Sinus Tarsi Syndrome
The sinus tarsi is a canal formed at the articulation of the two bones of the rearfoot (talus and calcaneus) where a ligament which holds the two bones together runs. It is seen on the picture as a tunnel on the outside part of the rearfoot just below the ankle joint.
Pain will present over the area shown and can be caused by compression of the canal due to specific foot posture or injury to the structures which run through it.