Laminitis

Laminitis essentials
What is laminitis?
What causes laminitis? HAL / SRL / SLL
Diagnosing laminitis - clinical signs of laminitis
Treatment and management of laminitis - emergency & longer-term
How to prevent laminitis
Further information

Laminitis essentials

If your horse has, or if you suspect your horse has laminitis (is lame and/or showing signs of pain), call your vet immediately.

Laminitis means damage - mostly stretching and separation - of the lamellae (also called laminae), which can result in misalignment between the pedal bone (P3) and the hoof capsule (rotation/sinking), and affect blood flow and hoof growth.
Laminitis is poorly named, because, although "-itis" means inflammation, laminitis often does not involve significant inflammation; "lamellopathy" (or "laminopathy") would be a better name for the disease.

3 forms/causes of laminitis are currently recognised (see What causes laminitis below):
Hyperinsulinaemia associated laminitis (HAL)
Sepsis related laminitis (SRL)
Supporting limb laminitis (SLL)

Laminitis, regardless of the cause, involves 2 parts:
1. The cause: something - whether abnormally high insulin in the blood (HAL - systemic) or other "trigger factors" in the blood (SRL - systemic) or reduced blood supply to the lamellae (SLL) - causes the lamellae to become damaged, stretch, weaken and/or separate.
Once this has happened,
2. Mechanical changes: the forces of the horse's weight, increased by movement, can cause the pedal bone and hoof capsule to become out of alignment with each other (rotation and/or sinking), and the hoof capsule to lose its normal shape. This is described as chronic laminitis.

In all forms of laminitis
1. the cause must be quickly and correctly identified and removed/treated/managed - damage to the lamellae is likely to continue until the cause has been removed; and
2. the feet must be quickly and correctly supported/protected and any misalignment corrected, to reduce the risk of further damage and to encourage correct new hoof growth and lamellar connections.

NEVER WALK A HORSE WITH (SUSPECTED) LAMINITIS A STEP MORE THAN ABSOLUTELY NECESSARY, AND ONLY AFTER PROTECTING THE FEET. Every step (breakover) puts strain on lamellar tissue, which, if damaged, may lead to rotation and/or sinking of the pedal bone.

What is laminitis?

To understand laminitis, we need to understand what happens inside the feet.

Healthy foot

In the healthy foot the pedal bone/P3 is attached to and suspended inside the hoof capsule by lamellae (laminae).

Epidermal lamellae on the inner hoof wall interdigitate with dermal lamellae that extend from the lamellar corium of P3, forming a very strong attachment. The epidermal lamellae do not have a blood supply and rely on nutrients from capillaries in the dermal lamellae.

The photo on the right shows (from left to right) the edge of the pedal bone, the lamellar corium, the dermal lamellae (red) interdigitating (interlocking) with the epidermal lamellae (white), the inner white (non-pigmented) hoof wall and the outer (pigmented) hoof wall.

The basement membrane - a thin sheet of connective tissue - runs between the epidermal and dermal lamellae (imagine interlocking your fingers with a thin latex glove on one hand) - this cannot be seen on normal photos.

Hoof U photo and healthy lamellae photo used with the permission of Lindsey Field - The Study of the Equine Hoof.
https://www.facebook.com/HoofStudies.

Laminitic foot

Laminitis is a failure of the normal attachment between the pedal bone/P3) and the hoof wall.
The lamellae stretch and/or separate.
Once the lamellar connection has weakened or failed, the forces of the horse's weight, increased by movement, cause the mechanical displacement of P3 in relation to the hoof capsule (rotation/misalignment and/or sinking/distal displacement), and normal hoof capsule growth and blood perfusion may be disrupted.

Laminitis is not inflammation of the lamellae. There will be some inflammation as a response to damage, but inflammation does not cause laminitis (HAL or SLL).

The photo on the right shows (from left to right) the edge of the pedal bone, the lamellar corium, the dermal lamellae (red) interdigitating (interlocking) with the epidermal lamellae (white), the inner white (non-pigmented) hoof wall and the outer (pigmented) hoof wall. Compare with the healthy foot photo of the lamellae above - in this photo the regular appearance of red dermal lamellae interlocking with white epidermal lamellae has been lost.

Laminitic lamellae photo used with the permission of Lindsey Field - The Study of the Equine Hoof.
https://www.facebook.com/HoofStudies.

