Accessory Navicular Syndrome is a condition involving an extra bone or piece of cartilage located on the medial (inner) side of the foot, near the arch, just behind the navicular bone. While many individuals with an accessory navicular (ANB) are asymptomatic, the condition can cause significant pain and dysfunction in some cases, especially when associated with repetitive stress or trauma.
How Common It Is and Who Gets It? (Epidemiology)
Accessory navicular bones are relatively common, with studies showing a prevalence rate ranging from 2% to 25% in the general population. The condition is more prevalent in females, adolescents, and those with flat feet. It is often discovered incidentally during imaging for other conditions or after injury.
Why It Happens – Causes (Etiology and Pathophysiology)
The accessory navicular bone develops as a congenital variation or may form over time due to repetitive stress on the foot. The bone is closely associated with the posterior tibial tendon, which helps maintain the arch of the foot. Pain typically occurs when the tendon is irritated by mechanical forces, such as pressure or strain, causing inflammation and discomfort.
How the Body Part Normally Works? (Relevant Anatomy)
The navicular bone is located on the medial side of the foot and plays a crucial role in maintaining the arch. The posterior tibial tendon attaches to the navicular and supports the foot’s arch during walking. In accessory navicular syndrome, the extra bone near the navicular can cause abnormal mechanical stress on the tendon, leading to irritation, inflammation, and pain.
What You Might Feel – Symptoms (Clinical Presentation)
Symptoms of Accessory Navicular Syndrome may include:
- Pain along the inner side of the foot, particularly near the arch.
- Swelling and redness around the accessory navicular.
- Visible bony prominence on the inner side of the foot.
- Pain may be exacerbated by physical activity, wearing tight shoes, or pressure from footwear.
How Doctors Find the Problem? (Diagnosis and Imaging)
Diagnosis is typically made based on:
- Physical examination: Pain is often reproducible by direct palpation over the medial aspect of the foot.
- X-rays: To confirm the presence of the accessory navicular and evaluate its size and position.
- MRI or bone scintigraphy may be used in certain cases to assess inflammation or tendon involvement.
Classification
Accessory navicular bones are classified into three types:
- Type I: Small, round or oval-shaped bone, completely separate from the navicular bone. Usually asymptomatic.
- Type II: Connected to the navicular by a fibrocartilaginous plate. More prone to symptoms, especially under mechanical stress.
- Type III: Fused to the navicular bone by a bony bridge. Most likely to cause pain and dysfunction due to its size and anatomical changes.
Other Problems That Can Feel Similar (Differential Diagnosis)
Other conditions that can mimic Accessory Navicular Syndrome include:
- Tendinitis or tendinopathy of the posterior tibial tendon.
- Plantar fasciitis.
- Stress fractures or fractures of the navicular bone.
- Arthritis or inflammatory conditions affecting the MTP joint.
Treatment Options
Non-Surgical Care
- Rest and ice to reduce inflammation and swelling.
- NSAIDs (Nonsteroidal Anti-Inflammatory Drugs) to manage pain and inflammation.
- Orthotics: Custom insoles to support the arch and reduce pressure on the accessory navicular.
- Shoe modifications: Wearing wider, cushioned shoes to alleviate pressure on the foot.
- Physical therapy: Exercises to strengthen the posterior tibial tendon and improve foot mechanics.
Surgical Care
If conservative treatments fail and symptoms persist, surgical intervention may be required. Common procedures include:
- Excision of the accessory navicular bone.
- Kidner procedure: Removal of the accessory bone and transfer or rerouting of the posterior tibial tendon to restore normal foot function.
Recovery and What to Expect After Treatment
- Rest and immobilization: Patients may need to wear a cast or fracture boot for a few weeks after surgery.
- Physical therapy: A rehabilitation program to restore strength, mobility, and function to the foot.
- Most patients can expect full recovery within 3 to 6 months, though it may take longer for the bones to fully heal.
Possible Risks or Side Effects (Complications)
- Infection at the surgical site.
- Recurrence of symptoms if the accessory navicular bone is not fully removed or if postoperative care is inadequate.
- Nerve damage or numbness around the surgical area.
- Nonunion or delayed healing of the bones after surgery.
Long-Term Outlook (Prognosis)
- Most patients experience significant pain relief and improvement in function after excision of the accessory navicular bone.
- Recurrence of symptoms is rare but can occur if there is continued stress or strain on the foot.
- Postoperative physical therapy plays a key role in achieving long-term relief and functional restoration.
Out-of-Pocket Costs
Medicare
CPT Code 28315 – Sesamoid Fixation or Removal (Accessory Navicular Treatment): $109.30
CPT Code 28238 – Tendon or Ligament Repair (Foot and Ankle): $151.78
Medicare Part B typically covers 80% of the approved cost for these procedures once your annual deductible has been met, leaving you responsible for the remaining 20%. Supplemental Insurance plans, such as Medigap, AARP, or Blue Cross Blue Shield, generally cover the remaining 20%, reducing or eliminating out-of-pocket expenses for Medicare-approved surgeries. These plans work alongside Medicare to fill the coverage gap.
If you have Secondary Insurance such as TRICARE, an Employer-Based Plan, or Veterans Health Administration coverage, it will act as a secondary payer. These plans usually cover any remaining balance, including coinsurance or small deductibles, which typically range from $100 to $300 depending on your plan and provider network.
Workers’ Compensation
If your accessory navicular syndrome requires treatment due to a work-related injury, Workers’ Compensation will cover all medical expenses, including surgery and rehabilitation. You will not have any out-of-pocket expenses, as the employer’s insurance carrier will cover all costs directly.
