08 Oct An accessory navicular bone: What is it and the conservative treatment.
After having several patients present with this “extra” bone in their feet in the past month I thought it was a good time to write about this fairly rare condition.
This accessory bone occurs on the inner side of the foot at the top of the arch and sits within the tibialis posterior tendon which attaches in this area. It is a congenital (present at birth) and is not a part of the normal bones structure and therefore not present in most people (Foot Health Facts, n.d.).
“It is estimated 5 to 14 percent of all feet develop an accessory navicular bone.” (Niehaus, 2017).
Picture ref: (Foot Health Facts n.d.)
Symptoms of an accessory navicular bone
In my experience, the majority of clients who have presented to my clinic do not experience pain. They are often parents who bring their children in worried about a bone sticking out. Those that are painful I find are mainly due an accommodation issue in that it is rubbing on the inside of the shoes.
Other reasons why this area can become painful is that this extra bone can interfere with the normal functioning of the tibialis posterior tendon which is the major supporter of the foot arch. This particularly occurs with type 2 accessory navicular bones. These differ from type 1 and type 3 in that they are usually larger in size and often present with fibrocartilaginous synchondrosis (type of joint) to the navicular bone (Niehaus, 2017).
This means that the bone is able to move because it is attached via the cartilaginous joint and can therefore be more easily irritated by excessive forces in the tibialis posterior tendon. This can occur during an injury such as an ankle sprain. Or it can occur in a foot that excessively pronates (excessively rolls in) potentially causing the tibialis posterior tendon to have to work harder. Once irritated, if not already from the rubbing on the inside of shoes, it will now be even more sensitive to pressure and footwear will be even more difficult to wear as a result.
How to treat an accessory navicular bone
Treatment of this condition often involves footwear modifications and padding to reduce the pressure on the area.
An over-the-counter or soft form customised orthotic may also help to try and reduce both pressure on the area and excessive movement of the arch if it exists.
In my experience further arch and ankle support can be provided by figure 6 and reverse 6 ankle taping to further help lift the arch, especially during running and sports activities.
Active rest for 2 to 4 weeks from running and jumping activities may be required if there is still pain running.
Home treatment of ice and NSAIDs can help with managing symptoms and aiding in recovery when combined with de-loading.
The appropriate foot, arch and lower leg strengthening exercises are useful to re-gain normal functioning and hopefully reduce a re-occurrence of the problem.
Failing improvement, if pain persists with walking then placing the patient into a partial weight bearing boot may be required or even a cast if further immobilisation is required until the patient can be graduated into the appropriate footwear.
Failing conservative treatment, a referral to either a Sports Physician or an Orthopaedic surgeon to consider medical and surgical options is recommended. This may be removal of the accessory bone and/or repositioning of the tibialis posterior tendon (Niehaus, 2017). An experienced health practitioner preferably a Podiatrist specialising in musculoskeletal conditions will be able to direct you accordingly.
Foot Health Facts. n.d. Accessory Navicular Syndrome. [ONLINE] Available at: https://www.foothealthfacts.org/conditions/accessory-navicular-syndrome-(1). [Accessed 8 October 2018].
Podiatry Today/Saleena. 2017. Treating The Accessory Navicular In Young Athletes. [ONLINE] Available at: https://www.podiatrytoday.com/blogged/treating-accessory-navicular-young-athletes. [Accessed 8 October 2018].