Sinking Laminitis, Sinker

Sinking laminitis ("sinker") in horses denotes a condition resulting from the separation of the pedal (coffin) bone laminae from the layer of the inside of the hoof wall almost the whole way around the hoof. This results in loss of support for the horse's weight, and sinking of the pedal bone. Instead of the straight line from the front of the pastern onto the hoof, there is a depression around the coronary band most prominent at the toe. The horse will be lame for many months until new hoof growing down from the coronet re-establishes the laminal attachment.

Sinkers require specialized treatment by a remedial ferrier over many months and many do not respond. 1

Sinking of the pedal bone often cannot be prevented. Horse with sinking or displacement of the coffin bone have a poor prognosis. Attempting to prevent downward displacement of the pedal bone by putting pressure on the frog is ineffective. Trying to support the pedal bone by applying pressure to the sole, whether with a shoe, a pad, packing cast material, or bedding, causes severe pain and sole bruising. Medical treatment, corrective shoeing, or time to allow new hoof growth does not readily repair the lack of support that develops during this type of severe separation of the hoof and coffin bone. The only ways to help these horses when they will not lie down are to keep them on deep, dry bedding, provide pain relief, and treat the underlying cause. 2,3

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Key Terms

  • Laminae - the tissue inter-connection between the coffin bone and hoof wall
  • coronary band - the junction of the skin and the horn of the hoof
  • Pastern - the part of a horse's foot between the fetlock and hoof
  • Fetlock - a projection on the lower part of the leg above and behind the hoof


  1. Kieran O'Brien. Essential Horse Health
  2. Equine Research. Lameness: Recognizing and Treating the Horse's Most Common Ailment
  3. Nathaniel A. White II DVM MS, DACVS. Equine Laminitis

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