The Treatment of an Accessory Navicular in the Foot

An accessory navicular, also known as *os tibiale externum* or *os naviculare*, is a common congenital foot variant present in approximately 10-14% of the population. It consists of an extra bone or piece of cartilage located on the medial aspect of the foot, adjacent to the navicular bone within or near the insertion of the posterior tibial tendon (PTT). While often asymptomatic, it can lead to accessory navicular syndrome when irritated, causing pain, swelling, and functional limitations, particularly in adolescents and active individuals.

The condition is classified into three types based on morphology. Type I is a small sesamoid bone embedded in the PTT. Type II, the most common symptomatic variant, is connected to the navicular by a synchondrosis (fibrocartilaginous union). Type III represents a fully fused, enlarged navicular tuberosity (cornuate navicular). Symptoms typically arise from repetitive stress, trauma, or overuse, leading to inflammation at the synchondrosis, PTT strain, or adventitial bursa formation. Patients often report medial arch pain, a visible bony prominence, swelling, redness, and discomfort worsened by activity, shoe pressure, or flatfoot deformity.

Diagnosis begins with clinical history and physical examination, revealing tenderness over the medial navicular prominence. Weight-bearing radiographs (especially external oblique views) confirm the presence and type of accessory navicular. MRI may be useful to assess synchondrosis stress reaction, PTT pathology, or soft tissue inflammation. Differential diagnoses include midfoot sprains, PTT dysfunction, stress fractures, or other accessory ossicles.

• Conservative Management: The First-Line Approach

Treatment of symptomatic accessory navicular prioritizes nonoperative measures, as many patients, especially children and adolescents, improve with skeletal maturity or activity modification. Conservative therapy aims to reduce inflammation, offload the area, and strengthen supporting structures. Success rates are high for initial episodes, though recurrence is possible with ongoing stress.

Initial management follows the RICE protocol: **Rest** from aggravating activities, **Ice** application (wrapped, 15-20 minutes several times daily), **Compression** with a bandage or sleeve, and **Elevation**. Over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen help control pain and swelling. Shoe modifications are critical—patients should avoid narrow or high-heeled shoes that compress the prominence and opt for wider, supportive footwear.

• Orthotics** and arch supports can be beneficial but require caution. Standard arch supports may exacerbate pressure on the prominence; instead, medial heel wedges, custom orthoses designed to offload the navicular, or UCBL (University of California Biomechanics Laboratory) orthoses that invert the heel are preferred. Physical therapy plays a key role, focusing on calf and Achilles stretching, intrinsic foot muscle strengthening, PTT strengthening, proprioception, and ankle stabilization exercises. This helps address associated flatfoot or biomechanical issues.

For more acute or refractory cases, short-term immobilization in a walking boot or short-leg cast for 4-6 weeks can provide significant relief by preventing repetitive microtrauma. Corticosteroid injections into the area or bursa are occasionally used but are approached cautiously due to risks to the tendon. Emerging options like extracorporeal shockwave therapy (ESWT) have shown promise in case reports for persistent inflammation when other measures fail, offering a non-invasive bridge before surgery.

A 2019 retrospective study on pediatric patients highlighted the effectiveness of structured nonoperative protocols, with many achieving symptom resolution without surgery. Compliance with activity modification and orthotics is essential for success. Patients are typically advised to gradually return to activities once pain subsides, with ongoing use of supportive measures for prevention.

• Surgical Intervention: When Conservative Measures Fail

Surgery is reserved for patients with persistent, activity-limiting symptoms after 3-6 months of compliant conservative treatment, or in cases with significant deformity, tendon dysfunction, or associated flatfoot. Surgical goals include removing the painful prominence, addressing any synchondrosis instability, and restoring PTT function if needed. Outcomes are generally excellent, with high patient satisfaction and return to activity.

The most common procedure is the **Kidner procedure**, first described in 1929. It involves a medial incision, detachment of the PTT from the accessory navicular, excision of the extra bone (and any prominent navicular tuberosity), and reattachment or advancement of the tendon to the main navicular body, often using suture anchors for secure fixation. This addresses both the bony irritation and potential tendon dysfunction. Modified versions may incorporate additional soft tissue reconstruction.

• Simple excision** without tendon detachment has gained support in recent literature as a less invasive option with comparable outcomes and lower complication rates in select cases, particularly Type II. The accessory bone is resected through the synchondrosis, and the navicular is contoured smoothly. Studies suggest this suffices for many patients without compromising PTT function.

Other techniques include percutaneous drilling (to promote fusion across the synchondrosis), subtalar arthroereisis (for associated flatfoot), or, rarely, arthrodesis. A 2025 systematic review of over 600 patients found the Kidner procedure (or modifications) to be the most performed (about 52%), with good clinical outcomes across techniques. Complication rates were moderate (around 11% for Kidner), including infection, nerve injury, or persistent pain; higher nonunion rates were noted with drilling or arthrodesis. Age did not significantly affect outcomes.

Postoperative care typically involves 4-6 weeks of non-weight-bearing or protected weight-bearing in a cast or boot, followed by physical therapy for strengthening and gait training. Full recovery and return to sports often take 3-6 months. Risks include recurrence (rare), wound complications, or PTT weakness, though most patients achieve pain relief and improved function.

• Considerations and Prognosis

Treatment decisions are individualized, considering age, activity level, foot biomechanics, and symptom duration. In skeletally immature patients, conservative management is emphasized longer due to potential spontaneous improvement. Associated conditions like flexible flatfoot may require concurrent correction (e.g., medial soft tissue procedures). Athletes and dancers may need tailored rehabilitation for return-to-play.

Overall prognosis is favorable. Most patients respond well to conservative care, and surgical intervention provides reliable relief for refractory cases. Long-term studies show sustained benefits with low failure rates when appropriately selected. Prevention involves proper footwear, gradual training progression, and addressing biomechanical predispositions.

In conclusion, the accessory navicular represents a frequent but manageable cause of medial foot pain. A stepwise approach—starting with rest, modalities, orthotics, and therapy, escalating to surgery only when necessary—optimizes outcomes while minimizing risks. Advances in understanding subtypes and refined techniques continue to improve patient care. Early intervention by a foot and ankle specialist ensures accurate diagnosis and personalized treatment, allowing individuals to maintain active lifestyles with minimal long-term sequelae.