Meniscal lesion

Types of meniscal lesions:

1-Degeneration.

*Is presence of abnormality inside meniscus without touching borders.

*Borders of the meniscus are the superior articular surface, inferior articular surface and the border attached to the capsule is known as menisco-capsular attachment. 

*Types of degeneration:

Type 1: Appears as a dot of increased intensity inside meniscus not attaching to wall of meniscus.

Type 2:Appears as a line without attaching to any wall of meniscus.

If type 2 is extending to cut one of the meniscal border, this means a tear and not degeneration.

When this line extend to superior or inferior articular surfaces of the meniscus or both, this considered to be a tear, but if it extend to menisco-capsular attachment, here it is considered degeneration and not a tear.

*Simple tear is when this line extend to one border, while complex tear is when the line extends to both borders.

*Meniscal fraying: No abnormality could be seen inside the meniscus but its edge is serrated 9 here you find the apex of posterior horn is showing hyper intensity.

2-Tear: 

*Types of tears:

Simple horizontal tear which is usually degenerative in origin.

Simple vertical tear which is due to trauma.

Complex tear which could be Bucket handle tear or Flap tear.

*Flap tear means simply both simple horizontal and vertical tears at the same time( a tear has a horizontal component and vertical component).

*Bucket handle tear :

Is due to a crack in the substance of the meniscus.

Due to movement of the knee, this crack will be increased in length resulting in inversion of the inner part of the meniscus while the outer part is still in its normal position.

How to diagnose the Bucket handle tear:

The first sign is decrease in the size of the posterior horn of the medial meniscus.

Go to the intercondylar notch searching for missed part of the posterior horn. You will find it below the posterior cruciate ligament in the sagital plane what is known double posterior cruciate ligament sign.

In the coronal view, you will find the posterior horn is small in size while the fragment is also seen below posterior cruciate ligament in the inter condylar notch.

In case of Bucket handle tear of the posterior horn of the lateral meniscus, you will see double delta sign in which you will see the fragment of the posterior horn is present posterior to anterior horn of the lateral meniscus in the sagital plane. 

 3-Meniscal cyst.

-A cyst extending from a meniscal tear.

-Common sites:

Anterior horn of the lateral meniscus.

Posterior horn of the medial meniscus.

Appears as a ball of water seen at the base of the teared meniscus.

So you will see a horizontal hyper intense line joining menisco-capsular attachment withe evidence of  a cyst beside this capsular attachment.

4-Discoid meniscus(very common at the lateral aspect).

Diagnosed when you see meniscal body segment in 3 or more sagital images(normally it is seen in one or two section only).

Click diagram to enlarge