Sidebone (Collateral cartilage ossification)
Sidebone is ossification of the collateral cartilages of the distal phalanx (coffin bone) — a firm swell at the coronary band or quarters, not ringbone in the pastern or coffin joint, not a splint on the cannon, and not quittor (infection of those same cartilages). A photograph cannot diagnose sidebone. A still cannot tell sidebone from ringbone, a sprain, windpuffs, quittor swell, or a fracture. Diagnosis is a vet exam, often radiographs. The conformation scan is a first look at the coronary-band / quarter swell, not a verdict that your horse has sidebone, and there is no sidebone scanner.
Symptoms to watch for
A firm, bony swell just above the coronary band, on one or both quarters (the sides of the foot)
Heat, filling, or pain over the quarter or coronary band (an active, inflamed cartilage), or a cold, hard bump that has been there a while
A shorter, pottery stride, especially on hard ground or tight circles
Reluctance to land, turn, or work on that limb
Swelling around the coronary band or quarter that can look like ringbone, a sprain, windpuffs, quittor, or a fracture
Some horses stay even at walk; the first sign is a firm coronary-band / quarter swell after work — a reason to book a vet, not a photo verdict
Common causes
- Ossification of the collateral (ungual) cartilages of the distal phalanx (coffin bone) — bony remodeling of those cartilages can follow
- Concussion, upright conformation, age, or heavy work on hard ground — the work is a clue, not a diagnosis
- Draft or heavier horses, or an old sprain or trauma to the collateral cartilage
- Not ringbone (pastern or coffin osteoarthritis), not a splint (cannon / MC2–MC4), not quittor (cartilage infection), not windpuffs, and not a fracture — a still cannot tell sidebone from ringbone, a sprain, windpuffs, quittor swell, or a fracture, 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 coronary band and quarters for a new firm swell, heat, or filling and rest rather than working through it
- Do not treat a photo, a coronary-band / quarter swell, or a scan result as a diagnosis
- Conformation photos can help you and your vet look at the coronary-band / quarter swell — they do not confirm or rule out sidebone, and they cannot tell sidebone from ringbone, a sprain, windpuffs, quittor swell, or a fracture
What to do
- 1
Book a vet visit if you find a firm swell at the coronary band or quarters, 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 coronary-band / quarter swell hoping it will settle.
- 3
Photograph the coronary-band / quarter swell 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 coronary-band / quarter swell to share, not as a sidebone test. There is no sidebone scanner.
- 5
If sidebone (collateral cartilage ossification) 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 swell at the coronary band or quarters, if the swell 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 sidebone. A still cannot tell sidebone from ringbone, a sprain, windpuffs, quittor swell, or a fracture. Diagnosis is a vet exam, often radiographs. The conformation scan is a first look at the coronary-band / quarter swell, not a verdict, and there is no sidebone scanner.
Related topics
Get a first look at the coronary-band / quarter swell
Scan conformation in HorseCare. 5 free scans this month, then Pro.
5 free scans this month, then Pro. Scans run in the HorseCare app.
Educational content only. Not a substitute for veterinary advice.