Damage to one/both of the horse-shoe-shaped discs of cartilage (meniscus) in the knee, usually in the form of a tear in the meniscus on the inner side of the knee, caused by twisting the bent knee, as a result of which the foot cannot move properly. It often occurs in sports such as football. A ligament may be damaged at the same time. The symptoms are pain and swelling. The swelling is the result of increased production of fluid in the joint and possible haemorrhage (joint haemorrhage) in the knee. The injury can be associated with a feeling of something snapping and the knee sometimes locks in a bent position. Diagnosis is usually simply made but an X-ray of the knee may be necessary, using contrast materials or an injection of air into the knee to show up any possible damage more clearly. An arthroscopic examination may also be made. Treatment is by rest and a pressure banadage. If symptoms persist the damaged meniscus may have to be surgically removed (meniscectomy).