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Bones, ligaments and joints of the hip bone and femur.
With age comes wisdom, however, so do falls that often result in fractures. The hip bone and femur are common sites of fracture in the elderly and are often what we worry about when we think of our grandparents. However, the hip joint is also a ball-and-socket joint, meaning that it is one of the most mobile joints in our body and is what allows many of our grandparents to bust a move.
In today’s tutorial, we’re going to be looking at the bones that make up the hip joint – the hip bone and the femur. Before we begin, it’s important that we first define the bony pelvis. Now, the boney pelvis which we can see here from an anterior perspective and highlighted in green is formed posteriorly by the sacrum and the coccyx and laterally and anteriorly by a pair of hip bones or pelvic bones.
As I said earlier, this tutorial will focus specifically on the hip bones while the sacrum and the coccyx will be covered in more detail in other tutorials.
So now that you’re familiar with the bony pelvis, let me give you a quick overview of what we’ll cover in today’s tutorial. First, we are going to be looking at the hip bone and its characteristic features followed by the femur and its bony landmarks. Then we’ll move on to discuss the ligaments that connect the hip bone and the femur. We’ll then bring our tutorial to a close with some clinical notes relevant to the hip bone and the femur.
As I said, the hip bone is a paired bone so you have a left hip and a right hip bone, and we can see them both here highlighted in green. Each hip bone is actually comprised of three parts that fuse together towards the end of puberty and these parts include the ilium which is the largest and most superior of the three bones, the ischium which is located inferiorly, and the pubic bone which forms the most anterior portion of the hip bone. And we’re going to discuss these three components of the hip bone in more detail.
But before we do that, let’s first talk about a structure where they’ll meet which is known as the acetabulum. And in order to view the acetabulum more clearly, we’ve changed our perspective slightly. What we’re looking at now is the left hip bone from a lateral perspective. So, here’s the ilium superiorly, the ischium posteriorly, and the pubis anteriorly. And the acetabulum as I mentioned is a cavity formed by the synostosis or fusion of these three bones.
Remember how I said that the hip joint is a ball-and-socket joint? Well, the acetabulum forms the socket component of the hip joint while the ball component is formed by the head of the femur, as we can see in our image just here.
Now moving on, I want to talk about a few structures associated with the acetabulum. And the first one is this moon-shaped structure that is conveniently known as the lunate surface, and its curved articular surface surrounds the acetabulum and articulates with the head of the femur. And since it’s an articular surface, it is covered by the articular cartilage.
The next structure we’re going to look at is the margin of the acetabulum, and as you can see, this margin is bordering the acetabulum and is interrupted here by this notch, which is known as the acetabular notch.
The last structure of the acetabulum we’ll look at today is the acetabular labrum or the acetabular lip, and this structure can be confused with the margin of the acetabulum, however, they are not the same thing. The acetabular labrum is a fibrocartilaginous collar on the rim of the acetabulum as you can see here, and it surrounds the margin of the acetabulum.
So let’s move on to talk about the three bones that fuse during puberty to form the hip bone, and we’ll start, of course, with the ilium.
So, the ilium is divided into two main parts – the wing, or the ala, and the body – and the wing is this flattened portion that you can see here, and the body is the central part of the ilium that you see here contributing to the formation of the acetabulum.
Now let’s discuss some bony landmarks associated with the ilium, and the first one we’re going to talk about is the arcuate line. And we’ve changed perspectives again so let’s just orientate ourselves, and we’re now looking at the hip bone from a medial perspective. And we can see here that it is a smooth rounded border on the internal surface of the ilium and that it marks the transition between the body and the wing of the ilium and it also forms part of the border of the pelvic inlet.
Another structure we can see from a medial perspective is the iliac tuberosity, and the iliac tuberosity is a roughened elevated area found posterior to the iliac fossa and serves as an attachment point for the sacroiliac ligaments. Inferior to the iliac tuberosity, we can see the auricular surface, and as the name indicates, this is an ear-shaped surface and it articulates with the sacrum, and this surface is covered by fibrocartilage.
