A sesamoid bone is one of the main types of bones classified by shape.
Sesamoid bones develop in some tendons in locations where there is considerable friction, tension, and physical stress. Typical areas in which they may form include the palms of the hands and the soles of the feet. The presence, location and and quantity of sesamoid bones varies considerably from person to person.
Most sesamoid bones are un-named.
Only one type of sesamoid bone is present in all normal human skeletons and so has a name. That is the patella (singular), patellae (plural). Patellae are also called "kneecaps". Complete human skeletons include 2 of these, one in each leg.
See also books about orthopaedics.