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Hello and welcome to Noon Conference hosted by M R I Online Noon Conference

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connects the global radiology community through free live educational webinars

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that are accessible for all and is an opportunity to learn alongside top

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radiologists from around the world.

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We encourage you to ask questions and share ideas to help the community learn

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and grow. Today we are honored to welcome Dr.

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Donald Resnick for a lecture on meniscus of the knee function and dysfunction.

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Dr. Resnick is a renowned lecturer and his list of dozens of awards and honors

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include a twice awarded most effective radiology educator from ANT Mini 20

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eighteens,

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a C R Gold medal for his lifetime achievements and an honorary doctorate from

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the University of Zurich.

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We're thrilled he's here today to share his expertise with us.

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At the end of the lecture, please join Dr.

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Resnick in a q and a session where he'll address questions you may have on

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today's topic.

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Please remember to use the q and a feature to submit your questions so we can

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get to as many before our time is up. Dr. Resnick,

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thank you so much for being here today. Please take it from here.

1:02

Thank you, uh, very much. It's a privilege, uh, for me to be here and to, uh,

1:07

share some information with those of you listening. Uh,

1:12

I'm coming to you from my home in Delmark, California.

1:15

Currently it is dry.

1:17

It was wet about a few days ago when we had a large storm pass

1:21

through this area.

1:23

Today I've chosen the topic meniscus function and dysfunction

1:28

because I think for those of you doing MR Imaging of sports

1:34

medicine injuries,

1:35

the knee and specifically meniscal injuries represent a large part

1:40

of what you are doing.

1:43

So there are two particular objectives for this lecture.

1:47

They're listed here, number one, to review meniscal structure,

1:53

pathophysiology with emphasis,

1:55

as I'll show you on the collagen framework that is found within

2:00

the meniscus. And then knowing that framework,

2:04

we're gonna look at classic patterns of meniscal failure,

2:07

of which there are three.

2:09

And I'll try to explain why they look as they do on the MR images.

2:15

And here's a little point for you.

2:17

When you see this guy pay attention to what is written here.

2:22

You're gonna see him maybe four or five times during the lecture.

2:26

He'll be smaller than this, so be at the bottom left part of your screen.

2:32

So keep an eye out for him and when you see him,

2:35

please pay attention to what's written on this particular item.

2:41

So let's start with a few general features. Okay,

2:45

and what I would like to say at the very beginning,

2:47

I want to emphasize the similarities between things we call articular discs.

2:53

For example,

2:54

the triangular fibrocartilage disc of the wrist shown in the middle on your

2:58

right, the menisci of the knee and the labra as you know,

3:02

which we see typically in the hip and in the lumal joint.

3:07

These structures have similar tissue.

3:09

It's transitional tissue between fibrous connective tissue and hylan cartilage.

3:15

These structures are poorly vascularized and in general,

3:19

the vascularity is more prominent in the periphery than in the central

3:23

portion.

3:25

And all of these structures undergo age related degeneration and sometimes

3:30

degenerative failure that can lead to full thickness,

3:33

perforations or tears, trauma related abnormalities.

3:38

And we're gonna be emphasizing some of those today can lead to clinically

3:42

significant findings. Now, just the word at the beginning, at least,

3:47

if you go to an anatomy book and try to define the difference between a meniscus

3:51

and disc,

3:52

you will see that a meniscus partially divides a joint cavity

3:57

as you can see on your right, and a disc completely divides a joint cavity.

4:02

The list on the left contains those particular articulations that have either a

4:07

menis or a disc. The problem with that definition is with aging,

4:12

a disc may develop a full thickness perforation and then indeed it

4:17

is a partial division of the joint cavity that results.

4:20

So there's a little bit of confusion with regard to the terminology.

4:25

Now, in general, to understand pathology, you have to understand anatomy.

4:29

So let's look briefly at the meniscal anatomy. You are the femur.

4:34

You're looking down on the top of the tibia, the medial meniscus on your left,

4:38

the lateral meniscus on your right.

4:41

The first thing that is obvious is that the medial meniscus is more elongated

4:45

and the lateral meniscus is more circular of interest.

4:49

The lateral meniscus covers more of the lateral tibial plateau

4:54

than does the medial meniscus of the medial tibial plateau.

4:58

And the lateral meniscus absorbs more axial load than does the medial

5:03

meniscus. Now,

5:05

this drawing done number of years ago has other structures on it,

5:08

and I'm gonna emphasize four of them.

5:11

And they're labeled for you 1, 2, 3,

5:13

and four because we're gonna talk about those structures later on in the

5:17

lecture. These are the root ligaments. Two are anterior,

5:21

that's numbers one and three, two are posterior.

5:24

That number two and four two are related to the medial meniscus.

5:28

Two are related to the lateral meniscus.

5:31

And the one we're gonna emphasize is the one mark two on this drawing the

5:35

posterior root ligament of the medial meniscus.

5:38

But let's not skip ahead to that. Let's go first with the meniscus.

5:43

If you look at meniscal composition,

5:45

you can see initially as shown in the yellow boxes,

5:48

it is a well hydrated structure of the organic matter representing

5:53

30% of the wet weight.

5:55

I put an arrow next to collagen because it's the collagen that I wanna emphasize

6:00

today.

6:00

It's a major component of the meniscus and it transmits the force

6:05

extending through the meniscus. In general, if you go to anatomy books,

6:10

you will lead, uh, find out about the meniscus functions.

6:14

The five major ones that are listed here.

6:17

The meniscus can serve to protect articular cartilage. It absorbs shock.

6:22

It transmits load.

6:24

I show you a section of the knee at the bottom right showing you

6:29

that the menisci are protecting the adjacent articular cartilage.

6:34

Note all the abnormalities and the uncovered portion of cartilage,

6:39

but not in the part covered by the meniscus.

6:43

The other point I would make about meniscal function,

6:46

the meniscus generally are not considered primary stabilizers,

6:50

but if something goes wrong with a primary s uh stabilizer,

6:55

the meniscus may in fact assume an important stabilizing effect.

7:00

And the one I'm gonna talk about later is what occurs to the posterior horn

7:05

of the medial meniscus when there is failure of the anterior cruciate ligament.

7:10

Because you see in that situation,

7:13

the posterior horn becomes a resistance to anterior translation of

7:18

the tibia.

7:19

And a peculiar pattern of failure does occur in the posterior horn of the

7:23

meniscus known as a ramp lesion. More about that a little bit later.

