An accessory navicular bone is an accessory bone of the foot that occasionally develops abnormally causing a plantar medial enlargement of the navicular. The accssory navicular bone presents as a sesamoid in the posterior tibial tendon, in articulation with the navicular or as an enlargment of the navicular. Navicular (boat shaped) is an intermediate tarsal bone on the medial side of the foot. It is located on the medial side of the foot, and articulates proximally with the talus. Distally it articulates with the three cuneiform bones. In some cases it articulates laterally with the cuboid. The tibialis posterior inserts to the os naviculare. The tibialis posterior muscle also contracts to produce inversion of the foot and assists in the plantar flexion of the foot at the ankle. Tibialis posterior also has a major role in supporting the medial arch of the foot. This supports is compromised by abnormal insertion of the tendon into the accessory navicular bone when present. This lead to loss of suspension of tibialis posterior tendon and may cause peroneal spastic pes planus or simple pes planus. But, yet a cause and effect relationship between the accessory navicular and pes planus is doubtful and is yet unproved clearly.
People who have an accessory navicular often are unaware of the condition if it causes no problems. However, some people with this extra bone develop a painful condition known as accessory navicular syndrome when the bone and/or posterior tibial tendon are aggravated. This can result from any of the following. Trauma, as in a foot or ankle sprain. Chronic irritation from shoes or other footwear rubbing against the extra bone. Excessive activity or overuse.
If you develop accessory navicular syndrome, you may experience a throbbing sensation or other types of pain in your midfoot or arch (especially while or right after you use the foot heavily, such as during exercise), and you may notice a bony prominence on the interior of your foot above the arch. This prominence may become inflamed, which means it will likely feel warm to the touch, look red and swollen, and will probably hurt.
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
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.
If conservative measures do not seem to help, however, you may need to have surgery to make adjustments to the bump. This could include reshaping the little bone, repairing damage to the posterior tibial tendon, or even removing the accessory navicular altogether.