Overview

Laminitis is classified by cause and stage. Endocrine laminitis (most common in horses with EMS or PPID) — insulin dysregulation causes laminar vasculopathy and weakening. Sepsis-related laminitis — inflammatory cascade from systemic illness (colic, metritis, pneumonia, grain overload) causes blood diversion away from laminae and ischemia. Supporting limb laminitis — chronic overload when the opposite limb is non-weight-bearing (fracture, severe injury). The Obel grading system is used to classify stages: Grade 1 (subtle lameness, weight shifting), Grade 2 (obvious lameness, shortened stride), Grade 3 (marked lameness, reluctant to move), Grade 4 (recumbent, cannot stand). Lateral hoof radiographs are essential for staging — measuring the distance from the hoof wall to the extensor process and the angle of the pedal bone relative to the hoof wall quantifies rotation and displacement.

Common Clinical Signs

Weight shifting between front feet (classic sign) Reluctance to turn (increases hoof loading) Bounding digital pulse (palpate palmar digital arteries) Hoof temperature elevated (hot to the touch) Pain response to hoof testers applied over the toe Standing with front legs stretched forward (relieving laminae pressure) Severe lameness (3-4/5) in both front feet or all four Standing with front feet planted under body (if sinking) Recumbent position (Grade 4)

Diagnostic Approach

Diagnostic Test Findings & Interpretation
Clinical Examination + Lameness Grade Obel grading (1-4) based on clinical signs. Observe the horse standing and moving — note weight-bearing distribution, gait, foot placement. Palpate for digital pulse character and hoof wall temperature.
Lateral Radiographs (Both Front Feet) Essential for diagnosis and prognosis. Measure pedal bone angle (normal: 0-5° dorsal rotation vs hoof wall). Measure coronet-hoof wall distance at toe (increased = sinking). Measure distance from pedal bone to hoof wall (increased = displacement). Serial radiographs track progression or improvement.
Venography (Contrast Radiography) Contrast agent injected into the dorsal common digital vein and radiographed. Evaluates laminar blood supply — areas of non-filling indicate vascular compromise. Used in refractory or severe cases to guide treatment decisions and prognosis.
Bloodwork (EMS/PPID workup) Insulin testing (resting insulin, oral sugar test) — insulin >100 µIU/mL at rest is diagnostic for insulin dysregulation. ACTH for PPID (normal varies by season — higher in fall). Triglycerides, liver enzymes, fibrinogen to assess systemic inflammation in sepsis-related laminitis.
Hoof Tester Examination Apply over the toe region of each foot. Pain on toe testers is a key diagnostic indicator supporting laminitis. Document the response (mild/moderate/severe) for baseline tracking.

Differential Diagnoses

  • Subsolar abscess — Often sudden onset, single foot, marked lameness. Hoof testers may be diffusely painful. Radiographs show no rotation. Resolves with abscess drainage and packing — excellent prognosis.
  • Navicular syndrome (Palmar foot pain) — Bilateral forelimb lameness, subtle. Pain on flexion of distal limb. Hoof testers typically negative over toe. Responds to diagnostic nerve block of the palmar digital nerves. No coffin bone displacement on radiographs.
  • Distal interphalangeal joint osteoarthritis — Chronic lameness with joint effusion. Positive flexor flexion. Radiographs show joint space narrowing and osteophytes. Laminitis ruled out by normal coffin bone alignment.
  • Distal phalanx fracture — Acute onset, usually single foot, severe lameness. Often history of kick or traumatic event. Radiographs confirm fracture — may show fragment or depression fracture at the solar margin.

Treatment & Prevention

Acute phase: Strict box stall rest with deep sand or shavings bedding (allows the foot to conform). NSAIDs (phenylbutazone at 4.4 mg/kg BID for 5-7 days, then taper) for pain and inflammation. Cryotherapy (ice boots for 30-60 min q4-6h in first 72 hours) — shown to reduce laminar inflammatory mediators. Vasodilators: acepromazine (0.02-0.05 mg/kg IM/TQ q6-8h) — improves laminar blood flow. Topical nitroglycerin ointment (2% NTG applied to coronary band) for vasodilation. Therapeutic shoeing — heart bar shoes, reverse shoes, or custom orthotics to redistribute load. Endocrine laminitis management: Diet (no grazing, low-NSC hay, balancer feed) + exercise for EMS. Pergolide (Dopar) for PPID. Prevention: Manage insulin with diet and exercise in EMS horses. Keep at-risk horses off lush pasture. Regular hoof care and balancing. Routine PPID screening in horses >10 years.