Interactive Transcript
0:01
Knee anatomy on MRI, posteromedial corner,
0:05
focusing on the semimembranosus and its
0:08
expansions. Semimembranosus is a large muscle.
0:13
The semitendinosus rides along its posterior margin
0:16
or back up more approximately.
0:18
And as it comes down, it has
0:21
a very deep component known as the direct arm.
0:25
And this is the one you frequently
0:27
see attaching to the tuberculum tendinous along
0:30
the posteromedial aspect of the tibia.
0:35
It'll bifurcate into two structures
0:39
that one sees one anteriorly, not labeled here.
0:44
It's underneath the POL and the deep
0:46
portion of the superficial MCL, or superficial
0:51
portion of the deep MCL. Also known
0:53
as the tibial collateral ligament.
0:56
And here is the anterior reflected arm underneath, called the pars reflexa.
1:04
So you'll probably be able to see that.
1:06
You'll also be able to see the
1:08
distal continuation of the direct arm or
1:12
deep arm, more distally along the posteromedial aspect of the tibia.
1:17
More variable and often not seen on MRI
1:20
is the inferior (popliteal arm), which goes in between these two.
1:26
And then more posteriorly is the distal attachment of the inferior arm.
1:29
This goes a long ways down, and because of that,
1:32
it's sometimes more easily identifiable because of its distal extension.
1:37
And then, supporting the posteromedial capsule of the knee,
1:41
a little more in the front though,
1:43
is the capsular arm.
1:45
And then all the way in the back, becoming the oblique poploteal ligament,
1:51
is the OPL extension of the semimembranosus.
1:55
So the semimembranosus provides support
1:59
to the entire posterior capsule running from posteromedial
2:04
to posterolateral, along the back of the knee.
2:08
It's a little hard to appreciate on
2:09
this oblique projection, but you'll see what
2:12
we mean on other vignettes.
2:14
So those are the major expansion heads
2:17
of the semimembranosus.
2:19
As you can see, we've added an
2:20
important division here, the pars reflexa, which runs
2:23
anteriorly underneath the POL and the direct
2:27
arm, which runs more oblique inferior
2:31
and inserts on the tuberculum tenderness
2:33
a little protrusion or bony protrusion along the
2:36
posteromedial edge of the tibia.
© 2024 MRI Online. All Rights Reserved.