0:00

So now moving on to the poster lateral corner.

0:04

Now this is a whole complex of structures

0:07

which include primarily when we think about it,

0:10

the fibular collateral ligament,

0:11

or sometimes referred to as the lateral collateral ligament,

0:15

the biceps femoral tendon,

0:17

and the Pope ts tendon and muscle.

0:20

So those historically in the literature have been regarded

0:23

as the major three structures

0:25

that comprise the poster lateral corner of the knee.

0:29

But of course, there's more

0:30

structures and we'll get into these.

0:33

So as far as clinical testing of the poster lateral corner,

0:37

uh, I'll show you how these are done,

0:39

but these are examined using the dial test as well

0:42

as obviously Vera stress testing.

0:43

Similar to valgus stress testing for the medial aspect,

0:46

the knee and injury

0:49

to the poster lateral corner can result in

0:51

rotational instability.

0:53

And it's really important that we recognize these

0:55

because if these are not formally, um, repaired,

0:59

this can lead to failure of an ACL reconstruction.

1:03

So surgical repair is often needed in those cases.

1:08

It's important to notice that poster lateral, uh,

1:10

fat pet edema overall has a low specificity, um,

1:13

for postal lateral corner instability.

1:16

So don't use edema in of itself to, uh, be diagnostic

1:20

for a clinically important poster later.

1:23

Coronary injury. So here's just an example

1:25

where we see some edema about the poster later corner.

1:27

We can identify the fib, collateral ligament,

1:29

the bicep sms, and the P CS seven.

1:31

We see some edema, but we do need to investigate further.

1:37

So here's, uh,

1:38

what posterial out corner injury might look like.

1:40

I don't actually have an example, um, uh, in a sports, uh,

1:45

athlete, but, uh, this is Gavin Lux who, um,

1:48

for his ACL during spring training.

1:51

You can see they're playing our home team, uh, the Padres.

1:55

And you can see that his, uh,

1:56

knee does buckle into Vari as he plants.

2:00

And, uh, although the, um, reports

2:03

that came out subsequently said that he had an ACL tear,

2:06

I wonder with this mechanism whether he also had a poster,

2:09

lateral coronary injury.

2:11

And when you examine the patient's clinically when they

2:13

walk, you can see they'll walk with a varus thrust gate.

2:16

So you can see that the knee similar

2:18

to Gavin Lux buckles into, uh, varus.

2:21

And also when the patients are being examined under

2:24

anesthesia, they'll check for varus instability

2:27

and WA similar grading scale break one, two,

2:30

and three as to the medial part of the knee.

2:33

And if you, uh, are a Dodgers fan, you'll know

2:35

that Gavin Lux was unable to play shortstop,

2:37

which is probably the most athletic position on the field

2:41

for baseball, and, uh, unfortunately had to, um,

2:44

play at second base.

2:46

So here's the dial test that I was alluding to earlier.

2:49

This is TE testing for rotatory instability

2:52

of the poster lateral corner.

2:54

And here this patient has a positive, uh,

2:56

dial test on the right side. And this refers to

2:58

Excessive external rotation compared

3:01

to the contralateral side as a control.

3:03

And if there's more than a 10 degree side

3:05

to side difference, then this is indicative

3:07

of a postal out corner injury.

3:10

Like many tests, these are often done in

3:12

various knee positions.

3:13

So that's done at 30 degrees of knee flexion

3:16

and about 90 degrees of knee flexion.

3:18

And what happens at 90 degrees, an intact posterior uh,

3:22

intact PCL should reduce the degree of external rotation

3:27

of the, um, lower extremity.

3:29

However, if you have combined PCL

3:32

and poster lateral corner injury, then you will see, uh,

3:35

an excessive dial test as well at the 90 degree position.