If you suffer from pain in the arch of your foot, especially following exercise, you could have what's known as accessory navicular syndrome. Read on to learn more about this uncommon but treatable condition.
What Is an Accessory Navicular Bone?
An accessory navicular bone (AKA os tibial externum) is an extra bony protuberance on the inside of the foot below the ankle near the arch. It can be an overgrowth of the navicular bone itself or a small separate bone on top of the navicular separated by a layer of tissue.
Accessory navicular bones are congenital (there since birth) and are frequently bilateral (present on both sides). They often go unnoticed until activity or trauma cause problems.
What Are the Signs and Symptoms of Accessory Navicular Syndrome?
Problems with accessory naviculars usually show up during adolescence when athletic activity increases. Chronic problems with an accessory navicular or a pair of naviculars is called accessory navicular syndrome. Signs and symptoms of accessory navicular syndrome include:
- visual presence of bony protuberance over the navicular bone
- flat foot or lower arch
- discomfort from footwear or athletic wear (such as ice skates) rubbing on the bone
- pain in the arch or up the inside/back of the calf along the posterior tibialis tendon that attaches at the navicular
- pain when the navicular bone is pressed
- frequent sprains due to lack of stability
- fatigue and inability to complete athletic performance
The fatigue and pain felt by people with accessory navicular syndrome is due to loss of strength in the posterior tibialis tendon. Instead of pulling straight up to support the arch of the foot, the tendon has to pull medially (to the side) first. This weakens the tendon and may also irritate it as it rubs on the accessory bone.
There may also be hairline stress fractures of the accessory bone. Often a podiatrist or orthopedist consulted for the symptoms described above will confirm this with x-rays.
What Are Conservative Ways to Treat Accessory Navicular Syndrome?
If the pain from the accessory navicular syndrome isn't too severe, sometimes conservative measures can be used to treat it it. These include icing after activity or athletic workout, the use of NSAIDs (nonsteroidal anti-inflammatory drugs, such as ibuprofen or naproxen), and wearing orthotic inserts in the shoes.
What Happens When Conservative Measures Fail?
Unfortunately, conservative measures often fail when it comes to accessory navicular syndrome. In that case, surgery is usually recommended, called a Kidner procedure (or modified Kidner procedure). This can be performed in the operating room by a podiatrist or an orthopedic surgeon.
During a Kidner procedure, the accessory part of the navicular bone is removed, and the posterior tibialis tendon is repaired or reattached, as necessary. Patients wear an immobilizing cast below the knee immediately after surgery, then a weight-bearing cast, before graduating to rehabilitation with a physical therapist. Most patients are able to return to normal activity, including athletics, after this surgery.
If you think you might have an accessory navicular bone, it's a good idea to have it checked by a foot doctor sooner rather than later. If it's not causing you problems at present, you may be able to manage the condition conservatively. And if you are experiencing uncomfortable symptoms, the sooner they are addressed, the less chance for damage to the foot and the sooner you can return to normal activities.