Why splints form
Q:
I have a 6-year-old, off-the-track Thoroughbred that I’m retraining for the hunter show ring. The problem is he keeps popping splints. He’s had three in the past 18 months: two on one leg and one on the other. He goes lame when they first show up and are soft. With ice and bute and rest, the lump hardens and he’s sound again, but we lose a lot of training time. Are recurring splints a sign of weakness in the bone? Will he eventually grow out of this? Is there anything I can do to prevent them? Name withheld by request
A:
“Splints” is the colloquial term for a boney reaction involving the small second or fourth metacarpal/ tarsal bones adjacent to the cannon bone. As you correctly state, the condition is often painful initially but typically subsides quickly as new bone is formed to stabilize the area.
As for causation, in most cases mild instability between the bones results in inflammation and callus (bump) formation. When these are
“set” (that is, a mature bone callus has formed), the “splint” typically doesn’t bother the horse. I’d also note that, as horses age, the ligamentous union between these bones naturally mineralizes so not all splints cause lameness. In your horse’s case, however, acute re-injury seems to be occurring in various areas.
“Bench” knees (offset knees) and other knee conformation abnormalities make splints more likely because they result in asymmetries in the forces travelling down the leg. When recurrent splint episodes occur, especially in adult horses, conformation needs to be assessed to determine the risk of future episodes in the same or other limbs. Input from a remedial farrier may