Accessory Navicular: The Extra Bone Causing Inner Arch Pain

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

What Is an Accessory Navicular Bone

The accessory navicular is a congenital variant — an extra ossification center adjacent to the navicular tuberosity on the medial side of the foot. Present from birth, this additional bone is connected to the navicular by cartilage (synchondrosis) or fibrous tissue that may never fully fuse with the parent bone.

Three types exist based on anatomy and clinical significance. Type I is a small sesamoid bone within the posterior tibial tendon, rarely symptomatic. Type II — the most clinically relevant — is a large triangular bone connected to the navicular by a cartilaginous bridge. Type III represents a fused, enlarged navicular tuberosity (cornuate navicular).

The Type II accessory navicular creates problems because the posterior tibial tendon inserts partially onto the accessory bone rather than entirely onto the navicular. This altered insertion reduces the tendon’s mechanical advantage for arch support and creates a stress point at the synchondrosis that is vulnerable to injury.

Why Some Accessory Naviculars Become Painful

Most accessory naviculars remain asymptomatic throughout life. Pain typically begins during adolescence (ages 10-15) when the cartilaginous connection between the accessory bone and navicular experiences increasing stress from growth spurts, athletic activity, and weight gain.

Acute trauma — such as an ankle sprain or direct blow to the inner foot — can disrupt the fibrocartilaginous junction between the accessory and native navicular. This disruption creates a painful pseudoarthrosis (false joint) that moves with every step, producing chronic medial arch pain.

Shoe pressure on the prominent medial bump causes local pain, redness, and bursa formation independent of the synchondrosis status. Tight-fitting shoes, ski boots, ice skates, and cleats are frequent offenders because they compress the medial midfoot where the accessory navicular protrudes.

Progressive posterior tibial tendon dysfunction develops when the altered tendon insertion on the accessory navicular reduces the muscle’s ability to support the arch effectively. This leads to gradual flatfoot deformity that worsens the mechanical disadvantage in a self-perpetuating cycle.

Diagnosis and Imaging

Clinical examination reveals a palpable, tender bony prominence on the medial midfoot at the navicular tuberosity. Pain increases with direct pressure and with resisted foot inversion (turning the foot inward), which stresses the posterior tibial tendon insertion on the accessory bone.

Weight-bearing X-rays with oblique views confirm the accessory navicular and classify its type. The external oblique view best demonstrates the relationship between the accessory bone and the navicular, while the AP view shows medial prominence and any associated flatfoot alignment changes.

MRI is indicated when symptoms persist despite conservative treatment or when posterior tibial tendon pathology is suspected. MRI reveals bone marrow edema within the accessory navicular (indicating stress at the synchondrosis), tendon degeneration, and associated ligament injuries that guide treatment decisions.

Conservative Treatment Options

Activity modification and NSAIDs provide initial relief during acute flare-ups. Reducing high-impact activities that load the posterior tibial tendon — running, jumping, and pivoting sports — allows inflammation at the synchondrosis to subside over 2-4 weeks.

Custom orthotics with a medial arch support and navicular pad redistribute pressure away from the prominent accessory bone while supporting the arch. This dual action addresses both the external shoe pressure and the internal mechanical dysfunction simultaneously.

Immobilization in a walking boot or short leg cast for 4-6 weeks benefits patients with acute synchondrosis disruption or persistent pain despite activity modification. This rest period allows the inflamed pseudoarthrosis to stabilize before resuming progressive weight-bearing.

Physical therapy focusing on posterior tibial tendon strengthening, calf stretching, and intrinsic foot muscle conditioning improves the dynamic arch support that compensates for the altered tendon insertion. Eccentric exercises are particularly effective for associated tendinopathy.

When Surgery Is Needed: The Kidner Procedure

The Kidner procedure — surgical excision of the accessory navicular with reattachment of the posterior tibial tendon — is indicated when 3-6 months of conservative treatment fails to provide adequate pain relief and functional improvement.

Dr. Tom Biernacki performs the modified Kidner procedure through a medial incision, removing the accessory bone and any intervening cartilage while preserving the posterior tibial tendon’s substance. The tendon is then reattached to the remaining navicular through a bone tunnel or suture anchor, restoring its mechanical advantage.

Concurrent flatfoot correction may be performed when significant arch collapse has developed secondary to the posterior tibial tendon dysfunction. A medializing calcaneal osteotomy or spring ligament repair may be added to the Kidner procedure for comprehensive deformity correction.

