Within the ankle region of our foot there is a tiny osseous (bone) canal which is located under the talus bone, which is the part of the foot that makes up the ankle joint, wherein synovial fluid collects. When there is an excessive collection of such fluids or the growth of inflamed tissue, there is a tendency for the sinus tarsi to become inflamed and this is medically termed as Sinus tarsi syndrome.
In about 70% of the people suffering from sinus tarsi syndrome, the cause is traced to trauma. Trauma may consist of chronic over pronation which would create a jamming of the sinus tarsi or chronic over supination which would cause an overstretching. In other individuals, it is attributed to inflammatory conditions as ankylosing spondylitis, foot deformities resulting from a condition arising out of gout, ganglion cysts, rheumatoid arthritis and other collagen diseases.
The sinus tarsi is located just below the ankle joint on the lateral (outside) portion of the foot, (yellow arrow) specifically between the neck of the talus and the anterior superior aspect of the calcaneus (heel bone). However, it should be noted that due to the complex anatomy of the tarsal sinus and the inconsistencies observed in the inflammatory tissues and fibrosis conditions, medical professionals find it difficult to exactly diagnose the causes especially due to the fact that MRI imaging of the tarsal sinus is found to be difficult, but it still remains the diagnostic treatment of choice as this test may show inflammation or scarring of the contents of the sinus tarsi. Other tests may include x-rays, bone scan , CT scans and arthrograms. At times an injection of local anesthesia into the sinus tarsi with the anticipated reduction in pain, will allow for a diagnosis. In other instances, completely ruling out pathology in the surrounding tissue will lead to a diagnosis of sinus tarsi syndrome, by process of elimination.
One of the major causes of Sinus tarsi syndrome is an inversion ankle sprain, where the foot twists inward; this is exaggerated over supination. The common age group who exhibit persistent foot pain are those in their late forties, although it can certainly occur in any age group. The older the individual along with a history of repeated ankle sprains, the greater the incidence of pain. Firm pressure along the opening of the sinus tarsi on the outside of the foot will lead to pain.
Upon making a diagnosis of sinus tarsi syndrome, a conservative approach should first be undertaken which in most cases will be very effective. If the condition is from over pronation or excessive supination than either an orthotic to control the pronation or a shoe with a shock absorbing orthotic to reduce the supination would be indicated. Other treatment options may include a period of immobilization, the use of oral anti-inflammatory medication or even the use of an ankle brace to reduce the friction within the sinus tarsi.
In more resistant cases oral steroid therapy or even a cortisone injection may prove to be very helpful. At times a course of physical therapy may prove to be very beneficial. Additionally, a custom orthotic may be necessary versus an off the shelf orthotic, as specific customization may be required.
This is one condition that rarely requires surgical intervention although that option should remain on the table for those individuals where relief is not obtained through conservative means and the pain is severe enough to adversely affect the patient’s ability to ambulate. Surgery may either be done via an open incision or by arthroscopy or minimal incision surgery.