Normal forces placed on the hoof are then strong enough to tear the remaining laminae, resulting in a failure of the interdigitation of the epidermal and dermal laminae between the hoof wall and the coffin bone. When severe enough, this results in displacement of the coffin bone within the hoof capsule. Most cases of laminitis occur in both front feet, but laminitis may be seen in all four feet, both hind feet, or in cases of support limb laminitis, in a single foot. Mechanism
The mechanism remains unclear and is the subject of much research. Three conditions are thought to cause secondary laminitis:

Sepsis/endotoxemia or generalized inflammation
Endocrinopathy
Trauma: concussion or excessive weight-bearingInflammationInflammatory events that are associated with laminitis include sepsis, endotoxemia, retained placenta, carbohydrate overload (excessive grain or pasture), enterocolitis, pleuropneumonia, and contact with black walnut shavings. In these cases, there is an increase in blood flow to the hoof, bringing in damaging substances and inflammatory cells into the hoof. EndocrinopathyEndocrinopathy is usually the result of improper insulin regulation, and is most commonly seen with pituitary pars intermedia dysfunction (also called equine Cushings syndrome) and equine metabolic syndrome (EMS), as well as obesity and glucocorticoid administration. In cases of EMS, most episodes occur in the spring when the grass is lush. TraumaMechanical laminitis starts when the hoof wall is pulled away from the bone or lost, as a result of external influences.
Tendency to lie down whenever possible, and recumbency in extreme cases
Change in the outward appearance of the hoof in cases of chronic laminitis: dished (concave) dorsal hoof wall, "founder rings" (growth rings that are wider at the heel than the toe), a sole that is either flat or convex just dorsal to the apex of the frog which indicates P3 has displaced or penetrated, widening of the white line at the toe with or without bruising, "clubbing" of the foot. Change in the appearance of the coronary band: hair that does not lie in a normal position (not against the hoof wall), indentation or rim just above the hoof capsule allowing palpation behind the coronary band. In cases of sinking, it may be possible to palpate a groove between the coronary band and the skin of the pastern. Lameness evaluation
Hoof testingLaminitic horses are generally sore to pressure from hoof testers applied over the toe area. However, there is risk of a false negative if the horse naturally has a thick sole, or if the hoof capsule is about to slough. Obel grading systemThe severity of lameness is qualified using the Obel grading system:
Obel grade 1: Horse shifts weight between affected feet or continuously lifts feet up. It is sound at the walk but displays a shortened stride at the trot. Obel grade 2: Horse displays a stilted, stiff gait, although is willing to walk. It is possible to easily lift a front foot and have the horse take all of its weight on the contralateral limb.