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Hello and welcome to Noon Conference, hosted by MRI Online

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and share ideas to help the community learn and grow.

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of today's conference in previous Noom conferences

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by creating a free MRI online account.

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Today we're honored to welcome Dr.

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Steven Pomerance for a lecture entitled MRI of the knee.

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Dr. Pomerance is the CEO

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and Medical Director of Pro ProScan Imaging, chair

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of Naples, Florida Community Hospital Network,

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and the founder of MRI Online.

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He's authored numerous medical textbooks

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and MRI, including the MRI, total Body Atlas.

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He's also an AVID conference, lecturer

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and chairs the fellowship training program in MR.

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And Advanced Imaging.

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At the end of the lecture, please join him in AQ

1:00

and a session where he will address questions you

1:02

may have on today's topic.

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Please remember to use the q

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and a feature to submit your questions so we can get to

1:08

as many as we can before our time is up.

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With that, we're ready to begin today's lecture. Dr.

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Pomerance, please take it from here.

1:17

Okay. Um, it's a big day.

1:20

This is the beginning of, uh, black Friday for MRI online,

1:23

so you can see, uh,

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there are some discounts out there for all of you.

1:28

This is really beyond my area of expertise,

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but it's the busiest week of the year for MRI online

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and it's the most wonderful time of the year.

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It's a great time to sit by a fire and learn about MRI.

1:40

I know that sounds sounds kind of nerdy, but,

1:43

but I am, today we're talking about, uh, MRI of the knee

1:48

and, um, I'm gonna focus on really four major

1:51

areas, Hyland cartilage.

1:53

I'm gonna use the patella mostly as an example, the skeleton

1:57

ligaments and menisci.

1:59

And I'm, I'm going to at this mostly from a biomechanical

2:03

biophysiological approach to injuries of the knee.

2:07

So I'm not gonna be talking much about things like

2:09

gout and pseudo gout.

2:10

I, I might, I might refer to them briefly,

2:13

but this is really a discussion more about injuries

2:17

and how the knee relates to those injuries.

2:19

So let's start out with a pivot shift injury.

2:21

This is our famed quarterback, um, Carson Palmer,

2:25

who was injured by this, uh,

2:26

evil Pittsburgh Steeler who fell on his knee.

2:29

You can see the foot is externally rotated.

2:32

The tibia internally rotated.

2:33

The femur is externally rotated. That's hard to appreciate.

2:37

There is an outside valgus force applied a a a against the

2:40

knee, and most importantly, the toe is fixed on the turf.

2:45

Had the toe been free, uh,

2:47

that injury probably wouldn't have been sustained.

2:50

Uh, and we'll see some examples

2:52

of the pivot shift injury in a moment,

2:53

but we'll talk about

2:55

hyper rotational injuries.

2:59

Knee dislocation, we, we may or may not get to that today.

3:03

Uh, direct impact and the pivot shift injury.

3:07

So let's begin with hylan cartilage,

3:10

and I'm going to use the patella

3:11

and I'm also going to touch on the growth plate since most

3:15

people don't, don't focus on it, uh, all that much

3:18

as pediatric radiology is an island unto itself.

3:24

I'd like to show you the normal growth plate

3:27

and this white striped area,

3:29

which is a little thicker on the medial side,

3:31

a little thinner on the lateral side

3:33

consists of three zones.

3:34

The zone of resting cartilage, proliferating cartilage,

3:38

hypertrophying cartilage.

3:40

And then stacked upon that is the laying down of bone.

3:44

This thin black line delimited by the salmon color arrow.

3:49

And that thin black line represents the zone

3:52

of provisional calcification.

3:54

So that's how the bone grows.

3:56

The bone can also grow sideways from medial

3:59

to lateral via the zones of ro vier and the ring of LaCroix.

4:03

A subject for another day in the pediatric knee discussion.

4:06

But a common pitfall that may lead

4:08

to the misdiagnosis of assaulter Harris.

4:11

One is the metaphyseal spon, what I call shine

4:16

this shiny area right here, which is not edema,

4:20

that represents the normal loops of vascularity

4:23

that provides the ATP

4:25

and the oxygen that allows the energy for laying down

4:28

of bone, allows for the zone a provisional calcification.

4:32

If you injure that via repetitive trauma, such as running

4:36

and cutting on turf when you're a young person

4:39

and that goes unchecked, then the benjamins stack up.

4:43

What I mean by that is these three zones,

4:45

the yellow zones will get thicker and thicker and thicker.

4:48

They will not calcify, they will not ossify,

4:51

and you will end up with a leg length discrepancy.

4:56

Now the patella as promised, the patella has a medial facet,

5:00

an apex, a lateral facet, a lateral tubercle,

5:04

an odd patella facet

5:05

that is not really covered by cartilage.

5:08

And then the pre patella plate, which consists

5:11

of the continuity of the quadriceps tendon.

5:14

As it courses over the front of the patella,

5:17

we'll have a medial para patella reticulum,

5:21

a lateral reticulum,

5:22

and we'll see later on,

5:23

we'll have a medial patella fal ligament.

5:26

If the patient is under 18, the most common cause of pain

5:31

as someone under 18,

5:32

under age 18 in the knee is, is the patella.

5:36

We're gonna look at things like size, shape, facets,

5:39

the trochlea, we'll look for dysplasias position,

5:43

the plate status, the fat pads.

5:46

Let's take a look at some examples of

5:50

different patella shapes.

5:53

And I don't comment on these individually too often,

5:56

but the two that I, that i

5:58

that do come out most frequently are the weiberg shape

6:01

and patella magna.

6:03

Let's stick with the weiberg shape for right now.

6:05

Uh, in weiberg shapes, you are actually comparing the length

6:09

of the medial facet to the length of the lateral facet.

6:11

So the shorter this gets, the longer that gets,

6:15

the greater the degree of dysplasia,

6:17

the more likely the patient is to have some form

6:21

of patello femoral subluxation, dislocation

6:24

or mal tracking syndrome.

6:26

Another, uh, dysplasia that is, that is carried out is,

6:31

is the uh, dejure classification of dysplasia.

6:35

Let see if my panel work here, there we go.

6:39

So if we have a trochlear groove like this,

6:42

that's fine, that's peachy.

6:43

But what if the groove's a little shallow?

6:45

Then we would have a dejure.

6:47

What if the groove is completely flat all the way across?

6:50

We'd have a dejure B.

6:51

What if we have a bump in the middle of the groove?

6:53

That's a real problem. Then we'd have a dejure C.

6:56

So those are a little bit more sophisticated,

6:59

but they are very relevant, uh,

7:01

to young people with knee pain.

7:03

One of the few measurements, I don't measure a lot

7:05

of things, but one of the few measurements I do make is the

7:08

TT to TG ratio.

7:11

And that is something you can Google and look up.

7:13

Since we're time constrained, that is one

7:15

of the few things I will include in a report, not routinely,

7:18

but in young patients with patella femoral disease.

7:22

Now let's look at the arrangement of cartilage.

7:24

We said we were gonna use the patella as an example.

7:27

The these are T two relaxation maps.

7:31

So the colors reflect the T two relax

7:34

Darker color means shorter relax.

7:37

And because of the protio glycan

7:40

and cartilage cell arrangement, this area is more dense,

7:44

more hypo intense, shorter T two relax.

7:47

Therefore the color is darker.

7:49

The color lightens consistently

7:52

and smoothly all the way across.

7:54

As we get more superficial,

7:56

and this is known as the phenomenon of stratification,

8:01

you can see how disorganized the stratification has become

8:05

or lack thereof in this patient with a degenerated knee.

8:08

And you're probably wondering, well, blue

8:11

is not lighter than these other colors.

8:13

Yellow is, but, but what is this blue area?

8:15

The blue area is volume averaging of the zona splendid,

8:20

which is a superficial, very thin vesicular band

8:24

that sits on the surface of the cartilage, kind

8:26

of keeping it snug against the the osteocondral surface.

8:30

So that's a thing unto itself.

8:33

Let's look at stratification in real life.

8:35

This is an anatomic specimen. Here's a real Mr.

8:39

Medial facet odd facet apex lateral, facet lateral tubercle.

8:42

Let's take the apex for instance.

8:45

And in the apex, the deeper portion is a little bit darker.

