Accessory Navicular Syndrome

Some people have more bones in their feet than others. Actually, it’s not all that uncommon to have extra bones in the feet. These extra bones are called accessory bones. The navicular bone, one of the small bones located at the instep or arch of the middle of the foot, is an example of an extra bone people are born with. It’s called the accessory navicular bone. (See x-ray.) During the maturation process, the navicular and the accessory navicular never fuse into one solid bone but remain connected by fibrous tissue or cartilage. It is estimated that 4-14% of the population is born with an accessory navicular bone.

When does the accessory navicular bone become problematic?

Most of the time, this condition is asymptomatic and people may live their whole lives unaware that they even have this extra bone. The main reason the accessory navicular bone becomes problematic is when pain occurs. There is no need for intervention if there is no pain. The accessory navicular bone is easily felt in the medial arch because it forms a bony prominence there. Pain may occur if the accessory bone is overly large causing this bump on the instep to rub against footwear. This painful condition is called an accessory navicular syndrome. Accessory navicular syndrome (ANS) can cause significant pain in the mid-foot and arch, especially with activity. Redness and swelling may develop over this bony prominence, as well as extreme sensitivity to pressure. Sometimes people may be unable to wear shoes because the area is too sensitive. (See table.)
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

When there is an injury to the muscle, fibrous tissue, or soft tissue of the navicular and the accessory navicular bones, symptoms will arise. This injury allows excessive movement between the bones. Fibrous tissue, ligaments, and tendons have a poor blood supply and are prone to poor healing. Often, this extra navicular bone lies near or attaches to the posterior tibial tendon. (See figure.) When the posterior tibial muscle contracts with movements such as foot inversion or plantar flexion, the posterior tendon moves, and the accessory navicular bone moves. This can cause severe pain in those with Accessory Navicular Syndrome. It can become disabling to patients because the posterior tibial tendon attached to the navicular bone is responsible for supporting the medial arch during standing, walking, and running. Activities which most of us do daily!

How is Accessory Navicular Syndrome treated?

Traditional medicine often falls short when it comes to treatment for this painful condition. As similar to other chronic pain conditions, the following regimen is usually recommended: RICE, immobilization, anti-inflammatory medications, cortisone injections, and/or innovative surgical options. Clients familiar with Prolotherapy often say” no thanks” to those choices, as they know these treatments will only continue to weaken the area in the foot. Instead, they choose Prolotherapy to strengthen the structures in the medial foot.

Prolotherapy strengthens the ligaments, tendons, and muscle attachments affected by ANS

H3 Prolotherapy is a comprehensive injection technique that works to strengthen these ligament, tendon, and muscle attachments by causing a mild anti-inflammatory response in the tissues. Prolotherapy supports the body’s normal healing response to injury. The solution directed at the injured and weakened tissue will cause an influx of blood supply and regenerative cells to come to the area. As part of this healing cascade, collagen cells will also be deposited at the injured site. The tissue, which is made mostly of collagen, will become stronger and tighter as these new collagen cells mature. It is the opposite of injections like cortisone, which cause the tissue to degenerate but are often used in chronic foot pain for temporary pain relief. The goal of H3 Prolotherapy is long-term curative results.

The injured tissue becomes healthy again. When the weakness or injury in these structures is resolved, often times the symptoms with ANS are resolved and the patient no longer suffers from chronic foot pain. In our experience, patients typically feel better soon after treatment. However, if the person desires to run again or continue to be very active, it may take 3-5 treatments to fully resolve the condition. Activity is increased during treatment as symptoms resolve.

If you have Accessory Navicular Syndrome as diagnosed on x-ray and experience chronic pain in your medial arch, give Prolotherapy a shot! Learn more about the H3 Prolotherapy treatment series in our FAQ or foot pain treatment sections.