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So the popliteus on MRI,

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we've got a coronal AP water weighted image on the left.

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An axial T2 water weighted in the middle, and a sagittal

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lateral projection, water weighted on the far right.

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So it's easy.

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Just find the popliteus hiatus.

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It's slightly inferior to the origin of the fibular collateral ligament.

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So we go to the hiatus.

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And then if you want to follow the popliteus tendon

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out of the hiatus, you can just simply scroll.

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And it has this oblique course where it's

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going down, medial, and anterior to become the popliteus muscle.

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This location right here, at the myotendinous junction, is a not

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uncommon site where the popliteus myotendinous unit may rupture.

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Now, if we put our cursor back on here,

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we will find the origin, right there, of the popliteus tendon.

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Sometimes it looks like the origin is a little higher because you volume average

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cortical bone and behind it, the fibular collateral ligament.

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But the best way to isolate the origin,

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and then to follow the popliteus, is to track it from the hiatus on down using

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the coronal projection first and then go to the sagittal.

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Now, as we go down, we see just how oblique it is.

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And it has attachments to the fibula.

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Let's go a little deeper

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and we see a very important attachment called the popliteofibular ligament.

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In the spectrum of LCL complex injuries, the LCL may tear first, but usually is

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followed by, in order, the popliteofibular ligament.

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So this is a very important structure to concentrate on.

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If you rupture it, it'll kind of curl up

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in a ball that looks something like this, with a little tail to it.

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And this is known as the mermaid sign.

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Now, the popliteus tendon sits behind the lateral meniscus,

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and we said the meniscus has superior and inferior fascicles.

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Let's make it bigger.

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So here's the superior fascicle.

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Here is the inferior fascicle.

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This would be the popliteus hiatus.

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So, this would be the roof and floor of the hiatus.

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Let's scroll.

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They look a little differently as we come out more peripherally or more laterally.

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And then they get a little pointier

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and a little harder to see as we go deeper into the knee.

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Here's the inferior one.

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It's a little stippled-looking.

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The superior one has now been reduced to a triangle.

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And the tissues behind here represent the capsule.

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This is the capsular condensation that includes the OPL from the medial side.

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Now, let's go to the axial projection.

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Once again, pretty easy.

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We simply locate the popliteus tendon in the hiatus.

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We see where it is in the axial

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projection, even though it's a T2, and the FCL sits on top of it right there.

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And then we follow it down. So let's follow it down.

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Here it is sweeping backwards.

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It's kind of an arcuate-shaped structure.

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There it is.

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Still, we see it.

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We kind of lose it for a bit.

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And it comes back as the muscle.

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So this isn't the best projection to see, the myotendinous junction.

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This is the best projection to see the myotendinous junction.

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So if you're interested in a popliteus empty unit tear, you look here.

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If you're interested in a hiatus injury, then you can look virtually in any

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projection, but the axial is extremely valuable.

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If you're looking for a fascicle tear, in the roof or floor of the popliteus hiatus,

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you want to use the sagittal projection.