8:49

The superficial portion is a little bit lighter.

8:51

And we see the zona Splendas, that hyperintense area

8:56

that we referred to earlier, the outer shell, uh,

9:00

that incase is the cartilage.

9:02

Let's turn our attention now to cartilage grading,

9:05

which may be confusing for many of you.

9:10

For some reason, as radiologists, we turned our attention

9:13

to a pathologic grading system some 27 years ago ago,

9:18

the outer bridge classification system,

9:20

and we modified it for MRI.

9:22

Then our colleagues in the American College

9:24

of Orthopedic Surgery modified it even further.

9:27

So let me show you how we currently do it.

9:29

Grade one is either a pure intrasubstance abnormality

9:33

with no deformity

9:34

or less than 25% loss of thickness of the Hyland cartilage.

9:39

Grade 2, 25 to 50% loss of thickness

9:43

or an intra cartilaginous signal with a raised surface

9:48

or so-called blister grade

9:51

three full thickness tears.

9:53

They can either be focal or they can be broad-based

9:57

because they are full, full thickness.

9:59

When they're broad-based, they frequently take on the

10:02

appearance of crab meat.

10:04

Another word about these cartilage defects.

10:07

When these cartilage defects are very squared off like this,

10:10

they're usually acute cartilage defects,

10:13

traumatic cartilage defects,

10:14

whereas the degenerative ones are more broad, uh,

10:18

more goaling shape, more ized.

10:21

So that's something to keep in mind when you're looking at

10:23

the femoral tibial articulation.

10:25

Then in the lower right hand corner we have the exposed

10:27

osteocondral plate in medullary bone

10:30

of class four chondromalacia.

10:33

Let's take one example.

10:35

Here is a pathologic specimen showing the crab meat

10:39

configuration of grade three chondromalacia.

10:41

And on your right, the MRI demonstrating extensive fishering

10:46

of the apex

10:47

and medial facet in a crab meat like configuration.

10:51

Now he said, remember the hylan cartilage is darker, deeper

10:56

and becomes brighter more superficially,

10:58

but at least in the femur

11:00

and probably in the tibia, we're not so deep, we're kind

11:04

of in the middle and it looks very different than the other

11:08

cartilaginous areas.

11:09

And that's because this patient has the entity known as

11:14

CPPD, calcium pyrophosphate, dihydrate

11:18

deposition disease.

11:20

And sometimes you'll see something very similar to this,

11:23

but it'll be a little bit more superficial kind like here.

11:27

Or there'll be little dots

11:28

that are more superficial rather than in the

11:30

interstitium of the cartilage.

11:32

And this is known as the icing sign associated with gout.

11:36

So superficial hypo intensity, gout, interstitial,

11:41

mid cartilage, hypo intensity, CHONDROCALCINOSIS

11:44

or CPPD deposition.

11:48

Okay, let's take a breath, take a sip of tea

11:54

and turn our attention to the skeleton.

11:57

When I look at any joint in the body, the first thing I do,

12:01

I don't drill into the case right away.

12:03

I sit back and I look at the shape of the joint.

12:06

I look for conformity.

12:08

How does one one part of the joint fit into the other?

12:12

I look for deformities, I look for dysplasia

12:15

and I differentiate deformities from dysplasias

12:17

and that some may be acquired, some may be congenital

12:20

or developmental.

12:22

I also look at the bone pattern of injury.

12:26

This will tell me what I am looking for.

12:29

For instance, a fracture of the proximal fibula,

12:31

A board question, the arcuate sign poster,

12:34

lateral corner injury, the segun fracture

12:36

of the lateral tibia, LCL, lateral capsular injury,

12:40

pivot shift, non kissing contusions, ACL tear,

12:44

anterolateral femoral fracture, patellar dislocation,

12:48

contusion of the anterior tibia, PCL tear,

12:52

anterior femoral condyle

12:53

and tibial rim fracture, hyperextension

12:56

or knee dislocation injury.

12:58

Let's take a look at an example. Non kissing contusions.

13:01

What's kissing? Kissing is when they abut each other.

13:05

One here and one here, but we have one here

13:09

and we have one back here.

13:11

How did they end up touching one another?

13:13

How did this end up, you know, touching the anterior aspect

13:17

of the medial femoral condyle?

13:19

Well, because when you translate,

13:21

when the tibia comes forward,

13:23

now the anterior femur is gonna hammer the posterior aspect

13:27

of the tibia.

13:28

Using my fists as an example.

13:31

This is pathic mnemonic of a pivot shift injury.

13:36

And most of these people are gonna have

13:37

serious ACL injuries.

13:40

One that I promised I would show you is the patella

13:43

dislocation syndrome.

13:46

Uh, I'm not going to show you a full full out knee

13:49

dislocation, although I may have one later

13:51

on, I take that back.

13:52

But here's another example of non kissing abnormalities.

13:57

There's one microtrabecular, big time fracture,

14:00

anterolateral femur, but the other fracture is over here.

14:03

How did they find each other? The patella slid over the side

14:07

and the medial patella femoral ligament,

14:09

which usually tears over here

14:12

near the adductor tubercle about 80% of the time.

14:14

This time it tore at its patella reflection.

14:17

It completely tore off, uh, right there.

14:20

Patellar dislocation syndrome inferred by the pattern

14:25

of non kissing bone injuries.

14:27

Here's an example of kissing bone injuries.

14:30

They're kissing 'cause they're touching each other.

14:32

They're on the medial side.

14:34

So if you kiss on the medial side, you're going

14:37

to distract the lateral side.

14:38

If you kiss on the lateral side, then you're gonna distract

14:42

the medial side.

14:44

So this is an example of lateral side kissing injuries

14:48

that would result in an MCL injury.

14:51

Let's look at an example on the lateral side.

14:54

This is the lateral femoral condyle. The lateral tibia.

14:58

There are fractures with each

15:00

with the associated osteo edema, meaning

15:03

that there must be an injury on the lateral side.

15:05

Now I'm not showing you the lateral collateral, uh,

15:09

ligament injury which was there

15:10

because this shows the fractures a lot better.

15:13

But you can even see that the iliotibial band itself,

15:16

which is on the lateral side,

15:18

is attenuated and was affected.

15:20

The LCL was torn in this patient.

15:23

An example of kissing contusions as a manifestation

15:28

of a varus insult

15:30

and varus insults are often more serious

15:33

than valgus insults.

15:34

Let's look at the arcuate sign.

15:36

This you have to know for your core exam.

15:38

This is a an avulsion injury

15:40

that occurs in the proximal fibular styloid.

15:43

It's an indication of varus hyperextension, a lateral

15:48

or posterior lateral corner injury

15:50

and may be associated with injuries

15:52

of the arcuate ligaments, the fibular collateral ligament,

15:54

the biceps femoris, the fabelo fibular ligament,

15:58

and the popliteal fibula ligament.

16:01

Let's have a look at the arcuate side.

16:03

This one, non-displaced from the fracture.

16:06

There's edema and bleeding into the biceps femorals

16:10

and there is a ligament that should come out of here

16:13

that is missing the arcuate ligament.

16:15

That's not the purpose of me showing it.

16:17

I simply wanted to show you the common nuded appearance, uh,

16:20

of this abnormality, the arcuate sign.

16:23

And by the way, in this case,

16:25

the arcu had sign more indicative of a capsular

16:27

or a posterolateral corona injury or arcuate injury.

16:30

In this case, the fibular collateral ligament was

16:33

essentially intact.

16:35

There's another example of a pattern of bone injury.

16:39

Once again, non kissing femoral terminal sulcus,

16:44

posterolateral tibia.

16:45

Soon as you see that, even though you don't see the ACL,

16:48

you now know that the ACL is injured.

16:51

You now know that there's a pivot shift.

16:53

So now you could just go down your checklist.

16:56

ACL check, it's torn.

16:58

Is there a vertical wrist berg type tear?

17:00

Laterally check it's torn.

17:02

Is there a poster medial ramp lesion not shown, but yes.

17:05

Check it's torn. Was there a vari or valgus component?

17:09

Check. Let's look at the MCL check. Let's look at the LCL.

17:13

So these contusions and bone injuries are signs.

17:17

You go right down your mental checklist and you're good.

