Medial Foot Pain and Accessory Navicular / Os Tibiale Externum: Causes, Treatments, and Post-Operative Outcomes

Os tibiale externum, also known as the accessory navicular bone, is an extra bone or piece of cartilage located on the inner side of the foot, near the navicular bone. Many people have this extra bone their entire lives without any symptoms. However, trauma or repetitive stress can cause pain and swelling in this area. This blog post explores what os tibiale externum is, its types, symptoms, and the conservative and surgical treatments available, including the Kidner procedure. We will also discuss the post-operative course and what patients can expect after surgery.

Accessory navicular bone on the inner foot

What Is Os Tibiale Externum?

Os tibiale externum is an accessory bone that forms within the tibialis posterior tendon, which runs along the inside of the foot and helps support the arch. This extra bone is present in about 10% of the population and usually does not cause any problems. It is often discovered incidentally on X-rays taken for other reasons.

The accessory navicular can become painful when injured or irritated. This happens because the extra bone and its surrounding cartilage can become inflamed or swollen, especially after trauma or overuse. The pain is typically felt on the inner side of the foot, near the arch, and may worsen with activity or wearing tight shoes.

Types of Os Tibiale Externum

There are three main types of os tibiale externum, classified based on their size, shape, and connection to the navicular bone:

• Type 1: A small, round bone that is completely separate from the navicular. It is usually asymptomatic and rarely causes pain.

• Type 2: A larger, triangular or heart-shaped bone connected to the navicular by cartilage or fibrocartilage. This type is the most common cause of symptoms because the cartilage connection can rupture or become inflamed.

• Type 3: Also called the cornuate navicular or "gorilla form navicular," this type is a fused accessory bone that forms a prominent bony bump on the navicular. It can cause irritation due to its size and shape.

Why Does Os Tibiale Externum Cause Pain?

Pain usually arises when the cartilage connection in type 2 os tibiale externum does not fully fuse during growth. This incomplete fusion leaves two bones connected by cartilage, which can rupture or become inflamed over time. Trauma, repetitive stress, or tight footwear can irritate the area, leading to swelling, tenderness, and discomfort.

People with this condition often notice swelling and pain on the inner side of the foot, especially after physical activity or injury. The tibialis posterior tendon, which passes over the accessory bone, can also become strained, contributing to symptoms.

Conservative Treatments for Os Tibiale Externum

Most cases of symptomatic os tibiale externum respond well to non-surgical treatments. These include:

• Rest and activity modification: Avoiding activities that worsen pain helps reduce inflammation.

• Ice therapy: Applying ice to the swollen area can relieve pain and swelling.

• Anti-inflammatory medications: Over-the-counter NSAIDs like ibuprofen can reduce inflammation and discomfort.

• Orthotic devices: Custom shoe inserts or arch supports help reduce stress on the tibialis posterior tendon and the accessory bone.

• Physical therapy: Exercises to strengthen the foot and improve flexibility can support healing.

• Immobilization: In some cases, a walking boot or cast may be used temporarily to rest the foot.

  
  

These conservative measures often provide relief, especially if started early. However, if pain persists despite these treatments, surgery may be considered.

Surgical Treatment: The Kidner Procedure

When conservative treatments fail, the Kidner procedure is a common surgical option to relieve pain caused by os tibiale externum. This procedure involves removing the accessory navicular bone and repairing the tibialis posterior tendon.

What the Kidner Procedure Does

• Removes the painful accessory bone.

• Repairs and reattaches the tibialis posterior tendon to the navicular bone.

• Reduces irritation and inflammation in the area.

  
  

It is important to understand that the Kidner procedure does not correct flatfoot deformity if present. Its main goal is to eliminate pain caused by the accessory bone.

Post-Operative Course

After surgery, patients typically follow this recovery plan:

• Non-weight bearing for 4 weeks: Patients use crutches or a wheelchair to avoid putting weight on the foot.

• Gradual weight bearing: After 4 weeks, patients slowly begin to put weight on the foot using a walking boot.

• Physical therapy: Rehabilitation focuses on restoring strength, flexibility, and normal gait.

• Return to normal activities: Most patients resume regular activities within 3 to 4 months.

  
  

Overall, people do very well with the Kidner procedure. Most experience significant pain relief and improved foot function.

Summary of Key Points

• Os tibiale externum is an extra bone in the foot, often asymptomatic but can cause pain after trauma.

• There are three types of accessory navicular bones, with type 2 being the most symptomatic due to incomplete fusion.

• Pain arises from inflammation or rupture of the cartilage connecting the accessory bone to the navicular.

• Conservative treatments include rest, ice, anti-inflammatory medications, orthotics, and physical therapy.

• The Kidner procedure surgically removes the accessory bone and repairs the tendon but does not fix flatfoot.

• Post-operative care involves 4 weeks of non-weight bearing followed by gradual rehabilitation.

• Most patients recover well and experience lasting pain relief.

If you have been experiencing medial or "inner" foot pain, call us at 832-743-0508 to schedule an appointment. Or visit us at www.SelectFAS.com to schedule online.