7:31

I would a, uh,

7:32

first year medical student when I learned that the menisci were largely

7:36

avascular, not entirely avascular, but largely avascular.

7:41

There are actually are two sources of blood supply to the meniscus.

7:45

They're numbered here, one and two for you.

7:47

And if you look on the right at the top image,

7:50

you can see the number one and number two.

7:53

Number one is a per meniscal capillary plexus.

7:57

Number two are the synovial reflections adherent to the top and bottom

8:02

of the meniscus. And as you look at my drawing,

8:05

and you look at the section below it,

8:07

you can see that the vascularity involves the peripheral aspect of the meniscus

8:12

and not the larger or wider central portion. Hence,

8:16

the orthopedic surgeons offer refer to this as the red and white zones

8:21

of the meniscus.

8:23

Failure in the red zone can indeed be associated

8:28

with spontaneous correction of the failure.

8:32

That is the tear may heal or the surgeon may elect to go in.

8:36

When you have failure in the white zone,

8:39

we run into a problem where a resection of the damage meniscus may be

8:44

required.

8:45

Here's a beautiful slide on your left showing you a red zone tear

8:50

in the vascular portion.

8:52

A probe is showing you that in at the bottom of that image.

8:58

Now, in order to understand hairs,

9:01

you have to understand normal meniscal morphology. So what I've done here,

9:06

we're looking down at half of the tibia and I'm showing you three parts of the

9:10

medial meniscus. They're triangles the posterior horn at the bottom,

9:15

the anterior horn at the top in the distance.

9:17

Now what you need to know about the medial meniscus is its width based on

9:22

the literature.

9:23

The widest part of the medial meniscus is the posterior horn.

9:28

The mid portion, by the way, can be very narrow, although sometimes it is not,

9:33

but the posterior horn is the largest heart.

9:37

So a quick way to survey the integrity of the medial meniscus on sagittal images

9:43

is to compare the width of the posterior horn to the width of the

9:48

anterior horn. And in general, the posterior horn should be wider.

9:52

If it is not, there's a problem.

9:54

And we'll talk about what might be the causes for that a little bit later.

9:59

If we do the same experiment on the lateral side,

10:02

the results are different here.

10:05

The widest portion of the lateral meniscus tends to be it's mid portion or

10:10

body with a posterior horn and anterior horn being similar in width.

10:15

So a quick survey of the integrity of the lateral meniscus on

10:20

a sagittal image shown here is that the width of the posterior horn on your

10:25

right should indeed be about the same as the width of the anterior horn

10:30

on your left. Okay,

10:34

this is a critical slide. There's a lot of information.

10:37

Let me see if I can simplify it for you.

10:39

There's a beautiful image at the bottom left showing you indeed the collagen

10:44

framework of the meniscus.

10:47

There are two types of collagen bundles found within the meniscus.

10:51

The first of these, I'm showing in the here as these blue bundles here,

10:56

the arrow is pointing to them.

10:59

These are longitudinal circumferential collagen bundles.

11:03

They are found mainly in the peripheral 50% of the meniscus,

11:06

and they run in circumferential direction. So in simple terms,

11:12

they connect the anter and posterior portions of the meniscus.

11:17

The second type of fibers are known as radial tie collagen fibers.

11:23

I show them as the orange arrow. And these orange arrow heads,

11:27

they run in from the periphery all the way to the central portion.

11:31

You can see in the bottom right radial tie fibers,

11:35

beautiful specimen images. So what I'll do,

11:39

and I simplified it at the top right,

11:41

I'm showing you the longitudinal circumferential collagen bundles

11:46

in red cylinders connecting the anterior posterior

11:50

portions of the meniscus.

11:52

And I'm showing you radial tie fibers in white connecting the

11:57

peripheral and central portions of the meniscus.

11:59

And that's all you need to understand to realize the patterns that

12:04

may occur with meniscal tearing. Hmm.

12:09

Now there are classification systems.

12:11

The iica system listed here has seven characteristics that they feel

12:16

should be described at the time of surgery.

12:20

And many of these characteristics are part of our description when we are

12:25

looking at Mr images of the knee.

12:28

A comment on some of these as we go through this lecture.

12:32

Now there are all kinds, kinds of patterns of meniscal failure,

12:37

but the three basic ones are labeled here, one, two, and three.

12:42

And we're gonna be talking in detail about them. Longitudinal vertical tears,

12:46

number one,

12:49

horizontal or longitudinal horizontal tears labeled number two,

12:54

and radial tears labeled number three.

12:57

Those are the three basic patterns of failure. Now,

13:01

to understand why the meniscus fails,

13:03

you have to understand something called hoop stress.

13:07

And indeed it's hoop stress that's led to failure of the liberty bell in

13:12

Philadelphia.

13:13

So this is a sagittal section through the posterior horn of the medial

13:18

meniscus.

13:18

And I'm showing you now the femoral force coming in with axial loading

13:23

at an angle. Now if you remember how we deal with vectors,

13:27

we can divide that force into a horizontal vector.

13:31

That's this arrow and a vertical vector that's this arrow.

13:36

The tibial force is a vertical force that counteracts the vertical force

13:41

on the femoral side.

13:42

So what is left unopposed is this horizontal force

13:47

which leads to a pattern of trying to drive the meniscus from the joint.

13:53

That pattern of stress is known as hoop stress. Now,

13:57

there are other patterns including circumferential stress that try to drive the

14:01

meniscus posteriorly and anteriorly,

14:03

but it's the hoop stress that is the major cause for meniscal failure.

14:09

So I drew last week kind of a blue triangle of a meniscus showing you here's the

14:14

hoop stress extending to the periphery.

14:16

And the major counteraction to that are the longitudinal circumferential

14:21

fibrous.

14:22

And I show you the circumferential force here moving anteriorly and

14:27

posteriorly.

14:28

And the major resistance to that are the radial tie fibers.

14:34

It's of interest, although I won't go into detail,

14:37

that these three basic patterns of failure are delaminated tears,

14:42

at least in part because they are parallel to some of the collagen

14:47

bundles present within the meniscus.

14:50

So much as we see in tendons and in ligaments,

14:53

delamination failure of the meniscus occurs.

14:57

Now we come across across as the radiologist.