17:21

Let's take a look at another sign.

17:23

This one you also have to know for your core exam

17:26

and that is the saun fracture, the evulsion flake fracture.

17:31

Now normally off the fibular collateral ligament,

17:34

which looks horrific.

17:36

Here's the fibular collateral ligament seen

17:38

and here's the stump right there.

17:41

Now from the fibular collateral ligament,

17:44

this is just a mushy fibular collateral ligament.

17:46

This thing that I'm putting my

17:48

green dot over it now I'm gonna take it away.

17:51

That is a ligament that goes right here, that's known as the

17:56

lateral O gleek ligament

17:57

of the knee comes off the fibular collateral ligament.

18:00

When you have that, you have a lateral

18:04

or posterolateral corner injury.

18:06

This patient has both.

18:08

The fibular collateral ligament is torn.

18:10

The posterior lateral corner looks like just a mush pot.

18:14

This is blood and retracted ligaments and capsule

18:18

and even anteriorly in this poor unfortunate sole from this

18:22

vari internal rotation injury.

18:24

The ileo tibial band

18:25

and anterolateral capsule is also rupture.

18:30

Let's look at another Gord worthy arcuate sign.

18:34

Where is the proximal fibular styloid? Nowhere to be seen.

18:38

It's out of the plane of section,

18:40

but also nowhere to be seen is

18:43

the biceps femoris attachment.

18:45

The fibular collateral ligament.

18:47

The vertical limb of the arcu,

18:49

which it should come straight up here, we don't see it.

18:52

The oblique limb of the arcu, which is right there.

18:54

You can see it as a stump. It is also missing.

18:57

And this patient did not have a fabelo fibular

19:00

ligament, so that was irrelevant.

19:01

But the fabelo fibular ligament is inversely proportional in

19:05

size to the vertical limb of the arcu ligament.

19:10

Okay, ligaments, let's take a drink.

19:18

Let's start out with my favorite,

19:19

the anterior cruciate ligament, which most of you see

19:22

pivot shift injuries on television

19:24

and NFL National Football League contact sport.

19:29

But you also see it in Aussie ruse football.

19:30

And I know we have people from all over the world.

19:33

I don't know what the incidences

19:34

of ACL tears in is in the sport of cricket,

19:36

but I suspect it's pretty high in the sport of rugby.

19:39

The ACL shares a common sheath with a posterior

19:43

cruciate ligament

19:44

and that is why the posterior cruciate ligament is often

19:48

incorrectly diagnosed as torn with the ACL.

19:51

When you're simply looking at its sheath bathe in

19:54

fluid and blood.

19:56

If these two tear together, you better be worried about

19:59

a knee dislocation.

20:00

There are two main bundles,

20:01

an medial dominant posterolateral subdominant.

20:05

They arise from the lateral femoral wall

20:07

and insert in the inter tibial spinous notch

20:10

and to a lesser degree on the tibial spines.

20:13

Approximately 13 millimeters in diameter is the ACL.

20:17

In children it's about eight in women, it's about nine

20:20

or 10 lies inside a sheath.

20:23

Inside that sheath, there is no synovial.

20:26

So this is an intraarticular yet extra synovial structure.

20:30

I use the sagittal to look at the mid ACL, the coronal

20:34

to look at the tibial end

20:36

and the axial to look at the femoral end.

20:38

In other words, I use all three planes

20:42

taken from our total body atlas in MRI is the anterior

20:46

cruciate ligament

20:48

and we see its origin from the lateral

20:50

wall of the femoral condyle.

20:51

As it comes down, it gets a little more spread out,

20:54

a little more fan shape,

20:56

a little more triangular in shape along with its sheath,

20:59

which is also a little more triangular in shape right here.

21:03

And it gets a little gray as it fans out

21:06

and that's all okay.

21:07

That's totally and perfectly appropriate.

21:10

Now, sometimes when there is a complex injury

21:13

with a he arthrosis and a fracture and varus

21:15

or valgus, the ACL is concealed.

21:18

It's hidden, it's bathed in fluid and blood.

21:20

And you may have to resort to specialized ACL views,

21:23

which you acquire like this

21:25

off the sagittal projection tangent

21:28

to the anterior cruciate ligament.

21:29

And there we have its origin from the inner lateral femoral

21:33

condylar wall inserting on the tibia and tibial spines.

21:38

Now sometimes the ACL may be at risk if there's dysplasia.

21:43

Remember we said at the very beginning, sit back,

21:45

look at architecture, look at conformity.

21:48

Look for dysplasias, look for remodeling.

21:50

Here we have dysplasia.

21:52

The cross-section

21:54

or the length from medial to lateral

21:57

of the femoral knotch should be about two

21:58

centimeters or greater.

21:59

In men, this one's 1.5, so the ACL

22:04

and the PCL, but mostly the ACL is getting squished.

22:07

And you can see some signal in here,

22:09

even though there has been no trauma,

22:11

this is an anterior cruciate ligament that's at risk.

22:14

And here's what it is at risk for eventual rupture,

22:18

right in the mid portion, which is

22:20

where the sagittal view really shines.

22:23

Mid ACL tears for proximal tears.

22:26

I like the axial for distal tears. I like the coronal.

22:30

Here's the T two weighted image also

22:32

showing you this huge gap.

22:33

But buyer beware, what is the signal of ligament?

22:36

Ask yourself black. What's the signal of fibrous tissue?

22:42

Black. What's the signal of hemosiderin Black?

22:46

So you can have a pseudo ligament that is filled

22:49

with fibrous tissue and cirrhosis

22:51

and have it look like on AT two weighted image.

22:54

The ACL is intact.

22:55

And that's why you must have,

22:57

you must have a proton density, fat suppression sequence

23:01

to look at chronic ACL tears.

23:04

The PCL, it is curved lacquer

23:07

and thicker about 18 millimeters in thickness.

23:09

Rather than having two parallel bundles,

23:12

the bundles are more braided that cross over each other.

23:15

And this creates a scenario whereby the PCL does not

23:20

retract most of the time.

23:22

Most of the time the high grade tears are interstitial.

23:26

It shares a very close base

23:28

with the medial meniscus anterior to it, the ligament

23:31

of Humphrey posterior to it.

23:32

The meniscus femoral ligament of wrist spur.

23:36

It is a very broad, complex femoral insertion.

23:40

There are 13 insertion points as defined

23:43

by the esteemed orthopedic surgeon, Frank Noce.

23:46

There's an anterolateral bundle

23:49

and there's a poster medial bundle,

23:51

the exact opposite of the ACL.

23:52

The ACL is an medial and posterolateral.

23:56

So there are two PCL bundles. Here's your curved PCL.

24:00

Yes, it's curved, it's blacker, it's thicker.

24:03

It has a broad footprint on the femur anterior to it,

24:08

the meniscul femoral ligament of Humphrey posterior to it,

24:11

the meniscul femoral ligament of berg

24:15

and the capsule with the oblique popliteal ligaments sitting

24:19

directly behind in the midline.

24:20

Let's take a look at APCL mechanism

24:22

of injury falling on the tibial tubercle

24:25

with the toe pointed right there

24:29

driving the tibia posteriorly.

24:31

And this is what you get a large

24:35

functional full thickness tear even though it doesn't

24:37

retract interstitial tear of the PCL.

24:42

And a lot of times the tibia will sag posteriorly in an ACL.

24:47

You'll get anterior tibial translation this way in APCL,

24:51

you'll get it this way.

24:53

And we call that the SAG sign on MRI

24:56

of APCL deficient knee.

25:00

There's another example of APCL.

25:03

There's interstitial signal in this PCL,

25:05

they look a little bit similar to each other.

25:07

Here's the water weighted image.

25:09

Here's a water weighted image.

25:10

But this patient has had no trauma

25:14

and they have complex bursitis anteriorly.

25:17

And it's a man. And he is about 40 or 50 years of age.

25:21

He's got big bursitis. He's got complex bursitis.

25:25

He's got a big, big tendon, oh sorry, a big ligament.

25:30

He's also got a big tendon.

25:32

The popliteus tendon is buried in all

25:34

of this inflammatory tissue.

25:36

And the ACL is buried in all of this inflammatory tissue.

25:39

No, this is, this is gout.

