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The lateral collateral complex and the posterolateral corner have, within

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that subset, a lateral collateral ligament, also known as LCL, also known as FCL.

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It more or less combines with the biceps femoris to attach to the lateral margin

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of the fibular head but not the fibular styloid.

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So this is the reason why when you have an avulsion of the fibular head,

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there is more likelihood that you have injured the popliteofibular or fabellofibular

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or arcuate ligaments and less likely that you've injured the lateral

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collateral ligament or fibular collateral ligament, which is a subset, again,

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within the lateral collateral complex in the posterolateral corner.

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So let's look at this fibular head.

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Oh, it just looks like a big lump, right?

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I mean, here's your fibular head.

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I've got a...

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I've got a specimen right here of the knee.

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And look at how simply they have constructed the specimen.

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The only thing that they have put in here

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is the lateral collateral ligament which runs from the lateral condyle or

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epicondyle down to the lateral aspect of the fibular head.

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You can see that there's stress placed

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on this structure in the position known as varus.

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And the lateral knee will open.

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Now let's look at it in the axial projection.

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And let's go on to the fibular head.

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We've got, in yellow, the attachment

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of the lateral collateral ligament or fibular collateral ligament or FCL.

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And we've actually got two attachments, one pretty big one in the back and one

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smaller one sliding up alongside the fibula collateral ligament.

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Together, these have been named, perhaps misnamed, the conjoint tendon attachment.

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Now, more posteriorly along the tip

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of the fibula, along the styloidal aspect of the fibula, are going to be attachments to...

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By the arcuate ligament, which is seen here in blue, the fabellofibular ligament

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and back, which is kind of a darker blue purplish.

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And these are reciprocals of one another. This is big.

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That's little. That's big.

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That's little. And then the popliteofibular ligament,

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which comes from the popliteus tendon is attached a little more medial,

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and we can see that structure here in pink.

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Let's look at it,

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the fibular collateral ligament, on an MRI.

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On MRI, we've got a coronal water weighted image, like an AP projection,

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and axial, cross-sectional, and a sagittal or lateral view.

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Let's find the lateral collateral ligament

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or fibular collateral ligament, which again, is a subset of the lateral

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complex and also supports the posterolateral corner.

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Here is the fibular collateral ligament.

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There it is arising from the condylar protuberance of the femur.

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And then it kind of comes down, arcs down, and then merges with this fan-shaped

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structure, which is the biceps femoris posterior expansion.

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Let's see if we can scroll it a little bit

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and just get a feel for it and its relationship to the popliteus.

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The popliteus hiatus is deep to it.

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So here's our popliteus that has more of an oblique characteristic to it.

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So we follow the popliteus back. Let's do that.

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Right to that location. In the popliteus notch,

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the fibular collateral ligament is going to sit just above that.

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So that's an easy way to distinguish the two.

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Then once you lock into the fibular collateral, you can then track it down,

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and in its oblique orientation, it comes down from superomedial to inferolateral.

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But it's also going back into the screen

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as it goes down because it has a posterior course as well.

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Now, let's identify it in the axial projection.

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Now, one way to do that is to cross-reference it.

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So here is the fibular collateral ligament.

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It's a little hard on this one, first cut that I've shown you, to differentiate it

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from the popliteus tendon, which is right underneath it.

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But on the very next slice,

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as we come down, they separate, popliteus tendon, fibular collateral ligament,

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and who's the FCL going to meet at the train station?

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It is going to meet the biceps femoris.

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Let's watch it do it. There it does.

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So they meet along the lateral aspect of the fibula.

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Let's demagnify and remagnify the image so

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we can see the lateral expansion of the FCL and the biceps femoris

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inserting on the lateral aspect of the fibular head.

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Plain as day.

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Now, let's go over to the sagittal.

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That's a bit more challenging.

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So let's put our little marker here on the fibular head.

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So here's our fibular head.

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And here is our popliteus tendon.

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So our popliteus tendon has a very arc-shaped configuration with a very large

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footprint at its origin along the femoral condyle.

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But higher up than this, and more posterior to it, is going to be the FCL.

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So let's find the FCL by cross-referencing it.

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Here it is, right here.

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There is the origin of the FCL.

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It courses down and back, so it slopes from anterosuperior to posteroinferior.

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And it will merge with the biceps femoris, which is coming down this way.

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So the posterior expansion of the biceps femoris and the FCL will merge to form

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the conjoint tendon on the fibular head footprint.

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So let's look at it again.

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FCL.

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Here's the FCL in the back.

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There's some more FCL.

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And then here's the popliteus, much bigger, much more fans-haped.

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Also with an oblique course from inferoposterior to anterosuperior.

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They are more easily separated in the axial and the coronal projection.