What Are the Sesamoid Bones of the Body?

Sesamoid bones are bones found within a tendon where the tendon passes over a joint. They tend to be shaped like a sesame seed.

Composition

The sesamoid bones are primarily made of trabecular bone, also called cancellous bone or spongy bone.

Names

Examples of sesamoid bones include the patella, the medial and lateral sesamoid bones of the first metatarsal, the sesamoid bones of the thumb metacarpophalangeal joint, the sesamoid bone of the interphalangeal joint of the thumb, the sesamoid bone of the metacarpophalangeal joint of the index finger on the radial side, and the sesamoid bone of the metacarpophalangeal joint of the little finger on the ulnar side.

Locations in the body

Humans have sesamoid bones in the knees, feet near the big toe and hands.

Diseases of the Sesamoid Bones

Sesamoiditis is irritation or inflammation of the sesamoid bones.

Function

Sesamoids act as pulleys for the tendons and help you move.

References

• University of Michigan Health System
• American Academy of Orthopaedic Surgeons
• Journal of Hand Surgery