25:41

So when things don't match up,

25:43

you've gotta think a little bit obliquely, uh,

25:46

to get to the right answer.

25:48

And that patient had no trauma.

25:50

And even though even if that patient had had trauma,

25:52

I still would've been suspicious of the diagnosis of gout.

25:57

Let's talk about the roots and root ligaments and sles.

26:00

And let's start out with this lovely picture

26:03

of the posterior lateral and medial meniscal.

26:06

Look at the lateral meniscus. It fans out.

26:08

We see these tiny little ligaments. One right there.

26:12

It is inserting, uh, on the base of the tibia.

26:15

There it is again, looking rather beautiful.

26:18

Whereas this one is just

26:20

chopped like you took an ax and just cut it off.

26:22

There is no ligamentous attachment.

26:25

And while the meniscus is not drifting,

26:27

I medially it eventually will.

26:29

And that can be the initiating factor

26:32

for osteoarthritis even in young individuals.

26:35

Let's look at some of the other attachments.

26:37

Let's go to the poster lateral meniscus.

26:40

Here we have attachments to the pop tendon.

26:43

I have pointed out for you the popplet fibular ligament in

26:47

the posterolateral corner.

26:48

But let's pay attention to the lateral meniscus

26:51

and its superior

26:53

and inferior fascicle, which passed

26:56

through a hiatus in the popliteus tendon

26:58

but also attached to it, keeping it, keeping it anchored.

27:02

And then as we go to the anterolateral route, we start

27:05

to see that things get a little feathery, a little speckly.

27:08

And I don't mind if it does that as long

27:11

as it doesn't go out into the meniscus body

27:13

and more on that right now.

27:15

So let's go to the most difficult of all the roots,

27:18

the antola meniscus.

27:20

It can be feathery, it can be striated,

27:22

it could be punctate.

27:23

And sometimes you can even sort out what the structures are.

27:26

For instance, this triangular structure here

27:29

is the transverse meniscal ligament of Winslow.

27:31

This round gray structure here is synovium.

27:34

This is the anterior meniscocapsular ligament.

27:39

And that ligament has an intrasubstance attachment,

27:43

this gray line.

27:45

And then we have the antola meniscus synovial recess,

27:48

which is distended by fluid.

27:50

Now some of you who are first and second year residents

27:52

or new to MRI are saying, how in the world am I ever going

27:56

to differentiate this from a real tear?

28:00

And, and the answer is very simple.

28:03

You follow it out to the periphery.

28:06

And if these signals persist more than say two slices,

28:09

it's a very rudimentary way to do it.

28:11

But it works, then you, then you have a tear.

28:13

If you have uh, chondral disease,

28:16

if you have osseous disease, if you have complexity,

28:19

if you have change in shape as you move from the midline

28:22

to the periphery, you, you have a tear collaterals.

28:26

Let's start out with the MCL, the easier of the two.

28:30

We have three layers. They have all kinds of crazy names

28:33

that you'll read about in the literature,

28:35

but I'm gonna make it simple for you.

28:37

I'm gonna give you three layers.

28:41

Layer one, superficial layer, also known

28:43

by the synonym cruise layer layer two, also known

28:48

by the synonym middle layer.

28:50

There are some other synonyms I won't confuse you with,

28:53

but I refer to this as the middle layer

28:54

or tibial collateral ligament layer.

28:57

And then layer three, the capsular layer.

29:00

That includes the meniscal, femoral

29:02

and menis tibial ligament, also known as the

29:05

coronary ligament.

29:07

Now between these, between these levels are areas

29:12

of fat pad formation and bursa.

29:15

So you can get a deep

29:17

and superficial MCL bursitis.

29:20

Let's see how we can get a valgus event. And here we go.

29:26

Here comes the valgus event.

29:28

Somebody's rolling up into this poor guy's knee right there.

29:31

Now this time the foot is not fixed on the ground,

29:34

otherwise it would've been a much more severe injury.

29:37

So that's a good thing.

29:39

You can see the valgus pushing on the outside of the knee.

29:42

And now let's look at what happened.

29:44

The patient has an MCL injury. Let's go through the layers.

29:46

Layer number one, the cruise layer right there

29:50

and it stops, it's torn.

29:52

Layer number two, the tibial collateral ligament layer.

29:57

It is rolled up in a ball.

30:00

Now the overwhelming majority

30:02

of the time we do not operate on PCL tears

30:04

and we do not operate on MCL tears

30:08

unless the MCL

30:12

specifically the tibial collateral ligament is entrapped.

30:15

Entrapped by what? Entrapped by the joint

30:18

or entrapped by the pess and cine complex.

30:24

If it's entrapped by the pess and cine complex.

30:26

And it is, there's the pess

30:28

and cine, there's the tibial collateral ligament under it.

30:31

Then we call that a knee pseudo entner lesion.

30:36

It also happens to be entrapped in the joint.

30:39

The patient also has a detached meniscal femoral ligament.

30:43

They call it the meniscal femoral ligament

30:45

because it attaches to the femur, but this one does not.

30:49

So this is a three layer tear

30:51

that require surgical intervention.

30:54

Let's take a look at some meniscal attachments,

30:58

some unique ones.

31:00

These are sagittal images at the level of the posterior

31:03

and anterior horns.

31:04

There's a little bit of signal anteriorly here

31:08

as we have a synovial reflection between the meniscus,

31:11

which is getting smaller

31:12

and the transverse meniscal ligament of windslow

31:16

and a little bit more synovial interdigitation here.

31:20

Let's, let's pay more attention to this one though.

31:22

In the back, the meniscus is attached by

31:26

two pretty important structures.

31:28

One is the posterior meniscal tibial ligament,

31:31

which you can just barely see right there.

31:33

And the other one, which is more important

31:35

or as important, is the posterior oblique ligament

31:38

of the knee or POL.

31:39

There are three components to this ligament,

31:42

which we'll discuss in the more advanced knee lecture,

31:44

which I hope to give you later on perhaps

31:47

uh, early next year.

31:48

And here is this little nubbin of hypo intensity

31:52

where the POL attaches to

31:55

and anchors the posterial medial meniscus reflection.

31:59

So there are posterial, medial meniscocapsular attachments

32:03

that we have to pay attention to.

32:05

So you've seen an example of a a valgus injury.

32:09

You've seen an example of a knee dislocation.

32:11

You've seen an example of a pivot shift.

32:13

How about a hyperextension injury? Let's have a look.

32:17

Straight direct hyperextension.

32:20

These can be pretty nasty

32:22

if you stick your leg out under your desk,

32:24

wherever you're sitting, you'll feel a

32:26

little pressure on the back of your knee.

32:28

So if it's a really violent straight hyperextension,

32:30

you can injure the back corners and the back capsule.

32:34

But much of the time the only thing you're gonna see is a

32:37

microtrabecular fracture in the anterior femoral rim

32:40

and the anterior tibial rim.

32:43

And the recovery from this is very quick.

32:45

A lot of times they will go out

32:46

and play contact sport within a week

32:49

or so, as long

32:51

as it's very eccentric, very, very far forward.

32:53

And there's not a macro fracture.

32:56

There's an example of one that occurred just like that,

32:59

except this time the rim fractures,

33:02

I'm not demonstrating them.

33:03

There are also fractures in the back

33:06

and this patient has sustained a posterior capsular injury.

33:10

Let's go back for a minute and remember our

33:12

POL attachment right there.

33:14

Compare that to this one, which is seriously blunted.

33:19

There it is. It looks like a little arrow from a bow

33:22

and arrow and it's separated from the meniscus.

33:24

But we have more, we have blood in the capsule.

33:27

The meniscus tibial ligament is reduced to this

33:31

smudgy structure right here.

33:33

The capsule is wavy

33:36

and the upper portion of the capsule known

33:38

as the oblique popliteal ligament portion

33:41

of the capsule is torn

33:42

or ruptured with fluid leaking out a post medial

33:46

capsular corona injury.

33:48

And in this setting, you must turn your attention

33:51

to the semimembranosus

33:53

and it's five different attachment fassal,

33:57

which we won't review today,

33:59

but we do see the semimembranosus swollen

34:02

bent but not broken.

34:04

Now when you insult the post medial meniscal capsular

34:08

reflection, we've now learned that this has long-term

34:13

and we never paid much attention to this 10 years ago.

