Lightly paring the sole of the hoof may reveal the exact location of a bruise.

I have a gelding who had what seemed like an abscess in his hind foot. He wasn’t dead lame, but he did respond negatively to pressure from the hoof testers and had heat and swelling in his leg. We did an Epsom salt dressing, and the next day I saw obvious bruising in his hoof. I applied light pressure to the bruise, thinking I would open a pus-filled abscess. Instead, the sole opened with very little pressure and started bleeding—but no pus. I’ve never seen anything like this before and am wondering what it is and how to treat it.
JA/via the Internet

Dr. Kellon replies: The most likely explanation for this is a severe bruise. When working or playing on hard, uneven ground, your horse may have come down heavily on a hard object. There is a rich network of blood vessels under the sole in the area of the bottom of the coffin bone. With a severe bruise, the damaged vessels can bleed into this space causing pressure and pain. It’s also possible the bleeding may have been caused by a puncture wound. Much less likely, particularly with a problem in only one hind foot, is laminitis with rotation.

Treat the open area exactly like you would an abscess by keeping it clean and protecting it until it heals. If the horse does not show rapid improvement now that the pressure is relieved, call your veterinarian. Also call your vet if heavy drainage continues, or if the color or odor of the drainage changes.