Sinus Tarsi Syndrome

The sinus tarsi is a small cylindrical cavity on the hindfoot’s outside. The subtalar joint is located between the talus and the calcaneus (heel bone).
Sinus Tarsi Syndrome is most commonly caused by an ankle sprain or repetitive strain from running or walking on a flat foot.
Inflammation causes persistent pain and tenderness on the outside of the ankle, which is also known as Sinus Tarsitis.


Sinus tarsi syndrome is a rare condition that is typically caused by ankle subtalar joint instability. The following are the two most common causes of subtalar instability:

  • Abnormal Foot Biomechanics: People who have over-pronated or flat feet are more likely to develop sinus tarsitis. The changed foot position puts more pressure on the sinus tarsi region.
  • Ankle Sprains: Subtalar joint instability is a common problem after an ankle sprain.
  • Other activities that can result in sinus tarsi syndrome due to repetitive actions include:
    • Ballet: because of foot positions.
    • Sit with your feet tucked beneath you.
    • Baseball/Softball Pitchers: because of the trailing foot’s position.