The meniscus is a piece of cartilage in the middle of your knee.
Cartilage is tough, smooth, rubbery tissue that lines and cushions the surface of the joints.
If a meniscus tears, it can cause knee pain and can limit motion. A meniscal tear can occur when the knee is forcefully twisted or sometimes with minimal or no trauma, such as when you are squatting. You have immediate swelling with fluid in the joint, called an effusion. You can't fully bend or straighten your leg. Your knee locks or gets stuck in one place.