Contributing to most of the internal surface of the wing of the ilium is the iliac fossa, and as you can see it is a large, smooth concave surface found on the medial aspect of the hip bone. The iliac fossa is bordered superiorly by the iliac crest and inferiorly by the arcuate line.
If we flip our hip bone over to view its lateral surface, we can see some more bony structures. The first one we’ll look at is the gluteal fossa or the gluteal surface, and this fossa contributes towards most of the external surface of the wing of the ilium and provides various points of attachment for the gluteal muscles.
Next, were going to talk about the iliac crest which, as I previously mentioned, forms the superior border of the iliac fossa and the wing of the ilium. The iliac crest extends from the anterior superior iliac spine just here to the posterior superior iliac spine which is over here. And this crest serves as an attachment point for a large muscle of the body known as the latissimus dorsi.
Lastly, we’re going to look at the spines of the ilium. So the ilium has four different spines, and the first one we’re going to talk about is the one I already I mentioned, the anterior superior iliac spine. And as I said earlier, the anterior superior iliac spine is a bony projection that marks the anterior limit of the iliac crest and it is the origin of the sartorius muscle.
And now we have the anterior inferior iliac spine which is a bony process found at the anterior margin of the ilium inferior to the anterior superior iliac spine. And the spine serves as the origin of the rectus femoris muscle. The next spine is known as the posterior superior iliac spine which, as we already know, marks the posterior limit of the iliac crest. As you can see, it’s shorter than its anterior counterpart and serves as the attachment points for the oblique portion of the posterior sacroiliac ligaments and multifidus.
And let’s move on to the last spine of the ilium known as the posterior inferior iliac spine, and it’s found on the superior edge of this really important structure here known as the greater sciatic notch.
So, that’s us finished with the ilium. Let’s move on to talk about another bone that contributes towards the hip bone – the pubic bone.
So, the pubic bone is divided into three main parts – the body, the superior ramus, and the inferior ramus. The body is the wide medial and flat area we can see here which unites with its counterpart at the pubic symphysis. The superior ramus is this portion right here that is located just above the obturator foramen. The inferior ramus lies here between the pubic symphysis and the inferior ramus of the ischium. Again, the pubic bone possesses several bony landmarks and we’re going to talk about the ones that we can see from a medial perspective.
Starting with the iliopubic eminence. The iliopubic eminence is a flat prominence located at the proximal portion of the pubic bone, and it marks the point of union between the ilium and the pubis. Another structure found on the medial surface of the pubic bone is the symphyseal surface. This surface unites with its counterparts through a midline cartilaginous joint called the pubic symphysis which you can now see highlighted in green from an anterior perspective.
Next, we’ll have a look at the structure we can now see highlighted in green which is the pubic tubercle. We can see that it is located on the anteromedial portion of the superior ramus just lateral to the symphyseal surface. The pubic tubercle serves as an attachment point for the inguinal ligament.
Let’s keep looking at the pubic bone from an anterior perspective while we talk about the next two structures. The first one we’ll talk about is the obturator crest, and the obturator crest extends from the pubic tubercle here to the acetabulum here, and it provides a point of origin for the pubofemoral ligament. Inferior to the obturator crest, we find the obturator foramen which is the large opening you can see just here between the pubis and the ischium. And the obturator nerve, the artery and vein pass through this foramen to enter into the medial compartment of the thigh.
Now that we’ve covered the bony elements of the pubic bone, it’s time for us to move on to the third and final bone of the hip bone which is the ischium. And the ischium is divided into two main parts – the body and the ramus. The body is this portion right here located just behind the obturator foramen and the ramus of the ischium is found just here just below the obturator foramen.
Let’s have a look at the ramus of the ischium in a little bit more detail. And in this image, we’re looking at it from a medial perspective. So we can see that the ramus of the ischium fuses with the inferior ramus of the pubic bone and this is a meeting point between the ischium and the pubic bone.
