In earlier years, a diagnosis of navicular disease was often considered career-ending for a horse. Chronic lameness was typical, in spite of therapeutic shoeing, medication, etc., and sometimes the only option to help the horse travel sound was a neurectomy (the cutting of nerves leading to the foot), which meant he would no longer feel pain (or anything else) in the foot. Today we realize that what we earlier called navicular disease (the horse showing palmar–toward the back of the foot–foot pain, positive to hoof testers over the navicular area, and going sound after a posterior digital nerve block) includes a host of different problems within the foot, some of which are unrelated to the navicular bone and/or bursa (the fluid-filled sac that cushions the navicular bone against the pressure of the deep digital flexor tendon). The term navicular syndrome or palmar foot pain is now used instead.

Some cases of navicular syndrome have a good prognosis for healing and full recovery, if given time and proper treatment. Yet, for many years accurate diagnosis was elusive since it’s difficult to view the inside of a living horse’s foot. Ultrasound, X rays, and nerve blocks have been used to aid diagnosis, but results of these tests can be misleading or inconclusive.

Stephen O’Grady, DVM, MRCVS, owner of Northern Virginia Equine, says a posterior digital nerve block basically anesthetizes the entire foot. “When you block that foot and the horse goes sound, is the pain coming from the navicular bone, the navicular apparatus (the suspensory ligament, which anchors the navicular bone to the second phalanx, the impar ligament, which attaches the navicular bone to the coffin bone, etc.), a lesion in the deep digital flexor tendon, the bursa of the navicular bone, or the coffin joint?”