0:00

Okay, this is a youngish man,

0:03

but not a child, not a juvenile.

0:05

It's a man.

0:06

And let's just take a quick look

0:08

at the axial for a moment.

0:09

Those of you that do quite a bit of MRI may

0:12

notice there's an extra structure in here.

0:14

Not this one.

0:15

That's the posterior cruciate ligament.

0:16

This one. What is that thing?

0:19

Well,

0:20

it happens to be the anterior cruciate ligament.

0:22

That is fat and bloody and laying down anterior

0:25

early. That's not why we're here.

0:27

We're here to look at the sequela once again of

0:30

a pivot shift and what it does to meniscus.

0:34

You can see a little bit of fluid

0:35

in the capsule and posteriorly,

0:38

on the medial side is the structure known as the

0:41

posterior oblique ligament of the knee

0:43

or posterior ligament of the knee,

0:45

which we're going to talk about at a later date.

0:47

But I did want you to see it.

0:49

Here it is again,

0:50

seen right at the level of the meniscus.

0:53

Let's go to the sagittal projection,

0:55

and we have already established there's

0:57

a major pivot shift with an ACL tear.

1:00

There's the typical pivot shift bone injury.

1:03

There is the typical pivot shift bone injury of

1:06

the tibia as well as the femur that you just saw.

1:08

And you've got

1:10

the same bone injury in the posteromedial tibia.

1:14

So let's start on the medial side.

1:17

We said that the tibia will translate anterior

1:23

or the femur will translate posterior,

1:25

and then slam down on the back

1:28

of the stretched capsule.

1:29

And that's exactly what has happened here.

1:32

We've got bleeding in the capsule.

1:35

Then I know how many of remember we talked about

1:37

the sliver tear? The sliver tear is that thin,

1:40

tiny little vertical tear that sits right adjacent

1:43

to the capsule. And there it is.

1:45

And once again, that signal will persist.

1:48

It'll become much less swollen, much less hot,

1:52

much less hyper intense over time,

1:54

but it'll persist for many years, if not forever.

1:58

So we don't want to call this a

1:59

meniscocapsular separation,

2:01

but it is a meniscocapsular junction sprain or

2:05

injury or bleed. And there's also a peripheral,

2:08

one third red zone medial meniscus tear.

2:12

Let's continue on over to the lateral side.

2:15

There's quite a bit of space here to

2:17

house all this blood, by the way.

2:19

So let's scroll laterally now.

2:22

And as we're on our way over to the lateral side,

2:25

you may have noticed this big,

2:26

large structure that looks like a thumb.

2:29

It is the anterior cruciate ligament.

2:31

Filled with blood bent forward.

2:33

We are here at the lateral meniscus root.

2:37

And the posterior attachments of the lateral

2:41

meniscus. The superior and inferior fascicles.

2:44

Are a little bit stubby and fat.

2:46

It should be a millimeter in thickness.

2:48

So they're too thick. But also the capsule,

2:53

which should tether this attachment right here.

2:56

That is an attachment for these two structures.

2:59

That should be tethered to that.

3:01

See where the tether is broken.

3:03

So there has been a posterior capsuler disruption.

3:07

And that has allowed these attachments.

3:10

To squiggle up a little bit.

3:12

They also are torn.

3:14

If you keep scrolling right there,

3:16

there's no attachment between the popliteus,

3:20

the capsule, and the meniscus.

3:23

There should be a perforating linear structure.

3:26

Coming back from this triangle inferiorly.

3:28

And from this triangle superiorly.

3:32

So the posterolateral meniscocapsular

3:36

and popliteal attachments have torn.

3:39

Let's look at the popliteus tendon.

3:42

Because when that happens,

3:43

there is frequently an injury to the

3:46

popliteofibular ligament Either

3:48

in the form of a rupture.

3:50

With a squiggly little tail rolled up in a ball.

3:53

Or a wavy tail from a stretch.

3:55

And we have the wavy tail known as the mermaid

3:58

sign. There's the body of the mermaid.

4:00

And there's the wavy tail of the mermaid.

4:03

Which should be a straight shot right down

4:06

as a black line from here to here.

4:08

We don't have that. We have a gray,

4:10

somewhat waddling, wavy signal.

4:14

From the popliteus tendon.

4:16

As the popliteofibular ligament.

4:18

This little stubby structure right here.

4:20

Is what remains of the paplateo tibial ligament.

4:25

Let's look at the meniscus all the way

4:29

near the root. Here's the root.

4:31

And some of you may be struck by

4:33

this structure right here.

4:35

Which is a swollen

4:38

but present ligament of Wrisberg.

4:41

That is not a fragment of the meniscus.

4:43

That's the Wrisberg ligament.

4:44

Leaving the postero superior inner free edge.

4:49

Of the lateral meniscus.

4:50

And coursing supromeedial as

4:52

a ligamentous structure.

4:54

So don't get confused by that potential pitfall.

4:56

And you can see it reattaches right back

4:59

into the triangle. So in this case,

5:01

we have injured the posteromedial meniscal

5:05

capsuler attachment. With a vertical sliver tear.

5:07

On the medial side, there's our sliver tear.

5:10

And on the lateral side,

5:12

we have disruption of the meniscopopliteal

5:16

and capsuler fascicles posteriorly,

5:19

along with an injury of the popliteofibular

5:21

ligament and a frank tear of

5:24

the posterior capsule.

5:26

Just take a look at the coronal for a moment,

5:28

because this is such a nasty injury.

5:30

Just out of curiosity,

5:32

the collaterals are not too bad looking.

5:35

There's the tibial collateral ligament,

5:37

and here is the fibular collateral ligament.

5:39

So there hasn't been a major Varus or valgus force

5:43

or a major twist associated with this injury.

5:47

Okay, let's do another one, shall we?