Representative images of the distal end of the third metacarpal bone illustrating articular saucer stress fracture formation in a racing Thoroughbred horse with severe palmar osteochondral disease.

<p>(<b>A</b>) In reconstructed computed tomography images, a circular articular saucer fracture is present in both condyles. A halo of reduced bone density adjacent to the saucer fracture is caused by the reparative remodeling response in the subchondral plate. Extensive adaptive subchondral sclerosis is also evident. (<b>B</b>) Hyaline cartilage overlying the stress fracture has been replaced by fibrocartilage. (<b>C</b>) Extensive fatigue damage to the underlying subchondral plate is also evident, including parasagittal cracks in the condylar grooves (arrows). (<b>D</b>) Propagation of the fracture line at the interface of the vascular remodeling response to the fatigue injury in the subchondral plate is evident (arrows) on a microradiograph of an oblique frontal bone section.