The proximity of these structures and that they lie under a thick horn makes direct examination difficult, but diagnosis is still possible. The navicular region is a complicated mix of joints, bones, ligaments, tendons, and synovial bursas. All of these structures can succumb to the known causes of lameness referable to this area. This list however can usually be accurately diagnosed with a good exam and radiography. Occasionally you get to the bottom of your exam and radiographs and all you can find is two lame front feet that refers to the navicular region.
Ischemia means low oxygen levels in the tissues.
The bone is constantly remodeling to adjust to changing work loads. This remodeling requires many nutrients, including oxygen. If the bone cannot get enough oxygen, ischemia results. One of the results of ischemic tissues is increased sensitivity to painful stimuli. The navicular bone hurts because it cannot get enough oxygen.