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Bones, ligaments and joints of the knee and the leg.
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 swearing pouring out of my mouth like word vomit. But if you think that is bad, spare a thought for these lads who compete in the traditional English combat sport known as shin kicking. Yes, you heard me – shin kicking. The things you learn working for Kenhub!
Anyway, so why is the kick to the shin so sore? Well, it could be because there is no musculature cushioning the blow. After all, 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 periosteum which is filled with pain receptors.
So, today, we’re going to be discussing your shin bone, also known as the tibia, in our tutorial on the bones and soft tissues of the knee and the leg. Before we begin, I just want to clear up an issue that often arises when transitioning from everyday terms to anatomical terms. So, as a kid, your arm is your arm and your leg is your leg, but not in anatomy. Instead, your arm or upper limb is divided into the arm and forearm and your leg or lower limb is divided into the thigh and leg. So, when I say we’re going to be talking about the bones and the soft tissues of the leg, I’m really talking about this region here, between the knee and the foot.
Okay, so now that we’ve got the terminology down, I’d like to give you a quick overview of what we’re going to be talking about in this tutorial. So, first of all, I’m going to quickly introduce you to the knee joint and the bones that form this joint. We’ll then look at the bones of the knee and the leg focusing on their bony features and muscle attachment points. Next, we’ll talk about some soft tissues of the knee and the leg including the capsule and retinacula, the menisci, the ligaments and the bursae. Finally, we’ll bring our tutorial to a close with some clinical notes about shin splints.
So, without further ado, let’s get started with the knee joint.
So here we can see the knee joint highlighted in green from an anterior perspective, and you might be wondering why I want to talk about the knee joint. Well, our tutorial will feature bones that contribute towards this joint as well as soft tissues that support it. So it’s mainly for context. The knee joint is a synovial hinged joint which is formed by three bones – the femur, the patella, and the tibia – and it’s worth noting that the femur is actually a bone of the thigh, but because it contributes towards the knee joint, we’ll discuss it briefly in our tutorial.
As I just mentioned, the femur is a bone of the thigh, therefore, I don’t want to give too much of our time to it. So, today, we’ll be focusing on the articular surfaces of the femur that are involved in the knee joint. Distally, the femur has two condyles – a medial condyle and a lateral condyle – which articulate with one of the bones of the leg – the tibia. We can see both condyles here highlighted in green and this specific articulation of the femoral condyles with the tibia is sometimes referred to as the tibiofemoral joint.
They also articulate with the patella at what’s known as the patellofemoral joint. The patellar surface is formed by the medial and lateral condyles and is where the patella articulates with the femur, and you may have noticed that the condyles appear to have a different texture to the surrounding bone. And this is because they’re covered with an articular cartilage providing a smooth articular surface and efficient movement of the joint.
Okay, now that we’re familiar with the knee joint, let’s move on to the bones of the knee and the leg, starting with the patella.
So here we can see the patella highlighted in green from an anterior perspective, and it’s a bone of the knee and you might know it better as the kneecap. The patella is the largest sesamoid bone in the body which means it’s formed within a tendon, specifically, the quadriceps tendon. This bone is roughly triangular in shape and its posterior surface articulates with the patellar surface of the femur.
Like the femoral condyles, its articular surface is covered by articular cartilage, and as for its function, the patella covers and protects the anterior surface of the knee joint. It also functions as a sort of anatomic pulley for the quadriceps femoris muscle providing it with better mechanical advantage over the knee joint and allowing for more effective knee extension.
So now it’s time for us to talk about the next bone found in this region and this is the tibia. The tibia is a bone of the leg and is commonly referred to as your shin bone. It’s the weightbearing bone of the leg and is involved in both the knee joint and the ankle joint.
Let’s move on to talk about some bony features of this bone starting with the condyles of the tibia. And like the femur, the tibia has a medial condyle and a lateral condyle. The medial condyle serves as a point of insertion for the semimembranosus muscle, and if we flip our tibia to view it from the back, we can see the semimembranosus muscle inserting into the medial epicondyle, whereas the lateral condyle provides a point of origin for the extensor digitorum longus and the tibialis anterior muscle, and in our next image, we can see these two muscles pretty clearly.
If we go back to our original image, we can see that the tibia and the fibula articulates at the lateral condyle to form the proximal tibiofibular joint. Together, the tibial condyles form the structure we can now see highlighted in green which is known as the tibial plateau. And this smooth bony surface articulates with the femoral condyles forming parts of the knee joint. Lying between these two condyles, we find the intercondylar eminence which we can see here highlighted in green.
