A meniscal avulsion is a traumatic incident that results in the knee meniscus - or a portion of it - tearing away from its previously firm anchorage to the tibia bone.

menisco-tibial avulsion or floating meniscus
An avulsion of the menisco-tibial ligament results in an incompetent 'floating' meniscus. The injury is generally associated with other ligamentous damage in the knee, although the meniscus itself is usually intact. (left: intact, right: avulsed)

 

Floating meniscus

This may be due to a tear of the menisco-tibial (a.k.a. coronary) ligaments that are a normal part of the anchorage system for the meniscus, and may be the result of a high-force injury. The condition is also called a floating meniscus as the MRI scan shows a fluid gap between the bottom of the meniscus and the tibia bone. Generally, the meniscus itself remains intact, but without this anchorage the meniscus becomes incompetent as a shock absorber.

 

Meniscus incompetence after meniscal root avulsion

Avulsion of the meniscal root can lead to immediate incompetence, and the meniscus may extrude over the edge of the tibia.

Synonyms: 
Meniscus avulsion
Floating knee meniscus
Floating meniscus
Menisco-tibial ligament avulsion
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An explanation of what it means to have a 'floating' knee meniscus on MRI imaging.

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CLINICAL PUBLICATIONS

The “Floating” Meniscus: MRI in Knee Trauma and Implications for Surgery Bikkina RS, Tujo CA, Schraner AB and Nancy M. Major NM. American Journal of Roentgenology. 2005;184: 200-204.

Technique for Arthroscopically Assisted Superficial and Deep Medial Collateral Ligament–Meniscotibial Ligament Repair With Internal Brace Augmentation. Aaron K. Black AK, Schlepp C, Zapf M and Reid JB III. Arthrosc Tech. 2018 Nov; 7(11): e1215–e1219.


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Embedded courtesy of Christopher Adams, MD