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Knee anatomy, lateral collateral ligament or

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LCL complex, including the LCL or FCL, fibular collateral ligament.

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This comes from our Total Body Atlas

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in MRI where we see some important locking zones or insertion points.

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They're actually origins for structures

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like the popliteus, which is depicted here in yellow. The gastrocnemius, which is

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slightly posterior and maybe a little bit inferior to the one we're interested

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in right now, the fibular collateral ligament.

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So the fibular collateral ligament,

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often called the lateral collateral ligament is rounded.

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It's more narrow and less broad than its counterpart, the so-called medial

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collateral ligament, also known in some circles as the tibial collateral ligament,

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which is considered the middle layer or the superficial aspect of the deep MCL.

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The fibular collateral ligament stretches obliquely downward and backward

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

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But don't be misled, that insertion

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on the fibula, along with several other structures, is quite complex.

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In contrast to the MCL,

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it's fused with neither the capsular ligament nor the lateral meniscus.

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Now, I'm not talking about the LCL complex.

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I'm just talking about the lateral

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collateral ligament, formerly known as the artist fibular collateral ligament.

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The lateral collateral ligament is more

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flexible than its medial counterpart, so it's less susceptible to injury.

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So when it is injured, it's usually

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a pretty serious and potentially catastrophic injury.

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It's about 14mm anterior and slightly

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distal to the gastrocnemius origin, although there's some variability

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regarding the height related to one versus the other.

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But it always arises above and posterior to the popliteus tendon.

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It has an attachment to the tibia, little known.

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The attachment to the tibia, we'll see, is involved in severe various

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injuries and may lead to the segond fracture or the lateral capsular sign.

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LCL tears are associated with injury of other posterolateral and corner

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structures to be detailed in a corner section.

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Now, the popliteus muscle and its myotendinous unit, sit outside of the joint.

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The popliteus origin sits inside the joint.

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Intra-articular tears, involving the hiatus of the popliteus, and/or popliteal femoral

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attachment, are intra-articular injuries and they are less common than strains or

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injuries of the popliteus muscle and myotendinous unit.

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The LCL and the biceps femoris, can't talk about one without the other

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at the insertion because they attach right next to each other along the lateral

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margin of the fibular head, not the fibular styloid.

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This accounts for the reduced likelihood

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of an avulsion injury compared to injuries of the popliteofibular ligament,

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the fabellofibular ligament and the arcuate ligaments, all of which may

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be associated with avulsions of the fibular styloids.

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So this may help you on conventional radiography.

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So now let's have a look at our head

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of the fibula, which is a little more daunting than you might have thought.

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Here is our fibular collateral or lateral collateral ligament in yellow.

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We've also got a biceps femoris

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which we're going to detail, in greater detail, when we talk about the biceps

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femoris, but there are two components to it.

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The main component sits behind the FCL and they don't actually anatomically join

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but they are called on their insertion point, the conjoint tendon.

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There's another component of the biceps femoris that runs a little more anterior

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and slightly medial to the FCL and that will be a story for its own vignette.

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Now, the styloid process tip provides

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attachment for the arcuate ligament, which is seen here in blue.

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We said light blue but it's kind of like

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navy blue, anterior to the fabellofibular ligament, which you're going to see has

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an inverse relationship with regard to its size compared with components

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of the arcuate. Big arcuate, small fabellofibular ligament and vice versa.

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The popliteofibular ligament, which is a very important stabilizing

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structure, that's oft-overlooked, is attached medial to these two and we see

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it here articulated and demonstrated in pink.

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Now, let's look at some MR in the axial projection.