15:00

It's our job to diagnose meniscal tears. And as you probably know,

15:05

if you're doing m r of the knee,

15:07

there are two classic meniscal findings of a

15:11

meniscal tear. And I've numbered them there,

15:14

an abnormality of meniscal contour and an abnormality of meniscal

15:19

signal. As I'm gonna show you one of these is terrific.

15:24

And the other is a terrible finding that is not very reliable.

15:29

The normal meniscus tends to be smooth and triangular of gally low

15:34

signal.

15:36

The first alteration that we look for is an abnormality of meniscal

15:41

contour as drawn here. It can be truncated,

15:45

it can be irregular.

15:47

Any of those findings would represent an abnormality of meniscal contour.

15:53

I'm gonna talk more about that in a moment.

15:56

The second criteria is an abnormality of meniscal signal

16:01

with a classic teaching, be it that if you have altered signal,

16:06

be it gray or even bright like fluid that violates the top,

16:11

the bottom, or the apex of the meniscus, it's evidence of meniscal tear.

16:16

The periphery of the meniscus does not count as a meniscal surface.

16:22

The first criterion,

16:23

an abnormality of meniscal contour is simply

16:28

terrific if you can eliminate the possibility of prior surgery.

16:34

Now, I can tell you,

16:35

sometimes the surgeon tells you on the request slip there has been surgery.

16:40

Sometimes he or she does not worse.

16:43

Sometimes they tell you their surgery and there never has been.

16:47

So the first thing I always look at when dealing with m r of the knee is

16:51

evidence for prior surgery arthroscopy. And I look for scarring.

16:57

And we have found the best place to look for scarring is the antal medial

17:01

portion of the knee far more than the anterolateral.

17:05

You're looking for scarring and HFA fat pad.

17:08

You're looking in some cases top left, you may even get a cyclops lesion,

17:13

or you're looking for things like thickening of the ligamentum mucosa within HFA

17:17

fat pad,

17:18

there's one type of scarring or fibrosis that may be

17:22

significant.

17:24

And there are reports that indicate that if you have fibrosis in the anterior

17:29

interval of the knee,

17:29

and I show you that what that is in my section sagittal section of the knee

17:35

is pretty much all of Hoffa's fat pad that if you have fibrosis,

17:39

particularly in its deep portion as shown here,

17:43

it's associated with pain anteriorly in the knee. Typically on extension,

17:47

there may even be a flexion contracture.

17:51

So when I see extensive fibrosis in the anterior interval,

17:54

I mentioned the second criterion,

17:57

an abnormality of meniscal signal is simply

18:02

overrated. The results are inconsistent.

18:05

Now you remember the history of this in the 1980s and 1990s,

18:10

the grading system was introduced looking at signal within the meniscus.

18:15

Grade one might have a little bit, grade two had more extensive,

18:20

but it didn't violate the surface.

18:22

Grade three violated one of the surfaces of the meniscus.

18:27

Typically,

18:28

normal menisci have no signal or grade one degenerative menisci

18:33

were reported to have grade two signal. And when you got to grade three,

18:38

you were dealing with a meniscal tear. Now that sounds terrific,

18:42

but it doesn't work so well.

18:45

So here you can see at the top right what might be grade one or two,

18:49

no tear and grade three at the bottom a tear.

18:53

And the difference here is maybe a couple of pixels.

18:57

So what I have found through the years is that the resident or fellow gets

19:02

a very,

19:02

very close to the computer screen trying to make that last

19:07

pixel bright to change a grade two to a grade three. And they'll even use,

19:12

if you look at the image at the top meniscal window it to get that

19:17

to go out to the surface of the meniscus. In short,

19:21

you should be able to sit comfortably in your chair like this.

19:26

And this should be obvious at a distance. And indeed it's my view,

19:31

if you're not sure it is better to under call than to over call

19:36

a meniscal pair.

19:38

Clearly in some cases signal that initially was inside

19:43

the meniscus, look at the top row,

19:45

might later here five months later become obvious grade three signal

19:50

or a meniscal tear.

19:52

But the patient can come back for a second scan if the pain is

19:57

persistent. So I tend to under call,

20:01

not over call. And indeed,

20:03

another type of thing that was suggested is something called the two

20:08

slice touch rule to make this second criterion more reliable.

20:13

But the idea that if you saw disruption of the surface of the meniscus

20:18

in more than one image, either in the same plane or in multiple planes,

20:23

there are variations in the reports of this that it improves your diagnostic

20:28

abilities.

20:29

And you can see some data provided by the people at Wisconsin that shows

20:34

indeed that two slice touch increased the reliability,

20:38

the positive predictive value, particularly for the lateral meniscus.

20:43

All right, we're ready now for the basic error.

20:46

So with compression of the meniscus, we're gonna see our first tear,

20:50

a longitudinal vertical tear.

20:52

What occurs with compression is hoop stress.

20:56

So the initial pattern of failure related to this sort of loading is

21:01

a micro tear that is along the axis of the hoop stress. Watch the image.

21:06

Now I'm gonna put it in here. Here it's, and as it goes,

21:10

it encounters longitudinal circumferential collagen bundle and it

21:15

stops the micro tear.

21:17

The tear continues along the path of least resistance as a

21:21

longitudinal vertical tear,

21:25

longitudinal or circumferential,

21:27

because it has a circumferential dimension vertical because it is

21:32

vertical or vertical blank.

21:34

These tears may occur in younger people following injury,

21:38

and you see them in the outer half of the meniscus where you have these collagen

21:43

bundles. Here's my transparent meniscus,

21:46

I'm gonna draw a long longitudinal vertical pair in yellow.

21:51

The longer it's the more radial tie fibers that are

21:56

violated. And what do they do?

21:57

They tie together the central and peripheral portion.

22:02

So when you have a long vertical tear,

22:05

you may end up with a situation where the central portion displaces more

22:10

centrally. You have a bucket handle tear of the meniscus,

22:15

a bucket handle tear than a displaced longitudinal vertical tear.

22:21

Now let's go ahead and image one here is the tear

22:25

peripheral half of the meniscus.

22:29

The length of a longitudinal vertical tear is its circumferential dimension.

22:34

So here's our first image.

22:36

This is a complete one that goes from the top to the bottom that stay in the

22:41

same plane. We're doing that now. And its appearance is identical.

22:46

It's a boring finding, and by identical,

22:49

not that it vertical or complete,

22:51

but also it's at the same distance from the periphery of the

22:56

meniscus because it is paralleling those collagen fibers the

23:01

path of least resistance. So when you look at these tears,

23:04

here's the first image, the second image, the third image, they look the same.

