Accessory Navicular Syndrome

An accessory navicular is an extra bone adjacent and proximal to the tuberosity of the navicular in the inner arch of the foot. It is present in approximately 14% of the population, and of those, 50% have it bilaterally. The accessory navicular is usually asymptomatic but can cause pain and discomfort due to injury, trauma, or irritation of the posterior tibial tendon near its insertion to the tuberosity of the navicular.

There are 3 types of accessory navicular syndrome, each representing a different degree of fusion of the accessory navicular bone with the tuberosity of the navicular:

Type I: An accessory navicular or os tibiale externum within the posterior tibial tendon, not attached to the navicular. Generally asymptomatic.

Type II: Synchondrosis or forming of a tight joint with the navicular. Possible insertion of the posterior tibial tendon into the accessory navicular. The most common type.

Type III: Fusion of the accessory navicular or ossicle with the navicular to form a hooked tuberosity of the navicular.

• Pain local to the medial foot and posterior tibialis
• Signs of pain beginning as a young adolescent due to ossification of cartilage
• Increased pain with weight bearing, physical activity, or narrow footwear
• Bony prominence on the inferior and medial aspect of the foot
• Signs of irritation near the bony prominence

Diagnosing accessory navicular syndrome includes taking a thorough patient history and performing a physical examination of the inferior medial midfoot. Clinicians will examine for a bony prominence and local irritation. X-rays are typically required to confirm the diagnosis and classify the type of accessory navicular syndrome or degree of fusion.

Conservative, non-surgical treatment is the primary approach. Icing the area can reduce swelling and irritation. Physical therapy, activity modification, and orthotic management are common first-line treatments for symptom relief and healing. Custom orthotics with medial arch support and navicular offloading are particularly effective. Surgical intervention to remove the accessory bone and restructure local tissue may be considered as a last resort.