0:00

So let's look at some of the things that we can see here.

0:03

This is a list of, uh, the common masses,

0:07

uh, that we can see.

0:08

And by far the most common mass

0:10

that we get in the popliteal fossa is the, uh, baker cyst.

0:15

And for those of you that are interested in tumors

0:17

and masses, I will refer you to this article by Shaw, uh,

0:21

talking about the various masses

0:24

that can be in the popliteal fossa.

0:26

'cause I don't have time, uh, to show you all of these.

0:29

This is your typical baker cyst. You've all seen these.

0:32

Let's just remember the bony landmarks.

0:35

We should be behind the medial femoral condyle.

0:38

We have the medial tendon of the gastrocnemius, the me,

0:43

the tendon of the medial head of the gastroc anus on the

0:46

inside and the semimembranosus on the outside.

0:50

So those are the two landmarks.

0:52

And you wanna really be sure when you see a fluid collection

0:56

in here, that you are in the right place

0:58

to be diagnosing a popliteal cyst.

1:01

These are very common.

1:03

When people have fluid in their joint, it will frequently

1:06

be seen in the bursa as well,

1:09

because this communicates with the knee joint.

1:12

And it's been suggested

1:14

that small cysts like this are rarely symptomatic.

1:18

So I always look to see if there's leakage

1:21

because I think the presence of rupture, uh,

1:24

is much more significant 'cause that tends to be painful.

1:28

So here's another adult with the lot of arthrosis.

1:30

And, uh, with the effusion,

1:32

any pathology in the joint meniscal tear synovitis,

1:37

osteoarthrosis leading to a fusion,

1:39

can result in the development of a popliteal cyst.

1:44

That is not true about juvenile cysts.

1:47

Juvenile cysts are often isolated without underlying

1:51

joint pathology.

1:52

It's, uh, you can see in this child that we have a cyst

1:56

and we have no effusion within the articulation.

1:59

And interestingly, these juvenile cysts will often resorb

2:04

spontaneously and it's just recommended that they,

2:06

they be managed conservatively in adults.

2:09

You wanna look and try to see what the etiology is for

2:12

that fluid, uh, collecting.

2:14

So here in a specimen

2:17

and in a patient, you can see the landmarks of this, again,

2:21

the medial gastro anemia, tendon,

2:25

and semimembranosus tendon.

2:26

Notice that the neck is very thin.

2:28

It's slit like so it's longer top to bottom,

2:32

but it's very thin.

2:33

And I wanna point out this component.

2:36

When we talk about popliteal cysts, you have two components,

2:40

the gastroc anemia, semi menos versa, proper.

2:43

But there's also this thin component,

2:45

which is the sub gastroc anemia, versa bursa.

2:49

And you should, uh, differentiate these two

2:52

because this particular bursa, when it does rupture,

2:55

it often ruptures deep and ruptures intramuscular,

2:59

And it's a more difficult clinical diagnosis, uh, to make.

3:03

So let's take a look at that anatomy.

3:06

Again, there's the slit.

3:07

So this is a slit, like opening, very narrow medial

3:10

to lateral, but longer, uh, top to bottom.

3:14

The fluid that makes it

3:15

behind the tendon is in the gastroc anemia,

3:19

semimembranosus bursa proper.

3:21

This thin amount of fluid between the bone

3:25

and the tendons is in that sub gastrocnemius, uh, bursa.

3:30

You can get distension of one

3:32

or both of these regions in this patient.

3:36

We have bodies within the popliteal cyst.

3:39

This is really common and you even, you know,

3:42

when you get a small body that goes across,

3:45

they have the potential to keep growing in this space

3:48

and they often get stuck in there

3:50

and then they don't wind up coming back into the knee joint.

3:53

So as you're looking for bodies

3:55

and looking through the recesses of the knee, you want

3:58

to consider this as one of the recesses

4:01

that you're going to evaluate.

4:04

Here's that sub gastro anemia versa.

4:06

This is from a, uh, an article taken by, uh,

4:11

the messier showing you the tendon

4:14

and the sub gastrocnemius, uh, component.

4:18

I don't see bodies in this very frequently.

4:20

I see them much more frequently in the larger bursa located,

4:24

uh, more posteriorly.

4:27

So this patient has a massive, massive cyst.

4:30

Uh, uh, this was a patient with, uh,

4:32

juvenile inflammatory arthritis,

4:35

and you can see that the cyst is dissecting way

4:38

down into the calf.

4:39

So this is the popliteal cyst, proper dissecting.

4:43

And then here's the sub gastroc anemia,

4:45

aspera dissecting deep, uh, to the muscle.

4:48

So they have a little bit of a different course

4:51

and they have different symptomatology.

4:53

Uh, when they start, uh, start leaking,

4:58

sometimes the cyst will leak superior.

5:00

So don't forget about that.

5:01

About 10%

5:03

of cysts will have a proximal rather than a distal leakage.

5:07

And, you know, people forget that

5:09

and start thinking that this is post-traumatic,

5:12

uh, abnormalities.

5:13

But if you see a lot of streaky fluid here, again, you want

5:16

to go down and track it

5:18

and make sure that it's not just coming, uh,

5:20

from a popliteal cyst.

5:22

But again, remember, 90% are gonna leak distal,

5:25

the others are gonna leak, uh, proximal.