Table of Contents

• What Is an Accessory Navicular?
• Types and Classification
• Causes and Symptoms
• Diagnosis and Imaging
• Conservative Treatment Options
• When Surgery Is Needed
• The Kidner Procedure: Surgical Technique
• Recovery Timeline
• Best Products for Recovery
• Outcomes and Success Rates
• Most Common Mistake
• Warning Signs After Surgery
• Frequently Asked Questions
• Sources

What Is an Accessory Navicular?

If you have a bony bump on the inner arch of your foot that aches with every step or rubs painfully against your shoes, you may have a symptomatic accessory navicular. This is one of the most common congenital foot variants — present from birth — and while many people live their entire lives without knowing they have one, it can become a significant source of pain and disability when it does become symptomatic.

The navicular bone is a key bone on the inner (medial) side of the midfoot that serves as the attachment point for the posterior tibial tendon — one of the most important tendons for maintaining the arch and controlling foot motion during walking. An accessory navicular is an extra bone (or ossicle) that develops next to the navicular during fetal development, creating a prominence on the inner arch of the foot.

Accessory naviculars affect 4–14% of the general population, making them one of the most common accessory bones in the foot. They occur bilaterally (both feet) in approximately 50–90% of affected individuals and are more common in females than males. Most accessory naviculars never cause symptoms, but certain types — particularly Type II — are prone to becoming painful.

Accessory Navicular Types and Classification

Accessory naviculars are classified into three types based on their size, shape, and relationship to the main navicular bone. Understanding the type is important because it predicts which patients are most likely to develop symptoms and which will benefit from surgery.

Type I: Os tibiale externum. A small (2–3 mm), round, well-corticated sesamoid bone embedded within the posterior tibial tendon, separated from the navicular by a clear gap. Type I accessory naviculars rarely cause symptoms because they are small and do not alter the biomechanics of the posterior tibial tendon insertion. When they do cause issues, it is usually from direct shoe pressure over the prominence.

Type II: Prehallux or cornuate navicular. A larger (8–12 mm), triangular or heart-shaped ossicle connected to the navicular by a fibrocartilaginous synchondrosis (a cartilage bridge). Type II is the most clinically significant type and accounts for the vast majority of symptomatic accessory naviculars. The synchondrosis is a weak point that can develop shearing forces, microfractures, and inflammation — especially during sports and growth spurts. The posterior tibial tendon inserts primarily on the accessory ossicle rather than the main navicular, which can weaken its mechanical advantage and contribute to flatfoot.

Type III: Cornuate navicular. A large, horn-shaped prominence that represents a fused accessory navicular — the ossicle has united with the navicular bone, creating an enlarged, prominent medial navicular. Type III is essentially a very large navicular bone. It causes symptoms primarily through shoe irritation over the bony prominence rather than synchondrosis pathology. It is sometimes associated with posterior tibial tendon dysfunction due to altered tendon biomechanics.

What Causes Accessory Navicular Pain?

An accessory navicular is present from birth, but it often becomes symptomatic during specific life stages or circumstances that increase stress on the inner foot.

Adolescent growth spurts. The most common trigger for first-time accessory navicular pain is the adolescent growth spurt (ages 10–15). Rapid bone growth increases tension through the posterior tibial tendon, stressing the synchondrosis in Type II accessory naviculars. The combination of growth-related tendon tension and increased sports activity makes this age group particularly vulnerable.

Shoe pressure and irritation. Tight shoes, ski boots, ice skates, and cleats compress the medial prominence, causing bursitis (inflammation of the fluid-filled sac over the bump) and localized pain. This is the most common cause in adults with Type I or III accessory naviculars.

Trauma and ankle sprains. An ankle sprain or direct blow to the inner foot can disrupt the synchondrosis in a Type II accessory navicular, converting a previously asymptomatic ossicle into a painful one. The shearing force across the cartilage bridge causes microfracture, inflammation, and chronic pain.

Posterior tibial tendon dysfunction. Because the posterior tibial tendon often inserts primarily on the accessory ossicle (especially in Type II), its mechanical efficiency is reduced. This can lead to progressive posterior tibial tendon dysfunction, arch collapse, and adult-acquired flatfoot — particularly in overweight individuals or those with high-demand occupations.

Overuse in athletes. Runners, dancers, basketball players, and other athletes who place repetitive stress on the medial arch frequently develop accessory navicular symptoms. The combination of repetitive push-off forces, rotational stress, and inadequate arch support in athletic shoes creates chronic irritation at the synchondrosis.

How Is an Accessory Navicular Diagnosed?

Diagnosis of a symptomatic accessory navicular begins with clinical examination and is confirmed with imaging. The combination of a characteristic medial arch prominence and specific physical exam findings often makes the clinical diagnosis straightforward.

