High severity

Bone spavin (Lower-hock osteoarthritis)

Bone spavin is osteoarthritis of the lower hock (distal intertarsal / tarsometatarsal joints) — often a hard bony bump on the inside of the lower hock, not bog spavin (soft tarsocrural effusion), not a capped hock, not curb, not osselets in the fetlock, and not ringbone in the pastern. A photograph cannot diagnose bone spavin. A still cannot tell bone spavin from bog spavin, a capped hock, curb, a sprain, or a fracture. Some horses have no visible bump (occult bone spavin). Diagnosis is a vet exam, often radiographs. The conformation scan is a first look at the lower-hock bump, not a verdict that your horse has bone spavin, and there is no bone-spavin scanner.

Symptoms to watch for

A hard bony bump on the inside of the lower hock (the distal intertarsal / tarsometatarsal joints), not a soft fluid swell higher on the hock

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

A shorter stride with less hock flexion; the toe may drag, especially after rest or on circles

Reluctance to flex that hock, land, or work on that limb — lameness that may ease with work and return after rest

Lower-hock swelling that can look like bog spavin, a capped hock, curb, a sprain, or a fracture — or no visible bump at all

Some horses stay even at walk; the first sign is a hard lower-hock bump or a shorter hock stride after work — a reason to book a vet, not a photo verdict

Common causes

Osteoarthritis of the distal intertarsal and/or tarsometatarsal joints — bony remodeling on the inside of the lower hock can follow
Concussion, hard or fast work, sickle or cow hocks, or incomplete ossification of the distal tarsal bones — the work and the shape are clues, not a diagnosis
Not bog spavin (tarsocrural effusion), not a capped hock, not curb (plantar tarsal ligament), and not thoroughpin
Not osselets (fetlock traumatic arthritis), not ringbone (pastern osteoarthritis), and not a sprain or fracture of the hock — a still cannot tell bone spavin from those, and those need a vet

Prevention

Warm up before hard work and build hock-heavy work gradually
Match the work to the footing — avoid sudden heavy or fast work on hard ground
Watch the lower hock for a new hard bump, heat, or a shorter hock stride and rest rather than working through it
Do not treat a photo, a lower-hock bump, or a scan result as a diagnosis
Conformation photos can help you and the vet look at the lower-hock bump — they do not confirm or rule out bone spavin, and they cannot tell bone spavin from bog spavin, a capped hock, curb, a sprain, or a fracture

What to do

1
Book a vet visit if you find a hard bump on the inside of the lower hock, heat, or a shorter hock stride. Diagnosis is a vet exam, often radiographs — not a photograph.
2
Stop work. Rest the horse and do not ride through a hot, painful lower-hock bump hoping it will settle.
3
Photograph the lower-hock 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 lower-hock bump to share, not as a bone-spavin test. There is no bone-spavin scanner.
5
If bone spavin (lower-hock osteoarthritis) is confirmed, follow the plan your vet prescribes — that may include rest, controlled exercise, joint medication, 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 hard bump on the inside of the lower hock, if the swell is hot or painful, if the horse is short on that limb, or if the hock stride shortens 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 bone spavin. A still cannot tell bone spavin from bog spavin, a capped hock, curb, a sprain, or a fracture. Diagnosis is a vet exam, often radiographs. The conformation scan is a first look at the lower-hock bump, not a verdict, and there is no bone-spavin scanner.

Get a first look at the lower-hock bump

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.