23:09

The fourth image, knowing the thickness and spacing,

23:12

you could figure out the length of a longitudinal vertical tear.

23:16

If it's over nine or 10 millimeters,

23:19

it may in fact be unstable. That is something that has been reported.

23:25

Now, that ramp lesion

23:28

is something whose definition has changed through the years,

23:32

typically associated with anterior cruciate ligament failure,

23:37

be it now acute or chronic,

23:39

because now anterior translation is resisted by the posterior horn,

23:45

A peripheral peripheral vertical tear or tear.

23:49

Sometimes there are multiple occurs at or near the meniscal

23:55

uh, capsular junction. So here's a beautiful example of one.

23:59

This was in a patient with a c l deficiency.

24:02

You'll note one of the characteristic findings that I always look for,

24:07

not just the altered signal in the periphery, but look at the tibia.

24:11

There is marrow edema.

24:12

And that's often found when dealing with peripheral failure of the posterior

24:17

horn of the medial meniscus in patients who have a c l problems.

24:22

Okay, tear number two, longitudinal horizontal tear.

24:27

It's known also as a cleavage tear seen in older people,

24:32

horizontal in its appearance, often associated with meniscal degeneration.

24:37

It relates mainly to shear force.

24:40

This tear begins at or close to the apex and takes the path

24:45

of least resistance going between these longitudinal collagen

24:50

bundles. And sometimes as shown in the example, and in my drawing on your right,

24:55

because of so many of these bundles out in the periphery,

25:00

there may be branching of this particular pattern of meniscal

25:04

failure. So this is the cleavage here,

25:07

and often it divides the meniscus almost into two equal parts,

25:11

a top and a bottom. Here's what it looks like in my drawing,

25:17

right,

25:18

we're gonna go ahead now and show what happens when the tear becomes

25:22

large. It opens up like a fish mount.

25:27

The length of a longitudinal horizontal tear relates to its circumferential

25:31

dimension.

25:33

The width relates to its central peripheral dimension.

25:38

And indeed it is these tears that are often associated with para

25:43

meniscal ganglion cyst. Classically,

25:47

we're taught that those para meniscal ganglion cysts are bright because

25:52

fluid from the joint is passing through the tear and entering

25:57

the cyst.

25:58

But sometimes it's bright because of mucinous degeneration,

26:02

not joint fluid,

26:04

mucinous degeneration in the meniscus and also within the para

26:08

meniscal cyst. Now,

26:10

just a few words about these para meniscal ganglion cyst.

26:15

They're more frequent medially. They are larger medially.

26:19

The medial cysts are more aggressive.

26:22

The association with meniscal pairs is higher on the

26:27

medial side and bone erosions, although rare may occur.

26:32

So you can see in my drawing, and in this particular example,

26:35

these are aggressive lesions medially.

26:38

They can perforate or extend around the medial supporting structures as shown

26:43

on the right.

26:45

And another interesting thing is when they occur adjacent to the

26:50

posterior horn of the medial meniscus,

26:53

they may extend centrally becoming located behind the

26:58

posterior crusade ligament. So if you don't know this,

27:01

you're gonna call this a para cruciate ganglion cyst.

27:05

When you see this,

27:06

go back to the posterior horn to see if there's a tear and a para meniscal

27:11

cyst. Now, if you have a tall meniscus,

27:15

let's think of a discoid meniscus. Sheer forces can be extensive,

27:20

and a pattern seen,

27:22

particularly in a discoid meniscus is known as central

27:26

cavitation.

27:27

So our criteria changed when we have a discoid meniscus with a

27:32

lot of gray signal as shown here.

27:35

Even if it doesn't violate the surface of the meniscus,

27:38

often it is found to be cavitary at the time of arthroscopy.

27:43

So this is intra meniscal tear. Now,

27:47

I'm not going to be talking about discord menisci in this lecture,

27:51

but I can tell you the patterns of failure in a discord meniscus are very

27:55

different from the patterns of failure in a non discoid meniscus.

28:01

Okay, we're up to the third basic type of tear, the radial tear,

28:05

this is not a longitudinal or circumferential tear.

28:09

This is a tear that also starts from the apex and extends to the periphery,

28:13

but it is unique. Watch my drawing, I'm gonna draw you one now. Here it comes.

28:19

And as it goes out to the periphery,

28:21

it violates those longitudinal circumferential collagen bundles

28:26

that's shown nicely in my drawing on the right.

28:29

And you can see that nicely as this tear is extended all the way out to the

28:33

periphery of the meniscus. The bottom image shows that.

28:37

So if we go ahead to my transparent meniscus,

28:41

you can see a long radial tear in yellow.

28:45

The length is its central peripheral dimension.

28:48

It parallels the radial tie fiber shown in white in the distance.

28:53

The longer this tear,

28:56

the more of those red longitudinal circumferential collagen bundles

29:01

are disrupted. And what do they do?

29:04

They tie together the anter and posterior horn.

29:07

So a long radial tear is associated with opening

29:12

up of the meniscus,

29:14

like a book producing a meniscal gap,

29:18

which should be measured if you can, on the Mr images.

29:22

Now I can tell you,

29:23

I wasted 20 minutes of my life on the case you see on the right,

29:27

because you see,

29:28

I didn't know all this when this case came through a few decades ago.

29:33

And when I saw this image, I said, oh my gosh,

29:36

there's a meniscal fragment somewhere in this joint.

29:39

And I spent 20 minutes trying to find it, didn't find it,

29:43

because there is no fragment. This has opened up like a book,

29:48

very,

29:49

very characteristic pattern that occurs with large radial tears.

29:54

And you also know the disruption of the Botox that occurs with radial tears,

29:59

even those that are small. You can see a normal bow tie,

30:03

top image on your left and a disrupted bow tie.

30:07

And you can see that on the MR image, the top right and here in a specimen,

30:11

showing you two areas that a radial pair or tears has

30:16

disrupted the bow tie.

30:21

Now, let's go ahead and image this radial pair.

30:23

And if we image it through the gap,

30:26

we see an absent or empty meniscus.

30:29

The bottom left shows you a case where the anterior horn of the medial meniscus,

30:34

it's not a pretty image, but you can see it. Here's the gap.

30:37

There's no meniscus here. That's the gap related to the radial tear.

30:43

Single or multiple radial pairs are characteristic of

30:48

failure of a discoid lateral meniscus.

