The navicular (boat-shaped) bone forms the keystone of the medial longitudinal arch, articulating with the talar head posteriorly, all three cuneiform bones anteriorly, and the cuboid laterally. The tibialis posterior inserts primarily on the navicular tuberosity (medial prominence). The navicular receives blood supply from the dorsal and plantar arterial networks — its central zone is a vascular watershed area susceptible to avascular necrosis and stress fracture.
Navicular stress fractures are high-risk overuse injuries in running athletes, frequently delayed in diagnosis. They occur in the central avascular zone (the 'forbidden zone') and present as dorsal midfoot pain with activity. CT identifies the stress fracture in the central navicular that plain radiograph misses. Type I-II fractures (incomplete, no displacement) require 6 weeks non-weight-bearing in a boot; Type III (complete, displaced) require ORIF with internal screw fixation. Kohler disease (avascular necrosis in children 3-7 years) is self-limiting; adult navicular AVN is rare but causes midfoot collapse requiring reconstruction.
Running athletes develop dorsal midfoot pain from navicular stress fracture in the avascular central third of the bone; CT is required to characterise the fracture pattern as plain radiograph sensitivity is less than 40%; non-displaced fractures require 6 weeks non-weight-bearing and CT-confirmed healing before return to running.
