Many affected horses regain a normal state of soundness, with perhaps only a small bump on the leg remaining as a reminder of the injury. | Photo: Paula da Silva/www.arnd.nl

There is a bit of benign confusion about the area of the horse’s legs that house what most horse owners call the “splint bones.” On each side of the metacarpal or metatarsal bones (cannons front and back) is a small bone that is commonly called the “splint bone.” Each is attached to the cannon by an interosseous (between bone) ligament, thus the two small bones “splint” or support the large bone. (Now, probably for the first time, you know why that area got its name.) For many years, horse owners and veterinarians thought these were just remnants of toes from the prehistoric horse, but the splint bones–known as the second and fourth metacarpal (front legs) or metatarsal (hind legs) bones–provide considerable support to the cannons.

When a horse “pops a splint,” it can be painful to the animal and unsightly as well. The good news is that, generally speaking, the prognosis for a return to normal activity is positive. There are times, however, when problems with these small bones and their connections to the cannon bone can interfere with normal athletic endeavors. Following, you will find information on the area in question, the common problems associated with it, and treatments to alleviate those problems.

Splint Bone and “Popped Splint” Anatomy

The splint bones start at the knee in the front legs and run downward along the cannon bones. They are larger at the upper end that begins at the knee joint than they are at the lower or posterior end that stops about three-fourths of the way down the cannon