The next structure we’re going to be talking about is one that you can easily feel on your own leg just below your knee, and that’s called the tibial tuberosity. And this bony prominence serves as a point of insertion for the patellar ligament which we can see here on our next image, and we’ll cover this ligament in a bit more detail later on in this tutorial.
Moving laterally, we can see Gerdy’s tubercle, also known as the tubercle of the iliotibial tract, as it provides a point of insertion for the iliotibial tract, and we can see the iliotibial tract inserting into this tubercle in our next image.
The body or the shaft of the tibia is triangular in cross-section and consequently it consists of three borders and three surfaces where the borders are the corners of the triangle. And here we can see the anterior border highlighted in green which as I said at the beginning of the tutorial is palpable. In this illustration, we can label the other two borders – the medial border and the interosseus borders – which is where the interosseus membrane attaches.
The interosseus membrane is a thin sheet of fibrous connective tissue linking the two bones of the leg – the tibia and the fibula.
Alright, so now for the surfaces.
The medial surface lies between the anterior border and the medial border – and you can feel the surface on yourself as it is located just deep to the skin. The sartorius, gracilis, and semitendinosus muscles insert here via the pes anserinus.
Next, we have the lateral surface which lies between the anterior border and the interosseus border of the tibia, and this surface serves as a point of origin for the tibialis anterior.
Finally, let’s have a look at the posterior surface of the tibia, and the posterior surface lies between the medial border and the interosseus border. This surface provides a point of origin for the flexor digitorum longus and the tibialis posterior as well as an insertion point for the popliteus muscle.
Okay, so while we’re looking at the posterior aspect of the tibia, let’s talk about this structure highlighted in green which is known as the soleal line. As the name suggests, the soleal line is a bony ridge and it serves as a point of origin for the soleus muscle.
Moving distally, we find the last two structures of the tibia we’re going to be talking about, the first of which is the medial malleolus, and we can see it here highlighted in green and from an anterior perspective. Together with the lateral malleolus of the fibula, this bony prominence forms the upper part of the ankle joint and the medial malleolus is used as a landmark when palpating the posterior tibial pulse as the posterior tibial artery runs behind it, and this pulse is examined by physicians when assessing for peripheral vascular disease.
Lateral to the medial malleolus, we see this structure highlighted in green which is the fibular notch of the tibia. And the tibia and the fibula articulate here to form the distal tibiofibular joint.
Okay, let’s talk about our last bone of the day, which is the fibula.
In this illustration, we can see the fibula from an anterior view highlighted in green and as you can see, it is the smaller of the two bones of the leg and is located lateral to the tibia. The fibula does not contribute to the formation of the knee joint. Instead it articulates with the lateral condyle of the tibia to form the proximal tibiofemoral joint. And as I mentioned earlier, it also articulates with the fibular notch of the tibia to form the distal tibiofibular joint.
Again, let’s look at some bony features of the fibula starting with the head of the fibula and this is the portion of the bone that articulates with the lateral condyle of the tibia. The head of the fibula is a point of origin for the extensor digitorum longus, the fibularis longus, and the soleus muscle. The head of the fibula also serves as an insertion point for the biceps femoris which we can see here in our next image. This bony landmark can be palpated at the lateral aspect of the leg just distal to the knee joint.
The next structure that we’re going to be talking about is known as the neck of the fibula, and this structure connects the head with the body or the shaft of the fibula. Like the tibia, the body of the fibula is somewhat triangular in cross-section, therefore, it consists of three borders and three surfaces.
So here we can see the anterior border of the fibula which provides a point of origin for the extensor digitorum longus muscle, and while we’re here, I’ll label the interosseus border which is where the interosseus membrane attaches. If we flip the fibula over, we can see our last border, which is the posterior border. And this border serves as a point of origin for the soleus muscle.
So as I mentioned earlier, the fibula has three surfaces and as it happens, the leg also has three muscular compartments. And each compartment is associated with a surface.
The medial surface faces the anterior compartment of the leg and is a point of origin for the extensor hallucis longus muscle. The lateral surface faces the lateral compartment of the leg and it provides a point of origin for the fibularis longus and the fibularis brevis muscles. Lastly, we have the posterior surface of the fibula which of course faces the posterior compartment of the leg. And this surface serves as a point of origin for the flexor hallucis longus and the tibialis posterior muscles.
If we look towards the distal end of this bone, we can see the last feature of the fibula that we’re going to be talking about which is the lateral malleolus. And together with the medial malleolus of the tibia, this bony prominence forms the upper part of the ankle joint.
