Sesamoid bone
Os sesamoideum
Definition
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 of adductor 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 of flexor hallucis brevis). In some people, only a single sesamoid is found on the first MTP.
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