An accessory navicular is a supernumerary (extra) bone located on the medial aspect of the foot adjacent to the navicular tuberosity — the anatomical site of the posterior tibial tendon insertion. Present in approximately 4–14% of the general population, it is one of the most common accessory bones of the foot and a recognized cause of medial midfoot pain, particularly in adolescents and young adults during periods of physical activity intensification. Most accessory navicular bones are asymptomatic and require no intervention; a minority produce chronic pain and functional limitation that ultimately warrants surgical excision.

Classification: Three Anatomical Types

The Geist classification distinguishes three types based on anatomy and clinical significance. Type I (os tibiale externum): a small round sesamoid bone within the posterior tibial tendon itself, located 1–2cm proximal to the navicular — found in approximately 30% of accessory naviculars, usually asymptomatic. Type II: a triangular or heart-shaped bone connected to the navicular by a synchondrosis (fibrocartilaginous joint) — the most common symptomatic type (approximately 50% of accessory naviculars), vulnerable to injury at the synchondrosis from traction stress of the posterior tibial tendon insertion. Type III (cornuate navicular): complete fusion of the accessory bone to the navicular — sometimes called a “cornuate” navicular. Type II is the clinically significant type because the synchondrosis between the accessory bone and the navicular is the site of micro-fracture, inflammation, and pain under the repetitive traction of the posterior tibial tendon during activity.

Clinical Presentation and Conservative Management

Symptomatic accessory navicular presents as medial midfoot pain and a bony prominence at the medial navicular — more prominent than in a foot without the accessory bone because the navicular tuberosity is enlarged. Symptoms typically emerge in adolescence during periods of rapid growth and activity increase, and may resolve spontaneously as the synchondrosis matures. Non-surgical management: activity modification, UCBL-type custom orthotics with medial arch support and navicular padding that offloads the bony prominence, immobilization in a CAM walker during acute painful flares, and NSAIDs. The majority of symptomatic cases respond to structured conservative care over 3–6 months. When conservative management fails, the Kidner procedure — excision of the accessory navicular and, crucially, advancement of the posterior tibial tendon insertion to the navicular body to restore optimal tendon tension — provides reliable symptom resolution. Isolated excision without tendon advancement risks disrupting the PTT insertion and producing flatfoot progression. Dr. Biernacki at Balance Foot & Ankle evaluates medial foot pain with X-ray assessment, identifying accessory navicular and providing appropriate conservative or surgical management. Call (810) 206-1402.

When to See a Podiatrist

Many foot conditions can be managed conservatively at home, but some require professional evaluation. See a podiatrist promptly if you experience:

• Pain that persists for more than 2 weeks despite rest
• Swelling, redness, or warmth that isn’t improving
• Numbness, tingling, or burning in the feet
• A wound or sore that is not healing within 2 weeks
• Any foot concern if you have diabetes or poor circulation
• Nail changes that suggest fungal infection or other problems

At Balance Foot & Ankle, our three board-certified podiatrists — Dr. Tom Biernacki, Dr. Carl Jay, and Dr. Daria Gutkin — provide comprehensive foot and ankle care at our Howell and Bloomfield Township offices. Most insurance plans are accepted.