Sesamoid bones are unique because they are the only bones in the body that are not connected to other bones via joints. Instead, they are connected to other bones by tendons, or they are embedded in muscles in the body.
Examples of sesamoid bones in the body include the kneecap and two small bones in the foot, which are roughly the size of a corn kernel.
These foot bones are located underneath the foot, one on the outer side of the foot and the other near the middle of the foot. They are embedded in the tendon that helps move the big toe.
The sesamoid bones in the foot serve several purposes. They support the body's weight, allow tendons to exert greater forces on the body, and also help to lift the bones of the big toe.
Sesamoiditis occurs when the tendons surrounding the sesamoid bones become irritated and inflamed.
According to the American Academy of Orthopaedic Surgeons, ballet dancers, baseball catchers, and runners are more likely to develop sesamoiditis due to the forces placed on their feet during these activities.
People with high foot arches also have an increased risk of experiencing sesamoiditis because of the extra pressure put on the feet.
Older adults with osteoarthritis can also experience sesamoiditis because osteoarthritis can weaken bones and lead to inflammation.
The sesamoid bones are subject to breakage (fracture) as well as sesamoiditis. Sometimes, it can be difficult to tell the difference between the two conditions.
Pain will occur nearly immediately when a person fractures a sesamoid bone, but a person with sesamoiditis will experience pain gradually.
Other symptoms of sesamoiditis include:
- problems straightening or bending the big toe
- pain, particularly on the bottom of the foot
Because sesamoiditis develops over time, a person may find they experience a dull pain that comes and goes throughout the day. The pain usually occurs on the bottom of the foot and toes.
The discomfort caused by sesamoiditis can cause a person to limp. The person may also shift their weight to the other foot to alleviate the extra pressure and pain.
A doctor will begin diagnosing sesamoiditis by asking a person about their symptoms. Questions they may ask include:
- What activities are performed regularly?
- How did the pain start?
- What activities make symptoms worse or better?
- What medications or treatments make the toe feel better?
A doctor will also examine the toe and will likely ask a person to straighten and bend the toe. A doctor may also order an X-ray to examine the foot and toe to identify potential bone fractures.
In some instances, a doctor may recommend a magnetic resonance imaging scan (MRI) or a bone scan to identify potential damage to the bones.
However, sesamoid bones may vary in appearance, which can make it difficult for a doctor to determine if a fracture has occurred.
In most instances, a person can treat sesamoiditis at home.
Ways to treat sesamoiditis include:
- stopping or reducing the activities causing pain
- taking over-the-counter medications to relieve pain and inflammation
- applying an ice pack for 10 minutes at a time to reduce inflammation
- wearing comfortable, soft-soled, low heeled-shoes
- inserting a cushioning insole inside the shoes
- avoiding high-heeled shoes, which can further irritate the tendon
- wearing supportive shoes when returning to the activity that causes sesamoiditis to flare up
In some instances, a doctor may recommend taping the large toe in a slightly downward manner to stretch and relieve pressure on the toes. This is known as plantar flexion.
A doctor may also give a person a corticosteroid injection to reduce inflammation in the tendons. Occasionally, a doctor may recommend that a person wears a special leg fracture brace that can reduce pain and pressure.
It can take up to 6 weeks for at-home treatments to relieve pain associated with sesamoiditis.
If symptoms continue or worsen, a stress fracture may have occurred. If this has happened, a person should not put any weight on their foot for about 6 weeks.
In rare instances, a doctor may recommend surgery to treat a sesamoid injury or fracture. A person will need to see a foot and ankle surgeon who will determine if surgery is necessary.
Wearing comfortable and cushioning footwear can help prevent sesamoiditis. Shock-absorbing sneakers are especially effective. Shoes should be replaced every 6 months, or more often if the person is very active.
People may also choose to wear a supportive insole, or special pad called a metatarsal bar. This pad provides additional support to the bottom of the foot to reduce the pressure on the sesamoid bones.
Sesamoiditis sometimes occurs due to overpronation, where a person's foot rolls slightly inward as they take a step. To correct this, a person may benefit from running coaching, which can teach them how to reduce stress on the foot joints.
Ways to prevent overpronation include taking shorter strides and focusing on the middle of the foot, rather than the edge of the foot pad when the foot hits the ground. This is known as a midfoot strike in a running stride.
A doctor can prescribe custom-made orthotics to reduce the incidence of overpronation.
Once a person's symptoms improve, they may wish to change their activity patterns to reduce the risk of experiencing sesamoiditis again.
For example, if excessive running caused a sesamoiditis flare-up, a person may choose to alternate running with swimming or cycling, which place less stress on the joints.