On the list of injuries a horse might acquire, “popping a splint” is considered, at most, an inconvenience that requires laying the affected horse off his normal routine. However, when it keeps happening, that little inconvenience can become a major nuisance and perhaps a surgical problem.

Where the “popped splint,” or splint exostosis, occurs along the length of the bone is the key to the amount of concern it should cause the owner. The horse’s splint bone is actually what is left of what was once one of his toes. The bone is still there, it just no longer reaches the ground. It still carries weight passed down to it by the carpus (knee).

A popped splint occurs where the splint bone attaches to the cannon bone. The load from weight bearing causes a tear of the ligamentous attachment between the splint bone and the cannon bone. Calcium then builds in the affected area–the body’s repairing mechanism–and attaches the splint to the cannon bone by creating new bone in between. Problem solved naturally, if the injury is near the top of the bone.

If the splint “pops” and heals in the middle portion of the bone, it is more vulnerable to re-injury than a normal (higher) popped splint. Although the horse’s body dutifully sets about repairing the area with calcium, the calcium is more brittle than the ligament attachments above and below the fracture. So, as the horse goes back to work after the lameness has subsided, the repairing calcium cracks and breaks. Then you’re back to square one–or maybe even worse than the first time. In the normal splint exostosis, the healing attachment is high on the bone, very near the site of weight transfer to the splint bone, which is stronger. In the mid-splint exostosis, there is a long mobile piece of splint bone between the site of weight application and the site of attachment to the cannon bone, increasing the stress