The accessory navicular - also termed the os navicularum or os tibiale externum - is an extra bone or piece of cartilage on the inner side of the foot above the arch that attaches to the posterior tibial tendon within this area.

This extra bone, present at birth, is not part of the normal bone structure and found in approximately 10% of the population.

Some people with an accessory navicular may be unaware of the condition if symptoms are never experienced. But accessory navicular syndrome is a painful condition caused by aggravating the bone, the posterior tibial tendon or both.

The syndrome may result from any of the following:

The symptoms of accessory navicular syndrome commonly arise during adolescence, when bones are maturing and cartilage fuses into bone. In other instances, symptoms do not appear until adulthood. The signs and symptoms include:

Accessory navicular syndrome is diagnosed by asking about symptoms and examining the foot for skin irritation and swelling. Dr. Radovic may assess the area for discomfort by pressing on the bony prominence. Foot structure, muscle strength, joint motion and walking patterns may also be evaluated.

Dr. Radovic may order x-rays to confirm the diagnosis. An MRI or other advanced imaging modalities may help further evaluate the syndrome if patients experience continuous pain or inflammation.

A combination of the following non-surgical treatments may be used to relieve the symptoms of accessory navicular syndrome:

Immobilizing the foot with a cast or a removable walking boot allows the foot to rest and reduces inflammation.

Applying ice to the affected area is an effective way to reduce swelling and inflammation. Wrap a bag of ice with a thin towel and apply for intervals of 15 to 20 minutes. Never put ice directly on the skin.

Oral nonsteroidal anti-inflammatory drugs (NSAIDs) including aspirin or ibuprofen might be prescribed. Sometimes, a combination of immobilization and oral or injected corticosteroid medications may reduce pain and inflammation.

Physical therapy may be prescribed to include exercises and treatments that increase muscle strength, decrease inflammation and help prevent the recurrence of symptoms.

Custom orthotic devices worn in the shoe provide arch support and may prevent future symptoms from developing.

The symptoms of this syndrome may reappear even after successful treatment. If so, non-surgical treatments are often repeated.

Surgery may be an option if non-surgical treatment does not decrease the symptoms of accessory navicular syndrome. Since this bone is not needed for the foot to function normally, Dr. Radovic may remove the accessory navicular, reshape the area, and repair the posterior tibial tendon for improved function.