So if we change our view to a posterior perspective, we can see another key structure of the ischium which is the ischial spine. The ischial spine is a bony prominence found between the greater sciatic notch and the lesser sciatic notch, and it serves as an attachment point for some important muscles such as the coccygeus muscle.
So, let’s move on now and talk about the greater sciatic notch in a little bit more detail. So this notch lies between the posterior inferior iliac spine here and the ischial spine here that we just talked about. When we add this ligament here – the sacrospinous ligament – this notch becomes what is known as the greater sciatic foramen. So here we have the greater sciatic foramen and we can see the sacrospinous ligament just here hiding between the sacrotuberous ligament, and several important structures pass through this foramen including the piriformis muscle and the sciatic nerve.
We mentioned another notch earlier –the lesser sciatic notch – and this notch lies between the ischial spine just here and the ischial tuberosity. And when we add this ligament here, this notch becomes what is known as the lesser sciatic foramen. The lesser sciatic foramen has many important structures passing through it including the obturator internus muscle, the nerve that supplies this muscle, the internal pudendal vessels, and the pudendal nerve.
So, the last structure of the ischium that we’re going to be talking about today is the ischial tuberosity and its function is to bear the weight of the body in a seated position, therefore, we can also call it the sitting bone.
Okay, now, we finished talking about all of the bony elements of the hip bone. So, let’s move on now to talk about the other bone of the hip joint which is the femur. The femur, or the thigh bone, is the largest bone of the human body and you may recognize it from your childhood days of pretending to sail the seven seas as it actually contributes to the crossbones as seen on pirate flags.
Similarly to the hip bone, the femur has several bony landmarks, and the first one we’re going to talk about is the head of the femur. Now, if you remember, I said that this part of the femur forms the ball component of the hip joint which is a ball-and-socket joint, and the socket is formed by the acetabulum of the hip bone. If we look closely at the head of the femur, there’s a depression that is used for the attachment of a ligament called the ligament of the head of the femur, and this ligament which we can now see highlighted in green, help strengthen the connection between the hip bone and the femur.
Moving distally, we have the neck of the femur, and this is the portion of the femur found between the head right here and the next portion that we’re going to be looking at, which is the shaft of the femur. So, the shaft of the femur is the area we can now see highlighted in green, and this is also known as the body of the femur, and you can see it encompassing the majority of this bone.
The femoral shaft has three main surfaces – a medial surface, a lateral surface, and an anterior surface. It also has a popliteal surface which lies between the supracondylar lines which are structures that we’ll cover later on in the tutorial.
So, next, we’re going to talk about the greater trochanter which we can see here from both an anterior and a posterior perspective. And as you can see, it is a large prominence on the proximal lateral aspect of the shaft, and it serves as a site of attachment for various muscles, including the gluteus medius, the gluteus minimus, and piriformis muscles.
So if you have a greater trochanter, you must also have a lesser trochanter. The lesser trochanter is a small prominence found on the posterior medial aspect of the proximal shaft. It serves as a site of attachment for the iliopsoas muscle. And running between the two trochanters there is a line known as the intertrochanteric line which we can now see from an anterior perspective. The intertrochanteric line marks the transition between the femoral neck and the shaft.
So if we look at the femur from a posterior perspective, we can see another line, but this time it’s called the intertrochanteric crest. Again, this line runs between the two trochanters and marks the transition between the neck and the shaft of the femur. Before we move on, I’d like to quickly mention a feature of the intertrochanteric crest which is the quadrate tubercle, and this is an elevation of the intertrochanteric crest and is a point of insertion for the quadratus femoris muscle.
Now, enough about lines, let’s move on to – oh no! – another line. This line is known as the linea aspera, which in Latin means “rough line”. And it is indeed a rough, double line found on the posterior aspect of the femur. It serves as an insertion and attachment point for many muscles including the gluteus maximus, which is one of those muscles we used when we get out to work on.
