Grading of lameness associated with laminitis – the higher the grade, the greater the risk of permanent damage to the laminae of the feet. For example, if laminitis is not recognised until the horse reaches grade 3, then significant laminar degeneration may have already occurred, and the treatment and recovery phases will be longer than for grade 2 with a poorer overall prognosis for return to 100% soundness.
Grade 1: The horse seems uncomfortable, shuffling or lifting its feet repeatedly. It walks and picks up its feet willingly.
Grade 2: The horse moves willingly at a walk but the gait is characteristic of laminitis (landing heel first and wide). The horse does not resist lifting a foreleg.
Grade 3: The horse moves reluctantly and vigorously resists attempts to lift a forefoot because of pain in the opposite foot.
Grade 4: The horse must be forced to move and may be recumbent much of the time (lays down).
Mild laminitis grade 1 – 2 will have moderately increased digital pulses and warmth in the feet. The horse may shift its weight from foot to foot, there is mild lameness and the toe area of the hoof wall and sole may be sensitive to pressure. The symptoms often resolve without permanent laminar damage.
Severe laminitis grade 3 – 4 when all four feet are affected the horse will often lay down for long periods and when it does stand it has the hind feet up under the body to carry more of its weight. The hooves feel warmer and have bounding digital pulses. Anxiety, muscle tremors and increased respiratory and heart rates may be observed. The horse is very lame.
Sinking of the distal phalanx is more likely to occur if the horse is systemically ill. Cavitation or depression along the coronary band may be the first clinical sign. Over time, blood or serum may ooze from the coronary band and the sole will appear flatter. Laminar damage and chronic effects are likely.
Treatment should commence immediately. Sensitivity to hoof testers around the wall and sole varies. The horse may appear lame, but not necessarily sick. It may not show any of the classical symptoms or observe the rules of laminitis. Usually, the horse becomes progressively worse over a period of hours or days, with obvious distress if forced to walk. The coronary band at the toe and area just above it feels soft and swollen. A depression felt behind the coronary band at the toe indicates sinking of the pedal bone lower into the hoof capsule due to loss of laminitic bond. The further back towards the heels this is felt, the more severe the loss of laminitic bond. Discharge or rupture of the coronary band is seen only in the most damage is.
Many mild cases of laminitis are confused with loss of form in the horse’s usual activity, shoeing problems or bad temperament as the horse becomes disgruntled and miserable. When the laminitis is treated correctly, movement and personality both improve. The acute stage can last from hours to weeks, depending upon the severity of laminitis and speed of treatment.
Over a period of 2 – 6 weeks, the first chronic signs start to show as an inward ring just below the coronary band, growing down with the wall. Bruising in the sole and white line grow down to the ground surface and can be seen when the hoof is trimmed. In mild cases this confirms the diagnosis.