Overview
The accessory navicular (os navicularum or os tibiale externum) is an extra bone or piece of cartilage located on the inner side of the foot just above the arch. It is incorporated within the posterior tibial tendon, which attaches in this area. An accessory navicular is congenital (present at birth). It is not part of normal bone structure and therefore is not present in most people. People who have an accessory navicular often are unaware of the condition if it causes no problems. However, some people with this extra bone develop a painful condition known as accessory navicular syndrome when the bone and/or posterior tibial tendon are aggravated. This can result from any of the following. Trauma, as in a foot or ankle sprain. Chronic irritation from shoes or other footwear rubbing against the extra bone. Excessive activity or overuse. Many people with accessory navicular syndrome also have flat feet (fallen arches). Having a flat foot puts more strain on the posterior tibial tendon, which can produce inflammation or irritation of the accessory navicular.
Causes
Accessory navicular syndrome as it is called can result from a number of causes, excess or overuse syndrome as seen in an athlete. Trauma to the foot as in an ankle sprain or direct trauma to the navicular bone. chronic irritation from shoes rubbing against the extra bone, over time, may cause pain. Excessive pronation which strains the attachment of tibialis posterior muscles into the navicular bone. Keep in mind, the larger the actual accessory bone, the greater the chance of it becoming an issue.
Symptoms
One obvious problem with the accessory navicular is that it may be large and stick out from the inside of the foot. This can cause it to rub against shoes and so become quite painful. The fibrous connection between the accessory navicular and the navicualar, as well, is easy to injure, also leading to pain. This is kind of like a fracture, and such injuries cause the bone to move around too easily, leading to pain with activity. When the connection between the bones is injured in this way, the two bones do not always heal properly, so pain may continue unabated.
Diagnosis
Diagnosis is fairly simple based on an examination by your doctor. He or she will palpate the navicular bone, and based on the location of pain will suspect an accessory navicular. The doctor will also observe your gait to see if you are flatfooted. At this point an x-ray will make the definitive diagnosis. Other causes of pain in the same area of the foot would include a fracture of the navicular bone or possibly tendonitis or even a partial tear of the tibialis posterior tendon that inserts into the navicular. In these cases there is usually a history of trauma. People with a naturally "large" navicular bone may also develop a bursitis due to chronic shoe pressure.
Non Surgical Treatment
The treatment for a symptomatic accessory navicular can be divided into nonsurgical treatment and surgical treatment. In the vast majority of cases, treatment usually begins with nonsurgical measures such as orthotics, strappings or bracing. Surgery usually is only considered when all nonsurgical measures have failed to control your problem and the pain becomes intolerable.
Surgical Treatment
If conservative measures do not seem to help, however, you may need to have surgery to make adjustments to the bump. This could include reshaping the little bone, repairing damage to the posterior tibial tendon, or even removing the accessory navicular altogether.
The accessory navicular (os navicularum or os tibiale externum) is an extra bone or piece of cartilage located on the inner side of the foot just above the arch. It is incorporated within the posterior tibial tendon, which attaches in this area. An accessory navicular is congenital (present at birth). It is not part of normal bone structure and therefore is not present in most people. People who have an accessory navicular often are unaware of the condition if it causes no problems. However, some people with this extra bone develop a painful condition known as accessory navicular syndrome when the bone and/or posterior tibial tendon are aggravated. This can result from any of the following. Trauma, as in a foot or ankle sprain. Chronic irritation from shoes or other footwear rubbing against the extra bone. Excessive activity or overuse. Many people with accessory navicular syndrome also have flat feet (fallen arches). Having a flat foot puts more strain on the posterior tibial tendon, which can produce inflammation or irritation of the accessory navicular.
Causes
Accessory navicular syndrome as it is called can result from a number of causes, excess or overuse syndrome as seen in an athlete. Trauma to the foot as in an ankle sprain or direct trauma to the navicular bone. chronic irritation from shoes rubbing against the extra bone, over time, may cause pain. Excessive pronation which strains the attachment of tibialis posterior muscles into the navicular bone. Keep in mind, the larger the actual accessory bone, the greater the chance of it becoming an issue.
Symptoms
One obvious problem with the accessory navicular is that it may be large and stick out from the inside of the foot. This can cause it to rub against shoes and so become quite painful. The fibrous connection between the accessory navicular and the navicualar, as well, is easy to injure, also leading to pain. This is kind of like a fracture, and such injuries cause the bone to move around too easily, leading to pain with activity. When the connection between the bones is injured in this way, the two bones do not always heal properly, so pain may continue unabated.
Diagnosis
Diagnosis is fairly simple based on an examination by your doctor. He or she will palpate the navicular bone, and based on the location of pain will suspect an accessory navicular. The doctor will also observe your gait to see if you are flatfooted. At this point an x-ray will make the definitive diagnosis. Other causes of pain in the same area of the foot would include a fracture of the navicular bone or possibly tendonitis or even a partial tear of the tibialis posterior tendon that inserts into the navicular. In these cases there is usually a history of trauma. People with a naturally "large" navicular bone may also develop a bursitis due to chronic shoe pressure.
Non Surgical Treatment
The treatment for a symptomatic accessory navicular can be divided into nonsurgical treatment and surgical treatment. In the vast majority of cases, treatment usually begins with nonsurgical measures such as orthotics, strappings or bracing. Surgery usually is only considered when all nonsurgical measures have failed to control your problem and the pain becomes intolerable.
Surgical Treatment
If conservative measures do not seem to help, however, you may need to have surgery to make adjustments to the bump. This could include reshaping the little bone, repairing damage to the posterior tibial tendon, or even removing the accessory navicular altogether.