0:00

Now I'm gonna go right on to my uh, last lecture for today

0:05

and we're gonna talk about the cruciate ligaments.

0:08

And in particular,

0:09

because of the time we're gonna talk mainly about the

0:12

anterior cruciate ligament and if time permits.

0:15

At the end we will talk a bit about the posterior

0:19

cruciate ligament as well.

0:22

Through it all we're gonna emphasize MR Imaging

0:27

one general objective, then to review the anatomy

0:30

and injury patterns of the anter posterior crusade ligaments

0:34

emphasizing MR imaging findings.

0:37

Let's start with the anterior cruciate ligament.

0:41

Both of the cruciate ligaments are intracapsular,

0:45

but extra synovial here is a sagittal section

0:49

through the central portion of the knee showing you portions

0:52

of the anterior and posterior cruciate

0:55

ligaments in between the two.

0:57

A triangular area of fat, okay,

1:01

that is in fact extra synovial.

1:04

So most of the time when you have a joint effusion

1:08

and intact ligaments, you won't see fluid in this particular

1:13

triangle of fat.

1:14

Now, there are exceptions to the rule.

1:17

In fact, there may be small normal perforations within the

1:21

synovium allowing joint fluid to get in there.

1:24

But in general this will be a dry area

1:28

even when there is joint fluid present.

1:31

When we talk about the anterior cruciate ligament,

1:34

most people would suggest two bundles.

1:37

The antral medial bundle, which is the dominant bundle

1:41

of the anterior crusade ligament, said to be stronger

1:44

and stiffer than the second bundle,

1:47

which is the poster lateral bundle.

1:49

And I've placed here some differences

1:51

between these two bundles there.

1:54

Appearance, when the knee is flexed,

1:57

there are appearance when the knee is extended.

2:00

Okay, their function, this bundle being the primary

2:04

restraint against anterior translation

2:07

of the knee when the knee is flexed.

2:09

This bundle being a primary

2:12

restraint against rotational forces

2:14

when the knee is extended.

2:16

And then some tests,

2:17

and we'll talk briefly about these tests later on,

2:21

are better or worse depending upon which particular

2:24

bundle is involved.

2:26

So to give you an idea here,

2:27

with some pictures taken from the literature

2:30

and some of our MR images,

2:32

I'm showing you the anter medial bundle

2:35

with the yellow arrows

2:37

and the posterolateral bundle with the orange arrows.

2:41

The anter medial bundle is longer.

2:44

It goes all the way up to the roof of the intercon or notch.

2:48

The postal lateral bundle, the orange arrow is shorter

2:52

and attaches to the lateral sidewall

2:55

of the lateral femoral condyle. So those

2:58

Are areas that you need to look at if you're trying

3:01

to distinguish between them.

3:03

This looks like a normal anterior cruciate ligament

3:08

with normal anterior, with normal anter medial bundles

3:12

and postal lateral bundles.

3:14

And this is what they would look like in the sagittal plane.

3:18

Now let's look at an example of a partial tear, mainly

3:22

involving the postal lateral bundle.

3:25

The orange arrow show you the postal lateral bundle

3:28

and you can see some abnormal signal within it

3:31

as it attaches to the sidewall.

3:34

Doesn't look like a complete tear.

3:36

Whereas when we look at at least portions

3:39

of the antral medial bundle, we can see

3:42

that it looks relatively normal.

3:44

So here in large part,

3:46

a high grade partial tear involving the

3:49

posterolateral bundle.

3:51

Now, when we look at the footprints of these bundles

3:55

as they attach to the femur,

3:58

we will say the higher footprint

4:01

of the antral medial bundle.

4:03

Here you can see the footprint of the postal lateral bundle.

4:07

This is the posterior aspect of the lateral femoral condyle.

4:10

So we're looking in this particular region

4:14

and there is a elevated rim of bone known

4:17

as the postal lateral rim that is located just behind

4:22

those footprints.

4:24

Now there is another area of bone elevation known

4:28

as the lateral intercondylar ridge shown here, generally not

4:32

as prominent as this rim.

4:34

And it's sometimes called the residence ridge

4:37

because it's mistaken this ridge for this ridge

4:41

by junior residents.

4:42

And if they do that, they would, uh,

4:45

place any reconstructive tissue in the wrong spot.

4:49

So you'll hear the term resonance ridge.

4:53

Now let's look at the simple aspect,

4:55

and I think most of the people who do ne MR uh, know

4:58

what I'm gonna say here.

5:00

We look particularly in the sagittal plane.

5:03

Yes, the coronal plane

5:05

and maybe even coronal like plane if you're using that.

5:09

And axial planes are important.

5:11

But if you start in the sagittal plane,

5:14

the first thing we tend to do is find the roof

5:16

of the intercondylar notch.

5:19

Okay? And there it is.

5:20

And then we find the anterior cruciate

5:23

ligament, we trace it.

5:24

And as long as that particular ligament is parallel

5:29

to the roof or steeper than it, generally,

5:32

that ligament is normal.

5:34

Now, toward the end of my discussion of the ACL,

5:37

I'll show you some exceptions to that rule,

5:40

but that's generally a good rule to remember.