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The Posteromedial Corner: Posterior Oblique Ligament

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Knee anatomy on MRI, posteromedial corner,

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and a focus on the Posterior Oblique Ligament, or POL.

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Now, the posteromedial corner and the POL provide active support during flexion.

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And this is also further supported by the superficial portion of the deep

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MCL, otherwise known as the tibial collateral ligament,

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and the adjacent structure seen here in green, the POL immediately behind it.

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Now, the POL is a restraint against a valgus stress.

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It also supports both anterior

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and posterior translation, and internal and external rotation.

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Now, don't confuse the POL with something

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that occurs back here, which we haven't really discussed yet, called the OPL.

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The POL is the Posterior Oblique Ligament,

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the OPL is the Oblique Popliteal Ligament,

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and that is a primary restraint to knee hyperextension.

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It's important in preventing something

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called genu recurvatum, in other words, where the knee looks like it's kind

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of bowed at the level of the knee joint itself.

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So the POL is a support for translation and rotation,

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and it's even more important when the knee

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is PCL or Posterior Cruciate Ligament deficient.

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After an isolated MCL injury,

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the PCL may be an important secondary stabilizer for rotation and valgus stress.

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I'd like to draw a little bit for a moment.

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And this slide, I think, illustrates a somewhat triangular shape to the POL.

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We don't have the triangle,

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the back of the triangle down here because we just don't have enough room to draw.

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But the fibers are actually running down,

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and somewhat obliquely, and the triangle points

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back towards the semimembranosus or towards the posterior aspect of the knee.

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Whereas the second layer,

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the middle layer of the MCL, also known as the deep layer

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of the superficial MCL, also known as the tibial collateral ligament,

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it runs more straight up and down.

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Now, this is going to become relevant when I show you MRIs.

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You're actually going to be able to see,

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in the sagittal projection, the difference between this and this.

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Now, this is going to communicate

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with some fibers around the back over here, which form the OPL.

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So it goes OPL in the back to POL,

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transition into what we used to call the tibial collateral ligament or deep

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layer of the superficial MCL, so called middle layer.

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Now, there's some debate as to what layer the POL actually is.

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As you're more forward at this interface,

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many individuals consider the POL part of layer or middle layer number two.

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But as you move further back, getting towards the OPL,

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the oblique posterior ligament, most people consider that layer number three.

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So there's a transition of the POL from layer two to layer three.

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And this is the first time we're actually discussing this.

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And the capsule at the back, and the POL, are virtually inseparable.

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So it'll be hard to pick them out as two separate structures.

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Another name, by the way, for the POL is the ligament of Winslow,

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and most describe the origin to be near the adductor tubercle near the adductor magnus.

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Although some have found it to be slightly distal and posterior to it.

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Now, the distal end has three arms.

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It has a capsular arm, which blends with the joint capsule and also blends

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with the capsular arm of the semimembranosus.

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It's got a central tibial arm, which courses right underneath

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the anterior pars reflexa of the semimembranosus.

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And then the main component is the distal superficial arm.

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As we said, it has a somewhat triangular-shaped appearance.

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So we're going to look at the POL on MRI,

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and you're going to see it in its locations,

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sagittally, if we get lucky, axially.

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And remember, it sits immediately behind

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the tibial collateral ligament, the deep portion of the superficial MCL,

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or the middle layer of the MCL, this structure right here.

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So if you find this, which is easy, right behind it is going to be the POL.

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You're going to see it on MR.

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Description

Faculty

Stephen J Pomeranz, MD

Chief Medical Officer, ProScan Imaging. Founder, MRI Online

ProScan Imaging

Tags

Trauma

Syndromes

Musculoskeletal (MSK)

MRI

Knee

Idiopathic

Iatrogenic

Drug related

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