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Here's a 54 year old man with an injury

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and a small PCL,

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or posterior cruciate ligament,

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in the sagittal projection.

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This is a companion case that goes with another vignette.

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But let's review what s happening.

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PCL is too thin.

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Is it atrophied?

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Perhaps.

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Are you losing the PCL because you're not

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seeing some of the fibers that are torn?

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Perhaps the patient has a large Humphrey ligament

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right there, and there's your pcl,

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which becomes very hyper intense and blends

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into the surrounding background. In fact,

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these are all fibers of the PCL.

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We know that by simply looking in the short axis

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projection and seeing signal, high signal,

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within the confines. There's the edge of the PCL.

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There's the high signal in the PCL.

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We also see gray blob like signal on the T1,

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weighted image within the pcl,

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because sometimes you can volume average the

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tissues around the PCL that obscure it.

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So you have to go inside the PCL in the short axis

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projection to reaffirm the presence of an injury.

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But that is actually not the

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point of this vignette.

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The point of this vignette is to illustrate

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how important it is to check the corners.

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A PCL with a corner injury is a much different

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animal than an isolated pcl,

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which is not treated surgically in most cases.

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So let's look at the posteromedial corner in the

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sagittal projection. Let's go there immediately.

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What makes up the corner?

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Medial meniscus. Big oblique tear.

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It's torn.

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What else?

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The meniscocapsular attachment and reflection.

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Too bright, too thick. It's torn.

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What else? The pol.

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The posterior oblique ligament of the knee.

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Here it is. Right there.

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Too wavy.

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It's injured. It's torn.

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Let's look at the pol in the coronal projection.

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What should it look like?

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You should see a meniscus that has this shape and

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then coming off. It should be one solitary,

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band like structure that is delicate

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and thin and elegant.

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No,

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we have a structure that comes down and is mushy

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and ill defined there and maybe one little

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laminar structure right there,

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but the rest of it ill defined.

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Let me take it away,

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have a look at it again right at the point

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of the meniscus. I'm going to draw again.

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You should have a structure that looks like this

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should come right off the tip here and go up.

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That's why it's called the oblique ligament.

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It's oblique. So the pol is torn.

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Now let's go back to our sagittal behind the pol

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is the OPL, the oblique papaltial ligament,

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which is fused with the capsule.

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We come down, it's gone.

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So that's also torn. And finally,

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the last component of the postural medial corner

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is the semimembranosus. There it is.

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It's a thick, black structure.

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It's a little bit gray.

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So it's sprained and swollen at its attachment.

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We've got a posteromedial corner injury and a PCl.

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If those two existed by themselves,

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this patient would be at risk for amri

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anteromedial rotatory instability.