What causes laminitis?
Hyperinsulinaemia associated laminitis (HAL)/ sepsis related laminitis (SRL)/ supporting limb laminitis (SLL)

3 forms/causes of laminitis have been identified: hyperinsulinaemia associated laminitis (HAL), sepsis related laminitis (SRL) and supporting limb laminitis (SLL).
The cause, pathophysiology (what's going on in the body that shouldn't be), treatment and prognosis are different for each form, so it is important to know which form a horse has.

HAL: hyperinsulinaemia-associated laminitis
This form of laminitis is a consequence of insulin dysregulation (ID) and eating a diet high in sugar and starch. It can also be caused when a horse is given corticosteroids. Horses with PPID and laminitis have ID (whether PPID causes/exacerbates the ID isn't currently known).
Abnormally high levels of insulin in the blood cause the lamellae to stretch and weaken.
This is the most common form of laminitis - around 90% of all laminitis.
HAL is generally easier to prevent and to recover from than other forms of laminitis, may develop slowly, and signs of pain can be absent (sub-clinical) or mild, as well as significant to severe.
Treatment is to control insulin with a low sugar/starch diet, weight loss if needed, exercise when able, and possibly short-term SGLT2 inhibitor medication to lower insulin levels.

SRL: sepsis related laminitis.
This form of laminitis is a consequence of a serious inflammatory infection/illness e.g. colitis, pneumonia, infection after retaining placenta post-foaling.
Currently unidentified trigger factors associated with sepsis and inflammation damage the lamellae, often resulting in complete separation of the lamellae and significant sinking of P3.
SRL is rare but very serious - hospitalization will often be required - and often has a poor outcome.
Treatment is to control the primary illness, anti-inflammatory medication, and (before or in the early stages of laminitis development) cryotherapy (continuous cooling of the feet).

SLL: supporting limb laminitis.
This form of laminitis is a consequence of a serious non-weightbearing lameness in another leg, e.g. a fracture.
Laminitis is due to reduced blood perfusion (ischemia) in the supporting leg(s) from reduced limb load cycling.
SLL is very rare but very serious - hospitalization will usually be required - and often has a poor outcome.
Research is ongoing into the best treatment but likely involves increasing perfusion in the supporting leg(s).

Diagnosing laminitis - clinical signs of laminitis

The main clinical sign of laminitis is pain in the feet. The severity of pain can range from:

no perceptible pain/lameness (sub-clinical laminitis) but evidence of damage to the lamellae/chronic laminitis is seen when looking at the feet (e.g. divergent hoof rings, stretched white line or lamellar wedge) or x-rays of the feet (e.g. widened lamellar lucent zone, dorsal rotation, high palmar angle), to
mild clinical laminitis where the horse shows a slight shortening of stride, “feels his feet" or is "pottery” on hard or stony ground and finds it difficult to turn but seems normal on soft ground and in straight lines, to
unwilling to walk or pick feet up, shifting weight from foot to foot ("paddling"), strong digital pulse, slightly increased heart and respiration rate, likely still eating, to
total refusal to move or pick up feet, lying down a lot, heart rate may be over 80 bpm, respiration rate may be over 60 breaths/min, sweating, muscles hard, CK & AST may be slightly raised. Temperature usually normal unless raised by the primary illness leading to sepsis related laminitis (SRL).

BELOW - TO BE UPDATED

NB changes in stance are often noticed but the stance depends on the damage and the feet affected (any or all feet can be affected), and can include:
front feet out in front, hind legs forward under body;
front legs back under body, hind legs forward under body,
front legs back under body, hind legs normal;
normal stance (common when all 4 feet are affected).

Symptoms of laminitis

You are unlikely to see all of these signs - consider laminitis (and call your vet) if you horse shows ANY of these symptoms, but be aware that many are also symptoms of other hoof/lameness issues. Perhaps the most reliable and one of the earliest signs is paddling - but a horse with sinking may not paddle. Symptoms will change as laminitis progresses from acute to chronic. Every horse is different and will show different symptoms and different degrees of pain - recognise and investigate any of these signs - too many horses go undiagnosed because the early signs of laminitis are not picked up - the earlier you recognise the symptoms, remove the cause and support the feet, the better the outcome is likely to be.

