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Knee anatomy on MRI.

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The Medial Collateral Ligament.

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Layers number two and three.

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Layer two, unfortunately,

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the middle layer is also known as the Superficial MCL.

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This is confusing. You'll have to memorize it.

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Layer number three,

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also known as the Deep Layer,

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is composed of the joint capsule.

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And we're going to divide up layer number three into an

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anterior third, a middle third, and a posterior third.

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The anterior third of layer three is attached to the

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anterior horn of the medial meniscus, and includes the

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patellomeniscal ligament, which I'll show you.

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It's reinforced by some of the fibers very

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far anteriorly of the medial retinaculum.

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The middle third of layer three is known as the Deep MCL

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or medial capsular ligament.

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In other words, the capsule.

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And finally,

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the posterior third in the back of layer number three,

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the deep layer, is the posterior oblique ligament which

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is formed by fusion of layers number

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two and layer number three.

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There are three arms of this ligament,

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also known as the POL,

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superficial, tibial, and capsular.

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The oblique popliteal ligament is the last component of

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the posterior third of layer three and

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it's all the way around the back.

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The diagram will help make more sense of it.

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Here's a sagittal diagram showing the patella in the

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front and the medial gastrocnemius in the back

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to get you oriented, anterior to posterior.

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The anterior structures,

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the anterior deep structures are not really imaged here,

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other than the MPFL on this diagram,

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which is part of layer number two.

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The medial patellofemoral ligament goes right into the

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superficial MCL, which is the middle layer,

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which is vertically oriented,

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which many of you might have called

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it in the past, the tibial collateral ligament.

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And it's pretty short from front to back.

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It's in the middle of the coronal plane

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as we go from anterior to posterior.

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Now, when we get posterior,

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we start to blend layer number

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two into layer number three.

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There is a layer number three under here, but we can't

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see it because it's covered up by the middle layer.

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Layer number two, which is right there.

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Layer number three,

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which is merging or fusing with layer number two is

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called the POL or posterior oblique ligament.

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There might be a little plane of separation

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between the two for the surgeon.

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The POL has a triangular point to it posteriorly.

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If we were to wrap the POL around posteriorly,

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that would be part of the joint capsule, and that would

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be called the oblique popliteal ligament or OPL.

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So it would go OPL.

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layer three.

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POL,

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layer three.

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Superficial MCL,

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layer two.

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Underneath that is the capsule, part of layer number three.

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That may help make this more sensible for you using

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the diagram. Let's try a coronal diagram.

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Layer number one, the Crus layer.

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Layer number two,

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also known as the middle layer or

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superficial portion of the MCL,

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what many of you might have called

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the tibial collateral ligament.

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There is a fat pad between these two

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and sometimes between these two.

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Layer number three, the deep layer,

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has an anterior third,

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a middle third, and a posterior third.

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The middle third is composed of capsular tissue and the

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meniscofemoral and meniscotibial or coronary ligament.

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But as we get more posteriorly,

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let's see what happens.

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Here's layer number two,

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what we used to call the tibial collateral ligament,

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now known as the middle layer or superficial MCL.

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It is contiguous with the MPFL.

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This is also layer number two, which is fused,

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by the way, with layer number one.

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There's layer number one.

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And then finally, layer number three, the deepest layer,

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which is composed of the capsule,

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which becomes the OPL all the way around back,

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and is the POL in the posteromedial corner of the knee.

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Let's look at an MRI to help solidify these anatomic concepts.

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So, let's focus on layers number two and three

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in the axial projection on a T2 MRI.

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Here's layer number two,

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the medial patellofemoral ligament,

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which comes back posteriorly and becomes layer number

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two again, the superficial portion of the MCL,

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which you might have previously labeled as the

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tibial collateral ligament.

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Layer number two.

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Deep to this anteriorly is the meniscopatellar ligament.

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Layer number three.

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In the mid-coronal plane,

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the capsule makes up the deep

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layer or layer number three.

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And although it's difficult to see the capsule directly,

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we do see the meniscofemoral and meniscotibial

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coronary ligaments lining up in the mid-coronal plane in

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the middle of the knee to form layer number three.

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Then, as we move more posteriorly, let's do that.

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That tissue fuses layers number two with layer number three,

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the capsule, to form the POL.

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And sometimes with a little bit of joint fluid or a little swelling,

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you can clearly separate the POL from

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some of the surrounding structures.

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And then all the way around back is the OPL,

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the oblique popliteal ligament,

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which is the most posterior aspect of the deep

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portion layer number three of the MCL.

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This concludes our discussion of layers number two and

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three in the medial collateral ligament on MRI.