Moderate

White line disease

White line disease is an infection of the white line and inner hoof wall — the junction between the sole and the wall — not the frog. That is thrush. Moisture, poor horn, and packed debris let opportunistic organisms hollow out the wall from the inside. A photograph cannot diagnose white line disease, and the app scan is a first look at the hoof, not a verdict that your horse has white line disease.

Symptoms to watch for

A crumbly, chalky, or powdery white line when the foot is picked or rasped

A gap, hollow, or dark tract along the white line, often at the toe or quarters

Soft, cheesy, or crumbling horn under the wall rather than a solid connection

A wall that sounds hollow or looks separated from the sole in more advanced cases

Lameness only when the wall is badly undermined or an abscess forms — many horses stay sound

Common causes

Wet-dry cycling and prolonged wet standing that soften the white line
Debris packed into a stretched or opened white line
Long toes, poor balance, or infrequent farrier care that stresses the wall
Poor-quality or previously damaged horn after abscess or laminitis
Opportunistic bacteria and fungi that invade the inner wall once the white line is open
Not the same condition as thrush, which lives in the frog sulci

Prevention

Pick out all four feet every day and look at the white line, not only the frog
Provide dry standing — well-drained turnout, clean bedding, and time for the feet to dry
Keep a regular farrier cycle so the toe stays short and the wall can stay connected
After wet work or muddy turnout, pick the feet and let them dry rather than leaving the white line packed
Ask your farrier to check the white line at each visit — early crumbling is easier to manage than a hollow wall
Do not treat a photo or a scan result as a diagnosis

What to do

1
Pick the foot thoroughly and look at the white line in good light — note gaps, crumbly horn, colour, and smell. This is not thrush: thrush is the frog.
2
Move the horse onto clean, dry standing. White line disease will not settle while the foot stays wet and packed.
3
Ask your farrier to explore and trim out loose or necrotic inner wall so the tract can be cleaned and aired. Do not dig into the wall yourself.
4
After the farrier has opened the area, keep it clean and dry and apply only a product your farrier or vet recommends.
5
Keep the treated foot dry between visits. Avoid packing the white line with wet mud or heavy grease that seals in moisture.
6
If the horse is lame, the wall is painful, you see pus or a deep hollow, or the separation is spreading, stop home treatment and call the vet.

When to call the vet

Pick up the phone if…

Call the vet if the horse is lame, if the wall is painful or draining, if you can see a deep hollow or pus, or if farrier care and dry standing have not improved the white line within one to two weeks. White line disease can be confused with thrush, a hoof abscess, or laminitis — those need a vet, not a photo guess.