The proximity of the anterior talofibular ligament to the sinus tarsi requires very specific palpation to identify the source of pain. Pain can also be reproduced by testing foot motion in extreme supination and adduction. Pain and instability can be reproduced by having the patient walk down steps or on an uneven surface. It is very important to evaluate for ankle instability, because demonstrated ankle instability will rule out sinus tarsi syndrome. Ankle instability is diagnosed by excessive talar motion on inversion or on anterior drawer stress tests when compared with the opposite side.
Unilateral instability is always pathologic.
Because sinus tarsi syndrome involves subtalar ligament sprains and a subjective sense of instability, one might expect to discern increased subtalar motion with a physical exam. This is not the case. Examination of foot biomechanics will often reveal a hindfoot varus deformity that contributes to chronic inversion stress on the subtalar joint. Patients with sinus tarsi syndrome typically have normal radiographs. Subtalar ligaments can also be evaluated for injury, but they are sometimes not visualized because of inflammatory infiltration or simply because they have been disrupted.