Physical examination. A visible or palpable bony bump on the inner arch, directly over the navicular tuberosity, is the hallmark finding. Pressing on this prominence reproduces the patient’s pain. The foot may show a flatfoot posture (especially with Type II), and resisted inversion — asking the patient to turn the foot inward against resistance — often reproduces pain because it loads the posterior tibial tendon through the synchondrosis.

X-rays. Standard foot X-rays (AP, lateral, and oblique views) clearly demonstrate the accessory navicular and allow classification into Type I, II, or III. The oblique view best shows the synchondrosis gap between the ossicle and the navicular in Type II. Weight-bearing lateral views assess arch height and hindfoot alignment.

MRI. When the diagnosis is uncertain or surgical planning requires more detail, MRI reveals bone marrow edema (stress reaction) at the synchondrosis, inflammation in the posterior tibial tendon, and associated pathology like tendon tears or degenerative changes. MRI is particularly valuable for differentiating between a symptomatic synchondrosis and posterior tibial tendinitis, which may coexist.

Bone scan or SPECT-CT. In cases where multiple potential pain sources exist, a bone scan with single-photon emission computed tomography (SPECT-CT) can pinpoint increased metabolic activity at the synchondrosis, confirming it as the pain generator. This is occasionally helpful when clinical and MRI findings are equivocal.

Conservative Treatment for Symptomatic Accessory Navicular

Conservative treatment is always the first approach and is successful in managing symptoms for 50–70% of patients, particularly those with Type I and Type III accessory naviculars and milder Type II presentations.

Orthotic insoles with medial arch support. A quality orthotic insole that supports the medial arch reduces tension on the posterior tibial tendon and takes stress off the synchondrosis. PowerStep orthotic insoles provide the firm medial arch support needed to offload the accessory navicular area. The PowerStep Pinnacle or Pinnacle Maxx with their semi-rigid arch shell and deep heel cup control the pronation that stresses the synchondrosis during every step. We recommend orthotics as the foundation of all conservative treatment plans.

Immobilization. For acute flares, 2–4 weeks in a walking boot or short-leg cast allows inflammation to settle and the synchondrosis to rest. This is often the most effective initial treatment for an acutely symptomatic accessory navicular, especially in adolescents presenting with their first episode.

Shoe modification. Wearing shoes with a wider, deeper medial forefoot area that does not press on the navicular prominence reduces direct irritation. Avoiding tight-fitting shoes, narrow cleats, and stiff ski boots during symptomatic periods is essential. Shoe stretching over the prominence can also provide relief.

Physical therapy. Strengthening the posterior tibial tendon and intrinsic foot muscles helps support the arch dynamically and reduces reliance on the passive structures (synchondrosis) for arch maintenance. Calf stretching, arch strengthening exercises, and proprioceptive training form the rehabilitation foundation.

Topical and oral anti-inflammatories. NSAIDs help manage pain during flares. Doctor Hoy’s Natural Pain Relief applied directly over the navicular prominence provides targeted topical anti-inflammatory relief without systemic side effects — an especially attractive option for adolescent patients whose parents prefer to minimize oral medication.

When Is Surgery Needed for Accessory Navicular?

Surgery is recommended when 3–6 months of consistent conservative treatment fails to adequately control symptoms and the patient’s quality of life, sports participation, or daily function remains significantly affected.

Persistent pain despite orthotics and activity modification. If quality orthotic insoles, physical therapy, and shoe modifications do not reduce pain to an acceptable level, surgical excision should be considered.

Recurrent flares requiring immobilization. Patients who require repeated boot or cast immobilization (2 or more times per year) for acute flares are unlikely to achieve lasting relief without surgery.

Inability to participate in sports or desired activities. For adolescent athletes and active adults whose accessory navicular pain prevents sports participation, surgery offers a reliable path back to full activity.

Progressive flatfoot deformity. If a Type II accessory navicular is contributing to posterior tibial tendon insufficiency and progressive flatfoot, surgical intervention addresses both the pain source and the underlying biomechanical problem.

The Kidner Procedure: Surgical Technique

The Kidner procedure — first described by Dr. Douglas Kidner in 1929 — remains the gold standard surgical treatment for symptomatic accessory navicular. The procedure has been refined over nearly a century but retains its core principle: remove the accessory bone and reattach the posterior tibial tendon to the navicular in a mechanically advantageous position.

Incision and exposure. A 3–4 cm curving incision is made over the medial navicular prominence. The soft tissues are carefully dissected to expose the accessory ossicle and the synchondrosis. Care is taken to protect the posterior tibial tendon, which wraps around and attaches to the accessory bone.

Ossicle excision. The accessory navicular is carefully separated from the navicular bone at the synchondrosis and removed. The posterior tibial tendon fibers that attached to the ossicle are preserved and mobilized. The remaining navicular prominence is smoothed and contoured to eliminate the medial bump that caused shoe irritation.

