Veterinarians examine navicular disease cases using lameness exams and various imaging methods, but key to understanding this common debilitating disease and pinpointing treatment is knowing what’s going on at the microscopic level. Recently, a team of researchers evaluated microstructural changes in diseased navicular bone as compared to healthy navicular bones.

Stacie Aarsvold, BS, a fourth-year veterinary student at the University of California, Davis, School of Veterinary Medicine, presented the results of the study at the 2011 American Association of Equine Practitioners convention, held Nov. 18-22 in San Antonio, Texas.

"Navicular bone pathology (disease) is an important component of foot lameness in horses," Aarsvold said, adding that there are a number of common clinical radiographic findings related to the navicular bone including:

• Enlarged synovial invaginations ("holes" in the navicular bone that fill with synovial fluid—that fluid which is found in joints);
• Bone fragmentation;
• Enthesophytosis (small bone spurs that occur off the edges of the navicular bone);
• Flexor cortical lysis (decomposition of the surface of the normal outer tubular layer bone—the cortical bone— in contact with the deep digital flexor tendon); and
• Medullary sclerosis (increased density in the bone’s medullary canal–the marrow cavity).

"However, the pathogenesis and interrelationships of these changes remain poorly understood," Aarsvold noted. "The primary objective of this study was to more fully characterize alterations in microstructure of severely diseased navicular bones