Feet > Sesamoid Disorders

What are Sesamoid Disorders?

Your sesamoids are two small bones under the base of your big toe that help provide leverage for toe movement. Every time the ball of your foot strikes the ground, weight is transferred through your sesamoids. Functioning like your kneecap, your sesamoids enable your toe joint to bend with more strength and stability. Both sesamoid bones rest side by side inside a tendon called the flexor hallucis brevis. The bones are a key part of the muscle and tendon mechanism that bends your big toe’s joint, called the first metatarsophalangeal joint. Sesamoid disorders typically are overuse injuries with slowly worsening symptoms of pain and discomfort in the ball of your foot. Traumatic injuries, such as sesamoid fractures, are less common. Ordinarily, only one of your two sesamoids is injured, but you may suffer damage in both of them. Sesamoids generally can suffer three types of injury:

   Sesamoiditis – An inflammation of the tissues surrounding your sesamoid bones. It is a common overuse injury seen in runners and cyclists. The sesamoids and surrounding tissue become inflamed and pain results during activity.

   Fracture – Rare traumatic injury that happens when too much force cracks the bone. It can occur when someone falls on a bent big toe.

   Loss of blood supply – Called avascular necrosis. Injury to the sesamoids can cut off the blood vessels that keep the bones healthy. Bone tissue cannot regenerate and it can die or collapse.

Overuse of your big toe typically causes a sesamoid disorder. Runners, cyclists, and people who abruptly increase their training regimen are at an increased risk of suffering a sesamoid disorder if they overuse the muscles and tendons that bend their big toes. In rare cases, a large force may bend your toe too far, called a dorsiflexion injury, and tear tissue around your sesamoid. This type of injury is called acute, meaning that you typically can recall the moment when your big toe was bent too far and the pain began. A fracture can occur in your sesamoid due to a hard fall on the ball of your foot or someone falling on your foot when your big toe is bent. Loss of blood supply in your sesamoids is rare, but it can be caused whenever damage in the tissue surrounding the sesamoids decreases their blood supply.

If left untreated, sesamoid disorders typically continue to hurt and your big toe’s motion and strength may decrease. A lesion can develop beneath the ball of your foot that makes walking difficult. Arthritis may eventually develop and you can lose cartilage in your big toe’s joint with your foot. Most sesamoid disorders can be treated without surgery. A combination of treatments, including rest, orthotic shoe inserts, and immobilization may be needed to treat your sesamoid disorder. Surgery may be required if conservative treatment does not ease your pain after a few months. Surgery also is commonly prescribed if you have lost blood supply to your sesamoids. Surgery typically involves removing one or both of your sesamoid bones.

There usually are three parts to an orthopedic evaluation: medical history, a physical examination, and tests that your doctor may order.

Your physician likely will ask about your activities, which may have caused your sesamoid disorder. You will be asked when the pain began and to describe your pain’s duration and severity. If you have had previous foot injuries, your physician will ask about the treatments you have tried in the past. Your physicians may suspect an overuse injury when you describe a long history of slowly developing pain in the joint of your big toe. Physicians suspect a fracture when you describe direct contact to your foot followed by pain and limited motion in your big toe. Descriptions of swelling and increasing pain in the joint at the base of your big toe over a span of weeks also could be a sign of a fracture. Physicians typically ask about other conditions, such as diabetes and allergies, and medications currently being taken. You may also be asked about your physical and athletic goals – information that will help your physician decide what treatment might be best for you in achieving those goals.

our physician usually checks for certain signs of sesamoid dysfunction during a physical exam:

   Swelling in the joint that connects your big toe with your foot.

   Pain in your big toe and the ball of your foot when your physician presses upon those areas.

   Pain when your big toe is bent in different directions.

   Difficulty bending your big toe up and down.

   Inability to push with your big toe against pressure applied by your physician.

TESTS

X-rays are the standard test used to diagnose sesamoid disorders. X-rays can show if the bone has been fractured or if it has lost its blood supply. Bone scans or MRI (magnetic resonance imaging) may be needed to properly see the damaged tissue. Roughly 20 percent of people have a harmless condition called a bipartite sesamoid. This means that the sesamoid has a natural split in it because it did not completely form as one bone. A bone scan or MRI can help differentiate between a bipartite sesamoid and actual damage, such as a fracture or loss of blood supply.