What Is Sinus Tarsi Syndrome?

Sinus tarsi syndrome (STS) is a condition that causes ongoing pain on the outside of the foot, between the ankle and the heel. It is usually due to instability of the joint connecting the foot to the heel (subtalar). It can be caused by repetitive motions or traumatic injuries, especially chronic (persistent) ankle sprains.

The condition is considered a syndrome; a syndrome is defined as a group of associated symptoms that occur together.

History

The condition was first diagnosed in 1957 by Denis O’Connor, who also suggested a surgical procedure called the O’Connor procedure as the primary treatment for STS. The surgical procedure to correct STS involved removal of part or all the contents of the sinus tarsi—including the soft tissue structures.

Symptoms

The most common symptom is tenderness of the sinus tarsi area of the foot. When this symptom can be produced by direct pressure on the area, it confirms the diagnosis and rules out other conditions.

Common symptoms of sinus tarsi syndrome include:

• Chronic pain along the anterolateral (front and side) part of the ankle
• Pain with foot inversion (turned in) or eversion (turned out)
• A feeling of instability of the foot or ankle when bearing weight
• Difficulty walking on uneven surfaces, such as grass or gravel
• Swelling
  
• Ecchymosis (bruising)

Possible Causes

Sprains of the lateral ankle, anterior talofibular ligament, or chronic ankle sprains can lead to instability and weaken the other ligaments. This will affect more of the lateral ligaments and tendons, including the sinus tarsi.  

Other causes of sinus tarsi syndrome may include:

• Cysts
• Degenerative changes
• Injury to the extensor digitorum brevis muscle, which is located on the top of the foot
• A severely pronated foot

Foot pronation is a natural movement that occurs when the foot lands during running or walking. Overpronation of the foot can cause pressure on the sinus tarsi. This can result in sinus tarsi syndrome. The treatment for overpronation involves orthotics (special shoes) that can help control the motion of the foot.

Custom foot orthotics with modifications to the insoles or boots that lock the ankle and reduce ankle motion can help reduce ankle inversion and eversion.

Diagnosis

Diagnosis of Sinus Tarsi Syndrome may involve:

• X-rays
• A CT Scan
• An MRI can visualize changes in the soft tissue of the sinus tarsi such as scar tissue from previous injuries
• An ankle arthroscopy, which is a minimally invasive test that involves a narrow tube attached to a fiber-optic video camera, inserted through a very small incision [the size of a buttonhole] to view and diagnose joint problems
• Ruling out other problems of the foot

Injection with a local anesthetic, anti-inflammatory, or corticosteroid medication to reduce the swelling in the area can be helpful for both diagnostic and therapeutic purposes.

Treatment

Conservative treatment of sinus tarsi syndrome is considered “generally very effective,” according to the American Academy of Podiatric Sports Medicine (AAPSM). 

Conservative treatment modalities may include:

• Anti-inflammatory medications
• Steroid injections
• Physical therapy
• Orthopedic shoes or high ankle boots to stabilize the area
• Custom foot orthotics with deep heel cups can correct heel position
• Bracing or taping (to stabilize the area)
  
• Walking boot or ankle supporting brace
• Immobilization of the foot and ankle

Over the counter or custom devices can correct disorders of the limbs with the use of braces and other devices to provide support

Surgical Treatment

On rare occasions, surgery may be required when conservative treatment measures fail. The surgical procedure may involve open surgery (via a surgical incision) or closed surgery (conducted using arthroscopy). 

A Word From Verywell

Sinus tarsi syndrome (STS) is a condition that is common in those who have had an ankle sprain. It’s vital that a correct diagnosis is made for STS because the treatment is significantly different than that of other types of foot injuries. Although conservative treatment is often successful, surgical intervention is required in some instances of STS. Surgery is considered as the last resort for the treatment of sinus tarsi syndrome after all non-invasive conservative treatment modalities have been adequately pursued.