0:00

Here we have a 55-year-old man who has chronic

0:04

knee pain, both medially and laterally.

0:08

This is a 3D space,

0:10

T2 weighted sequence,

0:12

running through the posterior aspect

0:15

of the tibial plateau.

0:17

You can see the PCL coming down

0:19

to insert here centrally.

0:21

And then when we look at the root

0:23

insertions of the menisci,

0:26

we have the medial meniscus here

0:29

and the lateral meniscus.

0:31

What we are missing on the medial side

0:34

is the root insertion to the tibia.

0:37

So, this area here is missing from the picture.

0:43

And that is really, really important

0:46

because once we have a root tear

0:48

of the medial meniscus,

0:51

the hoop mechanism that provides biomechanical

0:55

function to that meniscus,

0:57

the capacity to absorb weight bearing force

1:02

through the medial joint space, is lost.

1:05

And we often see what is happening here.

1:08

The meniscus starts to slide medially out of the

1:12

joint space, what we call meniscal extrusion.

1:15

This patient has partial meniscal extrusion.

1:18

The typical finding on sagittal images in this

1:23

type of injury of the root insertion

1:25

is what we call a Gauss meniscus.

1:29

And I'm going to show you that right

1:32

now here on the sagittal images.

1:34

We start in the body segment and we're going

1:37

to walk our way on the posterior horn.

1:41

And then all of a sudden,

1:43

we lose that posterior horn.

1:45

So, this is a radial tear of the posterior horn of

1:50

the medial meniscus that has a positive ghost sign

1:55

because there is no substance seen in that slice.

2:01

And that's the reason to call the sign a ghost sign.

2:05

Now, as we go into the axial plane,

2:08

we are here parked right at the level

2:11

of the posterior root insertion.

2:13

And I want you to see the gap.

2:16

So, there is a fluid fill gap there,

2:19

going through the root insertion.

2:22

This is now amenable for surgical repair.

2:26

It can be tagged down using an anchor suture.

2:30

And it's a very important finding

2:32

to make on your report.

2:35

Full thickness tear,

2:37

posterior horn,

2:39

root insertion of the medial meniscus tear.

Wk 4, Case 4 - Review

HIDE

Prev Next

Interactive Transcript

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

0:00

Here we have a 55-year-old man who has chronic

0:04

knee pain, both medially and laterally.

0:08

This is a 3D space,

0:10

T2 weighted sequence,

0:12

running through the posterior aspect

0:15

of the tibial plateau.

0:17

You can see the PCL coming down

0:19

to insert here centrally.

0:21

And then when we look at the root

0:23

insertions of the menisci,

0:26

we have the medial meniscus here

0:29

and the lateral meniscus.

0:31

What we are missing on the medial side

0:34

is the root insertion to the tibia.

0:37

So, this area here is missing from the picture.

0:43

And that is really, really important

0:46

because once we have a root tear

0:48

of the medial meniscus,

0:51

the hoop mechanism that provides biomechanical

0:55

function to that meniscus,

0:57

the capacity to absorb weight bearing force

1:02

through the medial joint space, is lost.

1:05

And we often see what is happening here.

1:08

The meniscus starts to slide medially out of the

1:12

joint space, what we call meniscal extrusion.

1:15

This patient has partial meniscal extrusion.

1:18

The typical finding on sagittal images in this

1:23

type of injury of the root insertion

1:25

is what we call a Gauss meniscus.

1:29

And I'm going to show you that right

1:32

now here on the sagittal images.

1:34

We start in the body segment and we're going

1:37

to walk our way on the posterior horn.

1:41

And then all of a sudden,

1:43

we lose that posterior horn.

1:45

So, this is a radial tear of the posterior horn of

1:50

the medial meniscus that has a positive ghost sign

1:55

because there is no substance seen in that slice.

2:01

And that's the reason to call the sign a ghost sign.

2:05

Now, as we go into the axial plane,

2:08

we are here parked right at the level

2:11

of the posterior root insertion.

