Extra Bone In Foot Accessory Navicular


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.Accessory navicular syndrome is an irritation of the accessory navicular and/or posterior tibial tendon. This irritation can be caused by shoe rubbing, trauma, excessive activity, or overuse and can cause problems with the shape and function of your foot. Many people with this disorder also have flat feet which puts more strain on the posterior tibial tendon. Some people are born with an accessory Navicular because during development, the bones of the feet sometimes develop abnormally causing the extra bone to form on the inside of the foot.

Accessory Navicular


Like all painful conditions, ANS has a root cause. The cause could be the accessory navicular bone itself producing irritation from shoes or too much activity. Often, however, it is related to injury of one of the structures that attach to the navicular bone. Structures that attach to the navicular bone include abductor hallucis muscle, plantar calcaneonavicular ligament (spring ligament) parts of the deltoid ligament, posterior tibial tendon.


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 appAccessory Navicularear until adulthood. The signs and symptoms include a visible bony prominence on the midfoot the inner side of the foot above the arch. Redness or swelling of the bony prominence. Indistinct pain or throbbing in the midfoot and arch during or after physical activity.


To diagnose accessory navicular syndrome, the foot and ankle surgeon will ask about symptoms and examine the foot, looking for skin irritation or s welling. The doctor may press on the bony prominence to assess the area for discomfort. Foot structure, muscle strength, joint motion, and the way the patient walks may also be evaluated. X-rays are usually ordered to confirm the diagnosis. If there is ongoing pain or inflammation, an MRI or other advanced imaging tests may be used to further evaluate the condition.

Non Surgical Treatment

Most cases of accessory navicular syndrome may be treated conservatively with some sort of immobilization. This should allow the fibrous tissue between the two bones to heal. If a patient is extremely flat footed (pronated) then I lean more towards an orthotic than a boot as my main goal is to keep the patient's foot from flattening out too much and thus reduce the strain on the two bones. Supplementation with ice, oral anti-inflammatory medication. If the patient is athletic sometimes we can keep them active with an orthotic, but other times they have to give up their sport for a period of time to allow the condition to heal.

Accessory Navicular

Surgical Treatment

For patients who have failed conservative care or who have had recurrent symptoms, surgery can be considered. Surgical intervention requires an excision of the accessory navicular and reattachment of the posterior tibial tendon to the navicular. Often times, this is the only procedure necessary. However, if there are other deformities such as a flat foot or forefoot that is abducted, other procedures may be required.