Understanding splints

“Splints” is an oft-used term, but what exactly are they and how should they be treated? Phil Cramp MRCVS explains all

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FIRST, what exactly are splints? “Splints” is a common term used by vets, horse owners and professionals alike that refers to the splint bones. It can also be used – or in fact misused – even more specifically to refer to a lump or swelling that can form along the inside or outside of the cannon bone, as in, “My horse has a splint.”

“Splint bones” should correctly be called the second (medial) and fourth (lateral) metacarpal (front leg) or metatarsal (back leg) bones. These are the vestigial metacarpal/metatarsal bones that form integral parts of the supporting and stabilising structures of the horse’s leg. They are pretty significant and serve as a site for important ligament attachments (see figure 1, top right), which attach directly to the “splint bones”.

The medial splint bones form part of the joint with the carpus (knee) and the tarsus (hock) and weight is directly transferred through them. The same is true for the lateral splint bones, albeit far less so.

What do we mean when we say a horse has a splint? This refers to the swelling that you see, which will often feel like a hard bony swelling. It may appear suddenly, and may be very painful to the touch and make your horse lame.

THE CAUSES