Feeling “footy” - showing a preference for soft ground, a reduction in stride length on hard ground
Reluctance to turn
Stiff gait - walking on heels
Reluctance to move leading to total refusal to move
Shifting weight from foot to foot (paddling)
Abnormal stance - depends on feet affected and whether rotation or sinking
Reluctance/refusal to pick up feet
Feet feel hotter than usual (but may feel colder than usual)
Muscle tension in the shoulders, back, quarters - AST & CK may be slightly elevated
Bounding digital pulse
Pain on sole pressure between apex of frog and toe
Lying down more than normal
Signs of pain - pulse (>80 bpm?), respiration (> 60bpm?), trembling, sweating, depressed, off food

Horses with distal descent will be reluctant to move, have bounding digital pulses and have a depression at the coronet. They usually stand in a normal stance and may have abnormally cold feet.

See Rosie's case study to see her symptoms of acute laminitis.

Abnormal stance

Bounding digital pulse - take at fetlock or pastern

Abnormal heel growth

Change of angle, hoof rings

Stretched white line

Symptoms of chronic laminitis - rotation/sinking

Radiographs (x-rays) should always be taken when a horse has had, or is suspected of having had, laminitis. Many of the signs of chronic laminitis may not be seen until several weeks after laminar damage occurred, and not all of these signs will be seen - but the presence of any of these signs should be investigated.
See Chronic laminitis for more photos

Radiographic changes - rotation, distal descent
Abnormal hoof growth - heels grow quicker
Hoof rings wider at the heel
Change in hoof wall angle
Flared hoof wall, wall cracks
Bruising/blood in white line or wall
Stretched white line - deep black groove between wall and sole - laminar wedge
Depression just above the coronet - swelling at the coronary band
Bruising on the sole in front of the frog (below tip of P3)
Thin sole (or may be thickened sole)
Bulging/convex/dropped sole
Penetration of sole by pedal bone (P3)
Collateral grooves much deeper at back of frog than at apex.

Emergency treatment for laminitis

call vet (and farrier/trimmer)
remove horse from grass (but move as little as possible/support feet before moving)
confine on deep supportive bedding e.g. sawdust, shavings, possibly sand (but abrasive for horses lying down a lot, and risk of ingestion)
support the feet if the bedding isn’t sufficient to do this, e.g. with EVA foam, dental impression material, boots and thick soft pads (Easycare Cloud boots come with soft thick pads)
give NSAIDs e.g. Bute, Danilon, Equioxx to reduce pain as directed by vet, for as short a time as possible. All NSAIDs have potential side effects. Remember inflammation is not the cause of most laminitis.
for sepsis related laminitis, under veterinary supervision only apply cryotherapy (cold therapy) to the feet. Although cryotherapy has reduced lamellar lesions in experimentally-induced hyperinsulinaemia associated laminitis, it is not known whether cold therapy would be beneficial for naturally occurring HAL.

Management of laminitis

Feed low NSC (<10%) diet based on grass hay (+ protein, minerals, vitamins, linseed?) - do not starve
Diagnose the cause – test blood for insulin & glucose EMS plus ACTH for PPID
Treat the cause - pergolide for PPID, diet and possibly Metformin for EMS
lateral x-rays to assess damage and movement of the pedal bone
trim hooves & realign any rotation ASAP

Prevent and monitor for laminitis

Prevent laminitis by ensuring your horse

is not overweight,
is regularly exercised (as long as feet are correctly aligned and stable),
and if laminitis is a possibility, feed a low sugar/starch diet and restrict grass by using a muzzle, strip grazing or setting up a track, and allow grazing only when sugar levels are likely to be lowest - remember sun = sugar! If in doubt, don't graze! See www.safergrass.org for information about sugar levels in grass.

Daily checks that can help early identification of laminitis:

Walk on hard ground e.g. concrete - does the stride shorten, does he/she seem at all "pottery"?
Turn in a tight circle - normal or reluctant to turn/stiff behind?
Digital pulses - normal?
Regional fat pads - cresty neck, bulges in hollows above eyes, enlarged sheath, fat above tail? Hardening of neck crest or increase in any of these fat deposits can indicate imminent laminitis.

Disclaimer: The information, suggestions and links (hereafter referred to as “information”) contained in this website are provided for information purposes only and should not be relied upon nor replace professional veterinary advice. Information is non-veterinary, is based as far as possible on current research, does not constitute advice or diagnosis, and should be discussed in full with all relevant vets and hoofcare or other professionals. No responsibility is taken for the accuracy or suitability of information contained in this website, and no liability accepted for damages of any kind arising from use, reference to or reliance on any information contained in this website. If you suspect your horse has laminitis or is ill, please consult your vet.