34:16

But now we know when we lose these attachments

34:19

and we start to flex and extend the knee, it's like a tire

34:22

and it'll spit the meniscus out like you spit the gravel

34:26

and snow out on your car when you're trying to get out

34:30

of snow and ice.

34:32

And this becomes much more problematic when you lose the

34:35

meniscal posterior tibial attachment and you partially tear

34:39

or tear the semi menos attachment.

34:43

Okay, take a sip.

34:48

Now it's time for your ears to perk up

34:50

and for your energy level to rise.

34:54

I need you for this section 'cause it's hard.

34:57

This is the lateral collateral complex

35:00

and the posterolateral corner.

35:02

Let's look from the back.

35:04

So we're looking from the posterior aspect.

35:06

There's the fibula, there's the medial tibia,

35:09

and we have two bunny ears, a little bunny and a big bunny.

35:13

The little bunny consists of the vertical arcuate limb

35:17

and the oblique arcuate limb,

35:19

also known as the lateral limb.

35:20

And the medial limb. There is an inverse relationship

35:24

between the vertical limb and the fabelo fibular ligament.

35:27

Then we go to the big bunny ear.

35:29

The big bunny ear is composed

35:31

of the fibular collateral ligament

35:33

and the biceps femoris, which don't really fuse.

35:37

So this is not a completely accurate diagram,

35:39

but they're right next to each other.

35:41

So they receive the name conjoint tendon misnamed

35:46

'cause they're not really conjoined.

35:48

And then our fibular collateral ligament origin is slightly

35:51

above the pletus tendon origin.

35:55

And from our fibular collateral ligament is the

35:58

poster lateral oblique ligament of the knee.

36:00

A so-called saun ligament, which you've already seen.

36:04

And then one you have already seen normal is the

36:09

pop lillo fibular ligament.

36:11

Now we're gonna return to the popliteal fibular ligament.

36:14

I showed it to you in the sagittal projection earlier.

36:17

So now let's drill into the lateral side of the knee.

36:21

Now if you're squeamish, don't look 'cause this is ugly.

36:25

Yep, it looks like his ankle is dislocating.

36:28

He's a 300 pound, uh, Iowa, uh,

36:32

for former football player trying

36:34

to make the professional football team.

36:36

But really his knee is dislocating, uh, laterally

36:40

and it's a full knee dislocation.

36:42

His ankle is just bending.

36:44

He didn't have any serious ankle injury at all.

36:47

Look at it one more time. That's pretty ugly to watch.

36:50

And here is a normal diagram showing you the

36:53

fibular collateral ligament.

36:54

That's volume averaging.

36:56

And here is what the, the patient looked like.

36:59

He had ruptured the popplet.

37:01

He had ruptured the FCL, he had ruptured the biceps femoris.

37:04

The capsules is torn, fluid is leaking out and not shown.

37:08

He ruptured his perineal nerve

37:10

and was left with a permanent deformity and foot drop.

37:15

I promised I would drill into a little further

37:17

the pop fib ligament.

37:19

Let's do that. I am not showing you on the MRI,

37:22

the fibular collateral ligament whose origin sits

37:26

above the popple tendon.

37:29

But here's the popple tendon

37:31

and the popplet hiatus where gout loves to occur.

37:35

And it course is inferior, posterior

37:38

and medial into the screen, inferior posterior

37:42

and medial into the screen.

37:43

And that structure, which is that structure,

37:46

is not inserting on the fibular head.

37:48

And that is your pop fib ligament.

37:50

Now sometimes when it tears, it rolls up in a ball.

37:53

Here's a normal one. Here's one that's rolled up in a ball.

37:57

It looks like the mermaid's tail.

38:00

And that's what's known as the mermaid sign.

38:03

When you rupture the pop fib ligament,

38:06

there's no linear structure going down there.

38:08

Here it is right here going sideways.

38:10

And what's all this hemorrhage

38:13

and debris in the arcuate ligament.

38:15

So a very serious posterior lateral corner injury.

38:19

Okay, take a breath or onto menisci.

38:21

See how we're doing for time. We're doing great.

38:27

Menisci are fibro cartilage like they're shock absorbers.

38:32

They distribute axial load.

38:34

They are stabilizers of the knee. Make no mistake about it.

38:37

Many of your patients who come in say,

38:39

my knee feels like it's gonna give out.

38:41

And the ACL is fine. The PCL is fine.

38:43

It's the meniscus that creates that sensation.

38:47

The meniscus circulate fluid.

38:49

There are spongy radial areas in the menisci that allow

38:52

that fluid to imbibe

38:54

and course through it creating intra meniscal signal,

38:58

especially in the outer third of the meniscus.

39:02

Intra meniscal signal is also commonly seen in children

39:05

as meniscal vascularity.

39:07

And here is the vascularity with a reticular stain

39:11

and with a gross specimen showing you the the redness

39:15

of normal hyper vascularity in the outer third

39:18

of the meniscus where things do heal.

39:21

So I don't like to see operations for tears in this location

39:24

that are vertically oriented.

39:25

They will typically heal on their own unless they're gapped

39:29

or widened or, or they are very, very long.

39:32

Four or five, six centimeters long.

39:35

What else causes signal in in a meniscus?

39:38

It can be contused, you can have meniscal degeneration,

39:41

you can have intra meniscal tears,

39:43

especially in discoid lateral meniscus.

39:45

You can have meniscal cysts,

39:47

you can even have bleeding into the meniscus

39:49

that results in ossification of so-called meniscal ossicle.

39:54

Let's talk about our one-third double rule.

40:00

What does that mean? Double rule?

40:02

Well, the anterior meniscus, the body

40:05

and the posterior horn are divided up a third,

40:10

a third and a third.

40:12

So if we sort of put a line on it

40:15

and then we have to extrapolate in other projections,

40:18

which you as radiologists are very good at doing,

40:21

then this would be anterior third, middle, third posterior,

40:23

third anterior horn body, posterior horn,

40:27

body horn junction, body horn junction,

40:30

what's the other part of the double third?

40:33

The other part of the double third is inner third, middle,

40:35

third outer third white, white zone, inner third, no healing

40:41

red white zone may or may not heal.

40:44

And then the outer red red healing zone,

40:48

which you saw earlier.

40:51

The meniscus, as you now know, is anchored in its periphery.

40:55

Not completely all the way around, but for the most part.

40:58

And it's particularly anchored in the roots,

41:00

which you'll see in a few moments.

41:02

We have this outer third area,

41:04

which is a potential healing zone.

41:06

The zone of respect.

41:08

We don't operate on vertical tears here.

41:10

There is normal signal in this area.

41:12

And that signal in adults is related to diffusion

41:16

of synovial fluid into the radial fibers of the meniscus.

41:20

In children, it's related to vascularity.

41:22

The free edge of the meniscus is like the,

41:26

the free wings of a manta ray.

41:28

It is not attached to anything.

41:30

So when you put fluid in the joint like synovial fluid

41:33

or an effusion, it will be a little bit wavy

41:36

and may scrunch up on itself.

41:38

And this is known as meniscal flu.

41:41

Let's look at the menisci from this excellent article

41:44

by Thompson and Radiographics.

41:45

From this year. We have the radial fibers which allow

41:49

fluid to come in.

41:51

And that radial fiber shape is very consistent.

41:55

It's like a slingshot. Eventually it comes together.

41:59

It can, it can exit the capillary

42:02

'cause that's where the fluid comes in.

42:04

But it should stop just shy of the middle.

42:06

Third, if it keeps going past the middle third,

42:09

then you have a problem.

42:10

Then you have pathology.

42:12

You also have vessels out here in children,

42:14

there are circumferential fibers which we'll ignore today.

42:18

The meniscus is a stabilizer.

42:20

It also is a shock absorber for the hoop stresses

42:23

that come down when you perform athletic activity.

42:28

When Michael Jordan dunked the basketball,

42:31

he was measured at exerting 12 times his body

42:35

weight on his menisci.

42:36

So he was blessed with excellent tissues

42:39

and that he never had a meniscal problem.

42:43

And some people are just blessed.

42:45

So now let's go back to the root ligaments and fales

42:48

because this has become a critical jumping off point

42:52

for radiologists in the MSK world

42:55

and especially when you're assessing people for OA

42:58

or the potential for OA early on in life.

