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Martha from Washington, writes:

Dear Dr. Dave,

Can horses get outside splints? My 10 year-old gelding got pea sized bumps on his outside cannons last fall. He has had a real rough year and just came back from some virus that was going around after being at a cow horse trainer's. He was also treated for ulcers (he hates cows that much). So, we got a late start on him this year.

I have only run him a handful of times this year but his bumps on his legs are getting bigger. The one on his right cannon is 2-3" long and the one on his left is half that. He isn't obviously lame yet but seems achy and his stride seems to have shortened. I have a call out to my vet but would love to have your opinion also. I have been putting liniment on his legs and magnets.

Hello Martha,

Thank you for your great question about splints.

How many years has your horse been running barrels? Is he strictly a barrel horse or is he an "all-around" horse used for several disciplines? Was your horse at the trainer's for cattle work or for a generalized "tune-up?" Are the lumps on the actual splint bones themselves, or are they on the lateral sides of the cannon bones not involving the splint bones?

I know, so many questions, and so few answers. However, all this information is necessary for me to fully understand the situation and provide you with a sensible response.

The difficulty in discussing splints is that it is very confusing. Every horse has two splint bones per leg, one on each side of the cannon bone, usually referred to as a "splint bone." If a bump or a lump appears on the splint bone, then that is called a "splint." So now we have a "splint" on a "splint bone." Horsemen never make things easy!

In the young and physically immature horse, the splint bones are attached to the cannon bone by very strong interosseous ligaments. As the horse matures, the ligaments solidify into bone, in a sense seamlessly "welding" the splint bone to the cannon bone from the top downwards.

As I am sure you are aware, most "splints" occur on the medial splint bones. It is infrequent they appear on the lateral splint bones. Medial splints usually occur either from trauma or shear forces. Trauma typically occurs when the opposite hoof hits the medial splint bone causing a bruise. (I always think about when I've hit my shin on the trailer hitch, and how much that hurts!) The periosteum that covers the bone then reacts with inflammation and swelling, which in turn creates a boney lump, a "splint."

Splint creating shear forces occur with less than acceptable carpal conformation, usually "bench knees." When the cannon bone is not situated directly beneath the radius it puts an undue stress on the medial splint bone, stretching and tearing the attaching interosseous ligaments. In an attempt to strengthen the attachment of the splint bone to the cannon bone the body responses with boney "spot welds" creating "splints." This rarely occurs on the lateral splint bones.

Splints can also occur due to an actual fracture of the splint bone, but this is typically more painful than your horse is experiencing.

Horse people sometimes classify splints as being either hot or cold. Hot splints are fresh new occurrences and painful when palpated. As the inflammation subsides and boney formation develops, the splints turn cold and are typically not painful. However, if the splint is situated on the backside of the splint bone, it can interfere with the suspensory ligaments causing discomfort. But that's another story for another day.

So back to your question and your horse. As stated, it is atypical for a horse to form outside (lateral) splints. If your horse is conformationally correct, the only way I could picture lateral splints occurring would be from trauma, either from being hit or kicked. I have seen horses stand next to a panel or pipe fence and repeatedly paw or strike, usually playing with the horse on the other side, or because they are anxious to be fed. I suppose also a horse could get jumbled up on the back side of a barrel and reach up with a hind foot to hit the front lateral splint bone, but I think that would be exceptionally rare.

You mentioned your horse wasn't obviously lame but did appear a little "achy" and has a shortened stride. In my dictionary your horse is lame. Your horse is telling you things aren't right and that he hurts. Maybe not "head bobbing" lame, but anything less than 100% sound is lame in my book. I commend you for being observant and taking him to your veterinarian for further evaluation. Thank you for being a caring owner.

P.S. I use magnets for picking up nail nibs in my shoeing area and holding pictures on our refrigerator. I have found no use for them on my horses.

Best of luck and I hope you uncover the cause of your horse's splints.

Good Ground and Fast Times,

Dr. Dave