The type of meniscal tear is of relevance, as some tears can be treated surgically and some can not.
The meniscal damage may simply be a frayed edge - seen as ragged fronds on the sharp edge of the meniscus.
A frayed inner meniscal rim, seen frequently, is usually of little consequence. Surgeons usually trim away the area to tidy it up and prevent enzyme release from the area. All the surgeon can do here is to trim away the edge and hope that the fraying is contained.
More problematic is the degenerate meniscus, which refers to when the whole meniscus undergoes internal change, and simply collapses in a ragged fashion. The shock-absorber function is grossly impaired and the cartilage at the ends of the long bones of femur and tibia become stressed. Arthritis can ensue.
A sharp split from the medial rim towards the lateral rim (across the radius) is known as a radial tear. This is amenable to suture (stitching), but the inner part may not heal because of the poor blood supply in that area, so some trimming may be done by the surgeon. Still it is worth trying to get the outer part to heal, as this part is most important in the meniscus.
A neglected radial tear, usually an oblique one, may try to heal itself and round off into a rounded beak like a parrot's beak - the parrot-beak tear, and this can catch in the joint.
A circumferential tear extends along the length of the meniscus (along the circumference).
Such a tear renders the meniscus fairly incompetent, and the changed bio-mechanics of the knee may propagate the tear and prevent healing. These types of tear may not go through the full depth of the meniscus, but if they do, they are called 'bucket-handle- tears'.
The importance of the bucket-handle tear is that the 'handle' may flip over and be caught on the other side of the rounded condyle of the femur (rounded end of the thigh bone) and lock the joint, preventing full extension (straightening) and causing pain.
Each locking episode will stress the tear and cause it to get worse.
Again bucket handles in the white-on-white area (the inner area where blood supply is poor) are usually removed surgically as they do not heal, while surgeons may suture (sew) white-on-red and almost certainly will try to preserve red-on-red, which may even heal by themselves. The red-on-red area is the outer rim of the meniscus where blood supply is good.
A horizontal split in the body of the meniscus is usually called a 'horizontal cleavage tear'. These tears are a bit unusual. The tear usually begins quite hidden from view in the inner aspect of the body of the meniscus, although it may be evident on an MRI scan.
It most likely starts after a minor injury, followed by a degenerative process which starts in the damaged area. Regardless, the thing burrows away in the inside, splitting the meniscus into top and bottom sections. Eventually the tear breaks out at the inner aspect and reveals itself.
It may be a shock to an inexperienced knee surgeon, who opens the knee, to see what looks like a minor tear on the inner aspect. He/she trims this away, only to find the deeper and more drastic damage which just seems to go on and on.
The flap tear is also horizontal but at the surface of the meniscus rather than in the middle. The flap tends to flick over from time to time, causing symptoms.
The tear is fairly easily dealt with. The flap section is simply trimmed away - there is sufficient body of the meniscus to heal the defect and provide shock absorption to the knee.