0:00

Now let's look at the other things that we need

0:02

to look at in the poile fossa.

0:04

We have lymph nodes.

0:05

Uh, we have nerves, and we have the vascular structures.

0:09

Just a couple of words about the lymph nodes.

0:12

Everybody has these, they involute with aging.

0:15

So when you're looking at children, you're more likely

0:18

to see them, but you'll often see them With adults,

0:21

there's typically six to seven popliteal lymph nodes,

0:25

and they are generally located at

0:28

and above the joint line between the popliteal artery

0:31

and the posterior knee capsule.

0:33

So these are quite distinctive, uh, looking.

0:37

And when they're kidney shaped

0:40

or you can see a fatty highli, uh,

0:42

then you can be very confident that you're dealing,

0:45

uh, with a lymph node.

0:46

So they tend to have a speckled, uh, appearance.

0:49

And here's in a child, multiple lymph nodes.

0:53

These are normal. Uh, this is in an adult.

0:55

This is usually the last lymph node to involute.

0:58

This is usually where you're gonna see it is anterior

1:02

to the popliteal artery above the joint line,

1:05

behind the femur.

1:06

Notice here you can see that there's a fat,

1:08

uh, within the lesion.

1:10

It's got a speckled appearance.

1:11

That is a typical for a lymph node.

1:14

In fact, when you look for lymph nodes in, even in adults,

1:18

you will see them in about 40% of patients.

1:22

That incidence is much higher, of course,

1:24

in the young child,

1:25

and then declines, uh, with the patient age.

1:29

Here's just another one, again, that's speckled appearance.

1:33

Notice the fat within it,

1:35

nicely shown on the axial immediately in front of the, uh,

1:39

popliteal artery.

1:40

And I'm gonna discuss this structure later, which is, uh,

1:45

a vessel that comes from the popliteal artery.

1:47

It's the middle ICT that perforates the capsule,

1:50

but this is, uh, just, uh, we're gonna look at this later,

1:54

but this is one of the pathways by which disease

1:57

inside the joint can dissect out of the capsule

2:00

into the popliteal, uh, fossa.

2:06

You can see reactive, uh, lymphadenopathy.

2:09

This is a large, uh, enlarged, uh, lymph node,

2:13

uh, in a teenager.

2:14

This particular child, it was the son of one

2:18

of our orthopedic, uh, surgeons, actually.

2:21

Um, he did not undergo any surgery at this point here.

2:24

He had, uh, serious flu-like illness.

2:28

And I was told by the dad that this had involuted

2:32

spontaneously on an outside Mr.

2:34

Done later, which I don't have access to.

2:37

But I wanted to just point this out,

2:39

that this is what's published in the literature as

2:42

maximal size for lymph nodes.

2:45

And that if they're bigger than this,

2:46

that you should probably report them, uh,

2:48

on your, on your mr.

2:50

They can be reactive to anything.

2:53

Uh, often I see them reactive.

2:55

Certainly in patients with septic arthritis, with rheumatoid

2:59

Arthritis, even post knee arthroplasty.

3:01

You may get some reactive, uh, lymphadenopathy.

3:05

Uh, this is an example of a reactive lymph node in a patient

3:08

that had a septic knee.

3:10

Uh, this is a patient that had had a knee arthroplasty,

3:14

and this is presumably a response to some sort of, uh,

3:18

foreign body material or to infection.

3:21

Uh, both of those can lead to, uh, lymphadenopathy in, uh,

3:25

patients, uh, who have, uh, knee arthroplasty.

3:28

So it does not signal this patient had an infection, sorry.

3:31

But it does not necessarily mean that there's infection.

3:35

Uh, it may be just due to, due to wear of, uh, polyethylene,

3:40

uh, components or metal debris, uh,

3:42

from the knee joint leading to this.

3:45

Now, in terms of malignant lymphadenopathy, again,

3:49

we do sentinel lymph node mapping for staging of,

3:53

uh, malignancies.

3:54

Um, fortunately there are very few malignancies that we have

3:57

to deal with that are below the knee joint.

4:00

Uh, this was a patient who had a, uh, malignant desmoid,

4:05

uh, tumor, uh,

4:06

who had developed a proximal uh, lymphadenopathy.

4:11

But usually this, uh, this type of staging, uh, is going

4:15

to be done, uh, at least at our institution.

4:17

We typically use PET for staging of the lymph nodes, just,

4:22

uh, for completion of understanding, uh, the anatomy here.

4:26

This is an old case showing some malignant lymphadenopathy.

4:29

I don't remember what the original sarcoma was over here,

4:32

but there's a several lymph node, uh, pathways along the leg

4:36

that run along the greater saphenous and lesser saphenous.

4:41

And if you are interested in this, this is a great article

4:45

by koa, uh, showing you, uh,

4:49

the lymph node mapping that they did.

4:51

And I think the important, uh, features really is

4:54

to remember that the majority of foot tumors do not go

4:58

to the popliteal fossa.

5:01

The only ones that actually went

5:02

to the popliteal fossa were along the heel, the lateral side

5:06

of the heel, everything else on the foot, the dorsum

5:10

and medial side actually drains to the inguinal bed.

5:13

So it's not that common

5:15

unless you have a frank heel sarcoma

5:18

that you're gonna see anything, uh, in the,

5:20

in the popliteal fasa.

5:22

So remember that posterolateral foot is really the area

5:25

that you wanna worry about in terms of the popliteal nodes.