Chronic laminitis

Chronic laminitis is defined as the rotation or sinking (distal descent) of P3 (the pedal bone/coffin bone).

Distal descent - the distance between the top of the extensor process of P3 and the coronet. This horse has got rotation and significant distal descent.

Divergent hoof rings and a stretched or separated white line (sometimes with signs of blood or serum) are generally accepted as signs of chronic laminitis, and x-rays should always be taken if these signs are seen.

Symptoms of chronic laminitis

Abnormal hoof growth - this is extreme but does happen when feet are neglected. See Cedar's amazing rehab for a happy ending.

Reduced angle at hairline due to high heels

Heels grow quicker than toes, often causing a "boxy" appearance to the hoof with the hair line straighter than normal from toe to heel when viewed from the side (yellow line - left).Compare to the well trimmed laminitic hoof with sloping hair line (red line - right).

Sloping hairline

Rings are wider at heel than at toe (red lines)

Hoof rings lower to the ground at the heels

Divergent hoof rings - rings are wider or lower at the heels than at the toes.Rings on the hoof wall from coronet to ground are an indicator of ongoing chronic/endocrinopathic laminitis.Horses with distal descent (sinking) often have a hoof ring the same distance from the coronet the whole way around the hoof.It takes a minimum of 3 months for new divergent hoof rings to be seen following laminitis (1).Horses can have growth rings as a result of changes in diet or environment rather than laminitis - these will not be divergent.

Thin sole (above) or thick sole (below) - thickened sole seems to be more common in ponies.Sole thickness can be estimated by measuring the collateral groove depth.

Large difference in collateral groove depth between front and back of frog.For most horses a good collateral groove depth at the apex of the frog (measured to the sole by the white line) will be 10-20 mm - less than 10mm is likely to indicate a thin sole; and 15-30 mm at the deepest part (usually near the bars). The greater the difference between the collateral groove measurement at the apex and the back of the frog, the greater the palmar angle and therefore P3 rotation.

Frequently Asked Questions

Is it the bone or the hoof that moves?

Some people consider that phalangeal/bony rotation (rotation of P3) and capsular rotation (rotation of the hoof capsule) are separate issues. Others consider that there will always be a bit of both.Robert Eustace (1) says that he prefers to think of an increase in founder distance as proximal (upwards) displacement of the hoof in relation to P3, rather than distal (downwards) displacement of P3, because there is no evidence of increased tension in the DDFT or muscle following relative displacement.

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