© Ilka Robertson, DVM and David Hood, DVM, PhD
Based on clinical signs, horses suffering from laminitis can progress through four phases: developmental, acute, subacute and chronic. However, not every horse will progress through each phase.
Developmental phase. This is the time between the cause of the laminitis (for example, colic, retained placenta, etc.) and the first appearance of a lameness. The time frame is about 20-72 hours and is associated with very few clinical signs.
Acute phase. This begins with the onset of lameness which can be quite variable in severity. It can affect one, two, or even all four feet, but is most commonly seen in the forefeet only. In its mildest form, the horse may only appear to have a stilted gait or seem to be "walking on eggshells". A more severely affected horse may assume the classic laminitis stance, placing his hind feet underneath his body, while trying to keep the fore limbs extended out in front of him. It will appear as though the horse is trying to shift his weight from the front to the rear feet; however, we now believe that the horse is trying to place more weight onto the heels of the front feet and less on the toes. This may be less evident in horses suffering from laminitis in all four feet. When asked to move, the horse leans backwards and then slowly shifts his weight forwards as he moves his front legs. During the early acute phase, the hoof appears normal, but because inflammation is occurring within the foot (see question defining founder), another symptom that may occur is the presence of heat in the foot. This phase can last anywhere from 34-72 hours, depending on how quickly the disease progresses.
Subacute phase. Once through the acute phase, the disease can progress one of two ways. First, if the horse's foot does not show any signs of internal damage on an x-ray, the horse is considered to be in the subacute phase. A "fever ring" on the hoof wall may become apparent as the wall grows down, but otherwise the wall should appear normal. This condition would begin approximately 72 hours from the initial onset of lameness; full recovery may require twelve months, assuming that the disease does not enter the chronic phase, the second possibility.
Chronic phase. If the horse's foot fails mechanically, the disease has progressed into the chronic phase. This can last anywhere from the nine months it takes to replace the hoof wall to the lifetime of the horse. Several symptoms are associated with the chronic phase of laminitis, including pain, wall deformities, and draining tracts. As with the acute phase, there can be varying degrees of lameness. In addition, it may become evident over time that the hoof is becoming deformed. Examples of such deformities include a dished-out appearance to the wall, multiple rings on the outer wall and a flat sole instead of the normal concave shape. There may also be evidence of drainage from areas around the coronet or through the sole. This could result from an infective process or tearing of the damaged laminar tissues.
What to do for your horse. It is important that your veterinarian be consulted as early as possible during the acute phase so that proper and timely treatment can be initiated. Likewise, the diagnosis of chronic laminitis or founder usually requires x-rays made by your veterinarian. For further information on laminitis or founder simply e-mail the Hoof project with your questions or concerns. In addition to this, your veterinarian may be able to supply you with an informational pamphlet entitled Laminitis: prevention and treatment published by the American Association of Equine Practitioners.
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