0:00

Now a few words about some of the clinical findings

0:03

that we may see with meniscal pathology.

0:07

Meniscal tears are seen mainly in two clinical situations.

0:12

The first of these would be related

0:13

to an injury, a traumatic event.

0:15

And this is something we see in young persons off

0:19

of often active people involved in sports.

0:23

Okay? And often they relate to loads

0:25

that are axial or rotational.

0:28

Those are the forces that are involved.

0:31

The second situation

0:32

that we see in older persons are meniscal tears related

0:35

to meniscal degeneration.

0:38

In either case, there are a number

0:40

of clinical manifestations that may be seen.

0:43

I've listed some of them here.

0:45

We're gonna be talking about some of them such

0:47

as locking a little bit later on.

0:50

In this particular lecture, the orthopedic surgeon has many,

0:55

uh, ways in which to examine the knee

0:58

and to evaluate for the presence

1:01

or absence of a meniscal tear.

1:04

I've listed here a number of those tests.

1:07

I'm checking two that are particularly important,

1:11

and that is joint line tenderness,

1:13

which can be found in about 50 to 80% of cases in patients

1:18

with, uh, meniscal tears and the McMurray tests where pain

1:22

and clicking occurred during certain movements,

1:25

particularly flexion and rotation of the knee.

1:28

These are important tests.

1:30

There are other ones that are listed here

1:32

that also can be used.

1:36

Now one of the questions

1:37

that comes up in fact is a meniscal tear, the cause

1:41

of the patient's symptoms and signs.

1:43

And this is important

1:44

because you can see meniscal pathology in a symptomatic

1:48

knee, and yet that is not the cause

1:50

of the patient's symptoms.

1:52

There have been a number of studies

1:54

that have looked at this.

1:55

I'm giving you one reference at the bottom here,

1:58

but pairs that are radial, that are vertical

2:02

and longitudinal

2:03

or complex, that is they're multi-directional,

2:07

that those are more likely to cause meniscal symptoms

2:11

and signs than horizontal or OBL tears.

2:15

Another finding is the clinical manifestations

2:18

that can be seen when tears are unstable,

2:21

whereas stable tears often do not have significant

2:25

clinical manifestations.

2:27

Now, what is an unstable tear,

2:29

but unstable tear defined

2:31

by orthopedic surgeons is a tear in which the meniscus

2:35

or a meniscal flap or fragment is displaced

2:40

or can be displaced by a pro.

2:43

Now, let's look at some examples of unstable tears.

2:46

Here's my diagram to show you a tear.

2:49

This is a vertical longitudinal tear that on inspection

2:53

or a probing is greater than nine millimeters in length.

2:57

So here on an axial image, we can see a longitudinal

3:02

vertical tear that certainly looks longer than

3:04

nine millimeters in length.

3:07

Let me emphasize another type of tear

3:09

that may in fact be associated with instability,

3:13

and that is a tear that has more than one direction.

3:18

I show you with these two images on the bottom right,

3:22

that they, this is a tear with horizontal

3:25

and radial components, so it's multi-directional

3:29

and those tears generally are unstable.

3:32

Now, there is a meniscal classification system

3:36

that has been put forth by ISOs

3:39

and it includes these seven characteristics.

3:43

I'm not gonna go through these, I just want you to be aware

3:45

that this system does exist.

3:48

Your orthopedic surgeons may be aware of it

3:52

and they may utilize it.

3:54

Uh, some of the features here, including the, uh, presence

3:58

of, uh, and direction of the tear we will comment on.

4:02

But be aware that there is this popular

4:06

classification system.

4:08

Now, there are a number of types of meniscal tears.

4:12

And indeed I'm gonna talk about three

4:15

that are the classic ones.

4:17

So as we look at this numbers one, two,

4:20

and three, there is a longitudinal vertical tear.

4:25

You can see that in the periphery of the meniscus.

4:27

Number two is a horizontal,

4:30

sometimes called a longitudinal horizontal tear

4:34

that begins in the inner margin of the meniscus.

4:37

And number three is the radial tear,

4:40

which is a vertical tear

4:42

that begins in the inner margin of the meniscus.

4:45

We're gonna emphasize these in the next, uh, portion

4:48

of this talk, although combinations of these

4:52

and displacement of these tears may be seen.

4:56

Now, to understand the way a meniscus fails, you have

5:00

to know a little bit about something called hoop stress.

5:04

And I'm gonna show you this sagittal section through the,

5:09

uh, medial aspect of the knee with the posterior horn

5:13

of the medial meniscus.

5:15

To illustrate what hoop stress is,

5:18

if there is an axial load applied to the knee,

5:21

a femoral force comes in, this is the orange arrow,

5:24

and it comes in at an angle owing to the curvature

5:28

of the femoral condyle.

5:30

Now, if you remember vectors, you can break

5:33

that obliquely oriented vector into a vertical vector

5:38

and a horizontal vector.

5:40

When we look, there is in fact a similar vertical vector

5:45

on the tibial side, which counteracts this vertical vector.

5:49

But what is left unopposed is the horizontal vector,

5:53

and it is that horizontal vector

5:57

Trying to drive the meniscus from the joint

6:01

that represents hoop stress.

6:03

It's why the liberty bell has a crack within it.

6:06

In addition, that same sort

6:09

of force may drive the meniscus anteriorly

6:12

or posteriorly as well.

6:15

Now, I added a, my own diagram here to give you an idea of

6:19

what hoop stress looks like.

6:20

Here I show you that hoop stress with these orange lines.

6:24

Here are the longitudinal circumferential collagen fibers.

6:29

Remember, in the outer half of the meniscus, they tend

6:32

to resist the hoop stress, but they may fail,

6:35

and we'll talk about that.

6:37

If we talk about the circumferential stress,

6:40

this part going anteriorly

6:42

and posteriorly, you can see it's the radial tie fibers

6:46

shown as the orange lines that counteract

6:49

that particular force.

6:52

So hoop stress is a very important force

6:55

that can cause meniscal pathology.