Floating meniscus
A floating meniscus is really a radiological diagnosis where the MRI scan reveals a fluid gap between the bottom of the meniscus and the tibia bone, where the meniscus has avulsed from the tibia.
The meniscus itself is not actually torn, but without this anchorage to the tibia it becomes incompetent as a shock absorber.
The injury is generally associated with other ligamentous damage in the knee, although the meniscus itself is usually intact.
The issue is a "....detachment from the tibial plateau with an associated disruption of the meniscotibial coronary ligaments, which attach the meniscus to the tibia...."
"The presence of a floating meniscus on MRI is a result of significant trauma to the knee leading to meniscal avulsion and is often associated with significant ligamentous injury."
Meniscal root avulsion
A meniscus can also become incompetent due to an avulsion of the meniscal root.
This can lead to immediate meniscal incompetence, and the meniscus may extrude over the edge of the tibia (meniscal extrusion).
Other relevant links on KNEEguru
A-Z Keywords - Meniscotibial ligament, Floating meniscus, Meniscal root avulsion, Meniscal extrusion
Interpretations of Journal publications -
Primer - Part 3 - What kind of problems do you get with 'knee cartilages'?
e-Books