Final answer:
The patella is classified as a sesamoid bone because it is located within tendons and aids in protecting them against compressive forces. It articulates with the femur to prevent tendon rubbing and increases the leverage of the quadriceps femoris muscle.
Step-by-step explanation:
The patella is classified as a sesamoid bone because it is located within tendons, specifically the tendon of the quadriceps femoris muscle. These sesamoid bones are small, flat, and resembling a sesame seed in shape. They develop in tendons where there is significant pressure from joint movement, and their primary function is to protect tendons by helping them cope with compressive forces.
Additionally, the patella articulates with the patellar surface of the femur, preventing the tendon from rubbing against the bone and enhancing the leverage power of the quadriceps femoris muscle during knee extension. Unlike other bone types, sesamoid bones, including the patella, do not have a diaphysis and epiphyses, are not irregular in shape, nor are they longer than they are wide. The patellae (singular = patella) are the only sesamoid bones present in every person, located near joints such as the knees, hands, and feet.