2:13

And I want you to see the gap.

2:16

So, there is a fluid fill gap there,

2:19

going through the root insertion.

2:22

This is now amenable for surgical repair.

2:26

It can be tagged down using an anchor suture.

2:30

And it's a very important finding

2:32

to make on your report.

2:35

Full thickness tear,

2:37

posterior horn,

2:39

root insertion of the medial meniscus tear.

Report

Patient History
55-year-old man with left lateral and medial knee pain after walking up and down stairs.

Findings
Menisci:

Medial Meniscus: Chronic trizonal radial tear of the posterior meniscal root with slight meniscal body partial extrusion related to altered hoop tether. No displaced or flipped fragment.

Lateral Meniscus: Intact.

Ligaments:

Anterior Cruciate Ligament: Intact.

Posterior Cruciate Ligament: Intact.

Medial Collateral Ligament: Intact.

Lateral Collateral Ligament: Intact.

Posterolateral Corner Structures: Intact.

Posteromedial Corner Structures: Intact.

Extensor Mechanism:

Patellar Tendon: Intact.

Distal Quadriceps Tendon: Intact.

Medial Patellofemoral Ligament: Intact.

Medial and Lateral Patellar Retinacula: Intact.

Hoffa’s Fat Pad: Incidental 0.9 x 0.7 cm inferior pretibial multiloculated ganglion cyst. Diffusely thickened and swollen infrapatellar plica and superolateral edema consistent with chronic patellofemoral maltracking.

Articulations:

Patellofemoral Compartment: Low-grade trochlear dysplasia with mild trochlear groove insufficiency. Dysplastic Wiberg 3 patella with broad flat lateral facet and an elongated partially covered odd facet. Borderline TT-TG distance measuring 1.6 cm. No patella Alta or Baja. Full-thickness flap-like fissures at the patellar ridge and medial patellar facet with subtle underlying reactive osteoedema. Low-grade trochlear chondromalacia.

Medial Compartment: Smooth intermediate-grade chondral loss seen at the medial aspect of the medial femoral condyle and tibial plateau weight-bearing surfaces. No full-thickness or penetrating chondromalacia.

Lateral Compartment: Unremarkable.

General:

Bones: Unremarkable.

Effusion: Small to moderate-sized suprapatellar effusion with diffuse reactive capsular synovitis.

Baker’s Cyst: Moderate-size gastrocnemius-semimembranosus cyst measuring 6.7 x 2.8 x 1.4 cm and evidence for partial dehiscence (small amount of extravasated fluid at the inferior aspect of the gastrocnemius semimembranosus bursal cyst). No evidence for extension into the popliteal fossa. No neurovascular bundle compression.

Loose Bodies: None.

Soft tissue and Neurovascular: Unremarkable.

Conclusion
1.Chronic trizonal radial tear posterior root medial meniscus with associated intermediate-grade chondromalacia involving the weight-bearing surfaces of the medial tibial plateau and femoral condyle.
2.Partially dehisced gastrocnemius-semimembranosus bursal cyst (Baker’s cyst).
3.Focal full-thickness chondral fissures of the mid patella apex and inferomedial patellar facet with subtle underlying reactive osteoedema.

Case Discussion

Faculty

Omer Awan, MD, MPH, CIIP

Associate Professor of Radiology

University of Maryland School of Medicine

Stephen J Pomeranz, MD

Chief Medical Officer, ProScan Imaging. Founder, MRI Online

ProScan Imaging

Jenny T Bencardino, MD

Vice-Chair, Academic Affairs Department of Radiology

Montefiore Radiology

Edward Smitaman, MD

Clinical Associate Professor

University of California San Diego

Practice Cases

Worklist 1

Practice Cases

Worklist 2

Practice Cases

Worklist 3

Practice Cases

Worklist 4

Practice Cases

Worklist 5

Wk 4, Case 4 - Review