30:51

So that's another pattern of failure that we see with discoid

30:55

meniscus. Beautiful example shown here. Now,

30:59

the parrot beak tear is a displaced

31:04

radial tear called Aus. The shape of the beak of the parrot,

31:09

it's curved. So let's go ahead and see what happens when we image this tear.

31:13

Here's my first image, and what do we see?

31:17

A longitudinal vertical line in the inner half of the meniscus.

31:23

So the mistake that's made is to call this a longitudinal vertical tear.

31:27

They occur in the outer half, not in the inner half.

31:31

And let's image it again in the same plane. And in this case,

31:35

that longitudinal region is marching toward the

31:40

apex. This is called the marching cleft sign. It may march away,

31:44

it may march toward, depending on the exact pattern of failure.

31:48

This is characteristic of a radial tear,

31:52

particularly a parrot beak type of radial tear.

31:57

So here I'm showing you a case.

31:59

The red picture is that of the torn meniscus. You can see there,

32:03

I'm imaging it three sections in the sagittal plane, a, B, and C.

32:08

You can see there a marching cleft that goes all the way out to the

32:13

periphery. In this case, this is not a longitudinal vertical tear.

32:18

This is a parrot beat radial tear.

32:23

Okay, another critical slide.

32:26

The normal sagittal appearance of the posterior horn,

32:30

of the medial meniscus is shown in the bottom right.

32:34

So here is my central image, that's the posterior cruciate ligament.

32:38

The next image shown here should show a significant amount of

32:43

meniscus. We're moving medially.

32:45

And the next medial image should show the entire meniscus. That's normal.

32:50

Here's my case. There's the central image, and then on my next image,

32:54

similar to this, there's virtually nothing. Alright, that's abnormal.

33:00

And that's an abnormality of the posterior horn, of the medial meniscus,

33:04

or as we'll talk about in a couple minutes, the posterior root ligament.

33:08

So don't be surprised in a case like that.

33:10

If you get a coronal image and you see indeed that

33:16

abnormal space,

33:18

the normal posterior horn will curve down as the posterior root ligament

33:23

of the medial meniscus. Now, a number of years ago,

33:26

I got a call from one of our prior fellows who said, gee, I,

33:29

I really enjoyed my fellowship. They all start that way. And then they, he said,

33:33

you know, I'm really successful. I'm doing a lot of Mr images of the knee.

33:38

I want to shorten the examination.

33:40

Can you shorten it to one sequence? I said,

33:45

you know, I, I can't recommend that. But if I had to shorten it to one sequence,

33:49

it would be the fluid sensitive,

33:52

often fat suppressed coronal sequence shown in this particular

33:56

image because it shows ligaments, it shows contusions and fractures,

34:01

and it shows you some information about the meniscus.

34:06

And he got back to me and said, you don't understand, I'm really successful.

34:11

And you shorten it to one image. I said, you know, I,

34:15

I can't recommend that. But if I had to shorten it to one image,

34:20

it's the image you're looking at.

34:22

This is the most important image of an MR examination of the knee.

34:27

It's the coronal fat suppressed image. And what you wanna look, look at,

34:32

because of the frequency of problems, here is this area.

34:36

Spend 10 seconds at least looking at this image. I'm,

34:40

I'm gonna go a step further.

34:42

Here's the single most important one half image

34:47

of a knee. Mr examination. Always spend time on this image.

34:52

This could be a radial tear of the posterior horn,

34:55

it could be a posterior root ligament. Avulsion more about that in a minute.

35:01

Now there are tensile failure patterns of the meniscus.

35:05

I'm gonna show you two.

35:08

One of them relates to problems with the medial supporting structures,

35:12

and there are a lot of 'em.

35:13

I'm just showing you some in this kind of coronal drawing.

35:16

The tibial collateral ligament, the meniscal femoral meniscal tibial ligament.

35:21

When you have a valgus injury,

35:24

penile force is placed on the meniscus, often the body of the medial meniscus,

35:29

sometimes the posterior horn.

35:31

And what occurs is a corner pattern of tensile failure.

35:36

Here's what it looks like by drawing.

35:39

And here's what it looks like by mlo.

35:43

We can see with a blue arrow,

35:44

there's a problem with a deep medial meniscal tibial ligament.

35:47

You can see a little edema where it attaches to the tibia and the arrow is

35:52

showing you that corner failure may not look like much, but look at my drawing.

35:56

This is going through some longitudinal circumferential collagen bundles.

36:02

The second pattern of penile failure occurs

36:07

related to one of the arms of the posterior O blight ligament of the

36:12

knee. Now,

36:14

I'm not gonna get into detail today about the anatomy of this very important

36:18

ligament.

36:18

Other tend to indicate classically there are three patterns

36:23

of fibers within it.

36:25

And the largest one and thickest one is known as the central arm.

36:30

And it's shown here between the blue arrows in here,

36:33

taken from the literature by Lara, you can see that arm,

36:37

that arm attaches to multiple structures,

36:40

including the posterior horn of the medial meniscus.

36:43

So a corner pattern of failure may be seen typically of the

36:48

superior corner of the posterior horn, of the medial meniscus, again,

36:53

related to valgus injuries and failure of the medial supporting

36:58

structures.

37:00

There are three classic patterns of displaced meniscal pairs.

37:04

The bucket handle,

37:05

we've already talked about the displaced longitudinal vertical.

37:10

A displaced longitudinal horizontal tear is a

37:14

flap tear. Now I wanna remind you,

37:17

a flap in English means attached at one end.

37:22

A fragment means it's not attached at all.

37:25

Meniscal fragments are rare.

37:28

Meniscal flaps are common often with longitudinal horizontal failure.

37:33

Here's a displaced flap extending next to the medial portion

37:38

of the tibia.

37:39

And you can see in an erosion of bone and there's some fluid in the medial

37:44

collateral ligament person. The parit beat tear, as we've talked about,

37:48

is a displaced radial tear. Now,

37:51

there's one type of bucket handle tear that's known as a hemi bucket handle

37:55

tear. It can be a tough diagnosis,

37:58

typically associated with longitudinal horizontal failure.

38:02

You can see here I'm showing you two cases.

38:05

Here's the failure and that's half of that meniscus. That part,

38:09

that's a flap located centrally.

38:12

And here's a very similar case on your right.

