There are many causes for meniscus tears, the most common are results of activity or degeneration with age. The first and most common cause for a torn meniscus happens during physical activity or athletics. When your weight is planted and your knee twists is another direction, the cartilage in your meniscus can tear or rip. This will cause pain and swelling. The other main way that a meniscus can tear is due to age. Since the meniscus is made of cartilage, over time it becomes more brittle and is more prone to tearing. This is commonly known as a torn meniscus due to the degenerative process.