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Case number three is an 11-year-old male with

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grade 2 sprain of the medial collateral ligament.

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Knee pain since a football injury one month ago.

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So, we'll stay with the same theme of beginning

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with our axial projection.

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It's a child with open growth plates.

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The patella is nice and symmetric.

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The lateral facet is usually a little

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longer than the medial facet.

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The trochlear groove has an appropriate depth.

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These are things I look at.

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I look at the femoral ridges,

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I look at the Medial Patellofemoral Ligament

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as it comes back to the interface with

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the adductor tubercle. That's all fine.

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I'm not going to take the time to pick out the

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posterolateral corner structures right now.

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But in contrast to the last case,

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there's not as much tissue

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in the region of the ACL,

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although the actual linearity of the ACL is lost.

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So I should have a structure here,

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especially in a child.

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I should have a structure here that looks

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like this and I do not have that.

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So I'm immediately concerned,

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even though I don't have an effusion,

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that the ACL is ruptured.

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PCL is right here.

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Right there.

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And that is present,

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although not as easily seen as I normally like.

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And then, here's the MCL right there.

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There's the popliteus coming around.

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Here's the oblique popliteal ligament coming

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around in the capsule posteriorly.

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And just deep to the MCL,

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this little wobbly area right here,

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right there underneath the MCL.

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That's the MCL.

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The layer underneath that is called the POL,

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or Posterior Oblique Ligament of the knee.

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All right,

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so let's turn our attention now

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to something long axis.

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Let's take both sagittals together and scroll.

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Now, this is a little tricky.

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If you have a patellar dislocation,

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your contrusion is going to be

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over here and over here,

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and it's going to go all the way out

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to the periphery, to the side.

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So this one goes pretty far out,

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but it's not as far forward as usual.

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So, we have a decision to make.

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Do we have a patellofemoral dislocation

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or do we have an ACL tear?

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And the answer is pretty straightforward.

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You scroll to the ACL.

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We already said the medial patellofemoral ligaments intact,

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the ACL is transected right there.

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You got these floppy little fibers up front.

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You should have a nice straight,

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razor straight structure.

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You don't have that.

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You have this,

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you have this very floppy, very crimped.

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Right there.

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So the patient,

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even though he's 11 years old and it is not

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common to get ACL tears on 11-year-olds,

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this patient has one.

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Now, one of you made the diagnosis of a bucket

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handle tear, and I can see why you did that.

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You did that because you saw

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this structure right there.

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What is that structure?

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That structure, which is right here.

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There it is.

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There's the lateral meniscus.

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There's that structure.

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There it is again, and again, and again, and again.

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and now, we've lost it,

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is this.

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Very tricky.

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It's an intermeniscal ligament.

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The only named intermeniscal ligament is the

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ligament of Winslow and the ligament of barcal.

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So, an intermeniscal ligament simulating

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a bucket handle tear.

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How do we know it's not a bucket handle tear?

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Well, we were able to follow it anatomically,

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number one.

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Number two, the menisci are not small.

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Number three,

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it should come back together again

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in the back and in the front

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if it's a bucket handle tear,

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and it doesn't do that.

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It separates from the meniscus,

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but it never comes back to it on either side.

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So, that intermeniscal ligament was

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simulating a bucket handle tear.

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Further complicating matters,

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at the base of the notch is some ACL tissue.

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See, the ACL should be right here.

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Right there.

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And we don't have the ACL there because it's

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folded down a bit.

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There's your PCL.

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Unlike our PCL tear case, it looks perfect.

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MCL, perfect.

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Lateral collateral ligament, perfect.

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Okay, let's keep looking, shall we?

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So, one of you commented on non-ossifying fibroma,

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another commented on a cortical desmoid.

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Fortunately, they're both non-aggressive lesions,

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neither one requiring follow up.

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Neither one aggressive.

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And the desmoid is on the medial side at the

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adductor tubercle insertion.

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Here.

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Right there.

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It's traction periostitis and enthesitis

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that can produce new bone formation.

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Then on biopsy,

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can look very scary.

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If we go to the lateral side,

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we find this other lesion that is slightly

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serpiginous, sharply marginated,

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does not bow or expand the cortex,

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produces little to no scalloping,

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produces no periostitis and little to

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no osteoedema. It is not fluid.

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Right? It's almost the same signal as muscle.

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This is the signal of a fibrous industrial defect, small.

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Fibrous cortical defect, small.

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Fibrous medullary defect, bigger.

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And non-ossifying fibroma, biggest.

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Those are all names for the same thing,

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a fibrous inclusion defect.

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So, conclusion?

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Pivot shift injury, one.

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Two, ACL tear.

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Three, non-ossifying fibroma.

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Four, incidentally noted intermeniscal ligament.