The fabella (Latin for little bean) (or flabella) is a small sesamoid bone found in some mammals embedded in the tendon of the lateral head of the gastrocnemius muscle behind the lateral condyle of the femur. It is a variant of normal anatomy and present in humans in 10% to 30% of individuals. Rarely, there are 2 or 3 of these bones (fabella bi- or tripartita). It can be mistaken for a loose body or osteophyte.
The fabella is a standard finding on radiographs of the dog and cat, and both medial and lateral fabellae are typically present.