Osteoarthritis on Hip and Knee Xrays

0:00 · Start

Hi,, I'm Dr Chien-Wen Liew from Orthopaedics 360 in Adelaide, South Australia. Today, I thought we'd go a little bit into detail about what constitutes osteoarthritis on an x-ray. Now, an x-ray is a fantastic modality and a starting point for determining whether you have osteoarthritis. Typically, we would like to get a full history and examine you before we think about x-rays, but often, as a surgeon, this is done far in advance of you coming to see me.

Often, people have had several x-rays in their history before they've seen me. Which can show the progression of disease of a hip or knee before you come and see us to consider a hip or knee replacement.

0:48 · Radiation from X-rays

Now, an x-ray is radiation, but it's very, very low radiation. So there's nothing to be concerned about having a few joint x-rays over your lifetime. And certainly, we use x-rays quite a bit in determining how well your knee prosthesis or hip prosthesis position, but also in looking at people before the surgery. The other modalities that we sometimes use are things like CT scans and MRIs. However, today we're just going to go a little bit into x-rays now.

1:17 · Interpreting a Hip Xray

An x-ray of the hip is where we'll start, and an x-ray of the hip shows the pelvis as a whole. A typically good x-ray will be one which is rotated correctly, and also one which shows a little bit of the femur and the femoral shafts. Now you'll be able to see on the x-ray most of the pelvis, and often at the top of the x-ray, you'll see the last few lumbar vertebrae.

The sacroiliac joints here are also visible, and you'll also be able to see the joints very, very well. Now, as a hip replacement surgeon, I'm mostly interested in how the hips look, but we certainly look at all of the surrounding structures. As well as there can be competing pathologies to cause your discomfort.

2:04 · Hip Arthritis on an Xray

Now, the first thing that we look for is how much space there is between the joint. There are four main features of osteoarthritis, with the first one being joint space narrowing. Now, joint space narrowing occurs because the two bony surfaces of the ball and socket lose the cartilage between them and become narrower over time. So, when your hip is functioning well with no osteoarthritis in it, the bones are separated by cartilage that coats the bone.

There is a thin layer of fluid between those cartilage surfaces. Now, as you develop osteoarthritis, the cartilage is lost, and then eventually you get to the stage where it's bone on bone. Now, this translates as to often why people feel like one leg, or their disease leg, is slightly shorter than their good leg. Now, that's because you've lost that cartilage thickness when it goes to bone on bone.

Now, after a long period of time, the bone actually changes shape and the ball can actually start to collapse. The next most common feature of osteoarthritis are the appearance of what's called subchondral cysts, or geodes. These are holes within the bone where fluid has been pumped into the subsurface of the bone. And that causes a significant amount of abnormality within the bony matrix. Now, during surgery, we often scoop out all of these holes and replace it with graft material.

That graph material is something that we obtain from the off cuts from when we perform the surgery. So it's your own bone being placed into those small geodes that cause that bone to strengthen over time and reconstitute to that nice, strong bone under the surface. Often, one of the other features that we see are osteophytes. now osteophytes are the bone spurs that you can see surrounding a joint.

Now, the bone spurs are what causes. Often the stiffness that you'll feel, and once a hip replacement has been performed, that's stiff disappears now, those bone spurs are can be quite large and can actually be almost the size of my thumb or the tip of my thumb protruding off the edge of the bone.

4:24 · What are osteophytes

Now, osteophytes can occur both on the socket and the ball, when they occur on both sides. You have a very restricted range of movement of that hip. It is a very common feature of osteoarthritis and often arrives early in the course of the disease. The final feature of osteoarthritis is the presence of what's called subchondral sclerosis now. Subchondral sclerosis is a hardening of the bone underneath the cartilage, which occurs essentially when you're bone on bone.

That bone can get extremely hard and extremely polished over time. And that creates a thicker white line over the course of where. That bone should be a lot thinner and a lot weaker in the sense than it was before. Because your body does not have that protective cartilage covering over the bone, the bone does change its quality.

5:17 · When do I have symptoms?

Now, if you have some or all of those things on your x-ray, you often have symptoms. And at that point, it's time to decide whether a hip replacement is necessary. I've made a video about this previously, so please feel free to go through our library and have a look at when you should have a hip replacement. But certainly something to consider now. We certainly don't use x-rays as our sole decision for when you should have a hip replacement.

As we use it just as a way to make sure that what we have planned to do, which is a hip replacement, is the correct operation for your symptoms. Because occasionally we can get tricked because the body is an amazing thing. And lower back or knee pathology can also cause hip pain.