43:01

Here we have our more CS shaped bladder meniscus are more

43:05

banana shaped needle meniscus.

43:07

And these yellow areas are roots, anterior root,

43:10

posterior root, anterior root, posterior root, many

43:14

of which you've already seen, but we'll

43:15

revisit them in a moment.

43:16

We also have attachments to the periphery.

43:20

We have the meniscul femoral ligaments

43:22

and the meniscul tibular coronary ligament.

43:24

And these come around

43:25

and in the back, this is known as the ramp area

43:28

because you get ramp injuries

43:30

of the meniscocapsular reflection

43:32

when you have a pivot shift.

43:34

We also have peripheral attachment back here laterally.

43:38

And we have to deal with the popliteus tendon

43:41

and the meniscal femoral ligament of wrist berg, all

43:44

of which we will do.

43:47

And on the accompanying MR diagram, we see the anterior

43:50

and posterior roots, lateral and medial.

43:55

Let's turn our attention now

43:56

to these roots in the sagittal projection.

43:59

Let's start up with these two higher images, A and B.

44:03

Let's ignore the meniscal femoral ligament of berg for now

44:07

and we'll focus on our ACL and PCL

44:10

and their relationship to the roots.

44:13

The anterior medial meniscus root, not as s strided

44:17

as its posterior cousin.

44:20

This one's a little more s strided,

44:22

but don't be bothered by those vertical striations.

44:25

Look at the close relationship the posterior root has

44:29

with the PCL base

44:32

in the tibial PCL fossa.

44:35

Now let's go to C and D again,

44:37

let's ignore the meniscal femoral ligament of berg.

44:40

Here's our anterolateral meniscus root.

44:44

The yellow arrow, what's that? The ACL.

44:49

Look at the relationship

44:50

between the anterolateral root and the ACL.

44:53

It's intimate. And then look at the relationship between

44:57

the posterolateral root

44:58

and now the meniscal femoral ligament of berg.

45:02

It's also intimate.

45:05

Let's have another look back to a slide you saw earlier the

45:10

pop fib ligament, but we're more interested in the

45:14

attachments of the lateral meniscus that perforate

45:17

and also attach to the pope tendon.

45:20

One superior, one inferior,

45:23

and they have pretty good breath to them from side to side.

45:27

And then we also mentioned earlier

45:28

that there is some stippling

45:30

and linearity that's allowed in the

45:32

anter lateral meniscus root.

45:33

And this, this image you've already seen.

45:36

Let's turn our attention now to the Lara classification

45:40

for meniscal root tears.

45:43

I'm not here to try

45:44

and impress you with a bunch of classifications,

45:47

nor do I want you to memorize them.

45:50

I just want you to know that this is a now a focus

45:54

of musculoskeletal radiologists around the world.

45:58

To save the whales, save the knees,

46:02

save the meniscus.

46:04

These are important injuries.

46:05

And frequently it's a woman who feels a pop

46:09

and the radiologist overlooks this one small tear in the

46:13

back of the knee in the meniscus root.

46:14

That is either a partial radial tear

46:17

or a full depth radial tear.

46:19

These are the two most common.

46:20

Let's ignore the rest of the grading system,

46:22

which you can Google and learn on your own.

46:26

You're in diagrams of all five.

46:28

Again, I don't want you to learn all five right now.

46:32

I just want you to pay attention to one and two.

46:35

The two most common, a partial radial tear

46:38

and a full depth radial tear.

46:40

Inner third, middle third, outer third.

46:42

For some of you that are learning,

46:44

and especially those of you in other countries

46:46

that don't do a lot of M-S-K-M-R-I-A radial tear is this,

46:51

it's a subtype of vertical tear.

46:54

It comes from the inside like the spokes of a wheel.

46:57

On the other hand, another kind

46:58

of vertical tear is the longitudinal al

47:02

circumferential vertical tear.

47:04

And is there one more? There is.

47:06

There's one that occurs in the middle third

47:08

of the meniscus that'll then get wider and wider and wider.

47:12

And that becomes a bucket handle tear.

47:14

So there are actually three kinds of vertical tears.

47:17

The bucket, the circumferential longitudinal tear

47:20

and the radial type tear in the roots.

47:23

We're interested in the radial type tear.

47:26

You saw this slide earlier. Chop chop.

47:29

We chopped off the attachment of the meniscus to the tibia.

47:33

Now here's another little pearl.

47:36

We had that Lara classification

47:38

and it talked about, uh, different kinds of tears

47:41

and avulsions, but, but

47:42

what it didn't talk about was the ligaments.

47:46

This is not a meniscus tear, this is a ligament tear.

47:50

The meniscus is absolutely perfect.

47:52

It is the attachment that's gone.

47:55

So sometimes it's very important,

47:57

especially from a therapeutic aspect to differentiate

48:00

what is a pure ligament tear,

48:03

what's a pure meniscal tear and what's both.

48:07

And then we also have the normal attachments

48:09

that you've already seen on the lateral side.

48:12

So this is a particularly informative and instructive case.

48:15

So here's a patient that's had a pivot shift injury.

48:19

The tibia translates anteriorly

48:21

and puts a, puts a pretty big

48:24

stress force on the meniscocapsular reflection.

48:26

So you bleed into the capsule,

48:28

you get this vertical ill-defined signal.

48:32

The posterior meniscal tibial ligament is no more.

48:35

We don't see it at all.

48:37

And this is referred to as a ramp one type injury.

48:41

We refer to these ramp injuries in the setting

48:43

of pivot shift injuries.

48:45

What are some other kinds of ramp injuries?

48:48

Well the one is when you tear the capsule

48:50

and you bleed into the capsule

48:52

and you get this funny looking serrated reflection

48:55

between the capsule and the meniscus.

48:57

A two partial tear upper surface, three partial tear,

49:01

lower surface four all the way up

49:04

and down five, two tears right next to each other.

49:07

So-called double tear.

49:09

So an example of a four would be this.

49:11

An example of a five would be this.

49:14

Pretty simple, but taking a little bit to memorize.

49:17

But, but who memorizes better than you Doctors.

49:20

You're the best memorizers on the planet

49:24

when NFL football players tell me

49:25

how great they are at sports.

49:28

I say, well that's fantastic,

49:29

but you know what, my guys, my docs, my colleagues

49:34

have some of the greatest minds in the world

49:35

and they can memorize entire textbooks in a month or two.

49:39

How's that for athletic capability? And it's true.

49:42

So here's a sagittal projection demonstrating

49:46

a full depth ramp four abnormality,

49:48

just like that right there.

49:49

Had there been another one next to it,

49:52

it would've been a ramp five.

49:56

And we do have to pay pretty close attention to these

49:58

because they can result in detachments

50:00

and they can result in osteoarthritis.

50:03

If left completely unchecked, when they are higher grade,

50:06

the lower grade ones will heal on their own.

50:09

So here is an example of a higher grade one

50:12

that did not heal on its own.

50:13

It's a meniscal capsular separation.

50:16

When do I use the term separation?

50:18

When I have meniscal migration?

50:21

About 30 years ago, one of our esteemed MSK colleagues, uh,

50:25

reported that an eight millimeter distance was required

50:28

to diagnose meniscocapsular separation between here

50:31

and the edge of the tibia.

50:33

That turned out not to be true,

50:35

but when you have, you know, a centimeter

50:37

and a half, two centimeters and blood in this space

50:40

and the meniscus is clearly forward

50:42

and you have displacement, you have

50:44

a meniscal capsular separation.

50:47

And this requires an operation.

50:51

So what contributes to making a meniscal tear Unstable?

50:55

Because most meniscal tears should really be left alone

50:58

cleavage tears, leave them alone.

51:01

Vertical tears in the red red zone

51:02

with a, with a pivot shift.

51:04

Leave it alone.

51:07

When do you start getting nervous about terrors?

51:10

When they're really long? Over four centimeters when there's

51:13

gapping or separation.

51:14

Folding displacement or detachment.

51:17

Full depth, you know, superior

51:18

to inferior when it involves the inner third,

51:20

the middle third and the outer third when there's migration

51:24

as in meniscal capsular separation

51:26

or the knee is locking from your meniscal pathology

51:29

and you can correlate the exam with the MR findings.

