A variety of different circumstances can lead to tearing of the meniscus. Forceful twisting of the knee is a common mechanism of injury.
However, tearing sometimes occurs when a person is simply standing up from a squatting position.
The main symptom is a sharp shooting pain in the knee, which may be accompanied by "locking" of the knee. Extensive swelling of the knee is common. The pain generally occurs during knee activity, e.g. when climbing stairs or bending the knees. However, the pain symptoms sometimes start at night when a person is resting (e.g. lying in bed) and can be very annoying.
Meniscus tears can also develop gradually due to degenerative changes in the knee without a sudden event or accident occurring. This often begins after the onset of arthritis in the knee.
The main symptom in these cases is diffuse pain that generally begins during weight bearing.
However, sudden sharp pain is possible, as is locking of the affected knee, albeit less frequent.