The Posteromedial Corner on MRI part 3
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Knee anatomy on MRI, focusing on the posteromedial corner.
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We've got an MRI, an axial T2-weighted image,
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and then two sagittal images.
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One fat-weighted, one water-weighted.
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So these are lateral projections all the way out
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on the medial side of the knee. Now, I think the water-weighted image
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illustrates this perhaps a little bit better.
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So, let's focus our attention here.
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I want to focus on the POL.
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One of the five, one of the big five for the posteromedial corner.
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The other four, you should be able to raffle off
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if you've watched the other vignettes. You've got the POL, the OPL,
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the medial meniscus,
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the capsule, and the semimembranosus along with its expansions.
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So now I'm going to draw a little bit.
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We see the middle layer of the MCL right here.
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It's this black band. It's pretty thick.
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I'm going to color over it.
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Then I'm going to get myself a different color, maybe red.
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Now, behind it is a rather wispy but obliquely oriented group of fibers.
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They go from superoanterior to postero-inferior.
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These are the fibers of the POL,
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and they are going to attach to the capsule in the back,
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to the posterior meniscus in the back.
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There are three components to the POL.
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And I'm going to use my pen again.
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There's an upper component above the joint.
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It's a little blacker and a little more condensed,
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and a little more horizontal.
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And this is known as the capsular or superior arm.
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Then there is the central arm that goes obliquely back like this.
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It's a group of fibers that runs from proximal anterior to distal posterior.
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And this is the most important component of the POL.
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The one that hugs in close to the middle layer of the tibial collateral
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ligament, this area right here is known as the distal superficial arm.
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So we've got POL three components, component one.
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Now I'm going to draw component two,
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and then I'm going to draw component three.
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And if you really have terrific hallucinatory powers,
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you'll see a slightly wider area between this area and that area.
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That is the interface between the MCL and the POL.
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Let's draw it. Right there.
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So in some patients, you can actually separate out the two.
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Now let's turn our attention to the axial projection.
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We'll drop our drawing tool for a moment.
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Let's go to the MCL middle layer. Right there.
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Also formerly known as the tibial collateral ligament.
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We said we're interested in the POL.
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So if we go from the tibial collateral ligament to the structure immediately
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behind it and slightly deep to it, there's the arcuate-shaped,
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obliquely oriented POL.
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Posterior oblique ligament of the knee.
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The posterior oblique ligament of the knee will merge with the posterior
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capsule and OPL, and this will go over to the other side.
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So, as stated previously,
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the posteromedial corner has a bearing indirectly on what happens
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to the posterolateral corner.
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MRI emphasizing the POL.
Stephen J Pomeranz, MD
Chief Medical Officer, ProScan Imaging. Founder, MRI Online
ProScan Imaging
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