What describes the location of sesamoid bones?

Sesamoid bones are specialized bones that are embedded within tendons. They are often found where a tendon passes over a joint, which helps to reduce friction and improve the mechanical advantage of the tendons. The primary example of sesamoid bones in the body is the patella, or kneecap, which is located in the tendon of the quadriceps muscle. This relationship allows them to function optimally by altering the direction of muscle forces, thus providing stability and facilitating movement at joints.

The other options do not capture the unique characteristics and functions of sesamoid bones as accurately. While sesamoid bones might be present in areas associated with complex joints, their defining feature is their location along tendons. They are not inherently flat in shape or irregular in form specifically because of their location—rather, they can come in various shapes and sizes but their primary identification is their position within tendons.