Accessory Navicular Syndrome: The Extra Foot Bone Causing Your Arch Pain

Quick answer: Accessory Navicular Syndrome Extra Foot Bone Arch Pain has multiple potential causes including mechanical, neurological, vascular, and inflammatory. The most common causes we identify are overuse, ill-fitting shoes, and biomechanical imbalance. Red flags requiring urgent evaluation: warmth/redness (infection), inability to bear weight (fracture), and unilateral swelling without injury (DVT). Call (810) 206-1402.

That Bony Bump on the Inside of Your Foot Has a Name

You’ve probably known about it for years — that firm, tender bump on the inner side of your foot, just in front of the ankle. Maybe it only hurts after long days on your feet, or maybe it’s been limiting your sports activities since high school. If so, you may have an accessory navicular — an extra bone that affects roughly 1 in 10 people. When this extra bone becomes inflamed and painful, the result is accessory navicular syndrome: one of the most commonly overlooked causes of inner arch pain in active patients.

In our clinic, we see accessory navicular syndrome most often in two groups: adolescents going through a growth spurt (typically ages 9–15) and active adults who’ve increased their activity level or started a new sport. The common thread is increased mechanical stress on the synchondrosis — the fibrocartilage joint connecting the extra bone to the main navicular — that exceeds the tissue’s ability to adapt.

Why the Extra Bone Causes Pain

The navicular is the keystone of the medial arch. The posterior tibial tendon — the main arch-supporting structure in the foot — inserts directly into the navicular. When an accessory navicular is present, the tendon may split its insertion, with part going into the extra bone instead of fully into the navicular itself. This split insertion reduces the tendon’s mechanical efficiency. More importantly, during activity, repetitive shear forces across the synchondrosis between the accessory bone and the navicular generate microdamage, inflammation, and pain — a process similar to a stress reaction. The result: a painful prominence at the inner midfoot that worsens with walking, running, or prolonged standing.

Symptoms to Recognize

The hallmark symptom of accessory navicular syndrome is a dull to moderate aching pain at the medial midfoot, centered on the visible bony bump approximately 1 cm below and in front of the medial malleolus. The bump is tender to direct pressure — patients often notice it when wearing shoes that press against the area. Activity reliably worsens pain: prolonged walking, running, hiking, and sports that involve lateral cutting. Rest relieves symptoms. Associated findings include mild swelling at the bump, a flat foot deformity in many patients (the weakened tendon insertion contributes to arch collapse), and tight calf muscles that increase demand on the posterior tibial tendon.

How We Diagnose It

Diagnosis is primarily clinical and radiographic. Weight-bearing X-rays confirm the presence and classification of the accessory navicular (Type I, II, or III) and assess for associated arch collapse. MRI is the gold standard for confirming active inflammation — bone marrow edema at the synchondrosis on STIR sequences is pathognomonic for symptomatic Type II disease. MRI also evaluates the posterior tibial tendon integrity, which is critical for surgical planning if conservative care fails. Ultrasound provides a dynamic assessment and can identify tendinopathy or a partial tear in the adjacent posterior tibial tendon. The differential diagnosis must rule out posterior tibial tendon dysfunction without an accessory navicular, navicular stress fracture, tarsal coalition, and spring ligament injury.

Conservative Treatment: The First 3–6 Months

Conservative management succeeds in 85–90% of patients with accessory navicular syndrome. The cornerstone is custom orthotic therapy — a semi-rigid device with a deep heel cup, medial longitudinal arch support, and a specifically placed navicular pad that offloads the painful prominence. Prefabricated orthotics provide modest relief, but custom devices are significantly more effective for this condition. During acute flares — especially the initial presentation or after a reinjury — immobilization in a short-leg walking cast or CAM boot for 6–8 weeks allows the synchondrosis to settle. Physical therapy addresses posterior tibial tendon strengthening and calf flexibility. Iontophoresis (dexamethasone driven transdermally with a low-voltage current) reduces localized inflammation without systemic side effects. NSAIDs are a helpful adjunct for acute pain. Shoe modification — avoiding narrow, rigid footwear that compresses the bump — is equally important and often overlooked.

The Kidner Procedure: Surgical Treatment When Conservative Care Fails

When 3–6 months of comprehensive conservative care fails to provide adequate relief, the Kidner procedure is the standard surgical treatment. The operation excises the accessory navicular and advances the posterior tibial tendon insertion into the main navicular — correcting both the source of pain and the mechanical deficit. Modern techniques often use suture anchors to secure the tendon advancement, producing more reliable results than historical soft-tissue repairs alone. Reported outcomes are excellent: published series show 85–95% patient satisfaction at 2-year follow-up. In patients with significant associated flat foot deformity, additional procedures (medializing calcaneal osteotomy, spring ligament repair) may be added at the same sitting to achieve optimal alignment. Minimally invasive techniques are available for straightforward cases. Recovery involves 2–4 weeks non-weight-bearing, progressive loading in a boot at 4–6 weeks, physical therapy from week 6 onward, and return to sports at 4–6 months.

