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We're talking about the three-layered LCL complex.

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And we're on the biceps femoris.

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Biceps femoris ends in a tendon,

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which consists of two heads:

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a long head that arises from the ischial tuberosity,

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and a short head that originates off a lateral

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prolongation of the linea aspera of the femur.

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Now distally,

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both heads are composed of at least two tendinous

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components: a direct arm and an anterior arm.

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The arms of the long head insert on the anterior and

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posterior lateral aspects of the fibular head,

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whereas the anterior arm sends fibers that continue

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distally as an anterior aponeurosis.

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The direct arm of the short head inserts on the

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anteromedial aspect of the fibular head,

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while the anterior arm passes medial to the LCL to attach

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on the superolateral edge of the lateral tibial condyle.

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So let's have a look at the biceps femoris.

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It's a pretty big structure here in the back.

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We've got it depicted here in red.

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It sits behind the fibular collateral ligament.

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These two will almost unify.

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Not quite as the conjoint tendon, but the anterior arm,

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which I'm going to make here in red,

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will kind of course around the fibular collateral and

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it'll have an attachment along the anterolateral

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aspect of the fibula.

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So it's a little more complex than it looks at first

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glance, and it's a rather large structure.

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And that is evident when you look at the

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MRI because it looks like a big,

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black linear structure that descends and finally

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terminates as a ball right in this location with

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the fibular collateral ligament buried in it.

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Let's look at the MRI.

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So our MRI magnifies the fibular head in the coronal

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projection, water-weighted.

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Axial projection T2, also water-weighted.

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And also, another water-weighted image in the sagittal projection.

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Let's go all the way out to the free edge of the fibular head

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where the biceps femoris can be found.

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I think it's easiest to start in the back.

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So let's start in the back.

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We have the direct head of the biceps femoris.

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Remember, there's going to be a short and a long head,

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a direct and an anterior component.

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But that may be a little too much for right now.

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But do remember, there are two heads to the biceps femoris.

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And each one of them, by the way,

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has a direct and anterior arm.

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So there's the direct arm, has a contribution from

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the short head and the long head.

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The anterior arm has a contribution from

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the short head and the long head.

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So, we're in the back at the direct arm.

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Big Footprint.

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It's going to merge with the fibular collateral ligament.

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Again, big lateral footprint. But as we come forward,

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it's going to drape along the anterior edge and it has a

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slightly more medial position here as the anterior arm

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of the biceps femoris which receives, by the way,

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contributions from the short and the long head.

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Let's look at the biceps femoris a little more simply

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in the axial projection.

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There it is right there.

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It's a rather large structure.

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It has merged with the fibular collateral ligament.

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Let's find the FCL right there.

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There's the fibular collateral ligament.

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They come together to form the conjoint tendon.

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Very far anteriorly,

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this little tissue right here is all part of the anterior

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head that drapes over the anterior margin of the fibula.

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It may even send some fibers around the fibula,

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but that'll be a story for another day.

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And then let's look at the biceps femoris

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in the sagittal projection.

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Perhaps I should demagnify a little bit so you can

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appreciate the anatomy.

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Here is the biceps femoris.

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It's pretty far in the back.

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And here are the wispy fibers of the anterior component of

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the biceps femoris. Again remember,

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biceps femoris, short head and long head.

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Each head has a direct contribution and an anterior contribution.

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There's the anterior contribution.

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There's the more posterior direct contribution from both.

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And these are going to come together,

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hard to appreciate in the sagittal projection with

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the FCL or LCL to form the conjoint tendon.