Hoof ridge?

[Mouse&Bay]

I have just noticed this on one of mine, does anyone have any information on why a vertical ridge like this would form?

I don’t think it was there before, seemingly just showed up and I’m curious if anyone has an explanation as to why.

 

[Britestar]

It suggests an injury to the coronary band at some point.

It would be some time ago as it's grown nearly all the way down so at least 6 months ago.

 

[ycbm]

As above, possible coronet band injury. They can also appear when the foot is unbalanced, can you give us a view from dead on in front with the camera almost in the dirt?
.

 

[Pinkvboots]

Has the horse had laminitis in the past?

I only ask because of the bulging at the side near the heel and the horizontal lines often get wider there.