It might be easy to tell when a horse is noticeably lame, but finding the source of his pain isn’t always so simple.

“Horses are not able to tell us the region of pain, and sometimes there are no obvious signs of where the pain is coming from,” said Matthias Rettig, DVM, an equine veterinary surgeon at the Free University of Berlin, in Germany.

Veterinarians can use diagnostic analgesia (commonly known as nerve blocks) to help localize a lameness to a certain area. With this procedure, they desensitize the nerves in different areas of the horse’s leg, starting at the hoof and working slowly up the limb via carefully placed injections. Once a block is administered and takes effect, the veterinarians observes the horse trot. If a horse appears sound after a region is blocked, the practitioner evaluates that area as a potential pain source.

While nerve blocks are useful and effective in many cases, administering the analgesia can be challenging, especially in uncooperative horses