Laminitis, commonly known as founder, is a very common ailment veterinarians encounter every day. It can be a painful condition that acutely affects a horse’s quality of life and ability to move comfortably. However, it can be treatable, and many cases of the condition can be prevented entirely.
The anatomy of the hoof is complicated, but when it comes to laminitis, the laminae of the hoof are our primary concern. The outer layer of the hoof capsule, or the horn, consists of three layers that make up the structural integrity of the foot. Internally, the triangular shaped bone called the coffin or pedal bone, is the most distal bone in the leg that is entirely encapsulated by the hoof wall. The laminae are made up on numerous interdigitating finger-like projections that connect to the inner hoof wall and the coffin bone, essentially suspending the coffin bone within the hoof capsule.
In general terms, laminitis is inflammation of the laminae. It results in the connections inside the foot becoming more flexible and less structurally sound. The normal downward/backward tension of the deep digital flexor tendon on the coffin bone combines with softening laminae to allow the coffin bone to move inappropriately within the hoof capsule. This movement is generally seen as the classic downward rotation and distal displacement (sinking) of the coffin bone. Laminitis can affect all four hooves, but most commonly involves the front feet. The inflammation of the laminae that ultimately leads to laminitis can be secondary to other medical conditions or a result of diet and overall health of the horse.
In general, metabolic causes of laminitis are the most common and the most preventable. Metabolic causes include any case that results in rapid spikes in blood sugar, such as grain overload, overgrazing fresh grass, and overfeeding treats. Some breeds that are predisposed to Equine Metabolic Syndrome (EMS), for example Morgans, Quarter Horses, and miniature horses, are prone to develop hyperinsulinemia which in turn predisposes them to develop laminitis. The diet of horses predisposed to EMS should be carefully evaluated to prevent laminitis. The physiologic connection between hyperinsulinemia and laminitis is still an active area of research. Cushings Disease in horses is another metabolic cause for laminitis and as a result, horses over twenty years old should be tested for Cushings disease. Horses with Cushings can be managed to prevent the onset of a sequela laminitis episode.
Systemic illness, such as colic, enteritis, enterotoxemia, retained placenta in a foaling mare, and diseases that cause a high fever such as Potomac Horse Fever are other, less common causes of laminitis. Whenever a veterinarian is treating the illnesses listed, laminitis should always be considered as a potential sequela.
Traumatic laminitis can be caused by anything that causes concussion to the hoof, such as trotting down an asphalt road. Poor hoof health or conformation can make some horses more susceptible than others. Finally, miscellaneous causes of laminitis include high dose steroid administration and black walnut stall shavings.
Recognizing the early symptoms of laminitis is just as important as the initiation of treatment. Common symptoms of acute laminitis include shifting lameness when standing; heat irradiating from the hoof wall; increased digital pulses; a “sawhorse stance” when the horse has its feet stretched out in the front and back; and a reluctance to walk. Chronic laminitis can be more subtle to diagnose, but common symptoms include horizontal rings in the hoof wall; dishing in the front hoof wall; flat feet; and white line disease (also known as seedy toe).
Treatment, if caught early, is often successful. The mainstay for treatment is hoof support and anti-inflammatory/pain control. Horseshoes are often taken off by the veterinarian or farrier. The afflicted feet are often placed in a supportive boot with a small heel lift. This helps alleviate the inflammation and lessens the downward tension on the pedal bone. Anti-inflammatories such as Banamine (Flunixin) or Phenylbutazone can be used for pain relief and to lessen the inflammation of the laminae. This will prevent further rotation of the pedal bone.
For chronic cases other drugs can help treatment by allowing increased blood flow to the affected area. Radiographs can be performed to determine the severity of the pedal bone rotation and to determine if abscesses are present. Abscesses are common in acute laminitis cases and addressing abscesses properly is essential to recovery.
Once the patient has remained comfortable in supportive therapy boots for approximately one week, a plan to wean the horse off the anti-inflammatories can be initiated. And finally, when the patient is comfortable off medication, appropriate shoeing with sole support can be placed. Long-term, evaluation of diet and weight are essential to preventing recurrent onsets of laminitis – talk to your veterinarian about an appropriate diet for your horse.
With proper shoeing, routine wellness exams and appropriate diet evaluation, many cases of laminitis can be prevented! If you believe your horse is exhibiting signs of systemic illness or laminitis, please reach out to your veterinarian for evaluation.
Dr. Brandon King is an ambulatory veterinarian at Pilchuck Veterinary Hospital in Snohomish, Washington. He specializes in equine sports medicine.