Splints (Splint-bone periostitis)
Splints — splint-bone periostitis — is inflammation or bony exostosis of a splint bone (MC2/MC4 or MT2/MT4), often noticed as a firm bump on the cannon. A photograph cannot diagnose splints. A still cannot tell a hot (active) splint from a cold (inactive) bump, a splint-bone fracture, cellulitis, or other lower-leg swelling. Diagnosis is a vet exam, often radiographs. The conformation scan is a first look at the cannon-bone bump, not a verdict that your horse has splints, and there is no splints scanner.
Symptoms to watch for
A firm bump on the cannon — usually the inside of a front cannon (MC2) or on MT2/MT4 behind
Heat, filling, or pain over the bump (a hot, active splint), or a cold, hard bump that has been there a while
A shorter stride or reluctance to work on that limb, especially after a sudden increase in work
Swelling along the inside or outside of the cannon that can look like cellulitis, a bowed tendon, or stocking-up
Some horses stay even at walk; the first sign is a firm cannon bump after work — a reason to book a vet, not a photo verdict
Common causes
- Inflammation of the periosteum of a splint bone (MC2/MC4 or MT2/MT4) — bony exostosis can follow
- A sudden increase in work, concussion on hard ground, or a knock to the cannon — the work is a clue, not a diagnosis
- Young horses in early training, or conformation that loads the medial cannon
- Not cellulitis (a bacterial limb infection), not a bowed tendon (flexor tendinitis), and not ordinary stocking-up — a still cannot tell a hot (active) splint from a cold (inactive) bump, a splint-bone fracture, cellulitis, or other lower-leg swelling, and those need a vet
Prevention
- Warm up before hard work and build speed and jumping gradually
- Match the work to the footing — avoid sudden heavy work on hard ground
- Watch the cannon for a new firm bump, heat, or filling and rest rather than working through it
- Do not treat a photo, a cannon bump, or a scan result as a diagnosis
- Conformation photos can help you and your vet look at the cannon-bone bump — they do not confirm or rule out splints, and they cannot tell a hot (active) splint from a cold (inactive) bump, a splint-bone fracture, cellulitis, or other lower-leg swelling
What to do
- 1
Book a vet visit if you find a firm cannon bump, heat, or filling. Diagnosis is a vet exam, often radiographs — not a photograph.
- 2
Stop work. Rest the horse and do not ride through a hot, painful cannon bump hoping it will settle.
- 3
Photograph the cannon-bone bump in good light and keep it on the horse's record so you and the vet can see change over time — a first look to share, not a diagnosis.
- 4
Use a conformation scan only as a first look at the cannon-bone bump to share, not as a splints test. There is no splints scanner.
- 5
If splint-bone periostitis is confirmed, follow the plan your vet prescribes — that may include rest, controlled exercise, or further imaging. Do not start a treatment protocol from a photo.
- 6
Keep the vet on the same page. Share what you see; do not treat a photo as a verdict.
Pick up the phone if…
Schedule a vet visit if you find a firm bump on the cannon, if the bump is hot or painful, if the horse is short on that limb, or if filling appears after work. Call sooner if the horse will not bear weight, the limb is suddenly very swollen, or the horse is dull or off feed. A photograph cannot diagnose splints. A still cannot tell a hot (active) splint from a cold (inactive) bump, a splint-bone fracture, cellulitis, or other lower-leg swelling. Diagnosis is a vet exam, often radiographs. The conformation scan is a first look at the cannon-bone bump, not a verdict, and there is no splints scanner.
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Educational content only. Not a substitute for veterinary advice.