Accessory Navicular Syndrome: Types, Symptoms, and When Treatment Is Needed

Medically reviewed by Dr. Tom Biernacki, DPM — Board-Certified Podiatric Surgeon — Balance Foot & Ankle, Howell & Bloomfield Hills, MI. Last updated April 2026.

The accessory navicular — an extra bone on the medial side of the navicular where the posterior tibial tendon inserts — is present in 4–21% of the population and is typically asymptomatic throughout life. However, in a subset of individuals, the accessory navicular becomes symptomatic — producing medial midfoot pain that is often mistaken for plantar fasciitis, tibialis posterior tendinopathy, or medial ankle sprain. Accurate recognition of accessory navicular syndrome prevents months of inappropriate conservative treatment.

Types and Pathomechanics

Type I (os tibiale externum): a small sesamoid bone within the posterior tibial tendon substance — typically asymptomatic; no direct connection to the navicular. Type II (accessory navicular): the most clinically significant type — a secondary ossification center connected to the navicular by a synchondrosis (fibrocartilage bridge); the posterior tibial tendon inserts entirely or partially onto the accessory navicular rather than the navicular proper, weakening the tendon’s mechanical advantage. The synchondrosis becomes painful from shear stress — particularly in flatfoot (the posterior tibial tendon insertion is under chronic eccentric load in a pronating foot) and after acute plantar-medial midfoot trauma. Type III (cornuate navicular): complete osseous fusion of the accessory bone — generally asymptomatic. Clinical features of Type II syndrome: prominent medial navicular bony prominence (the accessory bone creates a visible bump on the medial foot border); tenderness directly over the medial navicular prominence (not along the tendon course); pain with resisted inversion; pes planus frequently coexists. X-ray: the accessory navicular is visible on standard foot views — an oblique view best profiles the synchondrosis.

Treatment

Conservative management: activity modification; immobilization in a boot for 4–6 weeks during acute flare (reduces synchondrosis stress); custom orthotics with medial arch support to reduce PTT loading; topical anti-inflammatory treatment at the prominent bump. Surgical treatment (Kidner procedure): excision of the accessory navicular and reattachment of the posterior tibial tendon to the navicular proper — restores the tendon’s mechanical advantage; 85%+ success rate in appropriately selected patients; recovery 6–8 weeks non-weight-bearing then gradual return to activity. Dr. Biernacki at Balance Foot & Ankle evaluates medial midfoot pain with X-ray and ultrasound to diagnose accessory navicular syndrome and provides both conservative and surgical management options. 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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Accessory Navicular Syndrome Treatment in Michigan

An accessory navicular bone on the inner foot can cause chronic arch pain, especially in active teens and young adults. Our podiatrists provide accurate diagnosis and treatment ranging from orthotics and immobilization to surgical excision (Kidner procedure) for persistent cases.

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Clinical References

1. Grogan DP, Gasser SI, Ogden JA. The painful accessory navicular: a clinical and histopathological study. Foot Ankle. 1989;10(3):164-169.
2. Kidner FC. The pre-hallux (accessory scaphoid) in its relation to flat-foot. J Bone Joint Surg Am. 1929;11(4):831-837.
3. Jasiewicz B, Potaczek T, Kacki W, et al. Results of simple excision technique in the surgical treatment of symptomatic accessory navicular. Foot Ankle Int. 2008;29(11):1061-1065.

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