Sinus tarsi syndrome is a relatively frequent cause of lateral ankle pain. Other features include a feeling of instability, and there may be a previous history of trauma. It has a number of underlying aetiologies, and the term does not relate to a specific pathology. MRI is helping to clarify the underlying changes within the sinus that may lead to symptoms, which will address the concerns of some experts that the term is inaccurate and the syndrome poorly understood.