Join Date: May 2009
Location: Mid Northern TN
Where it is sensitive/bleeding depends a bit on where the tissues are in the horse. Which I am sure seems like an odd thing to say, so let me explain.
In a horse that has foundered (but not perforated or come through the sole), the tip of the coffin bone, with it's sensitive tissue and blood supply will be about an inch forward of the tip of the frog and milimeters from the ground as the horse is standing. In a different, non-foundered horse with a good thick sole, that same tip of the coffin bone might be two centimeters off the ground and well protected, but in other flat-footed horses it's somewhere in between. In a horse with chronic white line separation at the toe, the tip of the coffin bone might actually have dissolved from chronic pressure, so what's left is further back (towards the heel) than you would expect.
If there is a chronic issue, the foot will try to protect the area by growing more tissue and laying it down as armor, so the actual sensitive tissues may be deeper/farther back than you would normally expect compared to a healthy foot.