Tendon reattachment. The posterior tibial tendon is reattached to the plantar-medial surface of the navicular using suture anchors or bone tunnels. This advancement technique repositions the tendon insertion to a more mechanically efficient location — slightly more plantar (toward the sole) and distal (toward the toes) — which improves the tendon’s ability to support the arch. This tendon advancement is the key innovation of the Kidner procedure and distinguishes it from simple ossicle excision.

Additional procedures. When significant flatfoot deformity accompanies the accessory navicular, additional procedures may be performed simultaneously: medial cuneiform opening wedge osteotomy (Cotton procedure) to restore arch height, Achilles tendon or gastrocnemius lengthening to address equinus contracture, or calcaneal osteotomy to correct hindfoot valgus.

Anesthesia and operative time. The procedure is performed under ankle block anesthesia with IV sedation (adults) or general anesthesia (children), typically taking 45–60 minutes for isolated Kidner procedure. Patients go home the same day.

Recovery Timeline After the Kidner Procedure

Recovery from the Kidner procedure follows a structured progression designed to protect the tendon reattachment while restoring function. The timeline is somewhat longer than simple bone excision procedures because the posterior tibial tendon must heal securely to its new insertion.

Weeks 0–2: Non-weight-bearing. A bulky dressing and posterior splint immobilize the foot. Non-weight-bearing with crutches or knee scooter. Elevation is emphasized to control swelling. Sutures are removed at the 2-week visit.

Weeks 2–4: Protected weight bearing. Transition to a walking boot with heel weight bearing progressing to full weight bearing by week 4. Gentle ankle range of motion exercises begin. DASS compression socks are worn daily to manage midfoot swelling.

Weeks 4–6: Full weight bearing in boot. Walking normally in the boot with gradual increase in distance and standing time. Physical therapy begins with gentle posterior tibial tendon strengthening, calf stretching, and balance exercises.

Weeks 6–8: Transition to supportive shoes. The boot is discontinued and the patient transitions to supportive shoes with PowerStep orthotic insoles. Physical therapy advances to more aggressive strengthening, proprioceptive training, and gait normalization. Most patients can return to desk work and light daily activities.

Weeks 8–12: Progressive activity. Gradual return to exercise, beginning with low-impact activities (swimming, cycling, walking) and progressing to running and sports by 10–12 weeks. Continue orthotics in all shoes for a minimum of 6 months.

Months 3–6: Full return to activity. Most patients achieve full return to sports and unrestricted activity by 3–4 months. Complete resolution of swelling and maximum improvement may take 6 months. Long-term orthotic use is recommended to support the arch and protect the tendon repair.

Best Products for Kidner Procedure Recovery

The right recovery products support healing and optimize long-term outcomes after the Kidner procedure.

Affiliate disclosure: Some links below are affiliate links, meaning we may earn a small commission if you purchase through them — at no extra cost to you. We only recommend products we use in our own practice.

PowerStep Orthotic Insoles — Critical for Long-Term Arch Support

Orthotic insoles become even more important after the Kidner procedure because the posterior tibial tendon is reattached in a new position and needs external support during healing and beyond. PowerStep orthotic insoles provide the firm medial arch support that protects the tendon repair, prevents excessive pronation, and maintains the arch correction achieved through surgery. We recommend the PowerStep Pinnacle for everyday shoes and the PowerStep Pinnacle Sport for athletic shoes. Begin wearing orthotics immediately when transitioning from the boot to regular shoes and continue long-term — ideally permanently — to prevent recurrent arch collapse and tendon strain.

DASS Medical Grade Compression Socks

Midfoot swelling after the Kidner procedure can be persistent and frustrating. DASS medical grade compression socks provide graduated 20–30 mmHg compression that effectively controls post-surgical edema, improves comfort during the transition to weight bearing, and supports the healing tissues. Begin wearing compression daily at week 2 post-op and continue for at least 3 months. Many patients find ongoing compression beneficial during athletic activities even after full recovery.

Doctor Hoy’s Natural Pain Relief

Doctor Hoy’s Natural Pain Relief gel provides targeted topical pain relief during the recovery phases. Apply around the medial arch area (once the incision is healed) for localized anti-inflammatory and analgesic benefits. Particularly useful during physical therapy sessions and after increased activity, Doctor Hoy’s helps manage discomfort without additional oral medication — a benefit valued by parents of adolescent patients and by adults seeking to minimize medication use during recovery.

Kidner Procedure Outcomes and Success Rates

The Kidner procedure has nearly a century of published outcomes demonstrating its effectiveness for symptomatic accessory navicular.

Pain relief: 85–95% of patients report significant or complete pain resolution after the Kidner procedure. The medial prominence that caused shoe irritation is eliminated, and synchondrosis pain is permanently resolved by removing the accessory bone.

