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Knee anatomy. Cruciates PCL.

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PCL is a central stabilizer arc-shaped, nice and black like most

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ligaments and tendons. Although because it's curved,

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it may be prone to a little bit of magic angle effect.

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We see its insertion on the deep posterior tibial notch,

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below the tibial plateau.

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Its origin and footprint, which is quite complex along the femur,

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in the inner aspect of the medial femoral condyle.

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This bumpy structure in front

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right here is the meniscofemoral ligament of Humphrey.

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Let's follow it and see it going up.

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And sometimes it'll have its own footprint of insertion.

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That's hard to discern in this projection.

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More linearly in this individual is the

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meniscofemoral ligament of wrisberg.

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Now, 80% percent of individuals have well-developed

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meniscofemoral ligaments. But 20%, they're hypoplastic

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and even absent. This patient has a very small hypoplastic

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meniscofemoral ligament of wrisberg, which may be a stabilizer

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of the lateral meniscus. So let's scroll it.

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We're more on the medial side now.

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So there is the most medial free edge of the PCL

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which is going to be the medial bundle or posteromedial bundle,

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which means there's an anterolateral bundle.

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Now, let's work our way backward and follow that

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meniscofemoral ligament of wrisberg.

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There it is, quite small, quite flat, rather hypoplastic.

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We lose it for a few moments, and then we gain it back right there.

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We gain it back right there. And it takes off from this

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superoposterior free edge of the lateral meniscus.

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Now occasionally, you will see a thin line at the site of takeoff,

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and I'm going to draw that line in.

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This patient doesn't have it,

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but you'll see it in many of the cases that I show, and that's a weak spot.

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For sometimes in pivot shift injuries and other causes of ACL tears,

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you will propagate a tear

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directly from this interface or takeoff of the ligament of wrisberg.

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This is the wrisberg ligament, which I'm drawing in right now.

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And then in some cases,

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you can follow it over when it's more well-developed.

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Let's look at the T1-weighted image and follow

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the arc shape and signal of the PCL.

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Now, it's a little grayer in the back and obscured

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because there's a sheath around the PCL.

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That sheath is continuous with the sheath of the ACL.

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So it's one sheath, but it sort of pops out or opens out the back.

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Doesn't open through the capsule,

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but it communicates with the posterior aspect of the knee.

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So if this thing becomes very distended,

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or there's an ACL or a PCL injury,

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it will become distended. It'll get nice and fat and juicy.

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Let me draw it for you.

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Get nice and fat and juicy.

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And sometimes it'll even wall off and make a cyst.

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It'll get sequestered.

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And occasionally,

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that cyst will pop through the oblique popliteal ligament,

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which I've drawn over right here.

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It'll pop out the back and go right into the popliteal fossa,

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and create some problems for the popliteal artery and vein.

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Now, when you're looking at cruciates, whether it's the PCL or the ACL,

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and especially in the sagittal projection,

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it is critical that you have a T2 that is aligned with the long axis of

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the ligament. And when I say T2, I mean a true T2, not a PD spur.

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Because in patients that have acute injuries with

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massive amounts of hemorrhage and swelling,

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everything may be obscured until you get that T2-weighted image

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except for the area of tear, which remains bright.

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So I do like to have a T2 spin echo for cruciates,

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in conjunction with my PD spur and my T1,

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at least until you get to the high-level expert to mastery level.

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So that's the anatomy of the PCL in the sagittal projection.

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Don't forget to tune into the other projections.