Because radiographs do not always correlate with clinical symptoms radiographs are poor predictors of future lameness from Navicular Syndrome such as in a prepurchase examination situation. Because of lack of visualization of all potential damage, a horse with normal radiographs can have Navicular Syndrome and a horse with apparently abnormal radiographs can be quite sound. Many of the structures in the foot are soft tissue and are not visible on radiographs. Radiographs (x-rays) can be useful in helping to diagnose the specific structure causing pain in the foot. If infusion into the navicular bursa resolves the lameness then primary navicular bone pain or primary bursal pain is the source of the lameness. If infusion into the coffin joint blocks the lameness then the palmar process of the distal phalanx, the distal sesamoidean impar ligament, the deep digital flexor tendon, or the joint itself is the cause of the pain. We can infuse mepivacaine into the distal interphalangeal joint (coffin joint) or the navicular bursa and assess the response. A horse with chronic navicular pain may show lameness in the opposite limb once the primary limb is blocked. If a lame horse is sound when the back half of the foot is numb than we know the pain is coming from the back half of the foot. Diagnostic nerve blocks consist of infusion of mepivacaine around the palmar digital nerves to temporarily numb specific structures of the limb and to assess the response. That leaves response to diagnostic nerve blocks and diagnostic joint blocks as the most reliable diagnostic tests. Most horses however are negative to these tests. Some horses with navicular pain will be sensitive to hooftesters, flexion of the lower limb, and/or the reverse wedge test. I prefer to diagnose lameness without a rider when possible because a rider can bias diagnostics. In some horses lameness may only be detected while being ridden. Some “navicular horses” have a tendency to stumble. Lameness is sometimes apparent when the horse is moving in a straight line on a hard surface, or may only be observed on the lunge with the affected limb on the inside or outside of the circle. This is a variable finding and should not be over interpreted as many normal horses will habitually stand with one foot extended forward. Horses with Navicular Syndrome may “point” a toe while at rest. Lameness may become apparent after a period of enforced rest from an unrelated problem or seasonal layoff. Lameness is often associated with change in ownership, management changes, farrier changes, altered periods of turn-out, or increased work load. True shoulder lameness is rare in the adult horse horses with shortened stride usually have pain in the hoof. Many owners and even trainers report “shoulder lameness” because of a shortened stride. Many horses however, present with acute unilateral forelimb lameness. The classic “navicular horse” presents with a history of an insidious onset of loss of performance, shortening of stride, or shifting bilateral forelimb lameness. The typical horse is 7 to 9 years of age and in the prime of its working life. I have seen horses present with Navicular Syndrome as young as 3 years of age and as old as 20 years of age. In other words a veterinarian cannot “watch a horse travel” and diagnose Navicular Syndrome.

Because of the complexity of Navicular Syndrome management can be challenging.Ĭlinical signs are little help in securing a correct diagnosis. Because Navicular Syndrome is actually several diseases and not a single disease, proper diagnosis is extremely important. This explains why “navicular horses” present so differently and why treatment options are so varied with varying degrees of success. Navicular Syndrome has long been thought of as a single disease process however, it is actually caused by several different closely related structures including: the collateral ligaments of the navicular bone, the distal sesamoidean impar ligament, the navicular bursa, the deep digital flexor tendon, or the navicular bone itself. Navicular Syndrome is chronic forelimb lameness associated with several structures inside the hoof capsule. Navicular Syndrome: clinical signs, diagnosis, management and prevention

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