What Is Sinus Tarsi Syndrome?

Sinus tarsi syndrome is painful swelling on the outside of the joint below the ankle known as the subtalar joint. This joint allows the foot to move from side to side. 


A common cause of sinus tarsi is flatfoot deformity. With flatfoot deformity, the arch of the foot drops and the two bones on the outside portion of the subtalar joint pinch against each other. This can put increased pressure on the soft tissue in that area, leading to inflammation of the joint lining or the tissue outside the joint.

Sinus tarsi syndrome also can occur due to arthritis in the subtalar joint, scar tissue, joint instability, or as a result of injury. 


Sinus tarsi syndrome commonly leads to pain over the outside of the back of the foot. Swelling over the hollow between the ankle bone and the heel bone can develop. The swelling can enlarge so that it can be mistaken for a cyst or tumor.  


This syndrome is usually diagnosed by an exam by a foot and ankle orthopaedic surgeon. Your surgeon will see swelling over the outside of the joint below the ankle and tenderness over a specific area of the foot. X-rays can be helpful in diagnosis. On X-rays, your doctor may see collapse of the arch or arthritis.  


There are non-surgical and surgical treatment options available. In most cases, your doctor will attempt non-surgical treatments first. Anti-inflammatory medications may decrease the swelling in the sinus tarsi. A steroid injection may be tried if other medicines do not relieve the pain. An arch support can be used to relieve the pinching of the subtalar joint. A brace can be applied to the ankle and back of the foot to support and rest the subtalar joint.

Surgical treatments vary depending on the cause of the sinus tarsi pain. Options include removal of inflammation and scarring of the sinus tarsi. This can be done in an open or arthroscopic technique.  

If a flatfoot is the cause of the sinus tarsi pain, your surgeon may recommend correction of the flatfoot. If the subtalar joint has advanced arthritis, your doctor may recommend a subtalar fusion (arthrodesis).


If surgery is performed, the recovery involves limited weightbearing until the stitches are removed and a fracture boot is placed on the foot. Weightbearing may be allowed at that time depending on the surgery performed. Usually, physical therapy is ordered to help regain range of motion and strength. A boot may be used for several weeks to aid walking.

Risks and Complications

All surgeries come with possible complications, including the risks associated with anesthesia, infection, damage to nerves and blood vessels, and bleeding or blood clots.


Are there things that make people more likely to develop sinus tarsi syndrome?

People with flat feet and those who participate in activities that require cutting maneuvers can be more prone to this syndrome. Also, repetitive activities on uneven surfaces can make someone more likely to develop symptoms.

How often is surgery necessary to treat sinus tarsi syndrome?

Surgery usually is not necessary in most patients who develop sinus tarsi syndrome. Non-surgical treatment can be very successful in relieving pain and swelling. Prior to considering surgery, it is important to see a foot and ankle orthopaedic surgeon to identify the cause of the sinus tarsi syndrome and the best treatment for that problem.


Original article by Brian Clowers, MD
Last reviewed by Robert Leland, MD, 2020

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