0:00

An older adult woman who complains

0:02

of knee swelling,

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but no discrete history of trauma.

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Let's scroll the axial fat-suppressed

0:11

water emphasized image first,

0:13

and that is a swollen extremity.

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There's swelling everywhere.

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There's swelling in the joint.

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There's swelling around the joint.

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And while we're here,

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let's take a quick gander at the ACL.

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It's nice and straight and linear.

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It's intact.

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The PCL,

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it's nice and round and robust,

0:31

and we can follow it from bottom to top.

0:34

It's intact.

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So we probably have to look elsewhere to determine

0:40

what is causing such a severe pattern of swelling.

0:44

When you look inside the effusion,

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you do not see a blood fluid level.

0:50

You do not see synovial hypertrophy.

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Therefore,

0:54

a rheumatologic explanation isn't very likely.

0:58

You don't see clots and you also don't

1:01

see bone erosion or destruction,

1:03

as you might in aseptic arthritis.

1:06

So right now, we have a little bit of an enigma.

1:10

While you're scrolling through the axial,

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you should always take note of the popliteal

1:17

fossil because patients can develop clots from

1:20

swelling like this due to encroachment

1:23

on the popliteal vein,

1:24

and the flow voids are not very prominent.

1:27

So that should be a potential area of concern.

1:30

But that's not why we're here,

1:32

although I guess it could be with a swollen lower

1:34

extremity. But let's keep going, shall we?

1:37

I've got two sagittals up,

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and the goal of this review is to

1:41

take you through the corners,

1:43

specifically the posteromedial corner.

1:45

So I'm going to stop at the posterolateral corner

1:47

for a minute. And, yes, there is a meniscus tear.

1:50

It's chronic looking, it's complex.

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That's going to go in the conclusion

1:54

with the word chronicity.

1:56

And there is class four chondromalacia present

1:58

both on the tibial side and the femoral side

2:02

surrounding this complex, macerated meniscus.

2:06

There is also a popliteus tendon with

2:09

a popliteofibular ligament rupture,

2:12

so that is blunted. And here is the arcuate,

2:15

which should come down and attach to the tip of

2:17

the fibula. It's just hanging down in the back,

2:20

so the arcuate is torn, too.

2:22

So there's a posterolateral corner injury.

2:25

Let's keep scrolling now and

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go over to the medial side.

2:29

Now, on the medial side,

2:31

there's also meniscus pathology.

2:34

There is an oblique under surface,

2:37

chronic appearing tear. Why do I say chronic?

2:39

Because it's not that bright.

2:41

She's older,

2:42

and she also hasn't had a history of trauma.

2:44

What does older have to do with it?

2:46

When you get older, you get more signal,

2:48

you get more incidental degeneration

2:50

and chronic tears in the meniscus.

2:53

But we're here to talk about the corners,

2:55

so I'm going to move my image over a little bit,

2:58

and I'm going to blow this one up.

3:01

And what makes up the posteromedial corner?

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Well, the posterior oblique ligament of the knee,

3:06

or the pol, the OPL,

3:08

the oblique popliteal ligament,

3:11

the semimembranosus and its five expansions,

3:14

or arms,

3:15

the medial meniscus

3:17

and its attachments, which are very swollen.

3:22

You can't really see an interface between the

3:23

meniscus and any other tissue other than boggy,

3:27

hyperintensed tissue. And finally, the capsule,

3:31

and the meniscocapsular attachments,

3:33

which are also obliterated by this swelling.

3:36

So immediately we've identified that the

3:40

meniscocapsular reflection is severely diseased.

3:44

How about the semi membranosis?

3:46

Wow. The semi membrinosis is hanging down.

3:50

It's pointing towards Florida.

3:52

It should actually point towards Texas.

3:54

There are five expansions,

3:57

or arms of the semi membrinosis,

3:59

the main one being the direct deep arm.

4:02

The second important one, which is seen here,

4:05

is the anterior arm,

4:07

also known as the pars reflexa,

4:08

or reflected portion of the semimembrnosis.

4:11

So the main arm,

4:13

the direct arm of the semimembrosis

4:14

has been pulled off.

4:16

So now we have at least three components.

4:20

There's a meniscal injury,

4:21

although it's pretty low grade.

4:22

There's a more serious meniscal capsuler injury.

4:26

The main attachment of the semimembrnosis

4:28

is pulled off. What do we have left?

4:31

We have the OPL, the oblique popliteal ligament,

4:36

that is not seen as a separate structure

4:39

because it merges with the capsule.

4:40

But let's follow the capsule down.

4:42

It should be a clean, straight, black structure,

4:45

and it is to right there.