38:15

So these are known as hemi bucket handle tears because the peripheral portion

38:19

that remains tends to be quite wide and the abnormality,

38:23

the tear may be difficult to identify. Okay,

38:28

we're gonna finish up in the last five or 10 minutes with a couple

38:33

other aspects of meniscal failure. We're gonna go to the root ligaments.

38:37

You know,

38:37

20 years ago there was virtually nothing written about meniscal root ligament

38:42

tears.

38:43

Now these tears occupy a large part of what is being written about the meniscal

38:49

in the literature.

38:50

It is suggested that root ligament tears account for maybe 10 or

38:55

more 15% of meniscal findings at the time of arthroscopy.

39:00

Posterior root ligament of the medial meniscus is most frequently involved.

39:05

I'm showing you images of it here on your right.

39:08

Other root ligaments, particularly on the lateral side,

39:12

may be involved in patients who have a c l tears.

39:15

I'm not gonna emphasize much about that today.

39:18

And these ligaments have both central and supplementary fibers.

39:24

So they may have a wide area of attachment. And what do they do?

39:28

They indeed hold the meniscus to the tibia so they

39:33

support the position of the meniscus.

39:37

You can imagine if there were a root ligament tear,

39:40

meniscal displacement often is seen, right?

39:44

And we look for that, all right?

39:45

Because there may be meniscal extrusion that is dramatic when you're dealing

39:50

with root ligament tears. Now, a number of years ago,

39:54

one of our visiting scholars from Korea did some beautiful anatomy of these.

39:58

These are some pictures taken from the work that he did to show you the the

40:03

three other meniscal roots. Just a couple words about 'em.

40:07

The anterior root ligament of the medial meniscus typically attaches to the

40:12

sloping anterior portion of the medial tibial plateau.

40:16

The anterior root ligament of the lateral meniscus is intimate with the

40:20

footprint of the anterior cruciate ligament.

40:23

It may be difficult sometimes to separate from it.

40:27

And the attachments of the po,

40:30

the posterior root ligament of the lateral meniscus are complex.

40:34

That root ligament may attach both to the lateral and medial cubicles

40:39

of the interocular eminence of the tibia.

40:43

But we're not gonna spend time looking at those.

40:46

What we're gonna look at is the posterior root ligament of the medial meniscus.

40:51

It is intimate with the posterior cruciate ligament. As you can see,

40:56

this is in the sagittal plane. Here's the posterior cruciate ligament,

41:01

and here is the posterior root ligament located just in front of

41:06

the P C L. Here are the specimen photographs showing you that.

41:10

Here's an axial section.

41:13

Here is the posterior cruciate ligament attaching to the tibia.

41:17

And here is the posterior root ligament of the medial meniscus intimate and

41:22

slight anterior to the posterior cruciate ligament.

41:26

And here in the coronal plane, this is the more posterior section.

41:31

This is slightly more anteriorly. Here is the attachment,

41:35

the footprint of the posterior crusade.

41:37

Here is the beginning of the attachment of the posterior root ligament.

41:41

And on the next most anterior uh section there is the full attachment

41:47

of the posterior root ligament. So it is, uh,

41:50

intimate with the P C L. This is what a tear,

41:54

a full thickness tear of the posterior root ligament of the medial meniscus.

41:59

Looks like it ends abruptly. There is a gap,

42:03

much like the radial tear that I showed you earlier in this lecture.

42:08

Now there is a classification system by by Lara. And by the way,

42:12

for those of you who like to read the literature,

42:15

whenever you see Lara read the article, because his articles are terrific,

42:20

a lot of 'em have to do with anatomy.

42:23

He has classified certain root ligament failure patterns.

42:27

And here I'm showing you one of his classifications. There are five types.

42:31

I'm not gonna go into detail about 'em,

42:34

but the one that I see most commonly is the type two,

42:38

A complete or near complete pair of the posterior root ligament of the medial

42:42

meniscus. And it is further divided into A,

42:46

B and C depending upon how far that particular

42:50

tear is away from the footprint of the root ligament.

42:54

So just to give you some examples of it, here are two A,

42:59

two B and two C cases.

43:01

So this one is a ra is a failure pattern,

43:05

a radial tear close to the root ligament.

43:09

And as we get further away, two B and two C, the gap becomes more prominent.

43:14

And I want to call your attention the further you get away from the footprint of

43:18

the root ligament,

43:19

the smoother is the end of the posterior horn of the medial

43:24

meniscus. When the root ligament is involved itself,

43:27

you have a shaggy irregular end.

43:30

So those are some patterns that we may see

43:34

the prequel to.

43:36

A posterior root ligament problem may be marrow edema in the sub

43:42

bone.

43:43

Here I show you on the left the prequel in the form of subtle edema.

43:48

Four months later,

43:49

this is a a root ligament hair or avulsion

43:54

almost complete with a gap that has developed.

43:58

So when you see cysts or edema beneath the attachment side

44:03

of that posterior root ligament, please pay attention.

44:07

Here's another beautiful example. This is a root ligament avulsion.

44:11

You can see there's a shaggy portion of the root ligament attached to the

44:15

posterior horn. The gap, this is the most important half image.

44:19

Remember we talked about there's the gap.

44:22

So seeing that you should not be surprised.

44:24

And when you look at the body of the medial meniscus,

44:28

there are a number of findings that you will see. The meniscus is extruded,

44:33

correct? The medial collateral ligament is complex, is bode.

44:38

There is per ligamentous edema around those ligaments.

44:43

There's often edema like changes in the medial

44:47

tibial plateau or medial femoral condyle.

44:51

And for those of you who are sharp eyed,

44:53

you will see the beginning of a small insufficiency fracture right there

44:58

in the medial tibial plateau.

45:02

We now know that tears of the root ligament,

45:06

posterior root ligament and other root ligaments can be associated with

45:11

insufficiency fractures.

45:13

Here's an example of a posterior root ligament avulsion full thickness

45:18

I think or complete. And here is the insufficiency fracture.

45:24

All right?

45:25

It's an altered signal merging with the subcon bone plate,

45:29

hereby the way I think this'll work as the arthroscopy picture showing you the

45:34

lucidity.

45:35

So insufficiency fractures are seen with root ligament tears

45:40

as well as radial tears. Uh,

45:42

in this particular location and what we used to call sunk,

45:46

which we thought was osteonecrosis something like this,

45:50

we now recognize not as necrosis,

45:53

but initial insufficiency fractures. Here's another example.

45:57

Classic sunk right what we used to call osteonecrosis

46:02

of the femoral condyle.

