Bone of the Lower Limb - Online Tutor, Practice Problems & Exam Prep

The thigh and leg consist of key bones: the femur, patella, tibia, and fibula. The femur is the largest long bone, forming a ball-and-socket joint with the acetabulum. The patella, or kneecap, is a sesamoid bone within the patellar tendon. The tibia, the larger medial bone, contributes to the knee joint, while the fibula, a smaller lateral bone, does not. The foot comprises tarsals, metatarsals, and phalanges, with the talus and calcaneus being significant tarsals. Understanding these bones is essential for grasping human anatomy and movement mechanics.

Bones of the Thigh and Leg

Now we're going to talk about the bones of the thigh and the leg. Specifically, we're going to talk about the femur, the patella, the tibia, and the fibula. Before we get going, though, let's just orient ourselves to our picture here. We're looking at an anterior or a frontal view of the right leg, and we see the four bones that we're going to talk about, all color-coded. And then we also just see the pelvis or just the pelvic girdle right there and the bones of the ankle and the foot there at the bottom, just for reference. Right. We're going to start off by talking about the femur. The femur, we're going to say, is going to be the strongest and the largest long bone in the body, and we can see it's right in green here. Now this bone, the femur, it's a big old honking bone. Right? It's really noticeable as the largest long bone, and the other thing that's really noticeable about it is this round head on it. In our picture, we have this round head right up here labeled as 1a, 1a. This round head, we're going to say, is going to be the round ball that fits into the acetabulum. So here's my coxal bone, and we did this in a previous video, but these two fit together just so clearly to make that ball and socket joint. The head of the femur is that round ball. Now as we look down the other end of the femur, well, this epiphysis, this is going to make up the knee joint, and it's going to articulate with two bones there, the patella and the tibia. So first, let's look at the patella. The patella, well, that's purple in our diagram over here, and it's going to be a sesamoid bone, we're going to say. Remember, a sesamoid bone is a bone that develops entirely within a tendon and the patella develops within the patellar tendon. That's the tendon that runs from the quad down to the tibia over your knee. Now the patella, if you remember when we learned parts of the body, patella comes from the Latin meaning a small dish, and this bone is just kind of well, it's just kind of this flattish, relatively roundish bone, so you can imagine it kind of looking like a really small teacup saucer or something like that. Now you probably just know your patella as your kneecap. And if you go down and you feel your kneecap, you move it around a bit, what you're touching there, what you're floating around, you're floating around the patella in that patellar tendon. Okay. The other bone that makes up your knee, the tibia. The tibia is going to be the larger, more medial bone of the lower leg, and we can see it in our image here in orange. That's going to be the tibia. So it's going to articulate with and make up the knee here. So we're going to say just that this contributes to the knee joint, and we really call that out because that's going to be different from the fibula. The fibula does not articulate with the femur. It does not make up part of the knee. That's different than your upper arm. Right? In your upper arm, your forearm, both bones articulate with the humerus to make the elbow. In your lower leg, only one bone, only that one bone of the lower leg, the tibia, articulates into that knee joint. Now other things that you just might notice about the tibia, it has this real sharp front on it. That's that shin. Right? Your shin, if you ever whack your shin on stuff, you're whacking that part of the bone right there, hurts like heck. The other thing you'll just notice, it's a little bit longer on one end than the other. It comes down a little bit farther here. That's your inside ankle bone. It's also called your medial malleolus. Your inside ankle bone, that's another thing that sometimes you whack on stuff. So your tibia, you often whack it on things. Alright. The other bone of the lower leg is going to be the fibula, and the fibula is this bone that we see here in blue on the on the outer side of the leg there. So it's on the outer side of the leg, so we are going to say it is the smaller, more lateral bone. Right? Now, you can't really feel the fibula as well as you can the tibia. The only place that you really can feel it is down in your ankle, what's called your lateral malleolus, is this part of the fibula down at the end. That's your outer ankle bone. The rest of it sort of articulates well at the top. It articulates with the tibia, and the rest of it sort of inside the muscle that you can't feel that well. Now the way I remember the tibia and the fibula, because those words, a lot of times, people get them switched around in their mind, The tibia is tough. This is a big old heavy bone. The fibula is fine. The fibula is this kind of narrow, light-looking bone. So again, the tibia is tough. The fibula is fine. Alright. We're going to talk about these bones a little bit more going forward. I'll see you there.

Bone of the Lower Limb Example 1

Our example tells us that you forgot your shin guards at soccer practice and managed to get kicked in the shin, the inner ankle, and the outer ankle. Yowchers. Alright. Which bone is getting kicked in each scenario? To help us out, we have a picture here of the lower leg. We have an anterior view of the bones of the lower leg starting at the patella all the way through the toes. And so this is going to be the left leg that we're looking at, and we want to know what bone makes up the shin. So, what bone is the shin? Well, as I look at this picture, the shin is this bigger, heavier bone right here. The front of that bone is what you get kicked in when you get kicked in the shin, and remember the bones of those lower legs, that's the tibia and the fibula, and the tibia is tough. The fibula is fine. So that bigger, tougher, heavier bone, that's going to be the tibia, specifically the anterior border of the tibia.

