Inflammation of the sensitive laminae (lamellae) within the hoof is referred to as laminitis. Nearly 90% of laminitis cases result from endocrinologic abnormalities and insulin dysregulation associated with pituitary pars intermedia dysfunction (PPID or Cushing’s disease) and/or equine metabolic syndrome obesity, especially when associated with a rich diet. Hoof inflammation and changes related to endocrinologic laminitis occur slowly due to progressive lamellar stretch. Some horses develop hoof wall ridging or changes in the sole and white line months before demonstrating a full-blown laminitic attack.
Other metabolic abnormalities—dehydration, electrolyte imbalances, colic, and/or exhaustion syndrome that occur in distance sport horses—can cause acute onset laminitis. Intestinal illness such as sepsis from enteritis, colic or colitis events are known to induce acute onset laminitis. Limb fracture might cause supporting limb laminitis from too much pressure on the hoof in the uninjured leg. Excess concussion of the foot, particularly in a thin-soled horse, also has the potential for laminitis.
A laminitic horse develops a typical camped out stance, with as much weight as possible removed from the front limbs and more transferred to the rear limbs. Initially, he might appear “stiff” in the front end or might shift weight from foot to foot. As the process advances, the laminitic horse is reluctant to move and his front legs are camped out in front of his chest. When asked to turn, the horse shifts more weight to the rear and is overtly lame on the turns as if he is “walking on eggs.”
Bounding pulses tend to be present in the digital arteries just behind the fetlock of a laminitic horse. Many laminitic horses are reluctant to pick up their painful feet. Rapping on the front face of the hoof wall often causes an affected horse to flinch and withdraw the limb. More severe cases of hoof pain from laminitis result in sweating, anxiousness or colic behavior, while other individuals react to hoof pain by spending considerable time lying down.
Laminitis usually occurs only in the front limbs, but severe metabolic disease can lead to all four feet being affected. Laminitis is a true emergency condition requiring immediate veterinary attention to not only correct the underlying inciting problem, but to provide therapeutic strategies and support to the coffin bone within the hoof. Radiographic exam of the feet yields information about structural integrity within the hoof wall and the consequences this disease can have on a horse’s athletic future.