What Is an Accessory Navicular Bone and When Does It Cause Problems
- Dr. Chandana Halaharvi
- 2 hours ago
- 5 min read
Common Causes of Accessory navicular bone
An accessory navicular bone is an extra bone or piece of cartilage located on the inner side of the foot, just above the arch, adjacent to the navicular bone. This anatomical variant is present in approximately 10 to 14 percent of the population, making it one of the most common congenital skeletal anomalies in the foot. In most cases, the accessory navicular causes no symptoms whatsoever and is discovered incidentally on X-rays taken for other reasons. However, in a subset of individuals, this extra bone can become a source of significant pain and functional limitation that requires medical attention.
The accessory navicular is classified into three types based on its size, shape, and relationship to the main navicular bone. A Type 1 accessory navicular is a small, round sesamoid bone embedded within the posterior tibial tendon, usually measuring only two to three millimeters. Type 2 is a larger, triangular or heart-shaped bone connected to the navicular by a cartilaginous or fibrous bridge called a synchondrosis. Type 3, also known as a cornuate navicular, represents a fully fused accessory bone that creates an enlarged, prominent navicular. Type 2 is the most clinically significant variant because the fibrous connection between the two bones is inherently unstable and susceptible to mechanical stress.
The posterior tibial tendon plays a central role in understanding why an accessory navicular can become problematic. This important tendon runs from the calf, behind the inner ankle bone, and attaches to the navicular bone and surrounding structures. It is the primary dynamic stabilizer of the medial arch and is essential for maintaining normal foot alignment during walking and running. When an accessory navicular is present, the posterior tibial tendon often inserts partially or entirely into the extra bone rather than the navicular itself. This altered attachment can compromise the mechanical efficiency of the tendon and reduce its ability to support the arch.
Symptoms from an accessory navicular typically begin during adolescence, when the foot is growing rapidly and activity levels are high, though they can first appear at any age. The most common symptom is pain and tenderness over the bony prominence on the inner side of the foot, just above the arch. The area may become red, swollen, and warm to the touch, particularly after prolonged activity or when shoes press against the prominence. In some cases, the pain is aggravated by specific movements such as running, jumping, or walking on uneven terrain that place increased demands on the posterior tibial tendon.
Several factors can trigger the onset of symptoms in a previously asymptomatic accessory navicular. Trauma, such as an ankle sprain or a direct blow to the inner foot, can disrupt the fibrous connection between the accessory bone and the navicular, causing inflammation and pain. Repetitive stress from athletic activities, particularly those involving running and jumping, can produce similar irritation over time. New shoes or changes in footwear that place increased pressure on the medial foot prominence can trigger symptoms. Flatfoot deformity, which places greater strain on the posterior tibial tendon, is a common associated finding that can contribute to symptom development.
Signs and Symptoms to Watch For
Diagnosis of a symptomatic accessory navicular begins with a careful history and physical examination. The podiatrist will ask about the onset, location, and character of the pain and will examine the foot for the characteristic bony prominence on the medial side. Tenderness directly over the prominence and along the posterior tibial tendon supports the diagnosis. The function of the posterior tibial tendon is assessed through strength testing and gait observation. X-rays readily confirm the presence and type of accessory navicular and help rule out other conditions such as stress fractures or arthritis of the navicular.
Conservative treatment is the first-line approach for symptomatic accessory navicular and is effective for the majority of patients. Immobilization with a walking boot or cast for four to six weeks allows the inflamed tissues to heal and can be particularly effective after an acute flare-up. Ice therapy and anti-inflammatory medications help manage pain and swelling during the acute phase. Padding placed over the prominence or within the shoe can reduce direct pressure and friction on the irritated area. Activity modification, including temporary avoidance of sports and high-impact activities, gives the posterior tibial tendon and surrounding structures time to recover.
Patients throughout the Houston area trust Dr. Chandana Halaharvi at Thrive Foot and Ankle for compassionate, expert accessory navicular bone care. Our Sugar Land office is conveniently located to serve Pearland, Fort Bend County, and surrounding communities.
Custom orthotic devices are a cornerstone of long-term conservative management for accessory navicular syndrome. Orthotics that support the medial arch reduce the workload on the posterior tibial tendon, decreasing the stress transmitted to the accessory bone. The orthotic can be designed with a relief area over the navicular prominence to prevent direct pressure. For patients with associated flatfoot deformity, the orthotic addresses both the symptoms and the underlying biomechanical imbalance. Wearing the orthotics consistently in supportive shoes helps prevent recurrence of symptoms after the acute phase has resolved.
Physical therapy targeting the posterior tibial tendon and surrounding muscles provides additional benefit. Strengthening exercises for the posterior tibial tendon, intrinsic foot muscles, and ankle stabilizers help improve arch support and reduce the mechanical demands on the accessory navicular. Stretching the calf muscles improves ankle dorsiflexion, which reduces compensatory pronation and the associated strain on the medial foot structures. Balance and proprioception exercises enhance the neuromuscular control of the foot and ankle, contributing to overall stability and reduced symptom recurrence.
When conservative treatment does not provide adequate or lasting relief, surgical intervention may be recommended. The most commonly performed procedure is excision of the accessory navicular, which involves removing the extra bone and reattaching the posterior tibial tendon securely to the remaining navicular bone. This procedure, known as the Kidner procedure, has a long track record of successful outcomes. In some cases, particularly when associated with significant flatfoot deformity, additional procedures to reconstruct the arch may be performed simultaneously to address the underlying structural issues.
Treatment Options at Thrive Foot and Ankle
Recovery from accessory navicular surgery requires patience and adherence to a structured rehabilitation program. Patients are typically placed in a non-weight-bearing cast or boot for four to six weeks following surgery to allow the tendon to heal securely to the bone. Weight bearing is gradually introduced over the following weeks, with a transition from a walking boot to supportive athletic shoes. Physical therapy begins during the recovery period and continues for several months, focusing on restoring strength, flexibility, and normal walking mechanics. Most patients can return to full athletic activity within three to four months, though some may require up to six months.
In adolescents and young athletes, the decision to pursue surgery is carefully weighed against the potential for symptoms to resolve with skeletal maturity and conservative management. Many young patients respond well to a combination of immobilization, orthotics, and activity modification, and surgery is reserved for those with persistent symptoms despite adequate conservative treatment. When surgery is necessary in younger patients, the outcomes are generally excellent, with high rates of return to full athletic participation. Close follow-up during the recovery period ensures that healing is progressing as expected.
If you notice a painful bony prominence on the inner side of your foot, particularly if it is associated with arch pain, swelling, or difficulty with activities, evaluation by a podiatrist can determine whether an accessory navicular is the source of your symptoms. Early diagnosis and appropriate treatment, whether conservative or surgical, can relieve pain, improve function, and allow you to return to the activities you enjoy. Understanding that this common anatomical variant can occasionally become symptomatic empowers you to seek help rather than simply tolerating the discomfort.
At Thrive Foot and Ankle, we diagnose and treat accessory navicular syndrome with both conservative and surgical approaches. Book an appointment online to get a thorough evaluation and personalized treatment plan.
Comments