6:01 · Interpreting a Knee Xray

Now that brings me on to a knee. A knee x-ray is typically composed of four bones the femur at the top, the patella between the joints, and then below. That is the tibia and fibula, which are connected together. Now, the femur and the tibia are the main articulating part of the knee joint. And that is what takes most of the load when you walk on.

6:28 · Knee Mechanics

The inside or medial aspect of the knee is where you find most of the weight bearing occurs. And on the lateral aspect or outside of the knee is where there's a lot of agility and sliding motion of the joint. When you have arthritis on the inner aspect of the knee, you find it hard just to putting weight through the knee. When you have arthritis on the lateral aspect of the knee,

you find it hard on uneven ground, slopes and anything where you may need to pivot on your knee. Now, the patella, or the kneecap sits at the front of the knee.

7:03 · Patellofemoral osteoarthritis

When you have arthritis in the patellofemoral joint, you find it very difficult going up and down stairs, rising from a low chair, or getting up off the ground. The most common type of arthritis is when people have them on the inside of the knee. The second most common is the outside, and the third most common is the patellofemoral. People with patellofemoral joint osteoarthritis can often walk quite well on perfectly flat ground, but really struggle when it comes to any hills or stairs.

It's important as a surgeon for us to determine what kind of arthritis you have so that we can adjust the surgical plan according. And make sure that you get the very best that we can possibly give you out of the knee prosthesis now,

7:45 · Views of a knee x-ray

a knee x-ray is something that we look to start with three main views. Now there are additional views to this that we can ask for that give us a little bit more information about the morphology of the knee, but because I'm using something called patient-specific technology.

7:57 · Patient specific technology for knee replacements

We obtain a full, three-dimensional scan of the knee, which gives us all the information required to make a good decision about the type and position of your new knee replacement. When we look at an x-ray, we can see a few different things again, similar to the hip, we're looking at the same. Four key elements of the x-ray joint space narrowing the presence of subchondral cysts, osteophytes, and subchondral sclerosis.

So they're no different to the arthritic features on any x-ray of any joint. Now, in the knee, we can see a few additional things. You may find that your knee doesn't straighten fully when you try to get it nice and flat on the bed, or that it flops out to the side when you're trying to do so. This is usually because of one thing called a fixed flexion deformity, and that means that your knee is fixed in one bent position.

You can bend it, but you can't straighten it or flatten it. Now, if this occurs, we look at a particular portion of the knee x-ray, and that is the lateral view. On the lateral view. We can see osteophytes, and if you remember from before, when we were talking about the hip, an osteophyte is a small knuckle of bone that develops in an abnormal position.

9:15 · Posterior Osteophytes for Fixed Flexions

Now, if you look at this lateral x-ray, you can see that the knuckle of bone is on the back and on that lateral view. It occurs in a position where, as you try to straighten the knee, all of the tissues on the back of the knee are tight, and they no longer allow for that knee to fully straighten. Similarly, osteophytes and stiffness and inflammation can prevent full range of movement of the knee, inflection and extension. The Patella view shows the kneecap in a skyline view. The skyline view shows the Patella now.

9:46 · What is a skyline view?

The patella is something that can be very worn down in some individuals. The patella normally sits in the V-shaped groove of the femur, and there can be quite a variation in the shape and position of these elements. Now, the patella normally will start to degenerate on the outside aspect of the knee first, and can shift considerably and thin over time. As a patella gets quite thin, it becomes a little bit more difficult during surgery to resurface that patella appropriately without having the risk of damaging the patella.

So it is really important that we get a full picture of what that patella looks like before the surgery. Again, with our three-dimensional planning techniques, with the patient-specific technology, we will see all of this before we start.

10:34 · Other investigations for a knee condition

Now, there are other modalities that we can use to assess a knee. An MRI is typically used to look at the soft tissue elements of the knee. Or when the x-rays do not show those typical signs of osteoarthritis. Often if it's early in the disease, or if you have other pathology, like an ACL or an anterior cruciate ligament tear, or a meniscal pathology, or a meniscal tear.

We look at those on an MRI rather than an x-ray, whilst an X-ray is the only modality required to assess a knee for osteoarthritis, and MRI can be useful if the diagnosis is a little bit uncertain. I hope this has given you a little bit of insight into what we look for on an x-ray of the hip or the knee. And certainly for those little features that you might have that can show either osteoarthritis developing or advanced osteoarthritis.

If you're unsure, please don't hesitate to contact us and we can certainly guide you through the process and what it all looks like. Alternatively,

it is often the case that you're with your general practitioner or your family Dr before the surgery, and they can guide you through that process as well. I look forward to seeing you for the next video, thanks for tuning in.

Transcript edited lightly for readability.