Accessory navicular syndrome (ANS) is a symptomatic aggravation or inflammation of an accessory navicular bone. It is the second most common accessory ossicle of the foot. There are three variants, of which type II is the most common. It is large and forms a fibrocartilage synchondrosis, or immovable cartilaginous joint, with the navicular. Of the three variants, type II has the greatest propensity to become symptomatic. Often times, as in this case, the etiology stems from poor biomechanics; it may also occur secondary to trauma. 

Patients typically complain of medial sided foot pain and swelling, as well as tenderness to palpation at the insertion of the posterior tibial tendon (PTT) on the navicular. X-rays will reveal an accessory navicular bone. Magnetic resonance imaging (MRI) will likely demonstrate subchondral edema in the accessory navicular. Generally, this condition is treated with non-steroidal anti-inflammatories (NSAIDs) for pain and physical therapy to correct biomechanical deficiencies. In more severe cases, immobilization may be utilized in conjunction with physical therapy. Surgical intervention may be necessary for refractory cases.

 

In this case, a 26 year-old-male long-distance runner presented with a six-month history of pain over the inferomedial aspect of his right foot near his navicular. His pain was worse with running, particularly on initial foot strike. The injury was refractory to foot and ankle strengthening exercises, NSAIDs and rest. He also had a known history of right foot plantar fibroma and chronic plantar fasciitis.