0:00

Let's turn now to the extensor mechanism itself.

0:03

So the extensor mechanism, the components

0:06

that we wanna consider are going to be the quadriceps,

0:10

patella, patella art tendon, and the tibial tuberosity.

0:14

These make up the structures that extend the knee.

0:18

We also have to consider the medial

0:21

and lateral patella reac, which are also portions

0:25

of the extensor mechanism,

0:27

and allow for some communications between the anterior knee

0:32

and the medial and lateral soft tissue capsular structures.

0:36

So all of that is what we're gonna be, uh, looking at.

0:40

So the superficial portions of it extend

0:43

and stabilize the patello femoral joint.

0:46

So the superficial portions being the rectus ephemeris

0:51

and the reac contributions from the vastus medias.

0:56

And Alis, as we get deep

0:59

back into the posterior fibers of the medias and lateralis

1:03

and certainly the, uh, ssus intermediates,

1:07

its only function is going to be

1:08

to extend, uh, the knee joint.

1:10

So those are the two things

1:12

that we need are extension mechanism to do for us.

1:16

These are some sections from the visible human project

1:19

from up to down just to illustrate

1:22

how this tendon is formed.

1:24

So you'll see that this rectus femoral muscle

1:28

terminates quite a bit above the knee joint.

1:31

In fact, we often don't include any

1:33

of the rectus femoral muscle on our imaging.

1:37

So that is already becoming small.

1:40

And on the next image has formed the tendon

1:42

that's located most anteriorly.

1:45

The vast medias

1:47

and lateralis are gonna contribute tendon slips that

1:51

extends just behind the rectus.

1:53

And then the vastus intermediates its tendon forms on its

1:57

anterior surface and is located further posteriorly.

2:03

So on these images which are lower down,

2:06

you can see a trilaminar structure over here

2:09

with the rectus tendon.

2:10

Notice that the rectus muscle has already faded away.

2:14

Here we have the vastus medias and laterals tendon,

2:18

and at the back of it is going

2:20

to be the vastus intermediates, uh, tendon.

2:23

You can see that there are a few small muscle slips

2:26

located anterior the femur.

2:29

These are portions of the gen artis,

2:32

which are variable in size.

2:33

They tend to be larger in the, uh, patients who are very,

2:37

very athletic,

2:38

and you don't want to confuse those, uh, with,

2:41

uh, with pathology.

2:44

Here's an, a ex,

2:45

an a r specimen axial showing you those three layers.

2:49

And when we look at the tendon on Mr Imaging,

2:53

you can see a variety of different appearances.

2:56

In fact, it may change as you go medial to lateral,

2:59

But the classic appearance is a trilaminar tendon.

3:03

Uh, but it will often look quadri, laminar, or bi laminar.

3:07

So it's not unusual to see intermediate signal

3:11

between these layers.

3:12

That is a function of its anatomy,

3:14

and you don't want to confuse that with tendinosis

3:17

or longitudinal tearing of the tendon.

3:20

I think if you go to your axial images

3:22

and look at the tendon tissue itself, you can see

3:25

that it's not thickened at all,

3:27

and we don't have any, uh, striations

3:29

or any abnormality within the tendon tissue.

3:35

I mentioned earlier that the, uh, quadriceps

3:39

covers the anterior patella,

3:41

and this has been referred to as the, uh,

3:44

quadriceps continuation.

3:46

And it is the fibers of the rectus femoral that will travel

3:51

a fairly thin layer of fibers will go ahead

3:54

and cover their very deeply

3:56

and densely adherent, uh, to the, uh, to the, uh,

3:59

anterior patella.

4:01

So you may sometimes see abnormalities in there

4:04

with some tendinosis

4:05

or tearing, extending, uh, into those fibers.

4:08

And that can be associated with bone marrow edema

4:11

and certainly with enthesopathy at the patella insertion.