Keys To Patient Education And Accurate Diagnosis Of Sinus Tarsi Syndrome

A patient has been having pain on the outside of his ankle for some time and you tell him he might have sinus tarsi syndrome. The patient’s puzzled look does not surprise you and you proceed to explain what might be the cause of his pain.

What is the sinus tarsi? Explain to patients that the sinus tarsi is an anatomical depression on the outside aspect of the foot that is filled with soft tissue structures: ligaments, muscle, nerves, blood vessels and fat.1,2

What causes the pain? While there are a variety of possible etiologies, acute injury to the ankle or chronic ankle sprains seem to be the most common culprits.1 Pain is related to possible ligamentous injury and instability at the subtalar joint.1,2 Inflammation ensues and the sinus tarsi region may fill with synovial fluid and fibrotic tissue.1,2

Other possible causes of sinus tarsi pain may include: cysts, degenerative changes and injury to the extensor digitorum brevis muscle.

What are the clinical symptoms? These symptoms may include pain along the anterolateral ankle, a feeling of instability in the foot or ankle, swelling and ecchymosis. There must be tenderness within the sinus tarsi for diagnosis.

What about diagnostic studies? X-rays are not the best imaging technique for diagnosis. Magnetic resonance imaging (MRI) is the better choice due to its ability to assess soft tissue structures. Positive MRI findings include abnormal fluid collection within the sinus tarsi (increased signal intensity), synovitis within the subtalar joint (increased signal intensity) and possible disruption of ligamentous structures.1

Differential diagnoses include osteochondral defect, ligamentous injury, arthritis and tarsal coalition.

Conservative treatments for sinus tarsi syndrome include:
• steroid injection within the sinus tarsi;
• physical therapy with a focus on balance and proprioceptive training along with muscle strengthening;
• bracing/taping; and/or
• orthoses.

Conservative care is the mainstay of treatment. Alternately, one may perform exploratory surgery to inspect the subtalar joint and remove any osteophytes that may be in the area.

References
1. Coughlin MJ, Mann RA. Surgery of the Foot and Ankle, eighth edition. Elsevier, New York, 2013.
2. Helgeson K. Examination and intervention for sinus tarsi syndrome. N Am J Sports Phys Ther. 2009; 4(1):29-37.



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