Equine Navicular Syndrome Kylie Stephens, USU Equine Science and Management Karl H. Hoopes, DVM USU Equine Extension Specialist
Introduction Equine navicular syndrome greatly affects the horse industry by accounting for up to one-third of all chronic forelimb lamenesses.1 While the exact cause and development of this disease are still widely controversial, there are noticeable and significant changes to the internal anatomy and structures that could contribute to the possible onset of lameness. Three main causes are proposed that could play a role in the progression of this syndrome: biomechanical forces, vascular alterations, and chronic inflammation. The clinical signs of navicular syndrome can range from short, choppy strides to intermittent lameness, as well as gait changes and pain associated with the frog and heel.2 There are several options for diagnosing navicular syndrome, and many routes for treatment. While navicular syndrome is not curable, efforts can be made to slow the progression of navicular degeneration and reduce discomfort in the horse.
Figure 1. Equine Distal Limb Cross Section A – Third metacarpal (cannon) bone B – Proximal phalanx (long pastern) bone C – Middle phalanx (short pastern) bone D – Distal phalanx (coffin) bone E – Distal sesamoid (navicular) bone F – Deep digital flexor tendon (DDFT)
Causes of Navicular Syndrome The hoof contains a small bone called the distal sesamoid (navicular bone), located behind the short pastern bone and coffin bone joint (Figure 1).
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