 Welcome to our vignettes on the hip, and we're right on the cusp of transitioning from the anatomic sequence side to the anatomic pathology side. So you've heard a lot about sequences in the past, and we're going to continue framing the important sequences, but I think we need to get a few terminology issues out of the way. So I've created by hand, as you can tell, from my rudimentary art skills this line drawing, which shows a few key anatomic areas, and I'm sure you have noticed, while I make my line a little bit thinner, that we have a femur and an acetabulum. So here's our femoral head with a little notch in it, the fovea capidus where the ligamentum terris inserts both the pubic and the ischial head. When I look at a hip in the coronal, orthogonal projection, or in the coronal oblique, I am looking at the fit between the head and the cup. People that have a shallow cup under coverage are more prone to cam type impingement. People that have deep cups may be prone to pincer type impingement and the arthritis that goes with it. There are conventional radiographic measurements for a deep cup. But we're here to talk about MRI, and you can find these standard measurements on any Google search. But let's look at these lines as they might appear on a radiograph because we're going to translate them into MRI. Let's start out with this line, which is known as the ileopectinial line. And then this line right here, which forms a loop, which is known as the ileo-ischial line. On a plane film, when the femoral head projects medial to this line, so the head projects inward this way, that is known as coxa profunda. If the femoral head starts to weigh in on the center of the socket and protrude medial to the normal arc of the socket and protrudes into the pelvis, you all know that as protrusio acetabular. Now for reference, we have the ileum right here and the sacrum and the sacroiliac joint just to get you oriented. But here are two other key important lines. The anterior aspect of the acetabulum, which contributes to this loop on the x-ray, and the posterior aspect of the acetabulum as well as the roof. Now, if I simplify my drawing a little bit, and I'm going to go with a nice yellow color and a little thicker line. So let's make our acetabular roof in a single planar projection. If our acetabular roof is very vertically oriented, there's a pretty good chance that the femur underneath is going to be under covered. In other words, the acetabulum won't cover it at its drop-off. That is one form of a shallow cup. But when you have a cup that is not just arc-shaped but up and down vertically oriented, then most likely you have a form of developmental dysplasia of the hip which may have gone unrecognized at birth, last into adulthood, and the patient then presents with pretty severe osteoarthritis or the manifestations of CAM type impingement. On the other hand, if you have a very deep cup, not only may you see the phenomena of protrusioacetabuli or coxoprofunda, you may see these big large sweeping arcs of acetabulum coming around and simply over covering the femoral head in multiple projections, the coronal as well as the sagittal and even the axial. And we'll talk specifically about axial over coverage in a separate discussion because that has its own implications. A few other critical aspects of morphology before we move into the MRI. You will hear the term coxavalga. In coxavalga, the relationship between the femoral head and the neck and stem is laid out a little more laterally. In other words, it goes this way. In coxavara, the femoral head-neck junction will have more of an angulated appearance, a sharp angle between the two. Some additional basic terminology includes the reference of the femoral head to the neck and primarily the shaft of the femur, which when angulated out or laterally at or greater than 125 degrees is known as coxavalga. The opposite is when this angle between the head and basically the shaft and neck is angled inward or more medially and is 125 to 120 degrees or less. Another term you may hear is coxamagna, when the femoral head is too big for the acetabulum. So you could have a normal acetabular size, but it may be too shallow because simply the femoral head is just too large. Another term that you might hear is the term known as os-acetabuli, which in the past was considered to be an ossicle at the level of the labrum. We now know that many of these foci previously referred to as os-acetabuli are either osvacations of the labrum itself or they are areas of anterior column spur formation that have broken off in the scenario of pincer type impingement or type 2 impingement. So now let's take on some cases. You can move on to the next vignette if you'd like.