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All right.

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This case is another meniscally focused case.

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It's an adult man with a work related injury.

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Lord knows what he was doing.

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But often underutilized is the axial projection.

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And when you scroll thin section axials,

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less than 2 mm,

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you can pick up a lot of information.

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For instance,

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you can see a problem with the

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bone on the lateral side,

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which correlates with this fracture or

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osteochondral fracture on the lateral side,

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you also see distension of the posterolateral

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meniscocapsular reflection by fluid.

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So that already tells you that you probably have

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had some type of pivot shift related insult.

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And then when you go over to the medial

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meniscus side, to the root,

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the area of the root attachment,

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which is right here,

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is interrupted vertically from anterior

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to posterior by this high signal area,

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which represents a radial injury

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and a fairly large radial injury at that.

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So, you can get a depth of that radial injury.

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You can get a width which is a little more

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narrow here, but widens as it goes in.

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And now, it's time to look at the meniscus

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and another projection,

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even though there's lots more information about

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what's happening with the ligaments

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and the axial projection.

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But that's a story for another day.

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So now,

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let's look at the coronal since it's up

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and we have extensive bone marrow edema,

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which tells us posteriorly in the tibia

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that we've had a pivot shift.

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We also have the typical terminal sulcus injury,

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again, supporting the mechanism

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of injury of a pivot shift,

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which we will go over that mechanism

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when we focus on ligaments.

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But you should be dialed into the small

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character of the medial meniscus.

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It's got a little vertical signal in it,

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which is part of our tear.

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Let's follow our tear around.

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We can follow it into the posterior

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horn body junction region.

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So, there is a vertical component.

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There's a horizontal or oblique component.

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So there's some complexity to this tear,

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but I'm primarily showing it for this.

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The radial gap that you saw in the axial projection.

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Let's go back to it.

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Here it is right here,

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oft-overlooked but never understated.

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And it's got some width to it.

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Obviously,

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that width changes from anterior to posterior,

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so it'll change as you scroll

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from front to back.

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And it is just medial to the root attachment.

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There is the root ligament attachment

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arcing down next to a small bundle of the PCL

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that courses along the inner wall

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of the femoral condyle.

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It's intact,

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but it is the meniscus immediately adjacent

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to the meniscotibial attachment that is torn.

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So, functionally,

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you've lost your tether there,

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and that's going to allow, over time,

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with hoop stresses,

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the meniscus to start to migrate out.

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It has not done so yet.

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Let's look at the sagittal projection.

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We'll reaffirm our anterior cruciate ligament tear,

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although that's not why we're here.

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There is our fairly large tear,

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and here is our meniscus tear,

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which we said was rather complex.

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It had an oblique or horizontal component,

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and then it continues on with a little,

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tiny vertical component,

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which is so common in these pivot shifts.

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This signal will be there forever.

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It is going to sit directly atop

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the meniscal contusion.

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So, you don't want to get too excited about these

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when you see them a year or two later.

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But I also wanted to show you

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the meniscal ghost.

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Here we are,

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right through our radial tear.

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The meniscus is there.

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It's gone, it's back again.

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So you're missing that chopped segment right there.

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And meniscal ghosting,

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or loss of meniscal signal,

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can be seen with congenital absence

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of the meniscus,

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which is much more common laterally.

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Although, still a rare phenomenon.

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You can see it with auto digestion

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from rheumatoid arthritis.

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Get a big bucket handle tear that separates

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the meniscus into two pieces,

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you will lose the meniscus, a giant radial tear,

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you'll lose the meniscus.

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And even infiltrative processes like CPPD

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and gout may completely wipe out and

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obliterate the meniscus.

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So, let's move on to another meniscal case.