The accessory navicular is an extra bone or piece of cartilage fused within the posterior tibial tendon. It is above the arch, located on the inner side of the foot. This bone is congenital—meaning it is present at birth. It is not part of the foot’s normal structure; most people do not have an accessory navicular.

People with this extra bone are often unaware of it unless it becomes painful. When the bone or tendon becomes aggravated, accessory navicular syndrome can develop.

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What are the signs and symptoms of accessory navicular syndrome?

  • A visible bony bump located mid-foot on the inner side above the arch
  • Redness and swelling
  • Vague pain or throbbing in the midfoot and arch; pain usually occurs during or after an activity

What causes accessory navicular syndrome?

  • Trauma (e.g., a foot or ankle sprain)
  • Chronic irritation from shoes rubbing against the extra bone
  • Excessive activity or overuse

Many people with accessory navicular syndrome also have flat feet. Fallen arches put more strain on the posterior tibial tendon. This can lead to inflammation or irritation.

How is accessory navicular syndrome diagnosed?

  • Physical exam
  • X-rays

How is accessory navicular syndrome treated?

Treatment depends on the extent of your child’s condition. There are several non-surgical treatment options:

  • I.C.E. – Rest, ice, compression and elevation
  • Cast or boot
  • Anti-inflammatory medication (e.g., ibuprofen)
  • Physical therapy
  • Orthotic devices for arch support

Surgery is only necessary when non-surgical methods have failed to relieve symptoms. Doctors at Connecticut Children’s can help determine the right plan to treat your child’s condition.