People engaged in heavy physical or strenuous activities, in a certain action [foot and calf fixed, thigh and trunk by the body's inertial force or lateral impact, to the femoral condyles of internal rotation, calf adduction, external rotation, and the medial meniscus is squeezed between the tibiofemoral joint, and was forced to the center of the knee and the posterior side of the displacement. As the meniscus is tightly attached to the tibial plateau. The degree of movement is small, and it is easy to cause meniscus tear when the femoral condyle is strongly internally rotated].
Meniscus tear patients, due to the meniscus due to tear surface roughness, when the activities are easy to cause the knee joint strangulation, limited activities and other effects.
Arthroscopic manipulation of the meniscus is mainly to repair the non-smooth (rough) cartilage surface of the meniscus. The rough surface is planed to make it smooth and continue to function for knee joint movement.
The above is a personal opinion for reference.