0:00

So the first major structure as we move from front to back

0:03

as we encounter the poster lateral corner is the FCL.

0:07

And it's usually comprised

0:09

of a dark signal intensity structure.

0:11

I want to emphasize

0:13

that superiorly at the femoral attachment near the femoral

0:15

epicon, it does have a slightly thicker appearance.

0:18

So you don't necessarily mistake that for pathology.

0:22

I know a lot of residents when they're first,

0:23

first looking at MRI wanna call, uh, sprains

0:26

or partial tears in the proximal FCL when it's really quite

0:30

normal to be thick and superiorly.

0:32

As we move more posteriorly,

0:33

we'll encounter two other critical structures,

0:35

the pope tendon as it emerges from this pope groove

0:39

of the distal femur

0:41

and the biceps fems tendon inserting on the peripheral

0:43

lateral aspect of the fibular head.

0:47

And again, we can move from front to back.

0:49

We'll see the ant lateral ligament, first part

0:52

of the ant lateral complex,

0:53

and then the fibular co later ligament,

0:55

which a thickened superior attachment.

0:57

And finally, the biceps remus and pilla tendon.

1:03

We can also visualize as well on sagal images.

1:06

Uh, some people refer to this as kind of the bunny ear sign

1:10

where you see the fibular collateral ligament in front

1:12

and the biceps emus coming in from behind

1:15

forming a conjoin tendon at the periphery

1:18

of the fibular head.

1:20

And as we move more centrally, we'll encounter

1:22

yet another structure

1:23

that comprises the poster lateral corner,

1:26

and that is the popliteal fibular ligament.

1:28

The landmark for identifying this ligament is the fibular

1:31

syl, and you'll see often these low signal intensity

1:35

collagen fibers extending from that fibular styloid

1:38

to the pope tendon.

1:40

Also note at this level,

1:41

you'll also encounter the popal meniscal ligaments.

1:45

Here we can see the anter inferior popal meniscal ligament

1:48

and the posterior superior popal fibular ligament,

1:51

both important for stabilizing posterior horn

1:53

and lateral meniscus and the pope tendon.

1:58

So when I look at axial images, I try to look

2:00

for these big three structures, FCL, biceps Es,

2:04

and pope tendon.

2:06

So as we scroll from superior to inferior,

2:09

we'll find a lateral femoral epicondyle

2:12

and we'll find that fibular

2:14

or lateral collateral ligament attaching to that,

2:17

uh, epicondyle.

2:19

And we wanna make sure that we follow it inferiorly all the

2:21

way to its insertion on the fibula.

2:24

And I want you to observe,

2:25

as you see this going towards the fibula, you'll notice

2:27

that it interdigitates with the biceps femoris

2:31

and we'll talk about that in more detail of course.

2:35

Also, you wanna look for the papa's tendon

2:39

as it emerges from that fibular groove,

2:41

or excuse me, from that femoral groove that papa teal groove

2:44

and exiting the joint

2:46

and extending to the posterior aspect of the proximal tibia.

2:51

So what does injury look like?

2:53

Well, similar to things

2:55

that we might look at on the medial side

2:57

of the knee, we wanna look for

2:59

Intra ligamentous edema, ligament thickening,

3:03

and per ligaments edema.

3:04

Here with this patient with at least a moderate grade

3:06

injury, at least 50%

3:08

of the ligament thickness approximately, you can see, uh,

3:11

the high signal edema within the ligament along its deep

3:14

and mid portions

3:15

with a relatively more normal superficial portion.

3:21

We used to read for the then San Diego

3:23

Chargers back in the day.

3:25

As many of you know, they have relocated since

3:27

to, uh, Los Angeles.

3:29

But here's, uh, an example

3:30

of a poster lateral corner injury.

3:32

This patient, uh, taking a direct blow to the knee, so sort

3:35

of a hyperextension injury.

3:36

So you're already thinking your head, what kind

3:39

of injuries would I be looking for?

3:41

That would include maybe a posterior capsular injury,

3:44

posterior cruciate ligament ligament injury,

3:47

and maybe poster lateral or poster medial injury.

3:50

So here's the corresponding MRI.

3:52

In this patient, not only did they tear their PCL

3:55

as you can see here, but also toward their ACL

3:57

at its tibial footprint.

3:59

Um, you can see that the pope's tendon is actually

4:02

completely uls from the pope groove of the distal femur.

4:06

You can see this wavy antola ligament here

4:09

uls from its femoral attachment.

4:12

And uh, here's just some more, uh, c images, uh,

4:15

through this knee where you can see the whole host

4:17

of structures that have been injured.

4:19

So bi cruciate ligament injury,

4:21

but I really want to focus on the

4:22

lateral supporting structures.

4:23

This redundant antral lateral ligament vols from its

4:27

fibular femoral attachment.

4:28

The Pope is also torn off.

4:30

And as we go more posteriorly, we notice

4:33

that the biceps femoris too is a vols from

4:36

its osseous footprint.

4:37

So this is a high grade injury of the poster lateral corner.

4:41

And likewise, we want to make sure

4:43

that we look at it its entirety.

4:45

In other planes, we follow the fibular collateral

4:47

ligament inferiorly.

4:50

We see that we actually can't visualize it very well at all.

4:52

And if we go back to our sagal images,

4:55

really not seen very well at all.

4:57

So this is a complete tear

4:58

of the fibular collateral ligament.

5:00

The pop sees tendon, uh, is vols from the distal femur.

5:04

And again, if we follow the biceps fems down, we'll see

5:07

that it just basically disappears

5:09

and never attaches to the proximal fibula.