I admit I am no horsewoman ... to the point where I chose not to read Black Beauty as a child, because it was quite obviously at the root of an evil that sickened me (I grew up in the Blue Mountains, and saw plenty of half- and fully-starved animals neglected or abandoned in pokey little stables on bush blocks that the owners might or might not be able to get to a couple of times a week, or released into the bush by people who couldn't afford to/didn't want to put them down, and thought little about the welfare of their own pet, and much less about the survival of endangered endemic plants and animals).

All my knowledge comes from early nineteenth century veterinary/farrier books (just the parts about lameness) to see what Jane Austen and her readers might believe caused lameness, and what clues they provided about the geography of Highbury (I had planned to map Highbury for my GR focus, but it is too involved for a mere eight weeks). I doubt allowing a horse to drink water or eat clover as it sees fit, is likely to cause lameness, any more than changing its stockings as soon as it gets home is likely to prevent it catching cold, and I suspect even Black Beauty has not done as much to advocate animal cruelty as some of these books - I do not recommend their cures, and have learnt better than to offer my own universal remedy.

I got the impression from these books that founder was an inflammation of the soft tissue of the hoof, that it took a lot of time and care to treat, did not always respond to treatment, that the damage done was irreversible but if left untreated, the tissue would become necrotic and the horse would die.

As you say, there are many causes of lameness in horses, but I did not bother with certain types (eg. Arthritis, poor shoeing, excessive trimming of hoof,splents) because they did not provide clues to the personalities and geography of Highbury. Pebbles, sticks and holes I did consider - but it seemed a pebble in the hoof or a sprain would not keep a horse lame for a whole month after it had been identified and treated (unless it got infected).

Founder (Laminitis) and Mud Fever (Rain Scald) were two causes of lameness that I liked because they fitted in with the horse being in a particular part of Highbury that I believe Jane Austen was laying clues down about right from the beginning of Emma ("Dirty, sir! Look at my shoes. Not a speck on them."(1)) to the end (spoiler quote deleted)