Sesamoid bones

The patella (: patellae or patellas), also known as the kneecap, is a flat, rounded triangular bone which articulates with the femur (thigh bone) and covers and protects the anterior articular surface of the knee joint. The patella is found in many tetrapods, such as mice, cats, birds, and dogs, but not in whales, or most reptiles.

bone of the wrist

bone embedded within a tendon or muscle

The fabella 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 an accessory bone, an anatomical variation present in 39% of humans. Rarely, there are two or three of these bones (fabella bi- or tripartita). It can be mistaken for a loose body or osteophyte. The word fabella is a Latin diminutive of faba 'bean'.