Ilium – Osteology of Lower Limb

00:00 Let’s start by looking at the ilium. We can see the ilium is this large wing-shaped bone. It’s the most superior and largest of the three bones, and it forms the superior part of the acetabulum.

00:15 So if we look here on the lateral surface, this is all ilium here, and we can see it’s actually going to form the superior parts of the acetabulum. So a line going in approximately this direction here would be the separation of the ilium with the ischium and the pubis. So this line here is separating the ilium above. The body of the ilium, if we have a look here, on the lateral surface, we can see the body of the ilium. We can see it here with the superior surface, the body of the ilium, and that’s joining to the pubis and the ischium at the acetabulum like I said. Then we have this large wing of the ilium, and we can see two parts of that. We can see the ala here, this large flat surface. And then at the top of this wing, we can see we have the iliac crest. We can see the iliac crest is running over here. See, on the lateral surface, we can also see on this medial surface. Within the iliac crest, we can see on the superior surface, there are a couple of features. So if we look for the bony landmarks of the ilium. Then most anteriorly, we can see it here on this medial surface, we’ve got the anterior superior iliac spine. So, the iliac crest is coming around the top, and it finishes here as the anterior superior iliac spine. Inferior, we have an anterior inferior iliac spine. And these bony landmarks are important because they offer attachment sites for muscles. More posteriorly, we’ll find we have the posterior superior iliac spine, and then below it, we’ll have the posterior inferior iliac spine.

02:04 And we can see this on this medial surface. We can also see them on the lateral surface.

02:09 Here’s the anterior superior iliac spine, anterior inferior iliac spine. And here we have our two posterior iliac spines. And we could make them out on this superior view as well. If we were to just look at the lateral surface of the ilium, then this is important because it gives rise to attachments for gluteus maximus. In order to be comfortable with the attachments of gluteus maximus, we need to be aware of some gluteal lines. So here, we can see a whole series of gluteal lines; anterior, inferior, and posterior. Here, we can see an anterior gluteal line. See that here. Here, we can see inferior gluteal line running alongside the body of the ilium. Here, we can see a posterior gluteal line running alongside the posterior iliac spines. So it’s the important gluteal lines which you should be familiar with as we look at the attachment sites later on of the gluteal muscles.