Sesamoid Bones

 
  • Sesamoid bones are embedded in certain tendons and generally related to joint surfaces.
  • They increase the lever arm of the muscle, or muscle group they are associated with.

Upper extremity Sesamoid Bones

  • generally only on the palmar surface of the hand.
  • Metacarpophalangeal joint of the thumb always has two
  • Metacarpophalangeal joint little finger frequent has one
  • Metacarpophalangeal joint the index finger is common.
  • Sesamoid bones are occasionally located at the metacarpophalangeal joints of the middle and ring fingers, at the interphalangeal joint of the thumb and at the distal interphalangeal joint of the index finger. 
  • Biceps brachii tendon opposite the radial tuberosity: occasional

Lower Extremity Sesamoid Bones

  • Patella: the largest sesamoid bone.  Is in the Quadriceps femoris over the knee joint.
  • Metatarsophalangeal joint of the great toe always has two
  • Metatarsophalangeal joints of the second and fifth toes may have one
  • Metatarsophalangeal joints third and fourth toes occasionally have one
  • Interphalangeal joint of the great toe occasionally has one.       
  • Peronæus longus tendon: common
  • Tibialis anterior tendon
  • Tibialis posterior tendon
  • Lateral head of the Gastrocnemius, behind the lateral condyle of the femur
  • Tendon of the Psoas major
  • Tendon of the Glutæus maximus