The Skeletal System: The Appendicular Skeleton - Chapter questions - Problem 12F

The patella is a sesamoid bone because it developed in tendons . The pisiform bone of the ankle is also a sesamoid bone. Sesamoid bones by definition are bones that develop in the tendons( or joint capsules). Sesamoid bones are not present in babies at birth. In the case of the patella , the cartilaginous precursor of the bone begins to calcify in the tendon of the quadriceps femoris muscle during the 3-6 year period of life. By age 10-12 the patella is fully formed-- though further calcification may continue for a few more years. Sesamoid bones are also found at various places in the hands: these include the metacarpo-phalangeal and the interphalangeal joints of the thumb, and the metacarpo-phalangeal joint of the little finger. There are also sesamoid bones under the metatarso-phalangeal joint of the great toe. The patella serves the following functions: 1. It protects the knee joint 2. It increases the leverage of the quadriceps femoris muscle. 3. When it tracts properly, it maintains the tendon in position as the knee is bent and straightened.