About the Diagnosis
Laminitis (or founder) is a painful condition of the foot. It specifically occurs where the hard covering of the hoof meets the soft tissues inside the foot, known as the lamina. “Lamina” = soft tissues that connect the coffin bone to the hoof wall. “Itis” = inflammation. When this connection (lamina) is damaged, the coffin bone is no longer supported within the hoof wall and the weight of the horse pushes the coffin bone down onto the sole, tearing the lamina and crushing the soft tissue of the sole. This damage results in severe pain. Once these soft tissues are damaged the deep digital flexor tendon continues its pull on the bottom of the coffin bone, pulling away from the front of the hoof wall. Laminitis causes mild to severe lameness, abnormal hoof growth and abnormal hoof appearance. After any episode of laminitis, the lamina is permanently weakened and predisposed to recurrence.
Any horse can develop laminitis, but certain risk factors make horses more likely to develop laminitis than others. Pony breeds are at greater risk for developing laminitis than are horse breeds. Horses with evidence of previous laminitis are at increased risk of another episode. Any horse with other lameness problems is at an increased risk especially if the existing lameness is severe. Endocrine disorders (diseases that affect hormone production) such as obesity, hypercortisolism, insulin resistance, and pregnancy are also risk factors. There can be dietary factors that increase a horse’s risk for developing laminitis including feed high in starch, such as grain or spring grass. Horses that have to stand or exercise on hard surfaces are more at risk. Medical conditions that result in signs that affect the whole body (like fever) such as diarrhea, pneumonia, and retained placenta also put horses in a higher risk category for developing laminitis.
Laminitis has been classified into 4 different categories. Acute laminitis is inflammation of the lamina that has been activated for the first time and is associated with severe pain. Often the foot feels hot and the pulse that can be felt in the pastern area is bounding. Chronic laminitis is laminitis that has been present long enough to cause abnormal foot growth. This foot growth can appear as a “dished” foot or more subtly as growth rings that are close together at the toe and farther apart at the heel. The disease may or may not be painful. Acute laminitis becomes chronic laminitis at some arbitrary point. Developmental laminitis is the period of time between the event that caused the laminitis and the clinical signs associated with acute laminitis (foot pain, increased digital pulses, heat in the hoof wall). Horses may not be painful during this phase. Treatment during this phase can result in the best outcome for the horse. An example is treating a horse that gets into the grain room with activated charcoal, mineral oil and icing its feet even though it does not show foot pain. Endocrinopathic laminitis is acute or chronic laminitis associated with an underlying hormonal condition such as hypercortisolism (Cushing’s Disease or treatment with corticosteroids).
Horses with laminitis can present in many different ways depending on how severe the disease is, how long it has been present, and how many limbs are affected. Laminitis is more common in adult horses and ponies than in foals but does occasionally occur in foals. It most commonly presents as severe pain affecting both front limbs. Horses have increased heart rates and increased rates of breathing. They may appear anxious. Horses are reluctant to move and appear very stiff when asked to move. They will often place their hind legs underneath them and appear to lunge forward in an effort to spend as little time as possible with full weight on their front feet. Horses may lie down and refuse to stand. These horses should not be made to stand. When examining their legs, they may have some swelling above the coronary band (edema), the hoof wall may feel hot, and the pulse on the back of the pastern will feel very strong (“bounding”). Horses may develop a depression at the coronary band which is evidence of “sinking” which occurs when the coffin bone shifts low within the hoof capsule. When horses stand, they will often rock back on their hind limbs to try to transfer weight off of the painful forelimbs. They may tread by switching weight slowly from one foot to another trying to find a comfortable place to stand. Horses will try to bear weight on their heels and will therefore place the affected foot/feet far out in front of them. Horses will walk slowly and deliberately (“walking on egg shells”). It is very painful for horses to turn and they may pivot on the hind limbs and lift both forelimbs off the ground if asked to make a sharp turn. Signs of pain such as sweating, trembling, muscle tremors and rapid breathing may be apparent. Horses will have more difficulty walking on hard surfaces than on soft surfaces.
