sinus tarsi syndrome( RID3222 ) Scarring and edema within the sinus tarsi. In this case there was chronic tendinosis of the tibialis posterior with planovalgus deformity of the hind foot (all predisposing). There was also striking impingement between the lateral process of the talus and adjacent fibular tip with adventitial bursa formation - extraarticular sub fibular impingement.
Nice article from Dr. Rosenberg. [ Article ]