Accessory Navicular Bone: Symptoms and Treatment Options

Type	Description	PT Tendon Involvement	Symptoms	Frequency
Type 1 (sesamoid)	Small round separate ossicle within PT tendon	Embedded in tendon	Usually asymptomatic; rarely causes tendon pain	30%
Type 2 (synchondrosis)	Heart-shaped; connected to navicular by cartilage junction	Attaches to both navicular and accessory ossicle	Most symptomatic; synchondrosis motion causes pain; adolescent onset typical	50–60%
Type 3 (cornuate navicular)	Fused with navicular; prominent medial process	Normal insertion	Shoe irritation; PT tendon strain from altered mechanics	10–20%

Treatment	Success Rate	Timeline	Best For
Immobilization (boot or cast, 4–6 weeks)	~60–70% (short-term; recurrence common without follow-up)	4–6 weeks	Acute flares; first-line; before orthotics
Custom orthotic with navicular relief	75–80% long-term (combined with boot)	Ongoing; requires regular use	Long-term conservative management; arch support + pressure relief
Footwear modification	Adjunct benefit	Immediate	All symptomatic cases; reduces direct pressure
Corticosteroid injection (synchondrosis)	~60–70% significant relief (months)	1–2 weeks onset	Acute flares; bridge to conservative management
Kidner procedure (surgical excision)	85–90% satisfaction; 90% return to sport	3–4 months recovery	Failed 6+ months conservative care; recurrent disabling pain

Quick answer: Accessory Navicular Bone is a common foot/ankle topic that affects many patients. The 2026 evidence-based approach combines proper diagnosis, conservative-first treatment, and escalation only when needed. We treat this regularly at our Howell and Bloomfield Township practices. Call (810) 206-1402.

What Is an Accessory Navicular?

The navicular is the bone on the inner midfoot that forms the peak of the arch. An accessory navicular (also called os navicularum or os tibiale externum) is an extra bone or ossicle present on the medial (inner) side of the navicular, where the posterior tibial tendon attaches. It’s a congenital variant — present from birth — occurring in approximately 10% of the population.

There are three types: Type 1 is a small sesamoid bone within the posterior tibial tendon (usually asymptomatic). Type 2 is the most clinically significant — a larger ossicle connected to the navicular by fibrocartilage, prone to irritation and the most common cause of accessory navicular pain. Type 3 is a fused variant (cornuate navicular) — typically asymptomatic.

When It Becomes Symptomatic

Pain at the bony prominence on the inner ankle/arch area, worsened by shoes pressing against it, prolonged walking or standing, and athletic activity. Often first becomes symptomatic in adolescence during the growth spurt (ages 10–15), when the ossification center is consolidating. In adults, symptoms often triggered by ill-fitting shoes pressing on the prominence, acute trauma to the area, or a flat foot condition that overloads the posterior tibial tendon insertion.

Patients often describe feeling a “bump” on the inside of their foot that their shoe rubs against. The prominence is visible and palpable — easy to identify on clinical examination.

Treatment

Conservative (first-line): Wide, accommodative footwear that doesn’t press against the prominence. Custom orthotics to support the medial arch and offload the posterior tibial tendon insertion. Physical therapy to strengthen the posterior tibial tendon and reduce stress on the attachment. Activity modification during flares. Cast or boot immobilization for 4–6 weeks in acute symptomatic cases — this settles the fibrocartilage junction inflammation effectively.

Cortisone injection: Targeted injection at the fibrocartilage junction reduces pain and inflammation in the short-to-medium term. Useful bridge to activity or to get through a competitive season.

Surgery (Kidner procedure): Reserved for cases failing 6 months of conservative treatment. The accessory bone is excised and the posterior tibial tendon is reattached to the navicular. Success rates of 85–90%. Recovery: non-weight-bearing 4–6 weeks, full return to sports 3–4 months.

Frequently Asked Questions

Does an accessory navicular always need treatment? Only if symptomatic. Approximately 10% of the population has this variant and most never have pain. If your accessory navicular is asymptomatic, no intervention is needed.

Can I play sports with an accessory navicular? Yes — many athletes compete with it. Proper orthotics and footwear modification allow most patients to remain fully active. During acute flares, activity modification is appropriate.

Is it a fracture? No. It’s a congenital bony variant, not a fracture. However, the fibrocartilage connection between the accessory bone and the main navicular can become inflamed (similar to a stress injury), which is what causes pain.

Does it run in families? There is a genetic component — it appears more commonly in certain families. It’s also associated with flatfoot (pes planus), which itself has genetic factors.

Frequently Asked Questions

In-Office Treatment at Balance Foot & Ankle

If home treatment isn’t providing relief for your foot and ankle conditions, our podiatry team at Balance Foot & Ankle can help with same-day evaluations and advanced in-office care.