Approximately four to 14 percent of individuals are born with an extra bone in their foot known as the accessory navicular bone. This bone, which plays no role in normal foot function, is located just above the arch on the inner side of the foot. Most people with the condition are unaware that they have the extra bone and do not experience any problems.
In some instances, the bone or the posterior tibial tendon that attaches to the area can become irritated in a condition known as accessory navicular syndrome.
What Causes Accessory Navicular Syndrome?
Accessory navicular syndrome is common among people with fallen arches since this causes additional strain on the posterior tibial tendon. The condition can also occur following injury or trauma to the foot, after excessive activity or overuse, or as a result of footwear that rubs against the bone.
Symptoms of Accessory Navicular Syndrome
The symptoms of accessory navicular syndrome typically first appear during adolescence or adulthood. A noticeable bony prominence may develop above the arch on the inner side of the foot. The area may become red, swollen, and painful, especially after activity.
How Accessory Navicular Syndrome Is Diagnosed
A podiatrist may suspect accessory navicular syndrome based on the patient’s symptoms and a physical examination of the foot. An X-ray will reveal the presence of the extra bone. An MRI may also be used to rule out other causes of pain and inflammation.
The treatment of accessory navicular syndrome typically starts with conservative non-surgical remedies.
- The affected foot may be immobilized with a walking boot or cast to relieve the strain on the area and to allow the inflammation to subside.
- Ice may be applied intermittently to alleviate inflammation.
- Over-the-counter nonsteroidal anti-inflammatories can help ease pain and inflammation. In more severe cases, injected or oral steroids may be required.
- Physical therapy may help strengthen the affected muscles and reduce the risk of the symptoms recurring.
- Shoe inserts and orthotics may alleviate symptoms by supporting the arch and reducing the strain on the tendon.
If conservative remedies do not relieve the symptoms, surgery may be required. This involves removing the accessory navicular bone and reshaping and repairing the tendon.