The Posterolateral Corner: Biomechanics
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Knee anatomy on MRI.
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We're talking about the posterolateral corner.
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Let's address the biomechanics and the anatomy of the posterolateral corner.
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There are three main stabilizers
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the lateral collateral ligament, which is a subset of the LCL complex,
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also called the FCL, fibular collateral ligament.
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The popliteus tendon with some very important attachments,
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and the popliteal fibular ligament, which is one of those important attachments.
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The popliteus is a myotendinous unit.
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It consists of two bundles, a posterior bundle, which is taut in extension,
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and an anterior bundle that is taut in flexion.
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Now, most injuries to the popliteus involve the myotendinous junction.
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And when they're isolated,
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they're usually not treated surgically unless there's massive retraction.
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And so these heal.
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The popliteus may have a rare sesamoid bone
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found in the tendon called the cyamella.
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And I wouldn't mistake this
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for the fabella, for the fabella has a different function.
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As we'll see, it's inversely proportional in size to the arcuate ligament.
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Now, there is a debate about the exact number of popliteal meniscal attachments,
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and we're going to drill into those on MRI.
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But probably the most important one is the posterosuperior fascicle.
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The anteroinferior fascicles are also found and identified on sagittal MRI.
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But in my experience, when the posterosuperior fascicle goes,
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the meniscus can actually spin around or twirl and becomes unstable.
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And the patient may report locking.
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These attachments of the popliteus tendon,
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which we'll outline, will form a floor and roof of the popliteus hiatus.
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So I'm just going to draw a little bit here.
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I'll change my color to orange.
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So this would be your lateral meniscus.
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And here's your popliteus tendon.
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And then we're going to see, passing
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through the popliteus tendon, in the region of the hiatus.
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And maybe I'll make those a different color.
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We'll see these attachments, superior attachment and the inferior attachment.
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And they'll also be categorized as whether
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they're lateral superior and inferior or more deep or medial superior and inferior.
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So we're going to try and count about four
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of them or follow them across from side to side.
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In my experience, this one is more inconsistent and not as
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critical to stabilization as the superior one.
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Let's have a look on MRI.
Stephen J Pomeranz, MD
Chief Medical Officer, ProScan Imaging. Founder, MRI Online
ProScan Imaging
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