Section: Overview
What is laminitis?
Laminitis is a crippling and painful condition of the horse's foot. Affected horses are recognized based on lameness, stiffness, reluctance to move and prolonged recumbency. It usually affects more than one foot at a time. The laminitis disease process affects the connective tissues ("lamellae"), which attach and connect the inner lining of the hoof capsule to the coffin bone (the bone at the bottom of the horse's leg). Disease of this connective tissue is very painful and, in severe cases, may lead to disattachment and structural compromise.
What is "founder"?
The term "founder" is commonly used synonymously with laminitis. However, in the opinion of some veterinarians, the term "founder" should be reserved for those horses in which the attachment of the inner lining of the hoof capsule to the coffin bone, has actually broken down and caused the coffin bone to change its position within the hoof. The weight of the horse is important in this respect, as it contributes to the distraction process through the deep digital flexor tendon.
Predisposing Factors
Obesity. Heavier horses are at increased risk for severe laminitis because more stress is put on the lameinae
Certain plants. Ingestion of endophyte-infected Tall Fescue has been proposed to increase the risk for laminitis.
Hypothyroidism. Numerous hormonal imbalances have been proposed to increase the risk for laminitis. Other than elevated cortisol levels, no other hormone in excess or deficiency has been shown to cause laminitis. There is no evidence that hypothyroidism causes laminitis, but some obese horses have low levels of thyroxine. The reason is unknown.
Whole body potassium deficiency. Some diets may not provide sufficient potassium and might increase the risk for laminitis.
Stress. Stressful events lead to enhanced endogenous cortisol production that appears to lead to laminitis.
Hoof conformation/farriery. Small feet in relation to the size of the body and other poorly characterized hoof conformational changes may affect the likelihood of laminitis. Excessive farriery, especially coupled with hard work on hard ground, represents a big risk for laminitis.
Age. Laminitis probably never occurs in horses less than 10 months of age.
Breed/genetics. Miniature breeds do not appear to be at risk for laminitis.
Concrete and paved surfaces. Horses that spend substantial periods of time on very hard surfaces appear to be at risk for laminitis.
Previous lamellar disease. Any horse is at increased risk for further bouts of laminitis after developing the disease in the first place. This is especially true of earlier bouts of laminitis.
Use of certain drugs. Glucocorticoid steroids such as dexamethasone and triamcinalone appears to lead to laminitis.
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