Correctly diagnosing sinus tarsi syndrome is important because it is frequently misdiagnosed as chronic ankle sprain and, if improperly treated, will result in chronic pain and disability. A detailed history and physical examination will usually confirm the diagnosis. Clues include pain and instability when walking on uneven surfaces, and resolution of pain when the affected foot is at rest. Conservative treatment of sinus tarsi syndrome is usually considered first and consists of consecutive corticosteroid injections into the tarsal canal, along with physical therapy and correction of foot biomechanics. Sinus tarsectomy is reserved for patients who do not respond to conservative treatment.