51:33

Here's an axial T two. What's that?

51:35

The strangler shaped structure.

51:37

It's a meniscus that has been spit out.

51:40

There's been a root rupture, a trigonal radial root rupture,

51:44

and that's allowed the meniscus

51:45

to migrate out into the periphery, into the tibial gutter,

51:49

creating this little comma right here.

51:51

The so-called meniscal commas sign

51:53

of a lateral meniscus tear with an extrusion.

51:56

And the ACL by the way is truncated right there.

51:58

It's also torn. There's another example of an unstable tear.

52:02

It should have looked like this in the axial projection.

52:04

Now it looks like that is completely ripped off.

52:07

Its peripheral RIA attachments,

52:09

which you now have learned about ad nausea.

52:13

Let's look at some other tears. There is a vertical tear.

52:16

It's full depth. It's in the red, red zone.

52:20

What I operate on this tear.

52:22

If it's not gapped, absolutely not.

52:24

Here's another tear, a horizontal cleavage tear.

52:26

Let's say this in a 70 year old,

52:28

would I operate on this tear?

52:30

Absolutely not. What would make me operate on it?

52:33

If it started to split apart, if there's a big, big cyst

52:36

inside it, if it folded over on itself within maybe,

52:40

but cleavage tears, you really can't do much

52:42

with your sewing machine to show them back together.

52:45

So here are some of our tears. We said vertical tears.

52:48

There are three kinds. There's the radial,

52:50

there's the longitudinal,

52:52

and then there is the bucket handle tear.

52:54

The longitudinal is in the outer third,

52:56

the bucket handle is in the middle third and it widens.

52:59

We've also got the curved flap tear.

53:01

When you have a little flap tear in the ant lateral body

53:04

horn junction, we call that a parrot beak tear.

53:06

Sometimes flap tears will fold over on themselves

53:09

and I think that's enough on shape.

53:12

Now the meniscus, when you image it in the coronal

53:14

projection, should not make a tongue all the way on

53:19

to the tibial tubercle for more than one cut.

53:21

So if you see that tongue sitting on the tibial spine

53:25

for more than one cut, and this was,

53:28

you should be worried about discoid meniscus,

53:31

what else should prompt you to be worried about it?

53:34

If the femoral condyle is not as distal

53:38

as the opposite femoral condyle,

53:40

or if you have a giant large fibular head,

53:43

so-called fibular dysplasia.

53:45

So any kind of thermal dysplasia, any kind

53:48

of tibial dysplasia, any kind

53:50

of fibular dysplasia should make you conjure up the

53:54

diagnosis of discoid lateral meniscus or variant thereof.

53:58

Any signal that occurs outside

54:00

of the outer third in a discoid meniscus is a tear.

54:04

What do you do about it? Nothing until it ruptures.

54:07

This patient had locking, our hand was forced.

54:10

This was coming apart back together.

54:12

Coming apart back together.

54:14

We know that from the physical exam there was

54:16

audible clunking.

54:18

The meniscus looked pretty good from the outside.

54:21

At first glance it was convex upward,

54:24

but when we took it out and put it on the table, we had

54:26

to do a total menisectomy.

54:28

It kind of fell apart into two pieces. Meniscal flu.

54:34

We have spoken about the anchoring

54:36

of the meniscii peripherally

54:37

and we said that the inner tip is free.

54:40

Sometimes when synovium accumulates it'll push the tip up.

54:44

It may even blunt the tip.

54:45

So the tip will look something like this.

54:48

The tip will get a little crinkly

54:51

and it looks a little bit truncated

54:53

and you may make the false diagnosis of a radial tear.

54:57

This is a particularly common mistake.

55:00

Another important type of tear that's associated

55:03

with pivot shift injuries is the wrist berg rip type tear.

55:07

Here's the meniscal femoral ligament of wrist berg,

55:09

which arises from the posterior lateral horn,

55:13

not the root the horn.

55:15

In a pivot shift, you may

55:18

propagate this weak area laterally.

55:22

And when that happens, you have what's known

55:23

as the berg rip.

55:26

When you image it, Sally,

55:29

it will look something like this.

55:32

You'll see this curva linear interface

55:33

between wrist, berg, and meniscus.

55:35

Now you're allowed to see that on one cut,

55:38

but you're not allowed to see it on

55:39

2, 3, 4, 5 different cuts.

55:42

And it'll continue to get smaller and smaller and smaller

55:45

or bigger and bigger and bigger depending upon

55:47

what direction you're going in.

55:48

Let's ignore these other berg type of injuries,

55:51

which are described beautifully in the Thompson article from

55:55

Radiographics, the complete radial tear

55:57

and the meniscus On a string sign we have a radial tear

56:02

that spares the meniscal femoral ligament of wrist berg.

56:05

It displaces. And now you have the meniscus on a

56:08

wrist berg string.

56:12

There's an example of a wrist berg tear.

56:15

I don't mind that The meniscus femoral ligament

56:17

of wrist berg is separated

56:20

by a cleavage plane from the lateral meniscus root.

56:23

Now I mind, I don't like the looks of this.

56:26

It's too thick, it's getting bigger,

56:28

it's getting more conspicuous.

56:29

It should be getting less conspicuous

56:32

as I go from the root to the body.

56:35

And here we are again, more conspicuous berg

56:40

meniscus tear, berg meniscus tear.

56:45

And now it changes direction

56:47

because we're not looking at the tear anymore.

56:49

We're looking at the pop reflection.

56:52

Another type of tear is the vertical outer third tear.

56:55

Yeah, they can be a little bit oblique.

56:56

I don't mind, I leave those alone.

57:00

They're frequently associated with pivot shift injuries.

57:02

This one is how do we know

57:05

terminal sulcus injury Poster lateral tibial injury.

57:08

The ACL is injured or torn. It was torn.

57:12

There's another one, an oblique tear, also known

57:14

as a flap tear.

57:15

They can be pretty big and sometimes they're

57:18

so big they allow the upper border

57:21

or the upper surface to flop over on itself.

57:24

And that's exactly what's happened here.

57:26

It's flopping over on itself

57:28

and sometimes it can flop over on itself as a fragment

57:31

that is caught in the back of the knee

57:34

and very hard to retrieve, uh,

57:36

clinically with the arthroscope.

57:37

So mapping that out

57:39

for the clinician is incredibly important.

57:41

The radial tear, it's one

57:43

of the three types of vertical tears.

57:45

It's like the spokes of a wheel. They're small.

57:49

What's important depth?

57:50

Is it in the inner third, middle third or outer third?

57:53

In other words, is it in all three thirds?

57:56

You do not get an isolated radial tear in the outer third.

57:59

That does not happen. Do not use that descriptor.

58:03

But the ones that are worse are the ones that go

58:06

through all three thirds.

58:08

The ones that are worse are the ones that have a fair amount

58:11

of gapping at their base.

58:14

8, 10, 12, 16 millimeters of gapping.

58:18

So that's how you decide whether you're going

58:21

to intervene upon a radial tear in concert

58:23

with clicking and locking.

58:25

It used to be said that every radial tear needs to be fixed.

58:29

I, I think the orthopedic community has migrated away from

58:32

that particular statement.

58:35

In the sagittal projection.

58:36

When you perform anterior to posterior sagittal projection,

58:41

sorry, when you perform the anterior

58:43

to posterior sagittal projection,

58:44

it'll look something like this.

58:46

You'll volume average the free edge of the radial tear.

58:48

And here you've done just that. You've volume average.

58:51

The free edge of the meniscus.

58:54

Now very similar looking to the radial tear, but smaller

58:58

and having a predilection for the anterolateral body.

59:02

Horn junction is this little nubbin of a tear.

59:04

The parrot beak tear,

59:06

it's a lot like a flap tear but much smaller.

59:09

As stated, it likes the anterolateral body horn junction

59:12

and it has this sort of cur later look.

59:14

There is the snout of the parrott pointing in the opposite

59:17

direction as the diagram.

59:19

But so what, um, it gives you the,

59:21

it gives you the right idea.

59:23

It's a slightly curved tear. It's an inner third tear.

59:26

It has this little snout like curved characteristic.

59:30

And finally, the bucket handle tear.

