Definition: Long-term, low-grade inflammation of the soft laminae within the hoof. Chronic, recurrent and acute laminitis are terms that describe varying degrees of severity of the same disease process.
Acute laminitis occurs when a single, catastrophic event--the "horse breaks into the grain bin" scenario--triggers a severe case of laminitis characterized by a rapid detachment and rotation of the coffin bone.
Recurrent laminitis describes a case where a horse who has previously had an acute episode continues to experience periodic flare-ups with relatively little provocation.
Chronic cases of laminitis come on gradually--usually in response to the sustained intake of carbohydrate-rich foods or the development of a metabolic disease such as Cushing's--and are not severe enough to cause a rapid collapse of the connective apparatus between hoof and bone. Chronic laminitis also refers to a situation where, after an acute non-fatal episode, a horse's feet remain severely compromised.
Signs: Lameness that ranges from nearly imperceptible to mild or moderate. The horse will still be willing to stand and walk despite the discernable pain in his feet. Longer term cases may develop changes in the hoof, including circumferential bands of irregular growth in the hoof wall as well as a change in the overall shape--the foot will become elongated and narrow, with "slipper" toes.
Diagnosis: X-rays are needed to distinguish chronic laminitis from other causes of lameness. The radiographs will show only a few degrees of divergence between the leading edge of the coffin bone and the hoof wall.
Treatment: Trimming and shoeing with the goal of restoring the normal alignment of the coffin bone. Analgesic anti-inflammatory drugs may be given for pain relief. Steps must also be taken to mitigate the problems that caused the laminitis--dietary changes as well as treatment of any underlying disorders.