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Okay,

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the next case is a 59-year-old man

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with severe pain, discoloration, swelling,

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and weakness of the left knee after

0:08

sustaining an injury at work.

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The primary findings,

0:12

some of you suggested

0:14

was a rupture of the ACL,

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a rupture of the patellar ligament.

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Secondary findings were complex tears

0:21

of the medial and lateral meniscus.

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Tertiary finding,

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complete tear of the lateral collateral ligament.

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So, let's go with that for now.

0:31

That's not necessarily the answer,

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but that's what many of you did say.

0:35

So, let's begin with

0:39

the axial projection,

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which is where I usually start,

0:43

and there is very extensive swelling.

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Here's the helmet shape of the patella.

0:50

There are some spurs here, medially and laterally.

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I don't use the term osteoarthritis unless

0:55

I have spurring.

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And I do have spurring.

0:59

While we're coursing through the imaging,

1:02

on the medial side,

1:03

we can see the posterior cruciate ligament.

1:06

On the lateral side,

1:07

we can see some swelling in the neighborhood

1:09

of the linear anterior cruciate ligament.

1:13

I'll also use this projection to look for any

1:16

encroachment on the neurovascular bundle

1:19

to look for phlebitis,

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or what I call pseudo-phlebitis,

1:23

where there is a Baker's cyst that's

1:25

pressing on the popliteal vein.

1:27

Okay, now that we've looked at the axial,

1:29

we know we have a very swollen anterior knee.

1:32

Let's turn to the sagittal projection,

1:35

and we'll take them two up.

1:36

So on the left,

1:37

we have a water-weighted image

1:40

with excellent fat suppression,

1:42

a very nice TE close to around 40.

1:45

And let's tackle the patellar tendon first.

1:50

Once again,

1:51

we see osteoarthritis of the patella

1:54

with extensive spurring.

1:55

I use this projection to look at the trochlea.

1:57

The trochlea is abnormal.

1:59

There's an erosion.

2:00

There's a subchondral spur right there,

2:02

a very small one.

2:04

And the obvious finding is rupture of the patellar tendon.

2:09

So, we would describe where it is.

2:10

It's mid substance.

2:11

We would describe the gap.

2:13

You see it extremely well on the

2:15

sagittal T2 weighted imaging.

2:17

And that's going to be a major

2:19

finding for the case.

2:21

Now,

2:22

for those of you that thought there was an ACL,

2:26

anterior cruciate ligament tear,

2:29

a couple of teaching points,

2:31

most patients, not all, but most,

2:34

like 90%,

2:35

are going to have some form

2:37

of pivot shift bone pattern.

2:39

And what does that consist of?

2:41

An anterolateral femoral fracture,

2:43

a posterolateral tibial chip fracture,

2:46

posteromedial tibial chip fracture.

2:49

This patient has none of those,

2:51

so that should be a concern for you.

2:54

Second, the tibia should translate anteriorly.

2:58

In other words,

2:59

the tibia should translate this way,

3:01

not this way.

3:03

So the tibia should translate to the front.

3:06

That is not happening.

3:08

In fact, the tibia is translating posteriorly.

3:11

It's sitting a little bit back.

3:13

If we draw a perpendicular line along the back

3:16

of the femoral condyle,

3:18

in multiple locations,

3:20

as we scroll across,

3:21

the tibia is sagging the other way.

3:24

So, we have what's known as the tibial sag sign.

3:27

So, for those of you that said

3:28

there was a PCL tear,

3:31

you'd be right.

3:33

There is a PCL tear.

3:34

Now, unlike the ACL,

3:36

the PCL does not usually transect.

3:40

It usually tears interstitially.

3:42

This way maintains its shape

3:45

but does not maintain its signal.

3:47

Sometimes it'll take a piece of bone with it

3:49

and avulse from the base of the PCL.

3:53

That's about 10% of PCL tears.

3:56

Another way to corroborate your thought regarding

3:59

the PCL tear is to look at the coronal.

4:02

You find the PCL, which is medial.

4:05

That's medial.

4:05

That's lateral.

4:06

The PCL is filled with blood.

4:09

There it is.

4:10

There.

4:11

There.

4:11

And it makes what I call an archery target sign.

4:14

Now, admittedly,

4:15

the ACL is extensively swollen

4:17

and a little hard to see,

4:19

but you go back to the sagittal T2 weighted image,

4:22

and even though the ACL

4:23

is very thick and irregular,

4:25

there still is a linear structure.

4:27

It is surrounded by scar tissue.

4:29

So if you said chronic ACL tear,

4:32

scarred ACL,

4:33

I wouldn't argue with that.

4:35

But there's no acute ACL tear,

4:37

and there's no signs of ACL deficiency.

4:40

As we scroll along,

4:41

you can also see there is tibiofibular osteoarthritis

4:45

in keeping with our theme of osteoarthritis.

4:47

Let's go back and discuss our osteoarthritis.

4:50

We do have OA,

4:52

and I will Kellgren Lawrence grade

4:54

my osteoarthritis, one through four.

4:57

I would urge you to google that,

4:58

since it's a plain film classification system

5:02

that we extrapolate to MRI.

5:05

We also have a penetrating erosion,

5:09

weight bearing erosion in the

5:10

medial femoral condyle.

5:11

You are correct in that we have meniscal tears.

5:15

They are predominantly chronic,

5:16

degenerative meniscus tears.

5:18

One medially,

5:19

you can see right here.

5:21

The meniscus is small,

5:22

consistent with DJD and OA.

5:25

The meniscal root is truncated on both sides.

5:29

Consistent, in this case,

5:31

with DJD and OA.

5:33

And then when we look at the lateral meniscus,

5:36

it's a little beat up.

5:37

All of this stuff is chronic.

5:38

The menisci are a little bit extruded.

5:41

They're a little bit malformed.

5:43

They're a little bit small.

5:44

They have some inner third cleavage type signal.

5:47

The medial meniscus is really macerated here.

5:50

So, this is all chronic meniscus pathology.

5:53

There's bone on bone on the medial side.

5:55

There's eburnation and sclerosis.

5:58

So the overriding theme here is OA,

6:01

and with Kellgren Lawrence graded.

6:02

The patient has an acute PCL tear.

6:05

The patient has notch impingement syndrome

6:07

with a heavily scarred knee notch.

6:11

The main finding,

6:13

the first finding in the conclusion should read

6:15

patellar tendon rupture

6:17

with 3-4 cm of diastasis.

6:21

Anything else that is worth commenting on here?

6:26

Give it some thought

6:27

as we kind of scroll around.

6:29

There's some generalized muscular atrophy.

6:31

You can see especially on the lateral side.

6:33

Look how much fatty metamorphosis and replacement

6:36

we have in the lateral compartment.

6:39

And the patient, as we said,

6:42

has a PCL deficient knee.

6:43

Now, this is a gradient echo image.

6:46

In this particular case, it doesn't add much.

6:49

And I think we'll move on from this case.

6:55

I don't have anything else to add.

6:57

There is an effusion,

6:58

and there's extensive prepatellar swelling.

7:26

Okay.