So many times, a horse gets labeled as suffering from “navicular,” and people shy away from him as if he were Typhoid Mary, not knowing how to treat or even visualize the problem. In recent decades, however, much has been learned about the area where the navicular bone lies. And many “set in stone” diagnostics (such as “lollipops” in the bone seen on radiographs) have gone by the wayside. Veterinarians and horse owners now know that there are many problems that can affect that area of the horse’s anatomy; some can be helped, but not all of them can be fixed. It also is known that in certain breeds of horses, the problem can become worse with age. In this era of horses living longer, it behooves owners to recognize the early signs of navicular syndrome, and know the options for your horse.
The navicular bone is a small bone that sits deep within the hoof at the back junction of the coffin bone and the short pastern bone. The navicular bone has the physical shape of a small canoe, which led to the name “navicular” bone; the prefix “navicu” means “small boat” in Latin. The navicular bone is also known as the distal sesamoid bone (the commonly known sesamoid bones behind the fetlock joint are the proximal sesamoid bones).
Associated with the navicular bone are several soft tissue structures. On the upper (proximal) aspect of the bone is the collateral sesamoidean ligament, which attaches the navicular bone to the distal end of the short pastern bone (remember that a ligament attaches bone to bone and a tendon attaches muscle to bone). On the lower (distal) aspect of the bone are the impar ligaments, which attach the navicular bone to the coffin bone. Cushioning the navicular bone from the pressure of the DDFT is a thin, soft serous sac called the navicular bursa.