligament. And on the other side of the knee, you’re going to find the tibial collateral ligament.
We take a closer look at the fibular collateral ligament. We notice here that this ligament is located on the lateral side of the knee. If you do the same thing for the tibial collateral ligament, now seen here highlighted in green, sometimes, we also call it the medial collateral ligament, and it is located medial… on the medial side of the knee joint.
Now, both collateral ligaments are stretched when the knee joint is in extension and lax when the knee joint is flexed because their origin and insertions are brought closer together.
This pair of ligaments, thus, stabilize the knee joint in the coronal plane.
The next ligament that we’re going to be talking about is this one seen here, highlighted in green, known as the anterolateral ligament, and this is a relatively famous ligament because it has been in the news in the past year.
There is an article here at Kenhub that you can go and search for it and read a little bit more about the anterolateral ligament, but we wanted to cover it here on this tutorial.
Now, the anterolateral ligament is found on the lateral aspect of the knee, as you can clearly see here on this image—anterior to the fibular collateral ligament, as you can see here.
The main function of this ligament is that it stabilizes the medial rotation of the knee.
Now, the next set of ligaments that we’re going to be talking about are known as the cruciate ligaments, two cruciate ligaments. One is known as the anterior cruciate ligament, seen here highlighted in green.
If you notice at here on this image, the posterior view of the ligament, and here as an anterior view if we were to bend the knee. And you can clearly see here, then, the anterior cruciate ligament as well as the other ligament that we also will cover here: the cruciate, the posterior cruciate ligament, which also can be seen from a posterior view and from an anterior one if we were to remove, then, the anterior cruciate, as you can see here. You notice a bit of the posterior cruciate ligament.
Now, as you can notice here on this image, these… these ligaments, they form a shape, or they’re arranged like the letter X. The word cruciate means “cross,” so they are literally cross ligaments.
And these cross ligaments, they have a function, a main function to stabilize the joint, the knee joint, while allowing a very wide range of motion.
The next one that we’re going to be talking about is this ligament that you see here highlighted in green, known as the patellar ligament. And the patellar ligament is the continuation of the tendons of all four parts of the quadriceps femoris muscle.
This is a very strong and flat band and has about five centimeters in length.
The patellar ligament is essential for extension of the knee joint.
And if we take a look here at this image where we’re showing the quadriceps femoris muscle highlighted in green, the quadriceps tendon runs above the ventral side and through the periosteum of this bone here, the patella, and finally inserts at the tuberosity of the tibia. And this part below the patellar apex is, then, known as the patellar ligament.
Another set of ligaments, the popliteal ligaments. There are two. One is the arcuate. The other one is the oblique, as you can see here highlighted on both of these images.
Now, if we take a closer look here at the arcuate popliteal ligament, it’s an extra capsular ligament of the knee. It has a Y shape and is attached to the head of the fibula.
If we take now a closer look to, then, the oblique popliteal ligament, we see here that this is found posteriorly, and this is a broad and flat fibrous band and is attached to the upper margin of the intercondyloid fossa and posterior surface of the femur.
The oblique popliteal ligament serves as an insertion point for a muscle, the semimembranosus.
The next ligament that we’re going to be talking about is now seen here, highlighted in green, known as the transverse ligament. And this is a ligament of the knee joint. It is divided into several strips in ten percent of people, and its thickness varies considerably from person to person.
Now, the transverse ligament, when the knee is being extended, this ligament prevents the anterior horns of the menisci from moving forward, and the condylar surfaces of the femur and tibia from exerting pressure on the menisci.
This ligament also has what is known to be as restricting effect or restricting effect on anterior and posterior excursion of the anterior horn of the medial meniscus at lower degrees of knee flexion.