All You Should Know About Navicular Disease
Navicular disease is a lamellar bone disease of the foot. It’s also called coffin joint, or navicular fracture or bunion. Horses may show lameness after a period of standing with their weight off the foot, but this may not be always present and horses may also show sudden onset lameness in any circumstance.
Navicular disease can affect any age horse. It’s more common in horses between 2 and 10 years old, but horses of any age or size may be affected. There is a higher prevalence of navicular disease in Warmbloods, Thoroughbreds and Standardbreds than in other breeds of horses.
There are several contributing factors for the development of navicular disease. Those factors are:
? Obesity
? Artificial hoof trimming methods such as recurved shanks, narrow bands and extrusion heels, shoeing methods that force the foot into an unnatural conformation, etc.
? Increased stress on the coffin joint from poor conformation or poor balancing center with improper feet configuration (toe pointing out). Horses with soft feet or a lack of balance can develop navicular disease more easily than others. This is because the horse does not have strong support for the coffin joint.
? The angle of the pastern joint can contribute to navicular disease. This is because if the angle is too small, the hoof will be too high in relation to the coffin joint and will increase pressure on that joint.
? Poor hoof quality or a weak wall between the sole and the inner hoof may result in an increased risk of developing navicular disease.
? Foot conformation that is too upright or too weak can result in an increased risk of developing navicular disease. The foot should be slightly concave with a strong heel.
? Ageing can also cause an increased risk of developing navicular disease because the bones become less dense and more porous causing a decreased blood supply and may provide less nutrition to the bones. This decreases their strength and increases the risk of fracture and bunion development.
? Bone marrow disorders may also increase the risk of developing navicular disease.
? A high frequency of concussion to the foot or coffin joint due to faulty shoeing or conformation can result in an increased risk of developing navicular disease.
The most common symptoms are lameness, decreased range of motion in the ankle joint and a toe out “pigeon-toed” appearance. There may be pain in the heel, increased heat and swelling associated with inflammation which is called bursitis. There may be a slight bony lump (bunion) in the heel. There may be an increased hoof angle, a shortened toe-out position of the foot and a dropped sole on the affected side. There may be lameness with weight bearing or during exercise and an elevated heart rate.
The first step in treating navicular disease is to rule out any other possible causes for lameness. Diagnosis is made by radiography and a hoof analysis to determine the correct shoeing. The aim of any treatment is to rebuild or realign the navicular bone and coffin joint. Small hoof fractures may be realigned as long as they are properly supported at their new position.