4:47

And then at that point,

4:49

we see a spidery web of low signal intensities.

4:54

That is the torn, retracted capsule.

4:58

So if the capsule is torn, the OPL,

5:01

or oblique popliteal ligament got to be torn.

5:04

So another component of the posteromedial corner

5:07

is torn. How about the last component, the pol,

5:14

the posterior oblique ligament of the knee?

5:16

It's got three components.

5:18

It's got a superior capsuler component,

5:21

also known as the superior arm.

5:24

It's got a central tibial component which is the

5:27

main component that kind of slopes back like this.

5:30

And then it's got a distal superficial

5:32

arm that goes a little more forward.

5:34

Now let's look at the medial collateral ligament,

5:39

or the tibial collateral ligament,

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which is the middle layer of the MCl,

5:43

which is this black band right here.

5:45

Behind it is going to be,

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and I'll pick another color.

5:50

Behind it is going to be the more broad arcing

5:54

pol, which kind of has this shape.

5:57

I made it orange.

5:58

Maybe I should have picked another color.

6:00

Let's pick green.

6:01

So the pol

6:04

is behind it,

6:05

and it kind of has sort of a

6:06

triangular configuration.

6:08

And you should be able to see wispy oblique fibers

6:11

going this way from super anterior

6:14

to postero inferior,

6:15

and then going this way from superoposterior

6:18

to antero inferior.

6:19

Then these fibers will kind of come down and wrap

6:23

around the back of the knee to merge with the

6:25

posteromedial capsule. Now let's take it away.

6:28

Do you see fibers with that course behind the

6:31

tibial collateral ligament? No, you don't.

6:34

You might see something running up and down

6:36

right here, but after that it is a mess.

6:40

All you see is ill defined hyperintense

6:44

signal intensity.

6:46

Now let's go to the coronal projection

6:51

to seek out our pol,

6:53

our posterior oblique ligament of the knee,

6:56

which is one of the most important structures

6:59

of the postural medial corner,

7:00

along with the semimembrnosis and its expansions.

7:04

So let's pull down our water weighted

7:07

coronal and our T1 coronal.

7:09

I'm going to blow them up a little bit just

7:11

to make it a little easier for you to see.

7:13

Make them a little lighter.

7:15

Now, admittedly,

7:17

the patient has some meniscal pathology,

7:20

quite a bit of meniscal pathology,

7:21

but that's not why we're here,

7:22

both on the lateral side and the medial side.

7:25

And let's scroll.

7:27

I want you to look at the scroll for a minute,

7:30

and I'm sure you've recognized the

7:32

tibial collateral ligament,

7:34

which is the middle layer of the MCl.

7:37

layer number two.

7:39

Now follow the tibial collateral ligament forward.

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It's a little swollen. Now follow it backwards.

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There's the meniscofemoral attachment.

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There's the menisco tibial attachment.

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This is layer number three of the MCl.

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Let's keep going back because immediately

7:57

behind the tibial collateral ligament,

8:00

layer two of the MCl, you should run into the.

8:04

You should be running into it right now.

8:07

Might be a little pol.

8:09

That might be a little pol.

8:12

There's the broken pol. Let me make it bigger.

8:16

That should be a sweeping, contiguous structure.

8:19

There should not be a gap right here.

8:22

That is a pol tear.

8:25

So the trick is to follow the TCl,

8:28

tibial collateral ligament,

8:29

or middle layer of the MCl.

8:30

Back becomes quite attenuated, then gone.

8:34

So it's injured here, torn there.

8:37

It helps anchor or check the movement of the

8:41

meniscus along with the rest of

8:43

the posteromedial corner.

8:45

Now,

8:46

I put the T1 up so that you could see the

8:48

chondromalatia and some of the skeletal changes,

8:51

but it's much harder to recognize the ligaments on

8:54

the T1 than it is on the water weighted image.

8:57

So this patient has a pol tear,

9:00

a semimembranosus avulsion,

9:03

and a meniscocapsular ligament injury or tear.

9:08

Therefore,

9:10

they have lost the stabilization of the postural

9:12

medial meniscus and what we call the brake stop

9:15

mechanism of the postural medial meniscus.

9:17

But she has other problems that

9:19

I put into the conclusion,

9:20

including chronic chondromalacia meniscal pseudo

9:23

extrusion, chronic meniscus tears.

9:26

I described their length, their complexity,

9:29

their shape, et cetera,

9:31

and I would also add a pertinent

9:32

neg in the body of the report,

9:34

because the injury is pretty impressive

9:36

that the ACL and the PCL are intact.