0:01

Knee anatomy.

0:03

Cruciates.

0:04

The all-important, ACL or anterior cruciate ligament.

0:09

The ACL is a two-bundled ligament.

0:12

It's got a smaller anteromedial

0:15

and a larger posterolateral

0:20

Here's our ligament right here.

0:22

And this spot right here where it enters

0:25

the femur, is a critical position

0:30

The ACL comes down,

0:32

it slopes down obliquely from

0:37

We'll see in the coronal projection,

0:41

And as it gets down more distally, it starts to fan out.

0:46

And that fanning is normal.

0:49

The bundles of the ACL are arranged,

0:54

They're mostly parallel.

0:55

And you know that the end of a piece of a celery does fan out.

1:01

On an MRI, the upper portion

1:03

of the ligament looks a little pinched,

1:07

for when you look at it in the axial

1:14

Now, the functional ACL fiber recruitment

1:17

is more complicated than just a one

1:22

The ACL is the primary restraint

1:29

So if you have an ACL that is deficient,

1:35

high-grade or full-thickness tear,

1:40

the anterior cruciate ligament supporting structures,

1:45

you will see when you're lying on your

1:50

We'll talk more about this as this is

1:53

the sign of passive anterior tibial

1:59

in the diagnosis of ACL deficiency,

2:05

Now, the posterolateral bundle provides

2:08

principal resistance to hyperextension force.

2:12

The cruciate ligament is surrounded

2:16

I'm going to color it in just for fun.

2:18

I'll make it kind of orangey right there.

2:22

And that sheath is common to the ACL and the PCL.

2:27

And together, they have a little

2:31

I should make my blowhole

2:34

I'll pick black, in fact.

2:36

So there's a little blowhole coming

2:39

I'm going to make it black.

2:40

And here it is.

2:42

It communicates with the sheath of the ACL and PCL.

2:45

And it'll distend if there is fluid or injury in this joint.

2:50

And sometimes, it'll even poke through

2:56

sort of blue ligament, which is known

3:00

And it'll go right through it and can

3:06

So, in summary, we've got a two bundled

3:09

structure, an anteromedial and a posterolateral.

3:13

One a restraint to the tibia, the other supporting the knee

3:17

and hyperextension,

3:21

You have anterior tibial translation.

3:24

They're surrounded by a sheath that has

3:27

a little blowhole or connection hole in the back.

3:30

And when this sheath fills with fluid,

3:32

this area may distend and push

3:37

And there are key areas of penetration

3:42

One called the over the top position

3:44

back here, and the other one in the tibia

3:48

Let's separate that as a vignette for now

3:51

and you can move on to the next

Basic Anterior Cruciate Ligament (ACL) Anatomy

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Pro Tip: Click on a word in the transcript to jump to that point in the video

0:01

Knee anatomy.

0:03

Cruciates.

0:04

The all-important, ACL or anterior cruciate ligament.

0:09

The ACL is a two-bundled ligament.

0:12

It's got a smaller anteromedial

0:15

and a larger posterolateral

0:20

Here's our ligament right here.

0:22

And this spot right here where it enters

0:25

the femur, is a critical position

0:30

The ACL comes down,

0:32

it slopes down obliquely from

0:37

We'll see in the coronal projection,

0:41

And as it gets down more distally, it starts to fan out.

0:46

And that fanning is normal.

0:49

The bundles of the ACL are arranged,

0:54

They're mostly parallel.

0:55

And you know that the end of a piece of a celery does fan out.

1:01

On an MRI, the upper portion

1:03

of the ligament looks a little pinched,

1:07

for when you look at it in the axial

1:14

Now, the functional ACL fiber recruitment

1:17

is more complicated than just a one

1:22

The ACL is the primary restraint

1:29

So if you have an ACL that is deficient,

1:35

high-grade or full-thickness tear,

1:40

the anterior cruciate ligament supporting structures,

1:45

you will see when you're lying on your

1:50

We'll talk more about this as this is

1:53

the sign of passive anterior tibial

1:59

in the diagnosis of ACL deficiency,

2:05

Now, the posterolateral bundle provides

2:08

principal resistance to hyperextension force.

2:12

The cruciate ligament is surrounded

2:16

I'm going to color it in just for fun.

2:18

I'll make it kind of orangey right there.

2:22

And that sheath is common to the ACL and the PCL.

2:27

And together, they have a little

2:31

I should make my blowhole

2:34

I'll pick black, in fact.

2:36

So there's a little blowhole coming

2:39

I'm going to make it black.

2:40

And here it is.

2:42

It communicates with the sheath of the ACL and PCL.

2:45

And it'll distend if there is fluid or injury in this joint.

2:50

And sometimes, it'll even poke through

2:56

sort of blue ligament, which is known

3:00

And it'll go right through it and can

3:06

So, in summary, we've got a two bundled

3:09

structure, an anteromedial and a posterolateral.

3:13

One a restraint to the tibia, the other supporting the knee

3:17

and hyperextension,

3:21

You have anterior tibial translation.

3:24

They're surrounded by a sheath that has

3:27

a little blowhole or connection hole in the back.

3:30

And when this sheath fills with fluid,

3:32

this area may distend and push

3:37

And there are key areas of penetration

3:42

One called the over the top position

3:44

back here, and the other one in the tibia

3:48

Let's separate that as a vignette for now

3:51

and you can move on to the next

Report

Description

Faculty

Stephen J Pomeranz, MD

Chief Medical Officer, ProScan Imaging. Founder, MRI Online

ProScan Imaging

Lesson

MRI Mastery Series: Knee Pre Course Activities

Lesson

Knee - Anatomy of the Supporting Structures

Lesson

Supporting Structure Anatomy: Focus on the Posterior Corners

Lesson

Case Review: Supporting Structure Injuries

Lesson

Meniscus MRI

Lesson

Pivot Shift Injuries and Meniscal Pathology

Lesson

More Meniscus Tears with Case Examples

Lesson

Applying What You've Learned

Basic Anterior Cruciate Ligament (ACL) Anatomy