Subclinical, Acute, and Chronic Laminitis in Horses

This horse had some hoof drama several months ago. The dark ring tells us! Radiographs at the time showed subclinical laminitis.

Defining Laminitis

• The inflammation of the soft tissue laminae inside the hoof characterizes laminitis. It affects the front and hind feet and is a medical emergency. As the inflammation progresses, the weakening of the laminae allows the pedal bone, also called the coffin bone or distal phalanx, to possibly rotate or sink. The deep digital flexor tendon is under constant tension on the coffin bone, and compromised structures allow that tension to pull the bones out of place. There is also significant disruption to blood flow as the swelling constricts vessels.

• As you can imagine, the displacement of the coffin bone is wildly painful and can lead to a lifetime of pain.

This article from the UC Davis School of Veterinary Medicine explains this in greater detail.

Subclinical Laminitis is Largely Invisible

• Some cases of laminitis are considered subclinical because there is no visible lameness and no discernible signs of pain. This stage is the developmental stage of hoof damage, where there are changes to the laminae but no apparent lameness.

• However, a subclinical horse will still have subtle, telling signs. These clinical signs are most apparent in the hoof wall and sole, such as a white line that’s stretched or irregular, frequent abscesses, hoof bruises, seedy toe, cracks, and bold rings on the hoof wall.

• These bold rings indicate hoof growth and may indicate previous bouts of this condition. As the hoof grows, the rings grow out. A distinct line indicates past trauma to the hoof, and as it grows, it may warp and wave, indicating disruption of the growth cycle and possible changes within the hooves.

• You may also detect early clinical signs of laminitis, such as hoof heat, rapid digital pulses, and shorter strides.

• This stage of disease is closely linked to endocrinopathic laminitis, in which metabolic disorders such as pituitary pars intermedia dysfunction (PPID, formerly Cushing’s Disease), equine metabolic syndrome (EMS), and insulin resistance (IR) affect insulin, body weight, hoof blood supply, and the development of hoof problems.

• Detecting subclinical laminitis helps prevent progression to acute laminitis and long-term pain and lameness.

When laminitis progresses to the point of obvious pain, there is already damage inside the hoof.  

This article details a recent study on subclinical cases and their relationship to age. Older horses are more likely to develop this form.

What you can do

• Daily hoof care should include checking your horse’s digital pulses. It only takes a few seconds, and it’s great news if you can’t find it. Pulses will be stronger if there is inflammation in the hoof.

• You may also notice an increased heart rate, which signals exertion from play as well as pain. Take your horse’s vital signs when they are resting.

• Monitor your horse’s weight. Overweight horses are more likely to develop metabolic problems that increase the risk of laminitis.

• Work with your vet regularly to ensure your horse is healthy, and their diet supports long-term wellness and helps maintain a healthy weight. Follow your veterinarian’s advice on testing for metabolic disorders and adjust medications, diet, and lifestyle accordingly.

Ice helps fight inflammation.

Acute Laminitis Has a Sudden Onset – Usually

• It’s now understood that seemingly acute cases can develop over time. Scientifically speaking, the acute phase begins when your horse experiences a triggering event, and you notice lameness and signs of pain.

• A triggering event could be an overload of sugars and starches from lush pasture, grain, or sugary treats. This rapid carbohydrate intake is riskier for horses with metabolic conditions.

• Injuries, fevers, and running on hard ground, termed road founder, also trigger equine laminitis. Mares with retained placentas are also at risk.

• If we want to split hairs, the acute phase ends when the coffin bone (P3) begins to move, rotate, or drop within the hoof capsule. Then the distal displacement of the distal phalanx indicates founder.

What you may see in the acute stage of laminitis

• Your horse will tell you they are in pain. They will do their best to reduce weight-bearing by either shifting their weight more often than usual or by achieving utter stillness. You may notice that they shift the front hooves. You will also find they:

• • Have increased vital signs and digital pulses
  • Are reluctant to turn or walk from softer to hard surfaces.
  • Send some weight to the hind end, but not all horses will do this parked out stance.
  • Take shorter steps.
  • Have hot hooves.
  • Prefer soft, deep bedding.
  • Have changes to the sole of the hoof, including bruising and dents.

What to do if you suspect hoof trouble

• Call your vet immediately. First and foremost, your vet can guide you on pain-relieving measures such as icing, NSAID medications, using soft bedding, and removing all grains, grasses, and sugary treats from the diet. X-rays are vital for establishing a baseline, enabling subsequent X-rays to reveal more or less damage and bone movement.

• Long term, your vet and farrier can work together for therapeutic trimming and horseshoes, and you can implement a weight loss and low-sugar diet for your horse. Acute conditions may become chronic over weeks, months, or years.

• The long-term goal is to restore as much hoof health as possible and prevent future cases of acute and chronic laminitis.

This article shows great photos of X-rays and hoof structure.

Chronic Laminitis

• The chronic phase begins when movement to the coffin bone starts, also known as equine founder. This stage of disease ends when the coffin bone returns to a natural position.

• For some horses, this never happen and for others, it might take years. The horse with a chronic case is at risk of recurrent episodes of laminitis and frequent abscesses.

• As a horse owner and lover, it’s essential to understand that this disease starts long before your horse starts to become lame. Metabolic issues, obesity, and high starch diets and pastures all contribute to risk.

• You may see long-term hoof deformities, increased abscesses, unsoundness, and flares or acute episodes when exposed to triggers.

• Pasture grazing may not be part of your horse’s lifestyle, and dry lots with toys and slow feeders become the best way to keep your horse turned out and eating all day long.

• Regular X-rays will assess hoof structure and monitor overall hoof health. Ideally, the hooves can heal, and you never need to worry about acute and chronic laminitis again, and radiographs help tell the tale.

Distinguishing Between Acute and Chronic Laminitis

• While both types of hoof disease are painful, the trigger usually differentiates acute from chronic. Acute cases involve immediate pain and inflammation, whereas chronic cases are more long-term, may include bony changes and structural damage deep in the hoof.

• It’s tempting to assign time frames to these conditions, which can be roughly one week for acute cases and months or years for chronic conditions, but horses will always find a way to fool us.

• Horses will also find a way to throw all rules out of the window and royally mess up our plans. There’s also the chance that a previous case of founder will return to “normal,” but in actuality, things are still sub-clinical.

This article discusses the causes and stages in more detail.

ICE ICE ICE ICE and ICE some more for most cases.