Os Trigonum Syndrome: Causes, Symptoms, Treatment

What Is Os Trigonum Syndrome?

The Os Trigonum is the name given to a small extra bone found behind the ankle. The occurrence of this bone is extremely rare and occurs in not more than 10% of people. In majority of the cases, Os Trigonum is something that the affected individual may not even be aware of as it normally does not cause any symptoms. However, if an individual has Os Trigonum and incurs an injury to the ankle, especially sportsmen who need to use their ankles a lot then there may be development of symptoms.
This development of symptoms as a result of an ankle injury in an individual with Os Trigonum is termed as Os Trigonum Syndrome. The primary presenting feature of Os Trigonum is the presence of pain and stiffness in the ankle, which tends to get worse with any movement. There may also be visible swelling as a result of the injury. An individual may also feel a lump behind the ankle with tenderness.

What Is Os Trigonum Syndrome?

What Causes Os Trigonum Syndrome?

A combination of an extra bone behind the ankle along with an injury incurred to the same ankle results in the development of Os Trigonum Syndrome. Some of the major causes of Os Trigonum Syndrome are overuse of the ankle with the foot pointing downwards, especially seen in individuals who are involved with ballet dancing and football players.

Another cause for Os Trigonum Syndrome is a direct trauma to the ankle which has the extra bone or the Os Trigonum, which results in forceful plantarflexion of the foot. When these injuries occur, the Os Trigonum along with the surrounding soft tissues becomes trapped between the ankle and heel bones. There is also inflammation of the soft tissues causing pain, swelling, and stiffness of the ankle. The irritation of these soft tissues is what that causes Os Trigonum Syndrome.

What Are The Symptoms Of Os Trigonum Syndrome?

The primary presenting feature of Os Trigonum Syndrome

  • Pain generally behind the ankle which tends to get worse with plantar flexion of the foot and with lifting the ankle up while walking and eases off with rest.
  • There is tenderness around the region of the Os Trigonum and the surrounding soft tissue structures.
  • Swelling is also present as a result of inflammation of the soft tissue structures due to Os Trigonum Syndrome.

Sometimes, a lump may also be seen near the Achilles tendon sometimes.

In most of the cases, only one foot is affected but there are some cases where both feet are affected with Os Trigonum Syndrome.

How Is Os Trigonum Syndrome Diagnosed?

The diagnosis of Os Trigonum Syndrome is based on the characteristic features with which the patient presents with. Radiological studies may be recommended in the form of an x-ray or MRI scan to look at the area of pain and tenderness.

Since the symptoms of Os Trigonum Syndrome are quite similar to certain other conditions like Achilles tendonitis, peroneal tendonitis, or even a fracture thus radiological studies have a very important role to play in the diagnosis of Os Trigonum Syndrome.

X-rays and MRI scans will clearly show inflammation around the ankle region around the Os Trigonum and confirm the diagnosis of Os Trigonum Syndrome.

How Is Os Trigonum Syndrome Treated?

The frontline treatment for Os Trigonum Syndrome is to allow the soft tissues to heal and the inflammation to calm down. This is best done by application of ice and resting the affected foot. It is important to avoid activities that may aggravate the condition for a few weeks until the inflammation calms down and the symptoms clear.

Ice can be applied to the affected area for 15 to 20 minutes two to three times a day for a few days until the swelling and inflammation calms down. This can be done by either wrapping some ice cubes in a towel or by use an ice pack.

Additionally, the treating physician will prescribe NSAIDs in the form of ibuprofen or Motrin for pain relief and calming down inflammation. The physician may also recommend complete immobilization of the affected foot with a brace so as not to worsen the condition.

If these treatments do not cause any effective improvement in the symptoms of Os Trigonum Syndrome, then steroid injections will be given for treatment of the condition. Once the inflammation has calmed down and the symptoms of Os Trigonum Syndrome improve, then the patient will be sent to a structured rehab program for stretching and strengthening of the ankle which may have become stiff as a result of prolonged immobilization as a result of Os Trigonum Syndrome.

If there is persistence or recurrence of Os Trigonum Syndrome symptoms, then surgery may recommended to remove the extra piece of bone as a mode of treatment for Os Trigonum Syndrome. The overall prognosis of Os Trigonum Syndrome after this type of treatment is usually excellent with complete resolution of symptoms and return to activities of daily living and sports related activities within six to eight weeks postsurgery for Os Trigonum Syndrome.

Pramod Kerkar, M.D., FFARCSI, DA
Pramod Kerkar, M.D., FFARCSI, DA
Written, Edited or Reviewed By: Pramod Kerkar, M.D., FFARCSI, DA Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:October 20, 2018

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