0:01

So here we have a knee of a teenager

0:07

who's had pain for a very long time.

0:10

What do we notice?

0:11

We notice that there is a huge joint

0:12

effusion in the prepatellar space.

0:14

Look at all the soft tissue

0:16

density here, anteriorly.

0:18

And that soft tissue density

0:19

extends into the Hoffa's area also.

0:22

So there's a lot of edema in the Hoffa's fat pad.

0:25

There's fullness at the

0:26

posterior aspect of the joint.

0:28

So we know there's a large, dense effusion.

0:30

Could it be hemorrhage?

0:31

Maybe.

0:32

But we don't know.

0:33

So the plain film is sort of a screening device.

0:36

Once we see something like this, we

0:38

know the patient is probably going to

0:39

need some kind of cross-sectional study.

0:41

Just to give you an idea,

0:42

here's the frontal view.

0:44

Very hard to see anything here.

0:46

But we look if there are erosions

0:48

or fractures, any widening of the

0:50

growth plate; we don't see that.

0:52

Uh, sunrise view.

0:53

Here's another one.

0:54

Again, we see a lot of edema and a lot of

0:57

soft tissue density in the joint space,

0:59

indicating that there is a large joint effusion.

1:02

And finally, this is our notch view.

1:05

The notch view is obtained with the knee

1:07

slightly flexed, so we see the posterior

1:10

aspect of the condylar surfaces very well.

1:12

If there are any osteochondral

1:13

lesions or erosions in that area,

1:16

this is how we pick them up.

1:17

But basically, the plain radiograph

1:19

tells us that there's a lot of effusion.

1:21

So let's see what the MRI shows.

1:24

Here is a proton density fat-suppressed sequence.

1:27

What do we see?

1:28

Well, here is that very, very large effusion.

1:31

And there is very abnormal

1:33

stuff in the joint space.

1:35

It has a very frond-like appearance.

1:38

And you go, could that be fat?

1:39

Maybe, but it's hard to say because

1:41

it occupies a lot of the area.

1:44

It extends here in the knee joint proper,

1:47

causing inflammation in the joint.

1:51

In fact, there are also these serpiginous

1:53

areas, very tiny particle-like material

1:57

at the posterior aspect of the joint.

1:59

As we scroll back and forth, we see

2:01

that there's also that material more

2:05

posteriorly with fluid-fluid levels, areas

2:08

of irregularity, joint debris, if you will.

2:12

And where is this?

2:13

This is actually between the medial head of the

2:15

gastrocnemius and the semimembranosus muscles.

2:18

So what does this become?

2:19

This is a Baker's cyst.

2:21

So not only do we have inflammation in

2:24

the joint, but it has extended into this

2:27

communicating space, which is actually a bursa

2:30

and that material has gone into there and has

2:33

elicited an inflammatory reaction there also.

2:36

So wouldn't it be nice to see if

2:38

some of these things bloomed or not?

2:40

For that, we don't need a dedicated gradient

2:43

sequence because our dual echo steady-state, the

2:45

DEATH sequence, is a gradient sequence already,

2:49

so I call this the poor man's gradient because

2:51

it gives us information about the cartilage,

2:54

and it also tells us what the nature of that

2:57

effusion, or the nature of those debris is.

3:00

And look how black it becomes on the

3:02

DEATH sequence, telling me that there's

3:04

a lot of susceptibility artifact.

3:06

Meaning that there's probably a lot

3:08

of blood products in this location.

3:11

This is what blood products would look like,

3:13

in the brain, right, after a hemorrhage.

3:15

So we see that completely lining

3:17

that posterior aspect of the joint.

3:19

And if we go further along into that

3:22

Baker's cyst area, take a look at this.

3:25

Fluid-fluid levels.

3:26

Look, some of that fluid is very,

3:27

very dark, indicating hemorrhage.

3:30

So anytime I see inflammatory reaction with

3:34

a lot of hemorrhage, even though I haven't

3:36

yet seen erosion, it may come later on.

3:39

This is a good look for PVNS or

3:43

joint hemorrhage from hemophilia.

3:45

Typically, if there's hemophilia, you're going

3:47

to have a lot more destruction of the joint.

3:50

You're going to have a lot more

3:51

erosions, but not a hundred percent.

3:53

So when I see this, I always say pigmented

3:58

or hemophilia, but I'm favoring PVNS.

4:02

And that's what this ended up being,

4:04

based on the joint aspirate and biopsy.