Accessory Navicular Syndrome: Medial Arch Pain, Diagnosis,

Quick answer: Treatment for accessory navicular syndrome medial arch pain treatment follows a stepwise approach: 1) conservative care first (rest, ice, supportive footwear, OTC anti-inflammatories), 2) physical therapy and targeted exercises, 3) in-office treatments (injections, custom orthotics) if conservative fails at 4-6 weeks, 4) surgery for refractory cases. Most patients resolve at step 1 or 2. Call (810) 206-1402.

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

An accessory navicular is an extra bone (ossicle) present in approximately 10–14% of people, located on the medial (inner) side of the foot adjacent to the navicular bone. Most people with an accessory navicular never develop symptoms. But when the accessory navicular becomes symptomatic — a condition called accessory navicular syndrome — it produces medial arch pain, a prominent bony bump, and, often, an associated flat foot deformity.

Types of Accessory Navicular

Three anatomical types exist, with different clinical implications:

• Type I (Os tibiale externum): A small, free ossicle within the posterior tibial tendon at the navicular. Usually incidental and rarely symptomatic.
• Type II (Synchondrosis): A larger ossicle connected to the navicular by a fibrocartilaginous bridge (synchondrosis). The posterior tibial tendon inserts partially into the accessory bone rather than the native navicular. This type is the most commonly symptomatic — the synchondrosis can become inflamed, painful, and unstable.
• Type III (Cornuate navicular): The accessory bone is completely fused to the navicular, creating an unusually large navicular. Less commonly symptomatic.

Why Type II Becomes Symptomatic

The posterior tibial tendon — the primary dynamic arch support — inserts into or near the accessory navicular rather than the native navicular in Type II cases. This altered insertion point reduces the tendon’s mechanical advantage for arch support. The synchondrosis is subjected to tension and shear forces with every step. Repetitive stress, a sudden injury (ankle sprain, direct blow), or a period of increased activity can precipitate synchondrosis inflammation and pain.

Accessory navicular syndrome is more common in adolescent females during growth spurts, in flat-footed individuals (pronation increases posterior tibial tendon stress), and in athletes. The prominent medial bump can also cause direct shoe friction, adding an additional pain source.

Diagnosis

Clinical presentation: medial arch and navicular pain, a palpable bony prominence on the inner midfoot, tenderness directly over the accessory bone, and pain with resisted foot inversion (posterior tibial tendon testing). Flat foot deformity is commonly associated.

Weight-bearing foot X-rays confirm the ossicle type and size. MRI is indicated when the X-ray diagnosis is uncertain, to assess synchondrosis integrity, and to evaluate associated posterior tibial tendon pathology — particularly important if surgical planning is considered.

Conservative Treatment: Highly Effective in Most Cases

The vast majority of symptomatic accessory navicular cases respond to conservative management:

• Activity modification: Reduce high-impact activity during acute flares.
• Custom orthotics with medial arch support: Unload the accessory navicular and improve posterior tibial tendon mechanics by supporting the arch and reducing pronation. This is the cornerstone of conservative management.
• Immobilization: A walking boot or short-leg cast for 4–6 weeks reduces synchondrosis stress and allows acute inflammation to resolve, particularly in adolescents during growth spurts.
• Anti-inflammatory therapy: NSAIDs and cortisone injection (into the synchondrosis under ultrasound guidance) reduce inflammation.
• Footwear modification: Extra-depth shoes or shoes with a wide medial counter to avoid direct pressure on the accessory navicular.

Approximately 85–90% of patients achieve satisfactory symptom control with conservative care. Surgery is reserved for the 10–15% who fail 6 months of conservative management.

Surgical Options

The Kidner procedure (excision of the accessory navicular with reinsertion of the posterior tibial tendon to the native navicular) has been the historical standard. Modern modifications focus on preserving and advancing the posterior tibial tendon insertion to improve arch support. Recovery after surgical excision typically involves 6–8 weeks of protected weight bearing followed by progressive rehabilitation, with return to sports at 3–5 months.

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 treatment isn’t providing relief for your foot pain, our podiatry team at Balance Foot & Ankle can help with expert evaluations and advanced in-office care.

Related Care at Balance Foot & Ankle

Clinical navicular services at our Howell and Bloomfield Township offices.

Custom OrthoticsFoot BracingFlat Feet Treatment