0:00

Let's take a look at this 12-year-old young man,

0:02

boy, with anterior knee pain

0:04

and open growth plates.

0:06

We have on the left, the T1 fat-weighted image.

0:10

In the middle is a T2 star turbo field echo,

0:16

using a very short TR and TE,

0:18

but with very generous fat suppression.

0:21

And then another water weighted image,

0:25

also gradient echo.

0:27

This one, not as fat-suppressed

0:30

or not fat suppressed.

0:32

So, you can compare these two and sort of get

0:34

a feel for the difference between each.

0:36

If you are a stickler,

0:38

I'll certainly be happy to give you

0:39

a proton density fat suppression.

0:42

Now, I'll blow this one up.

0:44

This is a little more water-weighted than the

0:46

gradient echo that you saw on the far right.

0:48

In fact, it's a lot more water-weighted.

0:50

That standard non fat-suppressed

0:52

gradient echo image,

0:53

clearly not as sensitive in picking up areas of

0:56

marrow edema and soft tissue edema

0:58

as this fat-suppressed PD spur

1:01

and this center image,

1:03

which is a gradient echo with excellent fat suppression.

1:06

Now, there's another caveat here.

1:09

This study was done with a TE of 14

1:11

on the PD spur,

1:13

so they did not actually even maximize

1:16

the water sensitivity of this sequence.

1:19

Because, as many of you know,

1:20

I don't like to do PD fat suppression imaging

1:24

with short TEs.

1:25

I like to use intermediate TEs of 30, 35, or 40

1:29

to bring forth the water signal intensity even further.

1:32

That set aside,

1:33

we've got plenty of water signal intensity present.

1:36

Now, let's bring back our gradient echo.

1:39

Now, when we think about anterior knee pain

1:41

in the young juvenile,

1:43

by far, the most common cause is mild patellar dysplasia

1:48

or mild micro instability

1:51

with patellofemoral maltracking.

1:53

So, what do you see in cases like that?

1:57

Well, you might see the dysplasia

1:59

or the misshapen patella

2:00

or misshapen trochlea,

2:02

which will be a story for another day.

2:04

And we have different discrete shapes that we describe,

2:07

patella magna, pebble patella,

2:10

the berg shapes, or Weinberg shapes,

2:12

one through four, and so on.

2:14

But right now,

2:15

I'd like to just share with you this

2:17

this indurated appearance of the retro patellar fat,

2:20

which is a sign of shearing,

2:24

that there is excessive friction between

2:27

the patella and the tissues around it,

2:29

and it can cause some irritation

2:31

and inflammation of the fat pad

2:33

and can even hypertrophy the fat pad.

2:36

In fact, the fat pad can get so big

2:38

that it prevents a child or young adult from flexing

2:42

and extending the leg.

2:43

And that is called fat pad impingement syndrome.

2:47

And the fat pad may actually have to be

2:49

resected and that is a real entity.

2:52

You're also probably very familiar as imagers

2:56

and orthopedic clinicians with the entity

2:59

of Osgood-Schlatter's syndrome,

3:02

which is an apophysitis.

3:04

It's not just failure of union

3:07

of the tibial apophysis,

3:08

because lots of people have that,

3:09

and they have no swelling, no inflammation,

3:12

they're not symptomatic.

3:13

So, what do I call that?

3:15

Ununited tibial apophysis.

3:17

Pretty simple.

3:18

But when it's inflamed,

3:20

when there's cystic change,

3:21

when there's swelling of the tendon,

3:23

then I'll call it inflammation of the tibial

3:26

apophysis, or tibial apophysitis,

3:28

consistent with clinical Osgood-Schlatter's syndrome.

3:33

The same thing can be said here

3:35

in the inferior aspect of the patella,

3:37

where there is an apophysis that has

3:39

remained unfused in this child,

3:42

that is swollen,

3:44

that involves the patellar tendon.

3:47

So this is known as Sinding-Larsen,

3:50

or Sinding-Larsen-Johansson syndrome.

3:53

With the patellar swelling,

3:56

you might also invoke the clinical

3:58

syndrome of Jumper's knee,

4:02

because these two bony structures are wiggling.

4:06

In other words,

4:07

there's some micro instability between them.

4:09

You are seeing friction induced stress reaction

4:12

in the main patellar body and in this inferior,

4:16

ununited tubercle,

4:18

and it is clearly having an effect on the hoffus space

4:22

and even the suprapatellar fat space.

4:25

Now, another question

4:27

that you're probably asking yourself,

4:29

and you should, is, okay,

4:31

patellar tendon is sick, it's swollen,

4:34

it's inflamed, it's a child,

4:35

but is it torn?

4:36

Should I use the T word?

4:39

And perhaps,

4:41

that's when you turn to the other projections.

4:43

So, let's do that.

4:44

Let's turn to the axial,

4:45

and let's scroll down and see what a healthy

4:48

tendon looks like.

4:49

Nice and black, curved,

4:51

convex forward, and we see the tendon fibrils.

4:55

Those are not tears.

4:56

Those are areas of interdigitation of soft tissue

5:00

with the tendon.

5:01

Just fine.

5:02

They'll become a little more conspicuous

5:04

as the tendon gets swollen.

5:06

So, you're separating out the tendon subunits.

5:10

They're delicate, they're linear,

5:11

they're repetitive.

5:13

None is really brighter than the other.

5:15

Yeah, maybe that one's a little bit brighter.

5:17

I'll give you that, but not enough.

5:18

Let's keep going.

5:20

Now, we're getting into the piece of bone.

5:22

Let's keep going.

5:23

We're in bone.

5:24

Let's keep going.

5:25

e're in bone,

5:26

and now we're seeing the prepatellar plate.

5:28

This certainly is below my threshold

5:31

for reading a tear.

5:32

If you wanted to call it a microtraumatic injury,

5:35

that's fine.

5:36

But essentially,

5:37

this patient does not have a patellar tendon

5:41

macro tear.

5:43

Now, we're not done yet.

5:45

We can look at this tendon in the coronal projection,

5:48

and we should,

5:49

so that we decide whether we're going

5:52

to invoke the T word or not.

5:55

We're not.

5:57

Let's look at the coronal projection.

5:59

Do we see anything that is dominant as a gap,

6:04

that is etched, that is well defined,

6:06

that is fluid-like signal, and the answer is,

6:10

no, not really.

6:11

That is not in the tendon.

6:12

That's the soft tissue swelling.

6:14

When we get back in the tendon,

6:16

things look pretty darn good.

6:18

Yes, there is some swelling right here,

6:20

but that's bone.

6:21

That is a piece of bone.

6:24

That's swelling in the bone fragment.

6:26

But there is no gapping or separation

6:29

of this tendon.

6:30

These fibrillated areas of striation that are

6:34

repetitive, not very bright, very similar,

6:37

they line up all in a row,

6:39

they're redundant,

6:41

that is typical of the tendon fiber subunits

6:44

of an intact patellar tendon.

6:47

Sinding Larsen Johansson Syndrome,

6:50

jumper's knee, intact tendon,

6:53

patellofemoral maltracking

6:54

with retropatellar induration.

6:57

Next.