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Here's a 66-year-old woman

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with an awfully strange presentation

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of a PCL problem.

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Now, we've got both of her knees,

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which is fantastic.

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We've got her right knee and her left knee.

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And let's scroll the PCl on her right knee.

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As is often the case in adults,

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the PCL has a slightly hazy,

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smoky look to it because the sheath is often a

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little bit swollen, and it's pretty thick.

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The ACL and PCL share a common sheath,

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so I'm not at all disturbed by this sort of ill

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defined, heterogeneous signal in the PCL.

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Now,

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another character of the PCl which differs from

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the ACL is that the ACl tends to have

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a more parallel set of fibers,

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anteromedial and posterolateral bundles.

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So you have the AM and the Pl.

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The Am is about 70% of the restraint.

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The PL is about 30%.

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But in the PCL, we have the exact opposite.

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We've got an anterolateral and a posteromedial.

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And unlike the ACL,

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instead of them being parallel,

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they twist around each other almost

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like a braid of hair.

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And eventually, when you get up towards the femur,

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the PCl will often have a component that goes a

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little more distal part of the Humphrey ligament,

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and it may insert very far to create a broad,

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distant footprint along the

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anterior femoral condyle.

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Sometimes this footprint is misconstrued as a body

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or mass if you don't follow it back to the PCL.

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So because of this braided,

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tortuous course of the two bundles,

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anterolateral and postmedial,

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it's not common to really see an entrapped cyst.

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Now, I'm not a big fan of using the term ACl,

1:57

ganglion or mucoid degeneration.

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Unless I see a confluent area of water signal that

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I can actually spot on a T2 weighted image where

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I really have some proteinaceous cystic fluid.

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If it's just swollen,

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I tend to avoid the term mucoid degeneration

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or ganglion formation,

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and I'll simply refer to it as notch cinovitis or

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notch inflammation secondary to micro instability

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and or dysplasia of the knee notch.

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But when I really can wrap my arms around focal,

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well defined, etched high signal,

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that's when the term mucoid degeneration,

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muco cyst formation, ganglion formation,

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are permissible in my world.

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So let's look at the other knee, the left knee.

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Look at that PCl. That is really bizarre.

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Been doing this a long time.

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You don't see this very often.

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There is on this fat suppressed T2 weighted image,

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there is a. Actually, it's a fat suppressed PD.

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I apologize.

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There is a focal area of well defined signal

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right there that is within the pcl.

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But we're not done yet.

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Let's follow it.

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And right there,

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it exits the pcl and busts out

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into the posterior capsule.

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Now, here's a regular T2 without fat suppression,

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illustrating again that this is a heavily

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proteinaceous fluid containing abnormality.

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It's not just swelling,

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it's not just inflammation.

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It is a mass inside the posterior cruciate

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ligament and busting outside the

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posterior cruciate ligament.

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Now, what is this? Pathologically?

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Pathologically,

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if you give this to somebody with a microscope,

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they're going to call it a ganglion.

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It's going to be proteinaceous fluid with

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a fibrous rim around the outside.

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It's not going to be synovial line.

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So if you want to call it an intra ligamentous

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ganglion with extra ligamentous extension,

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that's fine.

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If you want to call it mucoid degeneration with a

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mucous cyst and extension beyond the ligament,

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that's fine.

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Calling a capsuler cyst or a capsule synovial

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cyst, that's not fine because, first of all,

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there's no synovitis.

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Patient doesn't have a lot of joint fluids.

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It doesn't have a lot of capsillitis.

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It's not lined by synovium,

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so that wouldn't be fine.

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And it has a different connotation.

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So this is an example of a highly unusual

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tcl there with mucous cyst formation,

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ganglion formation,

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intra substance with extra ligamentous

4:43

extension posteriorly.

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When you get these big cysts in the back,

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in the middle,

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you have to check on the popliteal vein and make

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sure there's no thrombosis. Let's move on,

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shall we?