Meniscus tears can happen during a sudden rotating movement while bearing weight, such as when twisting the upper leg while the foot stays in one place during sports and other activities. This is known as a traumatic tear. Or meniscal tears can develop over time (degenerative). This is when routine activities, such as jogging or yard work, cause tears in the meniscus that have been weakened over time because of age, arthritis, or other conditions. Degenerative meniscal tears are most common in adults older than 40. Tears can be minor, with the meniscus staying connected to the knee. Or they can be major, with the meniscus barely attached to the knee by a cartilage thread.