A sudden injury can tear the meniscus. This is often because of planting the foot and twisting the knee. Sports, such as soccer, football, and basketball, are often involved.
Between the bones of the knees are two crescent-shaped disks of connective tissue, called menisci, which also act as shock absorbers to cushion the lower part of the leg from the weight of the rest of the body. Meniscus tears can happen when twisting while bearing weight.