59:32

It's a vertical central third tear that then does origami.

59:36

It widens, it creates a huge space.

59:40

So when you perform your coronal projection,

59:43

let's say you start over here and then here and then here.

59:46

And then here you have meniscus, a giant hole

59:50

and then meniscus.

59:51

Now if you get all the way out front,

59:53

it'll come back together again.

59:54

But sometimes that bucket will rupture all the way

59:57

through the front and then you have a free fragment

60:00

and sometimes it'll rupture all the way out the back too.

60:02

Then you have a real free fragment

60:04

where the whole thing floats all the way into the knee

60:07

and has to be retrieved.

60:09

But here is how you infer a bucket Hale tear.

60:12

You look at the medium meniscus and you say, ah, too small.

60:16

Why is a meniscus too small in a young person?

60:18

Bucket handle, tear number one on your list.

60:21

Number two, radial tear. Number three, trimmed.

60:25

Number four, meniscocapsular inflammation from synovitis

60:30

due to rheumatoid arthritis.

60:32

Those would be some of the more common causes of a small

60:35

blunted meniscus.

60:36

And of course trimming.

60:38

This one is a virgin knee, never been trimmed.

60:41

We see the double PCL sign of a bucket handle tear.

60:45

We'll see how we get there in a moment.

60:47

We have fragment, we have a hole, we have fragment,

60:50

we have fragment, we have a hole, and we have fragment.

60:53

We have fragment, a hole in fragment.

60:55

And the same thing here.

60:57

Now, word of caution, couple pitfalls. First pitfall.

61:03

The lateral meniscus is very CS shaped.

61:05

And for those patients that have a very tight, tight C,

61:09

when you do your coronal, sometimes you will see meniscus,

61:13

then a hole right there.

61:15

And then a meniscus that is just the normal curvature.

61:19

How do you tell that from a real tear?

61:21

It's only present on one cut.

61:24

It doesn't persist slice after slice after slice.

61:28

Second pitfall, the PCL has a

61:32

very complex attachment.

61:33

It's footprint is divided into 13 zones.

61:37

One of those zones consists of the distal attachment

61:42

as part of the humphrey ligament mechanism.

61:45

And there it is right there. Look at

61:47

how close in proximity it is to the inner tip of the bucket.

61:51

You can appreciate how some

61:53

untrained observers might confuse that.

61:56

And that with a bucket handle fragment.

61:58

So two pitfalls of the bucket handle tear.

62:01

And I'm going to skip over this example

62:03

of an uls displaced bucket and stop right there.

62:07

I think we've looked mostly at non-experimental data

62:11

and given you as much information as we possibly can, uh,

62:15

to start your journey in MRI of the knee.

62:18

And don't forget, this is Black Friday.

62:21

So if you like what you hear on MRI online,

62:24

don't forget to pay us a visit.

62:25

Happy holiday to all questions.

62:31

Chat. All

62:33

Right, Dr. BI see a few in

62:34

the q and a feature for you QA.

62:36

All right. Any tips for distinguishing

62:41

tears with calcinosis in the meniscus?

62:43

Great question. Uh, yes.

62:47

Um, unfortunately, you know, when you think

62:49

of chondro calcinosis, you think of calcium.

62:52

So are you gonna see calcium against a

62:54

background of a black meniscus?

62:55

You're not. But when you see this razor thin,

62:59

very consistent cleavage type signal,

63:02

and then you have inflammation that kind of bays around it,

63:06

that's disproportionate to, to the, to the characteristics

63:10

of the tear, you,

63:11

you should then think about chondro calcinosis.

63:13

Go right to the cartilage, inspect the cartilage

63:17

and look for that interstitial, uh,

63:20

middle layer hypo intensity.

63:22

And if you're not sure, ask for bilateral knee radiographs.

63:26

How do I differentiate non kissing

63:27

and kissing contusions from edema?

63:31

Well, one, one way is the history.

63:33

You know, if a patient has had a traumatic event,

63:36

then then you're, you're going to call them contusions.

63:39

Now, a edema is a generalized term. Contusions are edema.

63:44

You can get edema from, you can get edema from a tumor,

63:47

you can get edema from trauma.

63:49

You can get edema from infection.

63:51

So edema is a more generalized term.

63:53

A contusion is something whose term you use when you have no

63:57

linearity, you have a history of trauma

64:00

and you can discern a mechanism of injury.

64:04

Thank you for the compliment.

64:05

I appreciate, appreciate that from Dr. Morris. Um, Dr.

64:09

Sadicki, uh, can you show the anatomy

64:11

of muscles on the backside of the knee?

64:14

Um, I'm not sure how to do that. I'll tell you what.

64:19

If you send us your email, Dr.

64:22

Sidiki, we will, I'll send you some anatomic examples

64:26

of the muscularity on the backside of the knee

64:29

and some snapshots from our atlas, total body Atlas and MRI,

64:33

and that should help you.

64:34

It's pretty hard to, uh, do that,

64:37

um, in, in this forum.

64:39

How do you, how do you measure the TTTG ratio?

64:44

Well, here's how you do it.

64:46

Um, let's see if my pointer will work.

64:51

So you have the, the trochlear groove. You got that.

64:56

And then you, you, you start scrolling down

65:00

and you, you put a little.here

65:01

and you leave your dot there on your, on your mr.

65:04

And you start scrolling down to your tibia.

65:06

And when you get to your tibia, you get to your,

65:08

your tibial tubercle.

65:10

Let's say your tubercle is over here, let not over here.

65:13

Let's erase that. Now.

65:18

You've kept your little dot right there. As you scroll down.

65:23

And now you measure this distance right here.

65:26

You measure that distance.

65:27

Let's say that distance is 1.5, that's an abnormal

65:31

TTTG relationship.

65:34

So that is how you do it.

65:35

You look at the, the, the deepest part

65:37

of the trochlear groove in the tibial tubercle,

65:39

and you see how malaligned they are medial

65:42

to lateral one to the other.

65:45

What is the benefit of axial thin slices in the meniscus?

65:48

Um, it's got moderate benefit.

65:51

You know, in some cases, when you have decent sized tears,

65:54

it doesn't add a heck of a lot.

65:56

But when you have to map out the anatomy of a tear

65:58

for a clinician when they're deciding,

66:01

do I have displacement, do I have gapping,

66:04

do I have folding?

66:05

Where do I go to find the fragment?

66:07

Axial thin slices can be helpful.

66:09

They're also incredibly, uh,

66:12

enticing when you're in academic medicine and you wanna show

66:15

and teach the architecture of a tear, I think that's,

66:19

that's probably as big a benefit as it is clinically.

66:22

How do you tell hypoxic ACL degeneration?

66:27

I'm not sure that I can answer that question

66:30

hypoxic ACL degeneration.

66:32

But I will say this.

66:34

When you see a swollen ACL without trauma,

66:39

there aren't that many things that can do it.

66:42

Here are the things that you should think about,

66:45

not stenosis with impingement.

66:48

Femoral tibial shift from osteoarthritis,

66:50

with impingement from tibial spines,

66:55

inflammatory synovial processes, tears

66:59

of the ACL sheath.

67:03

Remember though, there's been no trauma.

67:04

So those tears would've had

67:05

to occur in some time in the distant past.

67:08

And then finally, uh,

67:11

crystalline deposition disease, namely gout.

67:14

So those are the things that should really cross your mind

67:16

and be on your checklist for a diffusely swollen gray, ACL.

67:22

Let's see. I think that concludes, um,

67:26

our list of questions.

67:28

With that, I will wish you all a great

67:30

Thanksgiving and a happy holiday.

67:32

Appreciate MRI online having me.

67:36

Thank you Dr. Pomerance, for your amazing lecture today.

67:39

And for everyone else for participating

67:41

in this noon conference.

67:42

Those are some awesome questions.

67:44

You can access the recording

67:46

of today's conference in all our previous noom conferences

67:48

by creating a free MRI online account.

67:51

And be sure to join us next week on Thursday,

67:54

November 30th at 12:00 PM Eastern for a case review.

67:58

Live entitled Anatomy

68:00

and Pathophysiology of the Forefoot, with Dr.

68:02

Jan Jonathan Samit.

68:04

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68:07

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68:08

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68:10

Thanks again. Have a great day.