No-Fault Insurance
If your condition is related to an automobile accident, No-Fault Insurance will typically cover the full cost of treatment, including surgery and follow-up care. The only possible out-of-pocket expense may be a small deductible or co-payment depending on your policy.
Example
David Clark developed accessory navicular syndrome, which required sesamoid fixation (CPT 28315). The estimated Medicare out-of-pocket cost was $109.30. Since David had supplemental insurance through Blue Cross Blue Shield, his remaining balance was fully covered, leaving him with no out-of-pocket expenses for the procedure.
Frequently Asked Questions (FAQ)
Q. What is Accessory Navicular Syndrome?
A. Accessory Navicular Syndrome is a condition where an extra bone or piece of cartilage develops on the inner side of the foot just above the arch and causes pain or discomfort.
Q. What causes Accessory Navicular Syndrome?
A. It is often caused by irritation or injury to the accessory navicular bone or the posterior tibial tendon that attaches to it, especially during physical activity or trauma.
Q. Who is more likely to develop Accessory Navicular Syndrome?
A. It is more common in females, adolescents, and individuals with flat feet or fallen arches.
Q. What are the symptoms of Accessory Navicular Syndrome?
A. Symptoms include pain and swelling on the inner side of the foot, redness, and a visible bony prominence.
Q. How is Accessory Navicular Syndrome diagnosed?
A. Diagnosis is made through physical examination and confirmed with imaging studies like X-rays, MRI, or CT scans.
Q. What are the non-surgical treatments for Accessory Navicular Syndrome?
A. Non-surgical treatments include rest, ice, anti-inflammatory medications, immobilization with a cast or boot, physical therapy, and custom orthotics.
Q. When is surgery considered for Accessory Navicular Syndrome?
A. Surgery is considered when non-surgical treatments fail to relieve symptoms and the pain significantly interferes with daily activities.
Q. What surgical options are available for Accessory Navicular Syndrome?
A. Surgical options include removal of the accessory navicular bone and repair or reattachment of the posterior tibial tendon.
Q. What is the recovery like after surgery for Accessory Navicular Syndrome?
A. Recovery involves a period of immobilization, followed by physical therapy, and can take several weeks to months for full recovery.
Q. Can Accessory Navicular Syndrome recur after treatment?
A. Recurrence is rare after surgical removal, but continued strain or injury can cause similar symptoms in the area.
Q. Can Accessory Navicular Syndrome affect both feet?
A. Yes, it can affect one or both feet, although symptoms may be more severe in one foot than the other.
Q. At what age do symptoms of Accessory Navicular Syndrome typically appear?
A. Symptoms often appear during adolescence when bones are maturing and physical activity levels increase.
Q. What role does footwear play in managing Accessory Navicular Syndrome?
A. Supportive footwear can help reduce strain on the foot and relieve symptoms associated with the condition.
Q. Is physical therapy helpful for Accessory Navicular Syndrome?
A. Yes, physical therapy can strengthen the posterior tibial tendon, improve foot mechanics, and reduce pain.
Q. Can flat feet contribute to Accessory Navicular Syndrome?
A. Yes, flat feet can increase stress on the accessory navicular and the posterior tibial tendon, contributing to symptoms.
Summary and Takeaway
Accessory Navicular Syndrome is a common but often overlooked condition that can cause chronic foot pain and dysfunction, especially in individuals who engage in repetitive physical activity.
Most cases can be managed with conservative treatments like rest, orthotics, and physical therapy. In severe cases, surgical intervention, such as the Kidner procedure, can provide lasting relief.
Clinical Insight & Recent Findings
A 2025 study compared outcomes of the modified Kidner procedure—a surgery to remove the accessory navicular and repair the posterior tibial tendon—in athletes versus nonathletes. The study followed 42 patients (ages 10–37) and found that both groups experienced significant pain relief and improved foot function after surgery.
Interestingly, single-sport athletes (such as dancers or soccer players) reported worse pain and function before surgery, but after the procedure, their results were just as positive as multisport athletes and nonathletes.
The findings suggest that surgery is equally effective across patient groups, offering reliable pain relief and return to activity for those who do not respond to conservative treatments. (“Study on modified Kidner surgery for accessory navicular syndrome – see PubMed”)
Who Performs This Treatment? (Specialists and Team Involved)
Orthopedic surgeons specializing in foot and ankle surgery perform the surgery.
The surgical team may also include podiatrists and physical therapists for post-operative care and rehabilitation.
When to See a Specialist?
If you experience persistent pain, swelling, or difficulty with daily activities due to foot pain, it’s important to consult a healthcare provider to discuss potential treatment options.
When to Go to the Emergency Room?
Seek emergency care if:
- Severe pain or swelling occurs at the surgical site.
- Signs of infection such as fever, redness, or drainage from the incision.
- Inability to move the foot or bear weight despite treatment.
What Recovery Really Looks Like?
Post-surgery, patients will be immobilized for several weeks and will follow a physical therapy program to regain strength and mobility.
Full recovery generally takes 3 to 6 months, with some patients needing up to a year for complete healing.
What Happens If You Ignore It?
If left untreated, the pain may become chronic, leading to reduced mobility and an increased risk of stress fractures in the foot.
How to Prevent It?
Proper footwear is key to preventing further strain on the accessory navicular and posterior tibial tendon.
Strengthening exercises to support the posterior tibial tendon and improve foot mechanics can help reduce stress on the foot.
Nutrition and Bone or Joint Health
Adequate intake of calcium, vitamin D, and protein supports bone health and promotes recovery post-surgery.
Activity and Lifestyle Modifications
After surgery, avoid high-impact activities until the foot has fully healed. Follow your surgeon’s advice regarding gradual return to physical activities.
Dr. Mo Athar
