Accessory Navicular Syndrome (Os Tibiale Externum): Classification, Diagnosis, and Surgery

The accessory navicular (os tibiale externum) is an accessory ossicle located medial to the navicular tuberosity, present in 4–21% of the population. Most accessory naviculars are asymptomatic incidental findings — but a subset of patients develop symptomatic accessory navicular syndrome, characterized by pain over the medial navicular prominence during activity and with shoe pressure. Accessory navicular syndrome is one of the most common causes of medial foot pain in adolescents, frequently presenting in the context of pes planus (flatfoot) and overuse from sports activity.

Type Classification

The Geist classification distinguishes three types. Type I (os tibiale externum): a small, round sesamoid bone embedded within the posterior tibial tendon at its insertion — typically asymptomatic and not connected to the navicular. Type II: a heart-shaped ossicle connected to the navicular by a fibrocartilaginous synchondrosis — the most symptomatic type, because the synchondrosis can develop microinstability, inflammation, and stress reaction. Type II accounts for the majority of symptomatic cases. Type III (cornuate navicular): the accessory ossicle has completely fused to the navicular, creating an enlarged navicular tuberosity — typically less symptomatic than Type II because there is no synchondrosis to become inflamed.

Conservative and Surgical Management

Conservative management (first-line): activity modification, custom orthotics with medial arch support and a navicular pad to offload the prominent tuberosity, anti-inflammatory medications, and in refractory cases, corticosteroid injection into the synchondrosis. Physical therapy addressing posterior tibial tendon strengthening and arch neuromuscular control complements orthotics. Most adolescent cases resolve with skeletal maturity and conservative management. Surgical management (Kidner procedure and modifications): indicated for failed 6–12 months of conservative treatment. The classic Kidner procedure — excision of the accessory navicular with advancement of the posterior tibial tendon to the navicular — addresses both the pain generator and the tendon attachment. Modifications include simple excision of the ossicle with repair of the PTT insertion and concurrent medializing calcaneal osteotomy for flatfoot correction in severe cases. Recovery: 6–8 weeks non-weight-bearing followed by physical therapy. Dr. Biernacki at Balance Foot & Ankle evaluates accessory navicular syndrome and medial foot pathology. Call (810) 206-1402 at our Bloomfield Hills or Howell office.

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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.

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Board-certified podiatrists Dr. Tom Biernacki, Dr. Carl Jay, and Dr. Daria Gutkin see patients daily at our Howell and Bloomfield Township, MI offices.

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Differential Diagnosis: What Else Could It Be?

Not every case of accessory navicular syndrome is straightforward. In our clinic we routinely rule out three look-alike conditions before confirming the diagnosis. If your symptoms don’t match the classic presentation, one of these may explain the pain — which is why physical exam matters more than self-diagnosis.

Condition	How It Differs
Posterior tibial tendon dysfunction	Pain along the tendon course with progressive flatfoot; may coexist.
Medial midfoot sprain	Ligamentous tenderness without a prominent bony bump.
Navicular stress fracture	Dorsal midfoot pain with impact; confirmed on MRI, not an accessory bone.

Red Flags — When to See a Podiatrist Now

In Our Clinic: What We See

In-Office Treatment at Balance Foot & Ankle

If home care isn’t resolving your your foot or ankle concern, a visit with a board-certified podiatrist is the fastest path to accurate diagnosis and a personalized plan. At Balance Foot & Ankle Specialists, Dr. Tom Biernacki, Dr. Carl Jay, and Dr. Daria Gutkin offer same-day and next-day appointments at both our Howell and Bloomfield Hills offices. We perform on-site diagnostic ultrasound, digital X-ray, conservative care, advanced regenerative treatments, and minimally invasive surgery when indicated.

Call (810) 206-1402 or request an appointment online. Most insurance plans accepted, including Medicare, Blue Cross Blue Shield, Aetna, Cigna, and United Healthcare.

Most Common Mistake We See

The most common mistake we see is: Waiting too long before seeking care. Fix: any foot pain lasting more than 4 weeks, or any sudden severe symptom, deserves a professional evaluation rather than more rest.

Warning Signs That Need Same-Day Care