Horses can develop separation and drainage at the coronary band that may appear bloody or serous (like fluid in a blister). In severe cases horses can slough the hoof capsule, in which case the entire hoof capsule is loose and may even come off. If horses have had previous bouts of laminitis, they may have prominent growth rings of the hoof that are narrow at the front and wide at the heel. The bottom of the foot may appear “dropped” with little to no concavity. There may be a crescent shaped area of bruising on the sole of the foot. This may indicate that the coffin bone has lost its support in the hoof capsule. In severe cases it may be possible to see the coffin bone through the sole. Examination of the white line (the line between the outer hoof capsule and the sole) may reveal it to be widened.
Horses that develop laminitis secondary to lameness in another limb may appear to “improve” in the lameness condition on the original limb as a result of reluctance to bear weight on the limb that is now affected by laminitis. Any improvement in the original lameness, especially if sudden or unexpected, should be interpreted cautiously as it may be an ominous sign. Your veterinarian should be contacted immediately. Laminitis should also be suspected in horses that have an inflammatory process that does not resolve appropriately such as white line disease or a subsolar abscess. Laminitis can also happen in horses that exercise on hard surfaces, “road founder.”
In addition to a complete history and thorough physical examination, your veterinarian will perform a lameness examination which may or may not involve nerve blocks. Horses with laminitis are sensitive to hoof testers along the toe of the foot but can be sensitive anywhere. Because laminitis often affects both front limbs, lameness in the form of a head nod may not be apparent in horses with mild lameness until after nerve blocks are performed. Affected horses will have a short choppy gait (if they are not too lame to trot) and may demonstrate a head nod with whichever leg is on the inside of the circle (lameness on the leg on the inside). Most horses with acute laminitis will be too lame to trot and should not be forced to do so. If nerve blocks are performed, once one foot is blocked the horse may appear worse in the opposite foot and subsequently develop a head nod.
Severely affected horses may need nerve blocks performed to allow the feet to picked up to be examined. Radiographs will need to be taken to evaluate the severity of the disease and to establish a baseline to compare future radiographs as treatment is pursued. Nerve blocks will also help acquire the necessary radiographs as good quality images are imperative not only for diagnosis but monitoring response to treatment and determining how the horse may do in the future.
Radiographs should be critically evaluated. The relationship between the coffin bone and the hoof wall is evaluated for rotation; however, there are several other critical areas to evaluate. The dorsal hoof wall is supposed to be a normal distance from the front of the coffin bone, in horses with laminitis this distance is often increased. The bottom of the coffin bone should be examined in relation to the sole of the foot. In a normal foot the bottom of the coffin bone is parallel to the bottom of the foot. In a laminitic foot the lines can converge usually towards the toe but in some horses towards the heel. Also, the coffin bone should be an adequate distance from the sole. In some laminitic horses the distance between the coffin bone and the sole is narrow. The distance between the extensor process (top) of the coffin bone and the coronary band is also important. In some horses (“sinkers”) this distance is increased. Fracture of the border of the coffin bone is sometimes seen in horses with chronic laminitis.
Other diagnostics include blood work to determine any underlying cause for the disease such as an inflammatory response somewhere else in the body, Cushing’s disease, etc. Other tests that may help in determining the prognosis for a horse with laminitis include venography, magnetic resonance imaging (MRI) and computed tomography (CT). Venography can be performed using a radiographic machine and gives information about the blood flow to the foot. MRI and CT require special equipment and may also require general anesthesia.
Living with the Diagnosis
Horses with signs of acute laminitis such as foot pain, that receive prompt and aggressive treatment can completely recover. These horses should be monitored closely and rested for several months before any gradual return to work. If radiographic changes develop, the prognosis becomes related to the amount and severity of damage to the lamina. Horses with greater than 15 degrees of rotation and downward displacement of the coffin bone within 4-6 weeks of the initial episode have a poor prognosis. Horses with evidence of sinking have a poorer prognosis. Some horses will make a good recovery, but most suffer with months of foot pain, recumbency and eventually require euthanasia.