46:03

But this is an insufficiency fracture that has led to collapse

46:08

of the subc chondral bone plate.

46:11

Two months earlier we can see the posterior root ligament emulsion

46:16

with peripheral extrusion of the meniscus.

46:21

Now in the last five minutes or so, a couple other associations,

46:26

the meniscal oal,

46:28

for many years it was felt only to be a normal finding.

46:32

It was seen in large domestic hats such as lions and tigers,

46:36

and typically was in the anterior horn of the medial meniscus shown here.

46:41

Now, unfortunately,

46:42

you can't get much of a history from a tiger to know whether or not there had

46:45

been an injury. But we thought seeing it in animals, it was developmental.

46:50

In humans, it may be developmental in humans,

46:54

typically circular or triangular,

46:57

typically posterior horn of the medial meniscus within that part

47:02

all but it also may be associated with root ligament problems

47:07

with two possibilities,

47:09

an avulsion of the root ligament as shown in this case,

47:13

or a soft tissue avulsion with later secondary heterotopic

47:18

ossification. So when you see these OCIs,

47:21

before you call it a normal variant, check, the posterior root ligament.

47:27

And the other finding was the meniscal flo.

47:31

If you look at our literature or the arthroscopy literature,

47:34

it is considered a normal finding more commonly seen in the medial

47:39

meniscus than the lateral meniscus. It's an undulation of the inner portion.

47:45

You can see that undulation here.

47:47

But my advice to you is whenever you see it,

47:50

just go back and check to see if there's a problem here.

47:54

Here's a posterior root ligament avulsion.

47:57

This posterior horn has moved forward.

47:59

This is laxity now a pathologic clance within that particular

48:05

meniscus. And then finally, the posterolateral corner.

48:09

There are a lot of structures that attach to the posterior horn among those

48:14

structures. Something called the faciles or popliteal meniscal ligaments.

48:18

There are three of them, although some of us only have two.

48:22

If you look at sagittal,

48:25

starting laterally and progressing medially,

48:28

here is the anteroinferior popliteal meniscal ligament.

48:32

Here is the anteroinferior and posterosuperior.

48:36

This is known as the poppie hiatus the tendon located there.

48:40

And then here again, we can see those two more centrally.

48:44

We may get a postal inferior popal meniscal ligament.

48:50

So these are important attachments of the posterior horn

48:55

to the, uh,

48:57

capsule around the pope tendon that is passing through the joint.

49:03

Problems with these fassal can be developmental or they can be

49:08

traumatic Trauma.

49:09

Trauma may be a single episode of an injury or repetitive stress.

49:14

Here's an example of disruption of the antral inferior fassal.

49:18

And you can see the elevation of the posterior horn.

49:23

This is an interesting case.

49:25

A patient who had intermittent locking at the time the upper images

49:30

were obtained, the the knee was not locked,

49:32

but these are disrupted popliteal meniscal basles

49:37

here. One month earlier, the images became available when the knee was locked.

49:42

And you can see that that posterior horn has now displaced

49:46

anteriorally next to the anterior horn owing to these problems.

49:51

All right, creating the locking of the knee.

49:54

So always look at this particular area.

49:57

And then the final concept in the last couple of slides.

50:00

Look at all of the structures that kind of attach to the posterior horn,

50:05

not just these fales or ligaments,

50:08

but the L ligament of berg. And I'm showing you that in orange,

50:12

and by the way, this is how you spell Humphrey. No,

50:17

e humphrey did not have an E in his name.

50:20

That's another one of these menis femoral ligaments.

50:24

So when you have a tear of the anter cruciate ligament,

50:28

any of these structures may tug away at the posterior horn.

50:32

So what you may see these cases of a c l tears,

50:36

this is a popliteal meniscal ligament tear with some fibrosis.

50:41

And this is what is known as a iceberg rip,

50:44

where the iceberg ligament has created a tear in the posterior

50:48

horn of the lateral meniscus,

50:50

again in a person with a tear of the anterior cruciate ligament.

50:56

So what I've done in my allotted period of time,

50:58

of the two particular points I wanted to do, I've reviewed meniscal structure,

51:04

emphasized the collagen shown,

51:06

shown you the three classic patterns of meniscal failure based on an

51:11

understanding of its structure, function,

51:14

and dysfunction of the meniscus of the knees. And I wanna end with this slide,

51:19

uh, sent to me recently. This is just our conference.

51:23

If you're interested in upper extremity, Mr. I,

51:28

along with some terrific radiologists,

51:30

will be running a virtual conference both with lectures and cases.

51:35

You're certainly welcome to, uh, join us.

51:38

And with that in mind,

51:40

I'm gonna stop my share and open it up,

51:44

I guess for any questions.

51:48

Thank you so much for sharing your lecture, Dr. Resnick. At this time,

51:51

we're gonna open the floor for any questions and remember to use that q and a

51:55

feature to submit a question and we'll, we'll try to get to as many before Dr.

51:59

Resnick has to go. Dr. Resnick,

52:02

are there any nerve fibers in the meniscus?

52:05

Is meniscal failure itself the cause of pain? There

52:08

Are nerve fibers in the meniscus and indeed meniscal failure can, uh,

52:13

can cause pain.

52:14

So what are the types of tears that can cause pain

52:19

that's been written about in the literature?

52:22

Unstable tears are perhaps the most important one.

52:25

Unstable tears are long longitudinal vertical tears.

52:29

They are multi-directional tears. That's another one. They occur.

52:33

When you see a gap at the site of failure,

52:36

those are the causes of pain associated with meniscal tears.

52:44

Can you please address articular cartilage imaging?

52:47

Are you using any cartilage mapping or ultra short TE imaging?

52:52

Yeah, we, uh, as you know,

52:54

I have some incredible associates here at U C S D, one of which, uh, is,

52:59

uh, Christine Chung,

53:01

who is a someone who has written extensively on ultra short TE

53:06

sequences, not just for articular cartilage, but for other things as well.

53:11

We use them for research purposes. It's not part of our standard, uh,

53:17

m r assessment of articular cartilage.

53:20

We use some gradient echo imaging for some of that.

53:23

But the images with ultra shore TE sequences looking at

53:27

articular cartilage are marvelous. And uh,

53:31

so if you have that ability,

53:33

it might be something that you might wanna consider.

53:38

Is imaging an injury of wrist berg?

53:41

Ima similar to longitudinal vertical tear?

