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Knee anatomy.

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The posterior medial corner on MRI.

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A little different approach.

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We've got some very high-resolution coronal 3D images with 1 mm cuts.

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And then on the left, an axial T2 fast spin echo.

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Also with 1 or 1.2 millimeter cuts.

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Both are water-weighted. And on the right, the standard fare,

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which is a sagittal, water-weighted image or a lateral view.

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Let's focus on the posteromedial corner.

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There are five components: the POL, the OPL, the semimembranosus,

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the medial meniscus, and the capsule in the back,

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and the meniscocapsular attachments.

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Well, there is an inferior attachment.

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There's a superior attachment. There's the capsule.

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So we've already seen the meniscus and the capsule.

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Two of the components. This structure in the back, the OPL,

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the oblique popliteal ligament, is a third component.

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The fourth component, the POL.

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Let's have a look at it in the coronal projection first.

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The POL will merge with the tibial collateral ligament.

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So find the tibial collateral ligament

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and then work your way backwards.

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Once the tibial collateral ligament kind of changes,

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almost addresses or designations, watch it skip.

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Here it is. It's going to skip right there.

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There it skips. Now you're in the POL,

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the Posterior Oblique Ligament of the knee.

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Let's put a little dot on it.

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That shows you where the posterior

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oblique ligament of the knee is on the sagittal.

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It's behind the vertically oriented tibial collateral ligament.

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Although hard to see, but in other vignettes,

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the fibers are somewhat oblique.

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And there are three arms to the POL.

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Now, if we scroll anteriorly,

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we also see the anterior arm of the semimembranosus.

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And going straight down along the free edge

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of the tibia is the inferior popliteal arm.

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I'm going to blow that up a little bit since

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those structures are really small.

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So here's the anterior arm of the semimembranosus coming at you.

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Here's the inferior arm.

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And so now we're talking about a fourth component

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of the posteromedial corner, the semimembranosus,

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which will break up into two major arms,

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an anterior arm and a direct arm going down.

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There's the direct arm going down.

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And then there are three other arms that are a little

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bit beyond the scope of our discussion today.

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Let's see if we can see the POL in the axial projection.

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That's really tough on a T2-weighted image.

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So let's go back to our tibial collateral ligament.

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We're blown up a little bit,

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but it's this big fat structure here.

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If we cross-reference it, it's this big,

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fat structure here with a vertical orientation.

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So let's find our tibial collateral ligament in the axial.

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There it is in the mid-coronal plane.

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Now, let's find our POL.

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We've got to go backwards to find the POL.

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Let's look for the jump to the POL.

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By the way, that's a meniscocapsular attachment,

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part of the deep layer of the MCL.

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Let's keep going. And that is going to fuse with the POL.

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There's the POL. Let's see if the POL shows up on the axial.

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It does. Right there. It's a little deeper.

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It will fuse with the tibial collateral ligament or middle

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layer of the MCL. So middle layer of the MCL and POL.

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So I have shown you all five components with high-resolution

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imaging of the posteromedial corner.

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The POL, the Posterior Oblique Ligament.

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The OPL, the Oblique Popliteal Ligament,

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which is this component in the back.

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The semimembranosus,

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we talked a little bit about its expansions.

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The medial meniscus and the capsule,

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and the meniscal attachments.

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Let's move on to another one, shall we?