0:00

Now the differential diagnosis when you see cystic lesions

0:04

back here, uh, is mainly around, uh, the issues

0:07

of ganglia or buri.

0:09

Uh, in this patient here, we have

0:12

a ganglion along the medial side of the knee.

0:15

It's more multi lod, uh, than a typical, uh, baker cyst.

0:20

Does it communicate with it?

0:22

I don't know exactly in this case,

0:24

but when you see these in general, the most commonplace

0:28

that we see these arising from is from the medial head

0:32

of the gastroc anemias from the little recess underneath it,

0:35

but a variety of burs I can be seen in this area.

0:39

We can get semimembranosus bursitis, PEs anine bursitis,

0:43

or even meniscal cysts that dissect out of the joint.

0:47

And I can tell you that sometimes it's difficult

0:50

to sort these out.

0:51

This is a patient with semi menos bursitis in addition

0:55

to the standard baker cyst.

0:57

It's following the course of the semimembranosus.

1:01

The semimembranosus in this case has a lot of tendinosis

1:05

and low grade partial tearing with splitting of fibers

1:08

and cystic changes at its osseous, uh, insertion.

1:12

And I, I really have never been able

1:14

to find a really great reference outlining the different

1:18

potential communications

1:20

between these medial fluid collections, uh,

1:23

that we have to deal with.

1:24

This is a constant bursa that we see.

1:28

Um, and, uh, in this case it looked like they were, uh,

1:31

communicating, but again, that's very difficult

1:33

to prove without actually injecting one of them

1:36

and seeing if there is a communication.

1:39

This is pe anine bursitis.

1:41

This is generally gonna be located below the joint line

1:45

anterior to the semimembranosus bursa.

1:48

So here we're seeing the semimembranosus bursa,

1:50

and this is the PEs anserine bursa intimate with the gci,

1:56

sartorious and semi tendinosis tendons.

1:59

Now, it's supposed to be deep to them,

2:01

but I'll tell you, a lot

2:02

of times it winds up just wrapping all around the tendons

2:06

and it can be deep

2:07

and superficial as we see in this particular patient.

2:11

This can be painful

2:13

and, uh, can be treated, uh, with, uh, steroid uh,

2:17

injections if it's symptomatic.

2:19

So this is a pean, uh, bursitis. Here's another one.

2:23

In this case, it's staying deep to the tendons

2:26

and behaving more like a normal pean,

2:29

but notice that it's quite a bit more distal, uh, than

2:32

where we typically are gonna see pesan, uh,

2:36

semiosis bursitis

2:38

and much more anterior than where you would expect to see.

2:42

Um, the, uh, uh, standard, uh, baker's, uh,

2:47

cyst at the back of the knee.

2:50

This is the ganglion cyst

2:52

that I see most frequently at the post medial knee.

2:55

It can also occur laterally, and this is a cyst that

2:59

Communicates with the recess

3:01

below the medial gastroc anemia insertion.

3:04

Uh, David Connell was, this is the first article I'm aware

3:09

of describing these,

3:10

and in their small series,

3:12

it was equally common medially and laterally.

3:15

But in my experience,

3:17

I see these more frequently at the medial side of the joint,

3:21

and these are usually managed, uh, conservatively.

3:25

In fact, a lot of times we see them

3:26

and I'm not convinced that they have any association

3:29

with any symptomatology.

3:31

Now, one thing we should always be careful

3:33

of when we see a cyst is to not forget to look

3:38

for a meniscal tear,

3:39

because cysts from meniscal tears can dissect a long

3:44

distance from the tear, especially at the medial side

3:47

where the capsule is very tight.

3:49

And the fluid can track both towards the posterior

3:54

as well as towards the medial knee

3:56

and present as a mass inside

3:59

or outside the capsule at a distance from that tear.

4:03

So anytime I see anything that isn't in the classic location

4:07

between the gastroc anemia

4:10

and semi menos, then I also go

4:13

and look carefully to see if there's any tear extending

4:17

to the capsule of the medial meniscus

4:20

that might be allowing fluid, uh, to track.

4:23

And, uh, you saw several of these, uh,

4:26

earlier in the course.

4:28

Uh, here's just another example. They can be very large.

4:31

This one had dissected from the meniscus to present

4:36

behind the posterior cruciate uh, ligament.

4:39

And, uh, many years ago Don wrote this interesting paper

4:43

just talking about how easy it is to confuse, uh,

4:48

uh, meniscal cysts with posterior cruciate ganglia.

4:52

And in their series, a significant number

4:54

of these when you followed them, were able to be followed

4:58

directly into a tear, uh, at the posterior horn

5:02

of the medial, uh, meniscus.

5:05

Just for completeness, I'll show a couple of, uh, tumors.

5:08

Uh, this was a synovial sarcoma.

5:11

We all know that this can be quite cystic,

5:13

though on the contrast study, you can see

5:15

that there are quite a lot of, uh, solid,

5:18

uh, components to it.

5:19

It's very heterogeneous,

5:21

and I don't think anybody is going to confuse this.

5:24

Uh, with a baker cyst, first of all, it's, it's lateral

5:27

and the, remember the name is a bit of a misnomer.

5:30

Uh, it has a lot of, uh, components in it.

5:34

In fact, it's not a true synovial uh, neoplasm at all.

5:38

But these are generally gonna be extra articular with some,

5:42

uh, solid, uh, components.