There are a number of injuries that can cause extreme pain in the knee, and one of those injuries is a meniscus tear. This happens when the cartilage is torn, usually due to a twisting movement in the knee while it has weight on it. There are two types of meniscus tears, partial and total, and both are common conditions in athletes who are doing a lot of running, such as soccer players.
The meniscus is a very small piece of cartilage, one so small that it is hard to believe that tearing it can cause so much pain. The meniscus cartilage is small and c-shaped, and there are three that protect and cushion the knee joint: one between the thigh bone and shin bone (femur and tibia), one on the outside of the knee (known as the lateral meniscus), and the other on the inside of the knee (the medial meniscus).
The most common symptom of both partial and total meniscus tears is pain, especially when the leg is extended (held out straight). Depending on how badly the meniscus is torn, the pain can range from mild to severe.