Corpus: Sesamoid bone

Sesamoid bones act as spacers keeping the tendon away from the surrounding bones and as a kind of pulley (Hypomochlion). This optimizes the biomechanical effect of the tendon, achieving better leverage. Furthermore, sesamoid bones prevent pressure damage to the tendon as it passes over the joint.

The largest sesamoid bone in humans is the patella. Other sesamoid bones are partly accessory bones, which do not occur in all people.

Lower extremity

In the area of the lower extremity, distinctions are made between:

• Fabella: Sesamoid bone in the tendon of the gastrocnemius muscle (usually the lateral head)
• Cyamella: In the Popliteus tendon, usually lateral to the distal femur
• Os peroneum: In the Peroneus Longus tendon on the lateral plantar side of the cuboid bone
• Sesamoids of the Hallux (Ossa sesamoidea pedis): Medial and lateral sesamoid in the tendons of the flexor hallucis brevis muscle, in the area of the head of the first metatarsal bone.

Hand

In the hand, the pisiform bone is found in the tendon of the flexor carpi ulnaris muscle, and almost always two sesamoid bones in the area of the first MCP joint. Other locations include:

• Interphalangeal joint I (thumb distal joint)
• MCP joint II and V, less commonly III and IV

Neck

In the nuchal ligament, a sesamoid bone of the nuchal ligament not infrequently occurs.

• Sesamoiditis
• Fractures
• Avascular bone necrosis