The subtype 4A is a complete longitudinal vertical tear of the red-red zone of the meniscus,
The subtype 4B involves a complete tear of the junction itself where the meniscocapsular and meniscotibial fibers attach to the posterior horn.
A very peripheral meniscal tear(ramp type 4A lesion) can mimic ramp type 4B lesion.
(Type 4B ramp lesion) There are edema and irregularity of the meniscocapsular junction of the posterior horn with small bone bruise.
(Type 4A ramp lesion) In the normal medial meniscus, the posterior horn is larger than the anterior horn. If this free floating meniscal fragment is a thick posterior capsule, the posterior horn is smaller in size than the anterior horn. So it can be seen as a complete longitudinal tear, this is not a thick posterior capsule.
Is this case type 4A or type 4B?
(Type 4A vs type 4B) There is a fluid filled vertical line at the meniscocapsular junction.
It is difficult to distinguish meniscocapsular separation from far peripheral vertical longitudinal tears of the meniscal substance.
I think this is type 4B ramp lesion rather than type 4A lesion.
Because it is too small to be considered a meniscal fragment, it seems appropriate to consider this as a posterior capsule.
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