Explanation:

• The patella, also known as the kneecap, is a flat, circular-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 and birds, but not in whales, or most reptiles.
• In humans, the patella is the largest sesamoid bone in the body. Babies are born with a patella of soft cartilage which begins to ossify into bone at about four years of age.