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.

Frequently Asked Questions

Does everyone with an accessory navicular need treatment?

No — about 90% of people with an accessory navicular never develop symptoms and need no treatment. The extra bone is discovered incidentally on X-rays taken for other reasons. Treatment is only indicated when the bone becomes symptomatic.

Can accessory navicular syndrome cause flat feet?

Yes. Because the posterior tibial tendon partially inserts into the accessory navicular rather than fully into the navicular, its arch-supporting function is compromised. Over time — particularly with inadequate treatment — the arch may gradually collapse, creating an adult-acquired flat foot deformity. Early orthotic treatment and posterior tibial tendon strengthening help prevent this progression.

Can I run with accessory navicular syndrome?

During acute flares, running typically needs to be reduced or stopped temporarily. With proper orthotic support and a graduated return-to-sport program, most athletes return to full running activities — often without surgery. The key is managing load appropriately rather than pushing through pain.

The Bottom Line

Accessory navicular syndrome is a well-understood, highly treatable cause of inner arch pain. The extra bone itself is a normal anatomical variant — it’s the inflammation at the synchondrosis that creates the problem. Custom orthotics and targeted physical therapy resolve the vast majority of cases. When surgery is needed, the Kidner procedure has decades of excellent results behind it. If you have a persistent painful bump on the inner arch, a comprehensive podiatric evaluation will confirm the diagnosis and chart the most efficient path to relief.

Sources

1. Prichasuk S, Sinphurmsukskul O. Kidner procedure for symptomatic accessory navicular. Foot Ankle Int. 1995;16(8):500-503.
2. Scott AT, et al. Treatment of symptomatic accessory navicular. Foot Ankle Int. 2011;32(5):S553-S557.
3. Miller TT, et al. Symptomatic Accessory Navicular Bone: MR Imaging Appearance. AJR Am J Roentgenol. 1995;168(1):101-104.
4. Stavlas P, et al. The Kidner Procedure With Modified Reattachment Technique for Accessory Navicular. J Foot Ankle Surg. 2022;61(4):780-785.

What is Foot pain?

Foot pain is a common foot/ankle condition that affects mobility and quality of life. Understanding the underlying cause is the first step in successful treatment. Our podiatrists at Balance Foot & Ankle perform a hands-on biomechanical exam, review your activity history, and use diagnostic imaging when appropriate to identify the root cause—not just treat the symptom. Many patients have been told to “rest and ice” without a deeper diagnostic workup; our approach is different.

Symptoms and warning signs

Common signs of foot pain include pain that worsens with activity, morning stiffness, swelling, tenderness when palpated, and difficulty bearing weight. If you experience sudden severe pain, inability to walk, visible deformity, numbness or color change, contact our office the same day or visit urgent care—these can signal a more serious injury such as a fracture, tendon rupture, or vascular compromise. Diabetics with any foot wound should seek same-day care.

Conservative treatment options

Most cases of foot pain respond to non-surgical care: structured rest, supportive footwear changes, custom orthotics, targeted stretching and strengthening protocols, anti-inflammatory medications when medically appropriate, and in-office procedures such as ultrasound-guided injections. We also offer advanced therapies including MLS laser therapy, EPAT/shockwave, regenerative injections, and image-guided procedures. Treatment is sequenced from least invasive to most invasive, and we explain the rationale at every step.

When is surgery considered?

Surgery is reserved for cases that fail 3-6 months of well-structured conservative care, when there is structural pathology (severe deformity, complete tear, advanced arthritis), or when imaging shows damage that will not heal without intervention. Our surgeons have performed 3,000+ foot and ankle procedures and prioritize minimally-invasive techniques whenever appropriate. We discuss recovery timelines, return-to-activity milestones, and realistic outcome expectations before any procedure is scheduled.

OrthoInfo – AAOS: Accessory Navicular Syndrome

Recovery timeline and prevention

Recovery from foot pain varies based on severity and chosen treatment path. Conservative cases often improve within 4-8 weeks with consistent adherence to the protocol. Post-procedural recovery may range from a few days (in-office procedures) to several months (reconstructive surgery). Long-term prevention involves footwear assessment, activity modification, structured strengthening, and regular check-ins with your podiatrist if you have a history of recurrence. We provide written home-exercise plans and digital follow-up support.

Related Care at Balance Foot & Ankle

Clinical navicular services at our Howell and Bloomfield Hills offices.

Custom OrthoticsFoot BracingFlat Feet Treatment