Fibrillation of the meniscus is observed as fraying of the free edge of the meniscus. This can be seen on an MRI as an area of increased signal intensity at the apex of a normal meniscus.
At first the meniscus may start to soften. This is sometimes labelled as Stage I degeneration. Stage II is fibrillation or fraying of the cartilage. Fibrillation is a sign of meniscal degeneration. Usually this occurs with aging but it can also be caused by trauma.
Stage III is a more severe case of fibrillation or fragmentation. Stage IV indicates the cartilage is worn clear down to the bone.