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Knee Basic Anatomy focused on ligaments.

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Let's begin in the midline where we've got the

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all famous, anterior cruciate ligament.

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It's a little pinched at the top,

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fans out at the bottom.

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It's composed of an anteromedial

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and posterolateral bundle,

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inserting on the intratibial spinous region with some

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fibers headed towards the anterolateral meniscus.

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It's fan-shaped distally.

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It's straight with the knee in slight flexion.

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Then we've got the blacker, thicker,

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curved posterior cruciate ligament with its very broad

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origin footprint from the femur and its hidden insertion

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in the tibial notch posteriorly because the surgeon

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can't see back there with the anterior cruciate ligament

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in the way. So this is more or less a hidden area.

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In the front of the PCL is the ligament of Humphrey.

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In the back is the ligament of Wrisberg.

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More on that later when we get into

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individual ligamentous anatomy.

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These are stabilizers for translation

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of the tibia front to back,

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which we will also discuss a little bit later on.

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So let's head over to the lateral side.

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We've got the posterolateral corner.

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It consists of innumerable structures

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that will get its own vignette.

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One of the most prominent is the popliteofibular

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ligament, which is oft ignored,

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and the arcuate ligament behind it.

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But there are more structures buttressing

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the posterolateral corner.

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Then let's swing over to the posteromedial corner,

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where the highlight is a combination of,

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unfortunately, a tendon, the semimembranous tendon,

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the major stabilizer along with its five

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arms which we'll discuss on the tibia.

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And some reflect back a little more proximally,

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some reflect a little more anteriorly,

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and the capsule which provides further quasi ligamentous

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support of the meniscus and detailed discussion of

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the posterior medial corner will be undertaken.

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Now, let's go to the axial.

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Is there a ligament in the axial? You bet there is.

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There's an important ligament.

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It's the medial patellofemoral ligament.

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Let's follow it.

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Here it is, right there.

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It is often incorrectly called the medial retinaculum.

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That is not the medial retinaculum.

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The medial retinaculum is this very thinner,

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wispier structure on top of it.

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The MPFL or medial patellofemoral ligament comes back

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and merges with this thickened structure called the

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tibial collateral ligament, which is the middle

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layer of the medial collateral ligament.

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When this structure is interfered with,

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the patella now loses its stability and will

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drift sublux or dislocate laterally.

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So the cruciates stabilize the femotibial relationship.

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The medial patellofemoral ligament or MPFL stabilizes

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the patellofemoral relationship.

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Now, let's drop down and look at our coronal.

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We've got medial ligaments and lateral ligaments.

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Let's begin on the medial side.

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Now, not that well seen because it's a darker image.

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In other words, it's fat suppressed.

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So most of the soft tissues and muscles

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and bone are darker.

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But we do see a whispy, very thin, darker structure,

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superficially, and that is known as the superficial

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crus or layer one of the MCL.

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By the way,

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it fuses with the medial retinaculum

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next to the patella.

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Then we've got the middle layer,

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which is known as the tibial collateral ligament.

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That is the one that's going to fuse with the MPFL.

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Then we've got a deeper layer, which consists of capsular

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reflection tissues and the meniscocapsular

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attachment to the femur.

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Let me blow it up a little bit so you can see

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it a little better.

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Here it is, right there,

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the meniscofemoral ligament,

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and there's a meniscotibial ligament right here.

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It's a little obscured by some vessels but it curves

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down and inserts on the tibia, also known as the coronary

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ligament. Now, as we go back a little ways,

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this ligament, I'm going to draw over it right now.

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A posterior oblique ligament of the knee is often ignored

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and it's going to get its own vignette.

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But that's the basic story

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for the medial collateral ligament.

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We've got layer one right there,

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layer two right here, and layer three right here.

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And if I did or performed a T1-weighted image,

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you'd see a little fat pad in between.

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If this was a normal knee with no expression of

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inflammation or osteoarthritis, which this one is.

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I just don't have a T1-weighted image to show you yet.

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Now, let's go over to the lateral side.

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The lateral collateral ligament at

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first glance appears pretty easy.

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Now, frequently surgeons will say lateral collateral ligament

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and use that term interchangeably for this,

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the fibular collateral ligament.

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Perhaps we should call it a lateral collateral ligament

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complex, because we have a tendon that supports the

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lateral side in the popliteus notch

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called the Popliteus tendon.

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It takes off below the fibular collateral ligament.

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So this would be the footprint origin of the FCL.

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And the FCL comes down and it merges with the tendon of

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the biceps femoris, and what's known

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as the conjoint tendon.

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Now, this is a misnomer because they're actually

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not conjoined. They have separate footprints.

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But for all intents and purposes,

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they look like they merge,

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the fibular collateral ligament and the tendon of the

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biceps femoris, inserting along the lateral aspect of the

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fibular head. And these two are stabilizers

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in varus for the lateral side.

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And a stabilizer for valgus on the medial side.

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So now you've got some basic ligamentous anatomy.

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We've shown you the posteromedial corner,

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posterolateral corner, basic, basic. The MCL.

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Three layers. Basic.

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The LCL, some very basic structures. The Cruciates,

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which stabilize the femoral tibial translational relationship.

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And the MPFL,

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the medial patellofemoral ligament, which holds the

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patella in place and prevents it from dislocating.

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And it merges with the tibial collateral

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ligament more posteriorly.