A rare bone disease with characteristics of spontaneous adult-onset tarsal navicular osteonecrosis. Patients present with chronic mid and hindfoot pain, swelling and tenderness over the dorsomedial aspect of the midfoot, flattening of the medial longitudinal arch, and pes planovarus. Radiographic findings include comma-shaped deformity due to collapse of the lateral part of the navicular bone and medial or dorsal protrusion of a portion or the entire bone. The condition may be bilateral or asymmetric and associated with pathological fractures. [from
SNOMEDCT_US]