So then, which bone makes up your inner ankle bone? Well, again, as I look at this, the inner ankle bone, so that medial side here, is going to be right here. That's that inner ankle bone, and that's the same bone. This is part of the tibia. So the tibia makes up the inner ankle bone. There. Now I'm going to get a little bit more specific here. I'm just going to say, if you want to get really specific, you could say that that is the medial malleolus of the tibia. The malleolus is another name for the ankle bone.

So then, what bone makes up the outer ankle bone? Well, as I look at the picture, here's the outer ankle bone there. So what is that part of? Well, it's part of this thin bone here, the more lateral bone. And remember the thin bone, that's a finer bone. The tibia is tough. The fibula is fine. So this is going to be the fibula. And again, if I want to get more specific, I could say that that is going to be the lateral malleolus of the fibula. Alright. That's the answer to our question. More problems to follow, where are your shin guards?

With which bones does the femur articulate?

• A. The tibia, the fibula, the coxal bone, and the patella.
• B. The tibia, the coxal bone, and the patella.
• C. The tibia, and the coxal bone.
• D. The tibia, the fibula, and the coxal bone.

The structure of the upper limbs (the arms) and the lower limbs (the legs) follow a similar pattern. Which of the following statements comparing the limbs is not accurate? 

• A. Between the girdle and the wrist/ankle, the lower limbs have more bones.
• B. The radius and ulna bear weight roughly equally, where the tibia bears much more weight than the fibula.
• C. The humerus articulates with both bones of the forearm at the elbow, while the femur only articulates with one bone of the lower leg.
• D. The radius and ulna have less mobility between them than the tibia and fibula.

Bones of the Foot

To finish up our bones of the lower limb, we're going to talk about the bones of the foot. Now the foot and the ankle are made up of three sections of bones. And if you remember, that's just like the hand. In the hand, we have the carpals, the metacarpals, and the phalanges. In the foot, we have the tarsals, the metatarsals, and again, the phalanges. The toe bones and the finger bones have the same names. Before we go into these, let's just look at our picture here. We have a top-down view of the bones of the foot. We're looking at a right foot, and in green here, we can see the tarsals, in purple, the metatarsals, and in blue, we see the phalanges. This is going to be the big toe, the pinky toe, and the heel back there.

The tarsals, we're just going to start off by saying these are the seven short bones of the ankle. But we can liken this to the carpals. Remember, there are seven tarsals. There are eight carpals. Sometimes people get those numbers switched. So, seven tarsals. But just like the carpals we said are really more the bones of the back of the hand, well, that's even more so for the tarsals. These tarsals you can see in this picture here, they really make up a lot of the back of the foot. And what you think of as your ankle, probably, where your long bones of the lower leg meet your foot, that's going to be the joint in this first bone here that we've labeled 1a. Now like the carpals, you don't need to know the name of every tarsal, but you likely do need to know the name of this bone and one more bone that we will go over in a second. So this first bone where the tibia joins the ankle is called the talus, and you can see it here in my model foot. It's just this real smooth round bone on top of all the other tarsals. So, we're going to call this the talus, and we say the talus is the top of the ankle, and the talus is the top of the tarsals. Right? So when you look at all your tarsals, this round smooth one on top, that's the talus. And the reason it's round and smooth like that is you can take the tibia and articulate it there in the ankle. As you point or flex your toe, that talus is just going to sort of rock or hinge back and forth in that tibia. You'll see it also has a smooth section on the side—the fibula also articulates with that talus.

The other tarsal you're likely to need to know is going to be the calcaneus. The calcaneus, that's labeled 1b right here. This is your heel bone, and you can see it's sort of in this picture; it's sort of sticking out the back, but it's the biggest tarsal, and it's really noticeable if you look at the foot. Making up almost, like, half or more than half the length of the tarsals is this calcaneus. The heel bone sticks out in the back. If you have to ever have to identify it individually, it's just this really kinda lumpy weird bone. But in the foot, the heel bone calcaneus is very noticeable.

After the tarsals, we get to the metatarsals. The metatarsals are going to be the long bones, and these are going to create the arches of your foot along with some of the tarsals. You have that arch in your foot. That really helps you distribute weight along your foot, and the metatarsals are doing a lot of that job. Now these are going to be just like the metacarpals in the hand. There are five of them. One lines up with each toe. We're going to number them 1 through 5. The most medial one is going to be numbered 1. The most lateral one is going to be numbered 5. So this medial one is going to line up with your big toe, and this lateral one is going to line up with your pinky toe.