Return to activity: 90% of adolescent athletes return to their pre-symptom sport level within 3–4 months. Most patients can walk without limitation by 6–8 weeks and run by 10–12 weeks.

Arch improvement: Patients with accessory navicular-associated flatfoot show measurable improvement in arch height on post-operative weight-bearing X-rays. The tendon advancement component of the Kidner procedure contributes to improved arch support by optimizing posterior tibial tendon mechanics.

Patient satisfaction: Published series consistently report 85–95% patient satisfaction with the Kidner procedure. The most satisfied patients are those who commit to long-term orthotic use and complete their physical therapy program.

Complication rates: Serious complications are rare (less than 5%). The most common issues are persistent swelling (which resolves with compression and time), wound healing delay, and occasional hypersensitivity over the scar. Tendon failure or re-rupture is exceedingly rare with modern suture anchor fixation.

Most Common Mistake With Accessory Navicular

Warning Signs After the Kidner Procedure

Accessory Navicular Treatment at Balance Foot & Ankle

Dr. Biernacki at Balance Foot & Ankle provides comprehensive evaluation and treatment for symptomatic accessory navicular in both adolescents and adults. Our approach includes thorough clinical assessment, classification-specific treatment planning, and — when surgery is indicated — the Kidner procedure with modern suture anchor tendon fixation. We have extensive experience with pediatric and adolescent patients and work closely with families to develop treatment plans that minimize time away from sports and school.

Accessory Navicular: Understanding Your Options [Video]

Dr. Biernacki discusses foot conditions and treatment options in this educational video from Balance Foot & Ankle:

Frequently Asked Questions About Accessory Navicular Surgery

Is the Kidner procedure painful?

Most patients describe the first 48–72 hours as moderately uncomfortable, well-managed with prescribed pain medication and consistent elevation. The ankle block anesthesia provides 12–18 hours of numbness after surgery, making the immediate post-operative period very manageable. By one week, most patients transition to over-the-counter pain relievers. Topical relief with Doctor Hoy’s helps manage discomfort during the physical therapy phase.

Can an accessory navicular grow back after the Kidner procedure?

No — once the accessory navicular bone is surgically removed, it does not grow back. The ossicle is a congenital extra bone, not a growth, so there is no biological mechanism for recurrence. Occasional patients may develop residual prominence from bone remodeling at the resection site, but this is uncommon and rarely symptomatic. If medial prominence recurs, it typically represents inadequate initial resection rather than bone regrowth.

Do I need orthotics permanently after the Kidner procedure?

We recommend orthotic insoles like PowerStep for a minimum of one year after the Kidner procedure, and ideally on a permanent basis. The posterior tibial tendon has been repositioned, and long-term arch support optimizes the tendon’s function and prevents progressive flatfoot. Most patients find that orthotics improve comfort in all shoes and prefer to continue wearing them indefinitely. The investment of $30–40 every 6 months for replacement insoles is minimal compared to the benefit of protecting your surgical result.

When can my child return to sports after the Kidner procedure?

Most adolescents return to low-impact activities (swimming, cycling) by 6–8 weeks, running by 10–12 weeks, and full sports participation (including cutting, jumping, and contact sports) by 3–4 months. Return to sport is guided by physical therapy milestones including pain-free walking, adequate single-leg balance, and comfortable running. Wearing PowerStep sport insoles in athletic shoes is required during the return-to-sport phase and recommended long-term.

What is the difference between simple excision and the Kidner procedure?

Simple excision removes only the accessory navicular bone without reattaching the posterior tibial tendon. The Kidner procedure removes the accessory bone AND reattaches the posterior tibial tendon to the navicular in a mechanically improved position using suture anchors. The tendon advancement component is the key advantage — it improves arch support and reduces the risk of progressive flatfoot. For Type II accessory naviculars (the most common symptomatic type), the Kidner procedure with tendon advancement produces superior long-term outcomes compared to simple excision alone.

Sources

1. Kidner FC. “The prehallux (accessory scaphoid) in its relation to flatfoot.” J Bone Joint Surg Am. 1929;11(4):831-837.
2. Chung JW, Chu IT. “Outcome of fusion of a painful accessory navicular to the primary navicular.” Foot Ankle Int. 2009;30(2):106-109.
3. Prichasuk S, Sinphurmsukskul O. “Kidner procedure modified with suture anchor fixation for symptomatic accessory navicular in children.” J Pediatr Orthop B. 2015;24(2):167-170.
4. Malicky ES, Levine DS, Sangeorzan BJ. “Modification of the Kidner procedure with fusion of the primary and accessory navicular bones.” Foot Ankle Int. 1999;20(1):53-54.
5. Jasiewicz B, Potaczek T, Kacki W, et al. “Results of the Kidner procedure in the treatment of painful accessory navicular.” Ortop Traumatol Rehabil. 2008;10(1):42-48.

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