0:00

Here is a patient with signal in the lateral meniscus. Let's go all the way to the root.

0:05

Here's our root,

0:07

which we said is usually kind of a sloped triangle

0:10

or a truncated triangle.

0:13

And what's this?

0:15

It's a swollen area of tissue.

0:19

Hard to define what it is on one cut.

0:22

But let's keep going, shall we?

0:24

Around area of tissue.

0:26

The transverse meniscal ligament,

0:29

which looks a little strange.

0:31

And now they start to come together,

0:33

and we have some interdigitation

0:35

and some attachments anteriorly.

0:39

And now, they don't come together.

0:43

Well, we said that was the transverse ligament,

0:46

but Wait a minute.

0:48

That's the meniscus. That's a space.

0:51

That's a ligament. That's an attachment.

0:53

Let's keep going, shall we?

0:55

It's still there, but it's not round.

0:58

If it's a ligament, why isn't it round?

1:01

Let's keep going. Still not round.

1:05

Still not round.

1:07

Still not round.

1:08

And it's actually into the body of the meniscus

1:11

now. Well, let's go back for a minute.

1:14

What I convinced you was a transverse

1:17

ligament was not.

1:19

It's a fragment of meniscus that broke off.

1:23

There was no transverse ligament.

1:25

That's a piece of meniscus.

1:27

That's a piece of meniscus.

1:28

That's a piece.

1:29

That's a piece.

1:30

That's a piece.

1:31

That's a piece.

1:32

That's a piece. That is a piece.

1:34

And so it goes all the way into the body with this

1:39

obliquely oriented tear with a cleavage

1:41

component that finalizes in the body.

1:44

And you can see it coronally, too.

1:45

There it is.

1:47

There is no transverse ligament going

1:49

from meniscus to meniscus.

1:51

There is the root attachment.

1:53

There is your giant tear,

1:55

and the fragment is in front of this particular

1:58

slice. So a large, complex,

2:02

oblique cleavage tear with a fragment

2:06

of meniscus anteriorly,

2:07

whose true ideology is displayed in the fact

2:11

that on every single sagittal slice,

2:13

all the way from the root to the body, persists.

2:17

And that's how you make the diagnosis of an

2:20

anterolateral tear with these complex

2:23

anatomic characteristics.

2:25

In the next five minutes,

2:26

I want to just talk about the concept of

2:31

extrusions.

2:33

And I don't mean the kind in your back.

2:36

I mean the kind in your knee.

2:38

What you say the meniscus does displace in the

2:43

knee. You're walking around all day long,

2:45

and you've got these hoop stresses that are

2:47

pushing down on a structure that looks somewhat

2:50

like this. It actually isn't a triangle.

2:52

It has a nice little slope in it to accommodate

2:55

the femur, which I've drawn here in yellow.

2:58

And the femur drives down into

3:00

the meniscus and pushes it.

3:02

Unfortunately,

3:04

when we're young and healthy and vibrant,

3:06

in other words, under age 60,

3:08

the meniscus can tolerate it because the

3:11

attachments are nice and tight and firm.

3:14

But as we get a little bit older,

3:16

or if we abuse the meniscus by running ten k every

3:21

day and we start driving the femur

3:24

down onto that meniscus,

3:26

the attachments may get looser and

3:28

stretchier and more plastic,

3:30

and the meniscus starts to displace out of

3:35

a line between the edge of the femur.

3:37

We'll draw that line between the edge of

3:39

the femur and the edge of the tibia.

3:41

So the meniscus starts to migrate

3:43

beyond that line,

3:44

and that may be the primary cause of

3:48

DJD or osteoarthritis of the knee,

3:50

or it may be a secondary phenomenon.

3:52

Once osteoarthritis begins and we get a little

3:56

synovial hypertrophy and inflammation,

3:58

the ligaments digest,

3:59

the meniscus starts to get a little plastic

4:03

and deformed, and it starts to move out,

4:04

and then the arthritis gets worse,

4:06

and it's a vicious cycle.

4:08

We here at proscan refer to

4:10

this as pseudo extrusion,

4:12

or plastic deformation of the meniscal

4:14

attachments due to arthritis.

4:17

Now, what's a true extrusion?

4:20

A true extrusion for us means one of two things.

4:24

The attachments have given way.

4:26

In other words, something's ruptured,

4:28

allowing the meniscus to be displaced or extruded,

4:31

either out peripherally or in towards

4:34

the middle of the knee.

4:35

I also reserve it for one other situation,

4:38

and that is when the meniscus does this.

4:41

When the meniscus is squished out like

4:46

toothpaste coming out of a tube,

4:48

it's starting to get pushed out this way,

4:50

and it starts to migrate down the paratibial

4:55

or migrate up the paraphemeral gutter,

4:59

just to be a little clearer.

5:02

This would be the femur, this would be the tibia.

5:06

So now the meniscus is starting to prolapse along

5:08

the free edge of the tibia or the free edge

5:11

of the femur. In that scenario, also,

5:13

I'll use the term extrusion of the meniscus,

5:17

or displacement extrusion of the meniscus in

5:21

the periphemeral or the peritibial gutter.

5:24

Let's take a quick look.

5:27

Here's exactly just that here's our meniscus,

5:32

and our meniscus is truncated.

5:36

We'll get to that in a moment.

5:37

You already know one cause of truncation is a

5:40

bucket handle tear. But not the case here.

5:43

This is the most common cause of truncation.

5:45

The surgeon. The surgeon did it.

5:48

They truncated the meniscus.

5:50

They went and cut the inner

5:52

portion of the meniscus,

5:54

which actually has a lot to do with the meniscus

5:59

extrusion or displacement along the paratibial

6:04

gutter. And here it is right there.

6:06

Our meniscus is in trouble.

6:08

And this patient is lying on their back.

6:10

They're not even standing up.

6:11

There's no hoop stress driving down,

6:15

pushing the meniscus out.

6:16

When the patient is standing,

6:18

it's even more extruded.

6:20

Why did this occur?

6:23

Because the meniscus

6:25

got chopped right here and now.

6:29

When you drive the femur down into a structure

6:32

that is now paper thin and irregular

6:35

and has lost some of its depth,

6:38

you know from physics that that produces a

6:41

scenario that enhances the pushing effect

6:45

of the meniscus to one side.

6:48

And most of the forces are coming down and

6:51

out and down and out on both sides.

6:53

So the mere fact that there's a trimming

6:58

increases the likelihood,

7:01

the physical likelihood that a meniscus experience

7:05

produces more downward force, more hoop stress,

7:08

and greater likelihood of displacement,

7:11

and therefore,

7:11

displacement into the paraphemeral and peritibial

7:15

gutter, rendering it useless.

7:18

So menasectomies are not to be taken lightly.

7:22

And we'll talk about later on what circumstances

7:26

they are absolutely indicated. Thanks.

7:29

Bye.