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Knee anatomy on MRI, the lateral collateral complex.

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Not the lateral collateral ligament,

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but complex. The greatest show perhaps on Earth

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when it comes to knee anatomy. It's complex,

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but yet, once you've got it, it's pretty concrete. In the sagittal

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projection on this diagram, from our Total Body Atlas in MRI, in green,

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the origin of the LCL ligament or fibular collateral ligament.

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It's in front of the origin of the gastrocnemius lateral head.

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It's above the rather large footprint

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of the popliteus tendon, which is going to sweep down and obliquely.

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Now, there are three layers to the lateral

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collateral complex, analogous to the three layers on the medial side.

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But we don't often think of three structural layers.

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Layer one is the most superficial layer and it consists of the iliotibial tract

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with its anterior expansion, and then the superficial portion of the biceps

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femoris, which we're going to capture all into itself, with its posterior expansion.

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The biceps is going to have a short and a long head.

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Layer two, anteriorly,

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consists of the lateral extension of the quadriceps retinaculum, anteriorly,

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and two patellofemoral ligaments or retinacula more posteriorly.

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But still, we're not as concerned

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with these right now because we're talking about the posterolateral corner.

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So for review, layers one and two merge at the lateral aspect of the patella

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and we often refer to this as the lateral parapatellar complex.

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And sometimes, these areas have to be

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released when they're pulling or tugging, or contracting too hard on the patella.

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So layer three,

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the deepest layer. It consists of a lateral joint capsule that includes attachments

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to the lateral meniscus, which are somewhat complex,

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the lateral capsular ligament with its menisco-femoral and menisco-tibial

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components, which are highlighted in the back near the popliteus tendon.

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The lateral collateral ligament,

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or fibular collateral ligament is located posteriorly.

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It's origin you just saw in green

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and it's between the superficial and deep divisions of layer three.

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So it's kind of odd.

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The LCL is kind of in no man's land

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and many people consider it to be a layer two lateral collateral ligament structure.

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I don't think you really have to concern yourself with that.

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But just for giggles, do be aware that it's located in between

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some individual layers of layer number three.

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Now, the lateral collateral ligament, which we covered separately, is a pretty

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narrow structure that's far less broad than the medial collateral ligament.

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We're going to look at it on MRI.

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The FCL stretches obliquely downward and backward.

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So it goes from anterosuperior proximal to posteroinferior from the lateral

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epicondyle femur, above to the head of the fibula below.

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In contrast to the medial collateral ligament, it's fused with neither

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the capsular ligament, there's no POL over there, nor the lateral meniscus.

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So it's kind of almost like a freestanding structure.

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It's more flexible than its medial

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counterpart, so it'll take a lot more of a stress.

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So when it does tear, because it's less susceptible to injury, when it does tear,

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it's often the harbinger of something very, very bad.

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And because it can tear in an isolated way, you can miss it.

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So we're going to focus first

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on the anatomy of the fibular collateral ligament, or LCL.