Torn meniscus is a common knee injury. Each of your knees has two menisci—one at the outer edge and one at the inner—and each is a rubbery, C-shaped disc that cushions your knee. The menisci keep your knee steady by balancing weight across the knee.
A torn meniscus is often caused by twisting or turning quickly, with the foot planted and the knee bent. The tear can also occur when you lift something heavy or play sports. The menisci get worn with aging and can tear more easily. The injuries vary by degree of severity. In the most serious tears, pieces of the torn meniscus can move into the joint space causing your knee to pop or lock and you may not be able to straighten it. Your knee may feel wobbly and give way without warning, or swell and get stiff right after the injury or within two to three days.
Surgery to repair or remove part of the meniscus may be the required treatment.