The clinical signs, severity of damage to the foot, and the response to treatment varies considerably between cases making a treatment plan with an accurate prognosis exceptionally difficult to formulate.
Any underlying disease process needs to be treated. Examples include rehydration in horses with diarrhea, anti-endotoxic medications in horses with severe bacterial infections, removal of any placental remnants in mares with retained placenta. If the laminitis is suspected to be from corticosteroid use, corticosteroids should be judiciously discontinued. Immediately treating acute laminitis can improve the prognosis. It is known that damage to the soft tissue of the foot occurs before horses begin to experience pain (developmental phase). By the time horses are showing signs of discomfort, significant damage is likely to have already occurred. This is why many at- risk horses are treated as if they already have laminitis and why immediate aggressive treatment once the disease is recognized is so important. Any feedstuffs high in starch should be discontinued (grain).
Treatment includes restricting patient movement. Horses should be placed on stall rest only. Horses should be provided deep bedding to cushion the foot and encourage them to lie down. Sole support should be placed on their feet. Hard surfaces should be avoided. The breakover (toe) of the foot should be shortened. This is done by shortening and even squaring the toe of the foot. Modified shoes that can be taped on are often helpful since they elevate the heel and relieve tension on the deep digital flexor tendon (which attaches to the bottom of the coffin bone) and decrease breakover. Any circulation problems should be addressed, and horses given fluid therapy as needed. Medications will be given to combat endotoxemia since endotoxin is known to induce laminitis. Pain management is instituted to help keep the horse as comfortable as possible. Grain should be avoided, and feet should continue to be iced.
Medications are given to help control the pain associated with laminitis. Anti-inflammatory medications such as flunixin meglumine and phenylbutazone are commonly given. Because horses are likely to receive these medications long term, consideration should be given to anti-ulcer medication and monitoring kidney function. Other medications include butorphanol tartrate (Torbugesic ®), which is an opioid pain medication, to help manage severe pain. In a hospital setting other pain medications can be given constantly through an intravenous catheter such as xylazine, detomidine, ketamine, and lidocaine. DMSO can be given to help reduce inflammation. Anti-ulcer medications such as omeprazole or misoprostol are given. Horses with hind limb laminitis can be treated with epidural morphine. There are many other medications that have been used to treat laminitis but there is little evidence that supports their usefulness.
Proper foot care is an important aspect of caring for horses with laminitis. There are several different approaches, but the best results occur when there is a good veterinarian/farrier team. There is no “best approach” for all horses with laminitis and treatment should be finely tailored to an individual horse based on comfort and radiographic changes. The foot should be trimmed, and all excess toe removed. The heels are often trimmed to allow more weight bearing on the heel while relieving pressure on the toe. Sole support is often helpful but if a horse is immediately worse after any change, it should be removed. Careful removal of necrotic hoof wall should be performed, and any necessary support provided after its removal.
- Call your veterinarian immediately with any clinical signs of laminitis
- Keep your horse on stall rest
- Be prepared for a lengthy and expensive recovery
- Be prepared for a poor prognosis
- Be sure there is a good relationship between veterinarian and farrier
- Delay diagnosis or treatment
- Feed grain or allow access to spring pastures
When to call your veterinarian / Signs to watch for:
- Lameness characterized by a reluctance to move, treading, bearing weight on the hindlimbs, reluctance to turn
- Heat in both front feet with increased pulses
- Exposure to increased amounts of grain
- Any illness that causes signs of fever and dehydration
- In mild cases that respond well to therapy, follow up radiographs can be performed in a few weeks
- In more severe cases or cases that show rapid progression, radiographs may be taken every few days
- Severe cases will require hospitalization with daily and sometimes hourly treatments and treatment adjustments.
- Follow-up will be required by both your veterinarian and your farrier.