Sesamoid bones are small, rounded masses that are wholly or partially embedded in certain tendons, in those regions where they wrap around bony prominences.
Since these bones resemble sesame seeds in their form and structure, they bear the name “sesamoid.”
What Is Sesamoid Bone?
These bones are found in the knee, hand, and foot. Examples of such bones include,
1. The Patella: It is present in our knees and sits on the top of the femoral condyles’ interior surface. This sesamoid bone is responsible for supporting the knee flexion and extension so that the body can move with smooth movements.
2. Four (or five) sesamoid bones are found in hand. Out of these four, two are present at the metacarpophalangeal joint of the thumb, one at the corresponding joint of the index finger on the radial side, and another one at the same joint of the little finger on the ulnar side. Some people also have one sesamoid bone on the interphalangeal joint of the thumb.
3. Two of these unique bones are present in the foot, out of which one is present in the ball of the foot, beneath the big toe joint.
The fracturing, dislocation, subjection of bone to avascular necrosis, and inflammation and growth of tumors can cause hand pain and functional disability of the body.
Functions of Sesamoid Bone
1. These bones help to raise and move the big toe.
2. It pushes off the ground while we are walking or running. As a result, the strain on our foot is taken off by them.
3. As it passes in proximity to the joints, these bones decrease the friction and pressure of the flexor tendon.
4. They can also alter the direction of muscle pull in the body.
5. It acts like the weight-bearing surface for the first metatarsal bone, the long bone connected to the big toe, by absorbing the weight present on the ball of the foot when the person is walking, running, or jumping.
6. Sesamoid bone, present in the tendon, holds it at a distance slightly away from the center of the joint. As a result, its movement increases. As the load on the tension varies, this structure’s presence allows consistent movement of the body. The tendon doesn’t flatten as the tension increases.
>There are many types of sesamoid injury that occurs in the foot. Some of them are mentioned below:
Type of sesamoid injury that occurs in the body
1. Turf Toe: it occurs in the soft tissue that surrounds the big toe joint. When the big toe joint is extended beyond its normal range, turf toe results cause a shooting sharp pain and swelling that affects the entire big toe joint.
As a result, its motion becomes limited. The soft tissue attached to the sesamoid can also get injured, or the sesamoid can get fractured.
2. Fracture: This can either be acute or chronic.
An acute fracture is caused by a direct impact or blows to the bone. At the break’s site, immediate pain and swelling are produced, but the entire big toe joint is not affected.
A stress fracture causes a chronic fracture, i.e., repetitive application of stress or its overuse produces a hairline break. As a result, longstanding pain beneath the big toe joint in the foot’s ball is delivered.
This pain stays there and is aggravated at the times when the person does an activity.
3. Sesamoiditis: This term is coined for those overuse fractures that involve chronic inflammation of the sesamoid bones and tendons in which it is embedded.
When excess pressure is applied to the sesamoid bones, Sesamoiditis occurs. A person suffering from sesamoiditis has a dull, longstanding pain beneath their big tow joint that comes and goes with the use of specific shoes or performance of certain activities.
In the hands, pain in the wrists’ sesamoid bones and writings are not that common. In some instances, the rounded structure of the sesamoid bones turns bipartite means they are formed in two pieces.
These two pieces are visible on an x-ray and give the appearance of a fracture. But, most commonly, fracture of pisiform due to an outstretched hand or a direct blow occurs.
These are treated according to the symptoms they show, and the process of treatment generally begins with oral analgesia followed by a splint, rest, and gradual reproduction of activities.
Degenerative osteoarthritis between the pisiform and triquetrum can also affect the sesamoid bones.
Degenerative arthritis can also occur around the sesamoid bones of the flexor tendons.