Sesamoid bones

Sesamoid bones are a type of bone found within the tendons of the human body. They are named for their resemblance to a sesame seed. The primary function of sesamoid bones is to modify pressure, diminish friction, and alter the direction of muscle pulls. The most recognized sesamoid bones are the patella (knee cap) and the bones of the feet and hands.

Structure

Sesamoid bones can be found in several parts of the body, but they are most commonly located in the hands and feet. They are typically small, round bones embedded in a tendon. The largest and most commonly known sesamoid bone is the patella.

In the hand

In the hand, there are two types of sesamoid bones: those found in the thumb, and those found in the other four fingers. The sesamoid bones in the thumb are always present, while those in the other fingers are not always present.

In the foot

In the foot, sesamoid bones are typically found in the underside of the forefoot, near the big toe. They help to bear the weight of the body and act as a pulley for tendons, helping the big toe move normally and providing leverage when the toe pushes off during walking and running.

Function

The primary function of sesamoid bones is to protect tendons by helping to bear weight and reduce friction during muscle contractions. They also serve to alter the direction of muscle pulls, which can increase the muscle's capacity for movement.

Clinical significance

Sesamoid bones can be involved in several medical conditions, including sesamoiditis, turf toe, and hallux rigidus. These conditions can cause pain and difficulty in movement, and may require treatment ranging from rest and physical therapy to surgery.

See also

• Bone
• Tendon
• Patella
• Sesamoiditis
• Turf toe
• Hallux rigidus

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