The Anatomy of the Lateral Collateral Ligament Complex - FCL
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Knee anatomy.
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Collaterals.
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The LCL and the LCL complex,
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although the posterolateral corner will be covered on its own.
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In the back,
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we have the large structure of the biceps femoris, which you're
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going to see has a short and a long head and two separate
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footprints of insertion on the fibular head.
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Superficially located and extra-articular in some portions of it,
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mostly distally, intraarticular proximally
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is the popliteus tendon, which has an oblique course,
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and then continues on down into the screen as the popliteus muscle and
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myotendinous unit. Kind of crisscrosses and sits atop of the
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fibular collateral ligament, which some people refer to as
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the lateral collateral ligament.
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Perhaps correctly, perhaps incorrectly,
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but that will be a story for another day.
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And its origin is going to be about here.
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And then slightly posterior to it,
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although not drawn in because we're not in the right sagittal location,
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is the origin of gastrocnemius lateral head.
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So let's talk about the LCL complex.
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We're not going to address the corner right now.
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There are three structural layers of the LCL complex.
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Layer number one,
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the most superficial layer consists of the iliotibial tract and
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its anterior expansion, and the superficial portion of
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the biceps femoris with its posterior expansion.
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And most people don't know that
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the lateral collateral complex is divided
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up into layers like the medial side.
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Layer number two consists of the quadriceps retinacula anteriorly,
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and then two patellofemoral ligaments or
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retinacula posteriorly, which are variably seen.
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Layer one and layer two merge at the
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lateral aspect of the patella.
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And if you've seen the medial collateral vignette,
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so too, the layers one and two merge along the medial patella.
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Then we've got layer number three.
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This is the deepest layer.
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It consists of the lateral joint capsule.
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It includes attachments to the lateral meniscus, the lateral
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capsular ligament with its meniscofemoral and meniscotibial
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components, much like analogous to that seen on the medial side.
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The lateral collateral ligament or fibular collateral ligament
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is located posteriorly. And it's kind of weird.
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It's between the superficial and deep divisions of layer three
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which kind of split, and the LCL is caught in the middle.
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So it is technically considered by
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anatomists a layer two structure.
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Let's have a look at this anatomy on MRI.
Stephen J Pomeranz, MD
Chief Medical Officer, ProScan Imaging. Founder, MRI Online
ProScan Imaging
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