Sesamoiditis Symptoms and Causes

Sesamoiditis is an inflammation of the sesamoid bones in the forefoot. Most bones in the human body are connected to other bones through joints. Sesamoid bones are not connected to any other bones or joints, but instead are either connected to tendons or embedded in muscle. The knee cap is another example of a sesamoid bone and is also the largest one in the body. There are two very small sesamoids that exist in the underside of the forefoot under the big toe. No bigger than the size of a corn kernel, these two two sesamoids are located side by side under the base of the big toe. 

Like the kneecap, these sesamoids act as a pulley by providing a smooth surface for the tendons (tough fibrous bands that connect muscles to bones) to slide over. This, in turn, increases the ability of the tendons to transmit muscle forces and also helps to flex the big toe. The sesamoids also assist with balance and weight bearing function. Sesamoiditis refers to multiple conditions affecting the sesamoids tendons complex.

Sesamoiditis Symptoms

Sesamoiditis can be determined by its gradual onset, unlike other foot problems with symptoms that come on quickly. The most common symptoms of sesamoiditis include:

  • Pain – Mainly underneath the big toe on the ball of the foot. With sesamoiditis, your pain most likely will develop gradually over time, and is related to weight bearing on the area.
  • Swelling and bruising – These symptoms may or may not be present with sesamoiditis.
  • Bending difficulty – It can be difficult and painful trying to bend and extend your big toe.

Every time you push off your foot to take another step, the sesamoid bones are involved. As the sesamoids become more irritated over time, damage to cartilage can occur leading to arthritis.  Rarely fractures can occur as well.

Sesamoiditis Causes

Sesamoiditis is classified as a form of tendonitis due to the placement of the sesamoid bones inside of the tendons. These risk factors can cause sesamoiditis.

  • Increase in activity – This is the main cause of sesamoiditis. A sudden increase in your exercise routine or sports training can aggravate the sesamoid bones a great deal.
  • Activities that cause repetitive impact on the balls of your feet – Sesamoiditis is very common in ballet dancers, baseball catchers and track runners.
  • Bony feet – If you have bony feet, you may not have enough fat to help protect the sesamoids from impact. People with high arches in their feet tend to put most of their pressure on the balls of their feet.

Sesamoiditis Diagnosis

Your doctor will gather your entire medical history and follow up with a thorough physical exam. During the exam your doctor will ask you where you feel the most pain and which activities you are doing when the pain is at the worst. X-rays will also be used to locate and identify the problem. If the expected result is sesamoiditis but it fails to appear on an x-ray, your doctor will most likely order a bone scan or MRI to be sure.

Treatments for sesamoiditis do not normally consist of any operative procedures. The treatments generally range from decreasing activity to wearing orthotics or braces.

The multidisciplinary team of orthopaedic experts at North Shore-LIJ Orthopaedic Institute's Foot and Ankle Services in New York treats sesamoiditis as well as a broad range of foot and ankle conditions that can occur at any stage of life.

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