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 better posture make you taller? 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.
An injury to the fibrous tissue connecting the two bones can cause something similar to a fracture. The injury allows movement to occur between the navicular and the accessory bone and is thought to be the cause of pain. The fibrous tissue is prone to poor healing and may continue to cause pain. Because the posterior tibial tendon attaches to the accessory navicular, it constantly pulls on the bone, creating even more motion between the fragments with each step.
Many people with an accessory navicular do not experience symptoms, however some may notice a bump and/or swelling on the inside of the foot just above the arch. They may also experience pain in the middle of the foot, particularly with 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 swelling. 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
The goal of non-surgical treatment for accessory navicular syndrome is to relieve the symptoms. The following may be used. Immobilization. Placing the foot in a cast or removable walking boot allows the affected area to rest and decreases the inflammation. Ice. To reduce swelling, a bag of ice covered with a thin towel is applied to the affected area. Do not put ice directly on the skin. Oral nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, may be prescribed. In some cases, oral or injected steroid medications may be used in combination with immobilization to reduce pain and inflammation. Physical therapy may be prescribed, including exercises and treatments to strengthen the muscles and decrease inflammation. The exercises may also help prevent recurrence of the symptoms. Custom orthotic devices that fit into the shoe provide support for the arch, and may play a role in preventing future symptoms. Even after successful treatment, the symptoms of accessory navicular syndrome sometimes reappear. When this happens, non-surgical approaches are usually repeated.
If your pain and discomfort don’t go away with treatments like these, then it may be time to consider surgery. If you decide to go through with it, your surgeon will probably remove the accessory navicular once and for all, and will tighten up the posterior tibial tendon in order to make it better able to support your arch. You’ll probably have to wear a cast for a several weeks, and a brace for some months after that, but with patience, you may be able to say goodbye to your symptoms.