Horses that work over hard surfaces, for example, experience excessive vibrations that result in changes to the mechanics of joint movement. In other words, this theory suggests that environmental influences can result in stress on the navicular area during movement. (4) They propose that the pathological changes are the result of inflammation caused by vibration and friction. Proponents of biomechanics as a cause define navicular disease as pathological changes of the soft tissue of the navicular apparatus – the navicular bursa, and the articular cartilage of the joint. This theory, however, has been largely rejected because of a failure to reproduce clinical signs or pathological changes when researchers reduce blood supply to the navicular bone of horses in clinical studies.Ī second theory, which focuses on postmortem studies of horses with longterm chronic lameness and radiograph abnormalities, suggests that biomechanical factors may promote this degenerative disease. Researchers reportedly observed thrombosis (clotting) and arteriosclerosis (thickening arterial walls), leading to ischemia (insufficient blood supply) within the navicular bone in horses diagnosed with navicular disease. One theory suggests vascular problems as the cause of navicular disease. In fact, today’s veterinarian can subscribe to several theories on how the condition occurs (3) and this will determine how he decides to treat it. Researchers have been unable to reproduce navicular disease in experiments, so they can only speculate about what causes it. This has lead some researchers to question the term “navicular disease”, feeling that it no longer applies to many of the horses being evaluated for foot lameness problems. MRI evidence confirms that many other problems in horses cause the same clinical signs as those in horses diagnosed with navicular disease. Given the variety of symptoms that manifest in lameness of the fore foot, however, it is likely that several different conditions, with different origins, are responsible for pain associated with the navicular region. Navicular disease is considered degenerative in nature, resulting in progressively worsening lameness.Ĭonventional veterinary medicine defines navicular disease as a single disease. (2) These collective structures are sometimes referred to as the navicular apparatus. The conventional viewĬonventional veterinary medicine views navicular disease as chronic forelimb lameness associated with pain originating from the distal sesamoid (navicular bone) and its closely related structures, including the distal impar ligament, collateral ligaments of the navicular bone, the navicular bursa, and the deep digital flexor tendon. The term “disease” implies a known cause and a specific treatment (1) but by calling it a syndrome, prognosis is left to the discretion of the attending veterinarian. He doesn’t have to deal with the stigma that surrounds a diagnosis of true navicular disease, where the prognosis is seen as very poor. Disease is defined as a pathological condition of a part, organ, or system of an organism resulting from various causes, such as infection, genetic defect, or environmental stress, and characterized by an identifiable group of signs or symptoms.Ī syndrome is more generally defined as a group of symptoms that collectively indicate or characterize a disease, psychological disorder, or other abnormal condition.īy using the term syndrome, a veterinarian may feel he has left his options somewhat open. So what is the difference between a disease and a syndrome? The truth is, not very much. Instead many elect to simply classify any horse with navicular region pain as a navicular syndrome horse. Over the past decade, I’ve seen veterinarians diagnosing fewer and fewer cases of true navicular disease. Sadly, the actual cause of this lameness is poorly understood, probably because it’s difficult to pinpoint the true cause of foot pain. Navicular is the most common source of performance-limiting lameness in the front legs of horses today. If you’ve been around horses for any length of time, you probably know of some unlucky equine who has been diagnosed with navicular disease (or navicular syndrome).
What exactly is navicular, and what can you do to prevent it in your horse? This article looks at some of the latest research.
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