Alright, so now that we’ve discussed the hard tissues or bones of the knee and the leg, it’s time to have a look at some of soft tissues starting with the capsule and the retinacula of the knee.
So, the first structure we’re going to be talking about is the articular capsule which consists of two layers – the outer fibrous layer and the inner synovial layer. The outer fibrous layer which we can see here provides stability whereas the inner synovial layer lubricates the articulating surfaces.
Alright, so let’s talk about the retinacula, and here we can see the medial patellar retinaculum. The structure is an expansion of the vastus medialis muscle and as you can see, it’s attached to the patellar margin and the patellar ligament then extends backwards to the tibial collateral ligament and distally to the medial tibial condyle. The medial patellar retinaculum resists lateral patellar dislocation.
Next, we have the lateral patellar retinaculum, which is an expansion of the vastus lateralis muscle, and like its buddy, it is attached to the patellar margin and the patellar ligament and it then extends backwards to the fibular collateral ligament and distally to the lateral tibial condyle. The lateral patellar retinaculum helps stabilize the patella.
So before we go on to have a look at the numerous ligaments of the knee and the leg, let’s have a quick chat about the menisci.
So, humans have two menisci – a medial meniscus and a lateral meniscus – both of which we can see here from a posterior perspective. The menisci are C-shaped and attach to the intercondylar area of the tibia, and these fibrocartilaginous structures function to deepen the articular surface of the tibia which increases the stability of the knee joint. And the menisci also act as shock absorbers cushioning the tibia from forces generated during movement of the knee.
So, the medial meniscus is more C-shaped than the lateral meniscus and it’s attached to the tibial collateral ligament, therefore, it is vulnerable to injury when this ligament is disturbed, whereas the lateral meniscus doesn’t possess any additional attachments and is more circular in shape.
Alright, time to move on and talk about the ligaments of the knee and the leg.
So let’s start with two ligaments that are associated with the head of the fibula. So here we have the anterior ligament of the head of the fibula which extends from the front of the head of the fibula to the lateral condyle of the tibia. Posteriorly, we can see the posterior ligament of the head of the fibula, which extends from the back of the head of the fibula to the lateral condyle of the tibia, and together, these two ligaments function to reinforce the proximal tibiofibular joint.
Now, we’re going to have a look at the extracapsular ligaments of the knee joint starting with the collateral ligaments, and here we can see the tibial collateral ligament and the fibular collateral ligament, also known as the medial and lateral collateral ligaments respectively. And these ligaments work together to stabilize the knee joint preventing excessive medial or lateral movement.
The tibial collateral ligament extends from the medial epicondyle of the femur to the medial condyle of the tibia and it also attaches to the medial meniscus and this ligament limits extension and abduction of the leg. The fibular collateral ligament extends from the lateral epicondyle of the femur to the head of the fibula. And this ligament limits extension and adduction of the leg.
So if we view the bones of the knee and the leg on the side, we can see a ligament sitting anterior to the fibular collateral ligament and this is called the anterolateral ligament, and this ligament originates from the lateral epicondyle of the femur and inserts into the anterolateral aspect of the proximal tibia. And this ligament stabilizes the knee during medial rotation.
Okay so let’s talk about a ligament we mentioned earlier in the tutorial, and this ligament we’re going to be talking about is the patellar ligament. The patellar ligament is the continuation of the quadriceps tendon and inserts at the tibial tuberosity. And this ligament is essential for extension of the knee joint and protects the anterior aspect of the knee joint.
Time for another set of ligaments which are the popliteal ligaments, and let’s start with the one we can see now highlighted in green which is known as the arcuate popliteal ligament. It’s an extracapsular ligament of the knee and we’re looking at it from a posterior perspective.
If we look at our illustration, we can see that this ligament is Y-shaped with posterior and lateral expansions and originates from the head of the fibula. And this ligament functions to stabilize the posterolateral aspect of the knee joint.
Also located on the posterior aspect of the knee joint is the oblique popliteal ligament which is also known as the ligament of Bourgery or the ligament of Winslow, and this ligament runs between the femur and the tibia and provides a point of insertion for the semimembranosus muscle. And this ligament works with the arcuate popliteal ligament to stabilize the posterior aspect of the knee joint.
Okay so now that we’ve discussed the extracapsular ligaments, we’re going to move on to the intracapsular ligaments of the knee joint starting with the cruciate ligaments. And here we can see both the anterior cruciate ligament and the posterior cruciate ligament highlighted in green from a posterior perspective. So, cruciate means “cross” in Latin, and if we look at our images, we can see where these ligaments get their name as together they form a cross symbol.
