High severity

Osselets (Fetlock traumatic arthritis)

Osselets are traumatic arthritis / periostitis of the fetlock (metacarpophalangeal joint) — often a firm swell on the front of the fetlock in a young horse in hard work, not ringbone in the pastern or coffin, not a splint on the cannon, not sidebone at the coronary band, and not a bowed tendon. A photograph cannot diagnose osselets. A still cannot tell osselets from a sprain, windpuffs, a chip fracture, or ordinary fetlock filling. Diagnosis is a vet exam, often radiographs. The conformation scan is a first look at the fetlock swell, not a verdict that your horse has osselets, and there is no osselets scanner.

Symptoms to watch for

A firm swell on the front of the fetlock (often both fronts in a young horse in hard or fast work)

Heat, filling, or pain over the fetlock (an active, inflamed joint), or a cold, hard bump that has been there a while

A shorter, pottery stride, especially on hard ground or after speed work

Reluctance to land, turn, or work on that limb

Fetlock swelling that can look like a sprain, windpuffs, a chip fracture, or ordinary fetlock filling

Some horses stay even at walk; the first sign is a firm fetlock swell after work — a reason to book a vet, not a photo verdict

Common causes

Traumatic arthritis / periostitis of the fetlock (metacarpophalangeal joint) — bony remodeling on the front of the joint can follow
Concussion, hard or fast work, or a sudden increase in speed work on hard ground — the work is a clue, not a diagnosis
Young horses in training, or an old sprain or chip in that fetlock
Not ringbone (pastern or coffin osteoarthritis), not a splint (cannon / MC2–MC4), not sidebone (collateral cartilage ossification), not a bowed tendon, not windpuffs, and not a chip fracture — a still cannot tell osselets from a sprain, windpuffs, a chip fracture, or ordinary fetlock filling, 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 or fast work on hard ground
Watch the fetlock for a new firm swell, heat, or filling and rest rather than working through it
Do not treat a photo, a fetlock swell, or a scan result as a diagnosis
Conformation photos can help you and your vet look at the fetlock swell — they do not confirm or rule out osselets, and they cannot tell osselets from a sprain, windpuffs, a chip fracture, or ordinary fetlock filling

What to do

1
Book a vet visit if you find a firm swell on the front of the fetlock, 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 fetlock swell hoping it will settle.
3
Photograph the fetlock 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 fetlock swell to share, not as an osselets test. There is no osselets scanner.
5
If osselets (fetlock traumatic arthritis / periostitis) are 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.

When to call the vet

Pick up the phone if…

Schedule a vet visit if you find a firm swell on the front of the fetlock, 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 osselets. A still cannot tell osselets from a sprain, windpuffs, a chip fracture, or ordinary fetlock filling. Diagnosis is a vet exam, often radiographs. The conformation scan is a first look at the fetlock swell, not a verdict, and there is no osselets scanner.

Get a first look at the fetlock swell

Scan conformation in HorseCare. 5 free scans this month, then Pro.

Scan conformation

5 free scans this month, then Pro. Scans run in the HorseCare app.

Educational content only. Not a substitute for veterinary advice.