The fabella bone is a small sesamoid bone found buried in the gastrocnemius close to the proximal attachment behind the knee at the level of the mid-patella and posterior to the distal femur. It has no bony attachments.
Fabella is the Latin word for bean. It occurs in 3% to 5% of the population and is readily appreciable on lateral radiograph (X-ray) of the knee. It is sometimes mistaken for a bone chip off the femur in the inexperienced.