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This is a 14-year-old female with a history of an

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injury three weeks ago,

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complaining of posterior knee pain.

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So, we start out with the axial.

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We're keeping with the same theme.

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This time, we do see our absolutely straight anterior

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cruciate ligament right there.

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So, that's what it should have

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looked like in the child.

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There's our PCL.

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So, this is going to be our medial side.

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This is going to be our MCL.

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Here's going to be our

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posterior oblique ligament of the knee.

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There's going to be our oblique posterior

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ligament, so called OPL, posteriorly.

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Here's our popliteus tendon coming around.

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Here's our fibular collateral ligament right here.

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And here's the lateral retinaculum.

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And here's the medial patellofemoral

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ligament coming back, which, by the way,

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looks a little irregular.

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Right here.

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We've also got an effusion,

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which we should absolutely not have

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in a 14-year-old.

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It should essentially be a dry joint.

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So, we know we don't have an ACL.

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We know we don't have a PCL.

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We know we don't have a major MCL.

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We know we don't have a major LCL,

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and we've got to find an answer for our fusion.

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So, let's do that.

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Let's stay with the same protocol.

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First thing I notice is the shape of the condyle,

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the shape of the tibia,

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and the presence of open growth

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plates in a 15-year-old,

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14-year-old.

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We've got this unusual looking thing which is

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quite similar to the anterolateral osteochondritis dissecans

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I showed you earlier.

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I said the most common site for osteochondritis dissecans

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is the lateral aspect of the medial femoral condyle.

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And indeed, we have one.

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Surrounding, it is not fluid.

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We know it's osteochondritis dissecans as opposed

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to the other kinds of osteochondral defects such

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as fresh osteochondral fracture

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or broad saucerized,

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irregular shaped chondromalacia

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because it's elliptical, it's fairly clean-looking.

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It's a juvenile with open growth plates.

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It's in the lateral aspect

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of the medial femoral condyle.

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It is not fluid.

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It's high signal, not fluid.

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This is reparative granulation tissue.

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We would see if there is proud

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hypertrophic bone here.

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There isn't.

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We would see if there's some cartilage loss here.

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There is a little cartilage loss overlying

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the osteochondritis dissecans,

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we'd see if it's unstable with fluid around it.

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There is not.

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And we would see if there are any loose bodies.

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There are not.

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So, we do have osteochondritis dessicans.

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Our ACL intact, our PCL intact.

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And unlike our prior case,

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our quadriceps and patellar tendons are perfect.

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So, let's go to the sagittal projection again

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and look at our menisci.

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Let's make it a little bigger.

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And lo and behold,

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we have an extra meniscus anteriorly.

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So, what's the differential diagnosis of that?

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It could be a weird hypertrophic transverse

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ligament of Winslow.

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That's really rare.

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That's about one and a half a million.

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So, that's not likely.

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There's not a lot of choices here.

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Could it be a piece of cartilage?

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It's possible, but it's kind of triangular,

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so it's a piece of meniscus.

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We said that in bucket handle tear,

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the meniscus may be a bit small.

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And the back,

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we've got a little truncation of the meniscus

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right here.

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It is a little bit small.

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Let's look at the coronal.

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And indeed,

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the medial meniscus is smaller

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than the lateral meniscus.

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Now, unlike our intermeniscal ligament,

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which went side to side directly like this,

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this abnormality,

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we go to the back,

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we have separation of the meniscus,

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and they come apart.

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And then, they're going to come back together.

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So, watch them come apart.

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They come apart,

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and now,

4:35

back together.

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Together.

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Apart.

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And almost together.

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In the front,

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they don't quite come back together.

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And the reason is,

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we have a bucket handle tear that is like this.

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Okay. Here's an axial projection.

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So, here's a normal meniscus.

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Then we develop a vertical tear in the middle.

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Then that vertical tear turns into a gap

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with a big hole in the middle,

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and then sometimes, in the front,

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that gap can break apart.

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Right here.

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And a portion of the meniscus

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then goes underneath.

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So this portion goes underneath like that,

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and this portion sits on top.

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So, the bucket handle fragment tucks

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underneath the anterior horn.

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That is exactly what is happening here,

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producing when you perform a sagittal projection,

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a double meniscus sign,

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one in the front and then another one in the

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front, and then your meniscus in the back.

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And let's take a look at that.

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So, let's go to the meniscus.

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Let's go medial.

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This is medial.

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This is lateral,

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and here is our meniscus.

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Let's draw together.

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There's our meniscus,

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and there's a little piece of meniscus

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tucked up underneath it.

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Right there.

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Just like we've described earlier.

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So, let's take this away.

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Right here.

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And let's draw it again a little bit better.

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There's the meniscus tucked up inside.

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There's the rest of the native meniscus.

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And then,

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you have your double anterior meniscus sign

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when you perform a sagittal right there.

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And then,

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in the middle is the big giant gap or hole.

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Here's the hole.

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Then when you perform a coronal projection,

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you're going to get meniscus triangulated.

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Meniscus triangulated,

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and then separation in the middle.

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And they stay apart, apart, apart, together,

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apart, apart, apart.

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Now, this one is probably broken right here.

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So, we probably have a little break

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in the action right there.

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That's why it didn't come completely

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back together in the front.

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Now, let's go back to the coronal and look at it again.

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And the sagittal, look at it one more time.

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This is the most important case you're going to

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see today, because you just can't miss

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a bucket handle tear.

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See if I can get this to unmagnify.

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I cannot. Bummer.

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All right, let's take the sagittal, then.

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So, here's your posterior horn.

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It's truncated and it has a little flap in the back.

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Here's your truncated anterior horn.

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Sorry, I apologize.

8:03

Here's your anterior horn,

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and here is your meniscal fragment.

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Right there in the knee notch.

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So, this piece right here is,

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this piece.

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So, that piece is this piece.

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And let's scroll again.

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This is the anterior horn.

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That's the posterior horn.

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This is the fragment that's tucked up underneath.

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And then, you can also see that there is a little bit

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of a flap tear that involves

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the posterior rim.

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So, you do want to describe how deep the rim is.

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We could measure it and say,

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the rim is x millimeters deep.

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We do that in the coronal projection, as well.

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We want to say whether the meniscus rim is intact

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or torn because we have to sew that back together.

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And the reason this is such an important tear

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is it is fixable.

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The sooner you get to it,

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the better off you are.

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So, the answer in this case is bucket handle tear,

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displaced inner fragment, separation in the front,

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incidentally noted is stable appearing,

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four centimeter long,

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osteochondritis dissecans,

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classic type in the lateral aspect

9:25

of the medial femoral condyle.

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Okay, well,

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I'll show it to you in this projection.

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Sagittally, look at the medial meniscus.

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Now, look at the lateral meniscus.

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The lateral meniscus is separated into bow ties,

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into two bow ties,

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and it actually persists in the middle

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for quite a ways.

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Unfortunately,

9:45

this was a discoid meniscus that projects

9:47

best in the coronal projection.

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and I'll just leave you with that.

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That is one of the diagnoses in this case,

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discoid lateral meniscus with lateral

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femoral condylar dysplasia.