What is a Sesamoid?
A sesamoid is a bone embedding within a tendon. They are found in multiple spots in the body; in the foot, they are two pea-shaped bones located in the ball of the foot, beneath the big toe joint. Sesamoid bones act as pulleys for tendons, helping move the big toe and providing leverage when it pushes off while walking and running. They also serve as a weight-bearing surface for the first metatarsal, absorbing weight placed on the ball of the foot.
Types of Sesamoid Injuries
Sesamoid injuries are usually caused by activities that require increased pressure on the balls of the feet, like running, tennis, or ballet. People with high arches, or those who wear high-heels are also at risk. There are three types of sesamoid injuries:
- Turf toe is an injury of the soft tissue surrounding the big toe joint. Usually happening when the toe is extended beyond its intended range, turf toe causes immediate sharp pain and swelling, and limits the motion of the big toe.
- Fractures can be either acute (suddenly caused by trauma, and causing immediate pain and swelling) or chronic (a hairline break caused by repetitive stress or overuse)
- Sesamoiditis is an overuse injury, consisting of chronic inflammation of the sesamoid bones and the surrounding tendons.
During your exam, the doctor will focus on the big toe joint, pressing on it, moving it up and down, and may ask you to demonstrate the way you walk. X-rays are usually ordered.