Proximally, the medial line of the linea aspera becomes the pectineal line, and the lateral line becomes the gluteal tuberosity, which is where the gluteus maximus actually attaches. Moving distally, we can see that the linea aspera divides to form the medial and lateral supracondylar lines, and if you remember, I said that the popliteal surface lies between these two lines.
Okay, one more line before we move on. The spiral line is this line that connects the inferior end of the intertrochanteric line and the medial aspect of the linea aspera of the femur. Moving distally, we can see two condyles – the lateral condyle here and the medial condyle here. And these condyles contribute towards the formation of the knee joint, forming articulations with the tibia and the patella or the kneecap.
We can see that between these two structures, there’s another structure which is known as the intercondylar fossa. So we can see the lateral condyle here, the medial condyle here, and the intercondylar fossa lying between them. Each condyle is associated with an epicondyle and we’re going to be talking about them now.
So, on your screen, you can now see the lateral epicondyle here and the medial epicondyle here. And as you can see from the images, these condyles are roughened areas of bone especially when compared to the smooth articular surface of the condyles.
The last structure of the femur that we’re going to be talking about today is the adductor tubercle. And the adductor tubercle is an elevation of the medial epicondyle and is a point of attachment or insertion for the adductor magnus muscle.
Alright now that we’ve discussed all of the bony landmarks associated with the femur, let’s move on now and talk about the ligaments that connect the hip bone to the femur or vice versa.
The first one we’re going to be talking about is one I mentioned where we discussed the head of the femur which is the ligament of the head of the femur. And this ligament extends from this portion of the acetabular notch here to this depression here on the head of the femur. And as I said earlier, this ligament helps strengthen the connection between the hip bone and the femur.
The next ligament we’re going to look at is best seen from an anterior perspective and it is known as the iliofemoral ligament. And as its name suggests, this ligament extends from the ilium of the hip bone to the femur and is the strongest ligament in the human body.
Now the ligament we can see anteriorly is the pubofemoral ligament, and this ligament extends from the pubic bone of the hip to the femur and functions to limit extension and abduction of the hip joint. If we change to a posterior perspective, we can see this ligament highlighted in green, which is the ischiofemoral ligament. And this ligament extends from the ischium to the femur and it functions to stabilize the hip joint and limit extension and medial rotation of the hip joint.
And the last ligament we’re going to be talking about today is the transverse acetabular ligament. And as you can guess from its name, this ligament bridges the acetabular notch and completes the articular surface for the head of the femur helping it stabilize and stay inside the acetabulum.
Alright now that we’re familiar with the bones of the hip joint and the ligaments that connect them, let’s take a clinical slide and talk about hip replacement surgery.
So hip replacement surgery is a common type of surgery where a damaged hip joint is replaced with an artificial one or a prosthesis. In our image, we can see an x-ray showing the hip bone, the femur, and our prosthesis just here. The artificial joint is designed to last for at least 15 years and is made of plastic and metal components, and hip replacement surgery is carried out to reduce pain and to improve mobility in patients. However, it is a major surgery, therefore, it is normally only recommended if all other treatment options have proven ineffective. In terms of recovery, the patient will need a walking aid for the first four to six weeks and may be enrolled in an exercise program that helps them use their new hip joint.
Most patients are able to resume normal activities within two to three months, but it can take up to a year before they experience the full benefits of their new hip.
Before we bring our tutorial to a close, let’s quickly summarize what we’ve learned today.
So, first we looked at the hip bone and its bony landmarks. Then we saw that each hip bone is actually comprised of three parts that fuse together towards the end of puberty including the ilium, the ischium, and the pubic bone. Next, we discussed the bony characteristics associated with the femur followed by the ligaments that connect the hip bone and the femur. We then concluded our tutorial with some clinical note relating to hip replacement surgery.
And that brings us to the end of our tutorial on the hip bone and the femur. I hope you enjoyed it, thanks for watching, happy studying!