That brings us to the phalanges. The phalanges, just like the finger bones, are going to be these 14 tiny long bones. And, again, remember, long bones talk about the shape and how they grow, not about how big they are. This long bone right here at the tip of your toe, pinky toe, that's a really small bone but it's still a long bone. The singular of phalanges, remember, is phalanx, and that just comes from that word that means that Greek battle formation. And, again, just like the fingers, each toe is going to have three phalanges, a proximal, middle, and distal. And we can see that label on the second toe here. A is going to be the proximal, then we have the middle, and C will be that distal phalanx. That's going to be different for the big toe. So the big toe is only going to have two. It does not have a middle phalanx, and we can see that here. It just has the proximal and distal. Remember, that's just like the thumb, only two bones in the thumb, only two bones in the big toe.

That's the foot. Practice more going forward. I'll see you there.

Bone of the Lower Limb Example 2

Our example says that if you have 5 toes and proximal, middle, and distal phalanges, well, \( 5 \times 3 = 15 \). Then why do you have only 14 phalanges? And to finish the question, I should probably say on each foot. But regardless, let's take a look. I'm going to start out just by well, we have a picture of a foot here showing all the bones. I'm going to start by crossing out everything that isn't a phalanx. So that line is where your toes start. Now I'm crossing out the metatarsals. Now I'm crossing out the tarsals. So if we look at our phalanges here, I'm going to label the proximal, middle, and distal phalanx on that second toe. Well, what's the key to this question? Why don't you have 15? Well, the key is the big toe. Right? The big toe only has a proximal and distal. There is no middle phalanx on the big toe. So I'll write that out. No middle phalanx on the big toe. We can also call the big toe the hallux if we're feeling fancy. All right. That's, of course, also true for the thumbs. Remember that we answered a question.

How do the metatarsals contribute to the foot's ability to bear weight?

• A. Their irregular shape helps them distribute the weight of the body.
• B. The seven bones distribute the weight, so each bone only withstands a fraction of the total body weight.
• C. The bones have additional collagen to help them resist force and twisting.
• D. The bones help create arches that distribute the weight.

Distinguish between the Talus and the Calcaneus.

• A. The talus is considered one of the tarsals; the calcaneus is not. 
• B. The talus articulates with the tibia; the calcaneus only articulates with other tarsals.
• C. The calcaneus is the heel bone; the talus makes up the parts of your ankle bones that you can feel.
• D. The calcaneus is the largest tarsal; the talus is the smallest tarsal.

Here’s what students ask on this topic:

What are the main bones of the lower limb?

The main bones of the lower limb include the femur, patella, tibia, and fibula. The femur is the largest and strongest bone, forming a ball-and-socket joint with the acetabulum of the pelvis. The patella, or kneecap, is a sesamoid bone within the patellar tendon. The tibia, the larger and more medial bone of the lower leg, contributes to the knee joint. The fibula, a smaller and more lateral bone, does not articulate with the femur and does not form part of the knee joint. These bones are essential for movement and weight-bearing functions.

What is the function of the patella?

The patella, commonly known as the kneecap, is a sesamoid bone that develops within the patellar tendon. Its primary function is to protect the knee joint and enhance the leverage of the quadriceps muscle during leg extension. By increasing the angle at which the quadriceps tendon acts on the tibia, the patella improves the efficiency of knee extension, making movements like walking, running, and jumping more effective.

How do the tibia and fibula differ in their roles in the lower leg?

The tibia and fibula have distinct roles in the lower leg. The tibia, being the larger and more medial bone, is the primary weight-bearing bone and contributes to the knee joint. It also forms the medial malleolus, the inner ankle bone. The fibula, on the other hand, is smaller and more lateral. It does not articulate with the femur and does not form part of the knee joint. Instead, it provides lateral stability to the leg and forms the lateral malleolus, the outer ankle bone.

What are the tarsal bones, and which ones are most significant?

The tarsal bones are the seven short bones that make up the ankle and the back part of the foot. The most significant tarsal bones are the talus and the calcaneus. The talus is the topmost tarsal bone that articulates with the tibia and fibula to form the ankle joint, allowing for foot movement. The calcaneus, or heel bone, is the largest tarsal bone and forms the foundation of the rear part of the foot, providing support and stability during walking and standing.

How are the bones of the foot organized?

The bones of the foot are organized into three sections: tarsals, metatarsals, and phalanges. The tarsals consist of seven short bones that form the ankle and the back part of the foot. The metatarsals are five long bones that create the arches of the foot and are numbered from 1 to 5, starting medially. The phalanges are the toe bones, with each toe having three phalanges (proximal, middle, and distal) except for the big toe, which has only two (proximal and distal).