This is a common injury of the knee. Your knee joint is cushioned by two c-shaped wedges of cartilage called the "menisci." Each individual cushion is called a "meniscus." This injury is a tear of one of these cushions.
Meniscus tears are often caused by physical activity. Twisting or rotating your knee suddenly can cause a meniscus to tear. Kneeling, squatting and heavy lifting can as well. And as you age, your menisci gradually become thin and brittle, which can increase your risk for a tear.
Symptoms may include a popping sensation and pain in your knee. You may have trouble straightening your leg. It may swell and stiffen, and it may lock in place.
Treatment options include rest, ice and medications. You may benefit from physical therapy. If these are not helpful, you may benefit from a surgical procedure to repair the damage. Your healthcare provider can create a care plan that is right for your needs.