The anterior cruciate ligament runs between the anterior intercondylar region of the tibia and the lateral femoral condyle, and this ligament prevents anterior dislocation of the knee joint, whereas the posterior cruciate ligament runs between the posterior intercondylar region of the tibia and the medial femoral condyle, and this ligament prevents posterior dislocation of the knee joint.
The next ligament that we’re going to be talking about is the transverse ligament, also known as the transverse genicular ligament or the ligament of Weber, and in our illustration, we can see this ligament highlighted in green from an anterior perspective. The transverse ligament extends between the medial and lateral menisci and functions to stabilize the menisci. A corresponding posterior meniscomeniscal ligament may also be present.
The last intracapsular ligaments of the knee joint we’re going to be talking about are the meniscofemoral ligaments, and these ligaments are a continuation of the lateral meniscus and ascends to attach to the medial condyle of the femur. The anterior meniscofemoral ligament, also known as the ligament of Humphrey, passes in front of the posterior cruciate ligament, and the posterior meniscofemoral ligament, also known as the ligament of Wrisberg or even Robert’s ligament passes behind the posterior cruciate ligament. And we can see this in our image here quite nicely. Together, these ligaments function to stabilize the lateral meniscus.
If we look at the distal end of the leg and foot from the side, we can see the anterior tibiofibular ligament, and this ligament extends between the distal tibia and the fibula. We also have a posterior tibiofibular ligament which again passes between the distal tibia and fibula as you can see here, and sandwiched between these two ligaments, we have the interosseus tibiofibular ligament which is continuous with the interosseus membrane. And together, these three ligaments reinforce the distal tibiofibular joint.
Okay, so the last group of soft tissue structures we’re going to be looking at is the bursae. So, bursae are small fluid-filled sacs that are located around joints. More specifically, they’re found between bones in soft tissues and they act to reduce friction. So, firstly, we’re going to be focusing on bursae that are associated with the patella starting with the suprapatellar bursae, and we can see this bursa here in the sagittal plane, and as the name suggests, it is located superior to the patella. And the suprapatellar bursa lies between the quadriceps tendon and the femur.
Next, we have the prepatellar bursa which is found between the patella and the skin. Inferior to the patella, we have the subcutaneous and the deep infrapatellar bursae, and here we can see the subcutaneous infrapatellar bursa which is located between the patellar ligament and the skin, whereas the deep infrapatellar bursa lies between the tibia and the patellar ligament.
Okay, so time to move on now to some bursae that are not closely associated with the patella, starting with the anserine bursa. Now, this bursa lies between the pes anserinus and the tibial collateral ligament and the tibia, and the pes anserinus refers to the conjoined tendons of the sartorius, the gracilis, and the semitendinosus muscles which we mentioned earlier. The anserine bursae is one of the most commonly inflamed bursae in the lower limb. Lastly, we have semimembranosus bursa which is located between the semimembranosus muscle and the medial head of the gastrocnemius muscle.
Okay, so now that we’re familiar with the bones and the soft tissues of the knee and the leg, let’s get clinical.
In today’s clinical notes, we’re going to be talking about shin splints which refers to pain in the shins typically caused by exercise or overuse. So medically known as medial tibial stress syndrome, shin splints often occur in individuals who have recently intensified or modified their exercise routine. So, for example, it can occur in runners who increased their speed or the distance that they run and this leads to inflammation of the periosteal tissue surrounding the tibia and causes pain, and the pain is usually dull to begin with, but can become increasingly sharp and severe to the point where exercise is no longer possible.
Treatment involves taking a break from the exercise that cause the shin splints and switching to low impact sports such as yoga and swimming and often ice packs are recommended to reduce the 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.
Okay, so before we bring our tutorial to a close, let’s quickly summarize what we’ve learned today.
So we started off by talking about the knee joint which is formed by the femur, the patella, and the tibia. Next, we talked about the bones of the knee and the leg which consisted of the patella, the tibia, and the fibula, and as we talked about these bones, we focused on their bony features and muscle attachment points.
We then moved on to talk about some soft tissues of the knee and the leg including the capsule and retinacula, the menisci, the ligaments, and the bursae. And finally, we concluded our tutorial with some clinical notes about shin splints.
So that brings us to the end of our tutorial on the bones and the ligaments of the knee and the leg. I hope you enjoyed it. Thanks for watching. Happy studying!