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Knee anatomy.

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The posteromedial corner.

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On MRI, we've got a coronal high-resolution 3D image to help

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us see and separate out the POL and the OPL.

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An axial T2 fast spin echo, high-resolution 1 mm,

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and another water-weighted image,

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a side view or a lateral view, or a sagittal view.

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So let's start out with the easy sagittal view.

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We've got one component of the posteromedial corner,

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the posteromedial meniscus and the capsule.

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The attachments are also part of this complex.

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And then as we move a little more medially,

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we run into the posteromedial capsular condensation,

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which isn't that well sorted out,

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although we can see it in the coronal projection as this sheet.

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This is known as the posterior capsule.

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And fused to it, not separate and distinguishable, is the OPL,

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the Oblique Popliteal Ligament.

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So that's the Oblique Popliteal Ligament,

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it runs around the back and is perhaps best seen

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in the axial projection. Let's go to the axial.

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There it is, right there.

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And it goes all the way from the medial side,

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all the way over to the lateral side.

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So they're interconnected.

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But do remember that the OPL and the posterior

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capsule are often not separable.

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But my goal here is to separate out for you the OPL,

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the Oblique Popliteal Ligament, from the POL.

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So the POL can be best found by going back from the tibial

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collateral ligament or the middle layer of the MCL.

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So, here's the middle layer of the MCL.

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The front part,

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where you get this little step off right here.

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I'm going to blow it up a little bit so you can see the step off.

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When you see a step off in a transition,

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you're now more posteriorly in the POL.

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Now, some say the POL at this location is a layer two,

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and then at this location is a layer three.

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I don't really care.

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Let's call it a layer three portion of the MCL for now.

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But the POL then comes around and it is an oblique ligament.

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The fibers are oriented obliquely, or arcuate like,

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in both the axial and you've seen in other vignettes in the sagittal.

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So the POL is going to swing around and it's going to

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fuse with the posteromedial capsule and the OPL.

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Let's have a look at the POL in the coronal projection

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for a minute.

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So let's go to the POL.

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Let's cross-reference it.

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And there it is.

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It's this structure right here.

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Look at its intimate relationship with the posteromedial meniscus

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capsular attachment. And even this little structure right here,

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which is a superior meniscocapsular attachment at the

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posteromedial corner. There it is, right there.

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I'm even going to put an arrow on it with my pen right here.

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That structure is fusing with your POL, which is that structure.

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Now, if I take it away and move forward,

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you're going to run into the middle layer of the MCL or the tibial

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collateral ligament, which is much thicker and fatter.

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Thicker and fatter.

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Middle layer number two of the MCL.

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Deep layer number three of the MCL.

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Now, I'm going to go backwards and now I'm in the POL.

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And the meniscocapsular attachments intimate with the POL.

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Now, what happens if you injure the posteromedial corner

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and especially, the POL?

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I'm going to show you, my friend,

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Fred here.

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And so, here's Fred.

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When you're in external rotation...

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So, this would be external rotation.

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Got the femur in my right hand, the tibia and fibula in my left hand.

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When you're in external rotation in patients that

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have injuries to the posteromedial corner,

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especially the POL, then the tibia translates forward.

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It subluxes forward when you externally

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rotate more than it should. So we can see that Fred has a problem.

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When you have a posteromedial corner injury,

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90% of the time, the POL is injured.

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70% of the time, the semimembranosus is injured.

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30% of the time, the peripheral meniscus detaches and there may be

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simultaneous injury of all these about 19% or 20% of the time.

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And that'll be an area we'll focus on when we show

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you injuries of the posteromedial corner.