The accessory navicular is an extra bone or piece of cartilage located at the inner side of the foot just above the arch and is incorporated within the posterior tibial tendon.
Many people are unaware they have this congenital condition because it causes no problems. However, some people develop the painful syndrome when the bone and/or posterior tibial tendon are aggravated as a result of trauma, irritation from poor fitting footwear, or overuse.
In a number of cases, people with accessory navicular syndrome also have flat feet (fallen arches). This puts more strain on the posterior tibial tendon, causing inflammation or irritation to the accessory navicular.
Symptoms of this condition typically first appear in adolescence, when bones are maturing and cartilage is turning into bone. Some people don’t experience the following symptoms until adulthood:
- A visible bony prominence on the inner side of the foot, just above the arch (midfoot).
- Redness and swelling of the bony prominence.
- Vague pain or throbbing in the midfoot and arch, usually during or after a period of activity.
Your physician can diagnose this condition through evaluation of a patient’s symptoms and examination of the foot structure, muscle strength and joint motion. The doctor may also assess the patient’s gait. He or she may order X-rays to confirm the diagnosis and an MRI for a more detailed look at the tendons and cartilage.
The following non-surgical treatments can relieve the symptoms of accessory navicular syndrome.
- Immobilization with casting or a removable walking boot to rest the affected area and alleviate inflammation.
- Ice to reduce swelling.
- Oral non-steroidal anti-inflammatory drugs such as ibuprofen for pain and inflammation.
- Steroid injections may be used in combination with immobilization to reduce pain and inflammation.
- Physical therapy with exercises and treatments to strengthen the surrounding muscles can decrease pressure at the inflammation site. The exercises may also help prevent recurrence of the symptoms.
Surgical Treatment Options
Even after successful treatment, the symptoms of accessory navicular syndrome sometimes recur. When this happens, nonsurgical approaches are usually repeated.
If the repeated treatment fails to relieve the symptoms, your doctor may recommend surgery. The procedure usually involves removing the accessory bone, reshaping the area and repairing the posterior tibial tendon to improve its function. The accessory navicular is not needed for normal foot function.