Introduction to Calcium Pyrophosphate Deposition Disease (CPPD)

CPPD or calcium pyrophosphate deposition disease or Pseudogout as it's also called. It's actually pretty common and we can see it in various structures around the body, but the knee is one that's particularly involved and it's fairly common for us to see.

Common Locations of CPPD Deposition in the Knee

So, in this video, we're going to look at what are the common. Locations within the knee that we can see CPPD deposition. And some of the less common structures also that are involved.

Calcification in Meniscus

One of the most common would be the menisci and we get deposition of calcium pyrophosphate. Within the meniscus itself and, how we know that is because we have this triangular appearance. So, it takes on the form of the meniscus. And we get calcification of varying degrees within the meniscus. And that gives us the outline of the meniscus. Here, this is the same patient. So, we've got this calcification within the meniscus that triangular appearance.

Calcification in Tendons

We also have calcification in the region of the popliteus tendon. So, this has popliteus tendon calcification, we will come into the tendons that can be involved in just a moment.

Chondrocalcinosis: Two Forms of Deposition

The other very common site is cartilage. And with cartilage you can see two forms of deposition. One is this linear deposition of calcium pyrophosphate on the surface of the cartilage. It's almost like it's icing on a cake. So, we have these thin linear areas of increased density on the surface of cartilage. The thing that can be confused with that is capsular calcification. So, this is calcification within the capsule. Just it's a little bit more peripheral. Often you will see a second line in here, which is the calcium within the cartilage itself. But capsular cartilage tends to be more peripheral because that's where the capsule is. And if you're looking on a CT, you can follow the capsule, you can actually see it and here it's not windowed properly for the capsule, but this is the noncalcified capsule here.

The other form of chondrocalcinosis is actually calcification within the cartilage. The image we saw previously was on the surface of the cartilage. And here we have calcification that's actually within the cartilage itself. So, we've got two forms of chondrocalcinosis that linear icing type appearance, or this more diffused appearance within cartilage itself, and you can get them occurring individually or they can occur together. In this patient, we can again, see that we have meniscal calcification. And this is also within the popliteus tendon.

Uncommon Locations

More uncommon location and this is within ACL, and this is PCL, and this is pretty uncommon to see. Can occur really within any of the soft tissue structures around the knee. This is the same patient who had the ACL and PCL involvement. And it's just a reflection of a severity in this patient. So again, this is not a common thing to see.

What have we covered?

So, what we've covered is. The common sites of involvement within the knee of calcium pyrophosphate deposition disease Most commonly you're going to see it within the cartilage menisci and adjacent tendons particularly popliteus and gastrocnemius And if it's severe enough you'll see involvement of Other structures. But generally, the most common location is going to be within the cartilage and menisci and the adjacent popliteus and gastrocnemius tendon