Recovery involves 2-4 weeks of non-weight-bearing followed by progressive walking in a boot for 4-6 weeks. Return to sports averages 3-4 months. Success rates exceed 90% for pain relief, with most patients returning to full activity without restrictions.

Accessory Navicular in Young Athletes

Adolescent athletes with accessory navicular pain face unique management challenges because the growth plates are still open and activity demands are high. Conservative treatment is always attempted first, with surgery reserved for cases that significantly limit athletic participation.

The timing of surgical intervention in adolescents balances skeletal maturity considerations against the impact of ongoing pain on athletic development and quality of life. Most foot surgeons prefer to wait until skeletal maturity (around age 14-16) when possible, though earlier surgery may be warranted for severe cases.

Post-surgical young athletes typically return to full sports participation within 3-4 months with outcomes comparable to adults. Long-term studies show that Kidner procedure results are durable through adolescence and into adulthood with low recurrence rates.

The Most Common Mistake We See

The most common mistake with accessory navicular pain is treating it as simple plantar fasciitis or arch strain without obtaining X-rays that reveal the accessory bone. The treatment for accessory navicular syndrome differs significantly from standard arch pain — generic arch supports may actually worsen symptoms by pressing directly on the prominent bone.

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In-Office Treatment at Balance Foot & Ankle

Our team provides sport-specific evaluation and treatment to get you back to your activity safely. We offer same-day X-ray, in-office ultrasound, and custom orthotic fabrication.

Same-day appointments available. Call (810) 206-1402 or book online.

Frequently Asked Questions

Is an accessory navicular bone serious?

Most accessory navicular bones are harmless and never cause symptoms. When symptomatic, the condition is manageable but should be properly diagnosed and treated to prevent progressive flatfoot deformity from posterior tibial tendon dysfunction.

Can an accessory navicular go away on its own?

The extra bone does not disappear, but symptoms can resolve with conservative treatment including orthotics, activity modification, and physical therapy. Many patients manage the condition successfully without surgery throughout their lives.

How long is recovery from accessory navicular surgery?

Recovery involves 2-4 weeks non-weight-bearing, 4-6 weeks in a walking boot, and return to full activity at 3-4 months. Most patients experience significant pain relief within the first 6 weeks after surgery.

Can you exercise with an accessory navicular?

Yes, with proper management. Custom orthotics that accommodate the bony prominence and support the arch allow most people to exercise comfortably. High-impact activities may need modification during flare-ups, but long-term exercise restriction is rarely necessary.

The Bottom Line

An accessory navicular bone is a common anatomic variant that causes medial arch pain when the cartilaginous connection to the navicular breaks down or when shoe pressure irritates the bony prominence. Conservative treatment succeeds for most patients, while the Kidner procedure offers definitive relief for refractory cases.

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

Sources

1. Chung HW, et al. Accessory navicular classification and clinical correlation: updated imaging review. Skeletal Radiol. 2024;53(8):1567-1578.
2. Syed IB, et al. Modified Kidner procedure outcomes: systematic review and meta-analysis. Foot Ankle Surg. 2025;31(1):34-42.
3. Sullivan JA, et al. Posterior tibial tendon dysfunction secondary to accessory navicular: biomechanical analysis. J Foot Ankle Res. 2024;17(2):89-98.
4. Huang J, et al. Accessory navicular in adolescent athletes: management outcomes. J Pediatr Orthop. 2024;44(6):345-352.

Accessory Navicular Treatment in Michigan

An accessory navicular is an extra bone on the inner side of the foot that can cause chronic arch pain, especially in active individuals. At Balance Foot & Ankle, we offer both conservative management with custom orthotics and surgical excision (Kidner procedure) when needed.

Learn About Our Arch Pain & Flat Foot Treatment → | Book Your Appointment | Call (810) 206-1402

Clinical References

1. Kiter E, Erdag Y. Accessory navicular: diagnosis and treatment. Foot Ankle Spec. 2020;13(4):343-351.
2. Chung JW, Chu IT. Outcome of fusion of the symptomatic accessory navicular. Foot Ankle Int. 2009;30(7):659-663.
3. Leonard ZC, Fortin PT. Adolescent accessory navicular. Foot Ankle Clin. 2015;20(4):657-668.

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About 30% of patients I see for foot pain need MORE than a great shoe — they need a structured insole. Below: my complete 2026 orthotic ranking with pros, cons, and the specific patient I’d give each one to.