Sesamoid bone

A sesamoid bone is a bone embedded within a tendon.

Sesamoid bones can be found on joints throughout the body, including:

• In the knee — the patella (within the quadriceps tendon).
• In the hand — two sesamoid bones are commonly found in the distal portions of the first metacarpal bone (within the tendons ofadductor pollicis and flexor pollicis brevis). There is also commonly a sesamoid bone in distal portions of the second metacarpal bone.
• In the wrist - The pisiform of the wrist is a sesamoid bone (within the tendon of flexor carpi ulnaris).
• In the foot - the first metatarsal bone usually has two sesamoid bones at its connection to the big toe (both within the tendon offlexor hallucis brevis). In some people, only a single sesamoid is found on the first MTP.