53:44

Yeah, typically the, uh,

53:48

berg rip is a longitudinal vertical tear at the

53:53

periphery.

53:54

You have to be a little bit careful about that because there is normally an area

53:58

of intermediate signal between the berg ligament and the posterior horn of a

54:03

lateral meniscus.

54:04

But if that area of intermediate signal proceeds more laterally on

54:09

multiple images, it's likely a meniscal pair. And by the way,

54:13

that ligament of Humphrey can do a very similar thing, although less commonly.

54:18

We call that a Humphrey hitch, is the name we have for that finding.

54:23

What is the healing potential of a posterior root tear?

54:27

Uh, I don't think they heal. Uh, they, in fact,

54:32

uh, a tear, particularly one that is displaced is,

54:36

has the same significance probably of doing a partial or complete

54:41

medial mastectomy. It is likely,

54:44

highly likely that the articular cartilage in that compartment

54:49

will in fact become, uh, quite abnormal.

54:53

Remember when you have radial tears of that posterior horn or root ligament

54:57

problems, every step that you take,

55:02

the meniscus extrudes like a partial men mastectomy every step.

55:07

And indeed, when you look at patients who have those types of failure,

55:12

you often see edema and thickening of the me edema bout and thickening of the

55:17

medial supporting structures because it's an unstable knee with every

55:22

step.

55:23

The meniscus extrudes presses against the medial supporting structures.

55:27

So root ligament tears do not do well and often are repaired.

55:35

How do we measure long radial tears?

55:38

Well, if you know,

55:40

if you can see them well on sagittal images and you

55:45

know the spacing and thickness of those images, you just do simple mathematics,

55:51

you can figure out.

55:52

And the figure that's given in some articles is that if they get over nine or

55:57

10 millimeters, they tend to be unstable and painful.

56:03

When is surgery indicated in a meniscul tear?

56:06

When is a curve conservative approach adopted?

56:10

That's interesting. My own personal story is, uh,

56:15

uh, I had a meniscal tear. I'd like to tell you I was rock climbing,

56:18

but I rolled over in bed and I tore the anterior horn of my

56:23

lateral meniscus and I went to the orthopedic surgeon and a very good one,

56:27

and he examined my knee and he said, you know,

56:29

you've got a tear of the anterior horn of lateral meniscus. Let's get an R.

56:34

And I said, ah, yeah, we don't need an mr. I don't believe in mr. He said, well,

56:37

you're lucky because we have an opening in our, uh, surgical suite.

56:42

Two days from now I'm gonna put you in. And I said, nah, you know,

56:45

I've been reading the literature and some of these,

56:47

particularly the peripheral ones, will heal on their own.

56:50

I'm gonna put it off for a while. And sure enough, uh,

56:54

that tear must have healed because my knee pain went away over a period of about

56:58

three or four weeks. And one other point that, you know, that red zone,

57:03

which is a peripheral, uh, phenomenon in the meniscus,

57:07

the one area that may not have a red zone is the

57:11

posterior horn of the lateral meniscus where the pilla tendon goes through the

57:16

joint.

57:17

So that is why in the ICUs classification that is separated out

57:22

as a specific pattern of failure because there's no red zone there.

57:27

So my feeling is if you have a

57:31

longitudinal vertical tear in the red zone of the meniscus,

57:35

not displaced, you don't have me locking,

57:40

I would probably elect for at least trying conservative therapy.

57:44

I'm not sure every orthopedic surgeon would agree with that,

57:47

but that would be my, uh, philosophy based on my own personal experience.

57:54

Does discoid meniscus predispose meniscal dysfunction?

57:59

Yeah, discoid menisci,

58:01

you'll have to invite me back for a discussion about that because they are

58:05

really remarkable. Um,

58:08

one of the problems with discoid menisci are problems

58:13

in stability of the discoid meniscus.

58:15

They develop meniscal capsular problems and you can often see that

58:20

as high signal, uh, sometimes so high is called the Roman candle appearance.

58:25

And what occurs in those cases,

58:28

in some cases intermittently, is the meniscus displaces significantly.

58:34

And so the knee locks all right, intermittent,

58:37

and then the meniscus may flop back to its original position.

58:41

So clearly discoid meniscus can cause, uh,

58:45

meniscal dysfunction symptoms certainly can arise.

58:49

Awesome. How about one more and then we'll let you get back to rock climbing.

58:52

If we see truncated meniscus, what should we infer or look for?

58:58

Okay, so if you see,

59:00

remember that's the gold standard abnormal morphology.

59:03

I believe that so strongly not the signal,

59:07

the morphology spend time. Uh, yeah,

59:11

hopefully you have a history. There's been meniscal surgery.

59:14

That's the first thing you have to consider. All right,

59:17

so what I do is I said at the very beginning of this lecture,

59:21

I spend maybe 30 seconds or so scanning the

59:25

anterior soft tissues. And typically, as I mentioned,

59:29

you're gonna see scarring in one pattern or another.

59:33

It can be subtle sometimes in the antral medial rather than the antral

59:38

lateral. And,

59:39

and one of our fellows wrote a beautiful article on that if's interested,

59:43

you could Google my name. All I did was proofread the article. But, uh,

59:48

I don't know if in that article we separated out right-handed and left-handed

59:53

surgeons. We did find the preference for the antral medial soft tissues,

59:58

but maybe that's 'cause of right-handed surgeons who might put instruments

60:02

through that, the other aspect. But in any case, that's the first thing I do.

60:07

And if there is no history of surgery and I see no evidence of

60:12

surgical scarring, a truncated meniscus is an abnormal meniscus.

60:18

And I will read a meniscal tear, uh, in almost all of those cases.

60:25

Dr. Resnick, thank you so much for your lecture today.

60:27

We cannot wait for the upper Extremities conference in September and to learn so

60:32

much more from you.

60:33

And thanks for everybody for participating in the NOOM conference and asking

60:36

such wonderful questions.

60:38

You can access the recording of today's conference in all our previous noom

60:42

conferences by creating a free m r I online account.

60:45

And be sure to join us next week on Thursday, August 31st at 12:00 PM Eastern.

60:50

We are doing a noom conference from the archives where we will replay Dr.

60:54

Csh McCurdy's head and neck Space is made simple.

60:57

You can register for this lecture@mrionline.com.

61:00

Follow us on social media for updates on future NOOM conferences. Thanks again.

61:04

Thank you Dr. Resnick and everyone. Have a great day.