What is founder?

Founder is one of the most painful conditions a horse can encounter; and unfortunately it's all too common. If you've never heard of it before, in a nutshell, "founder" is inflammation inside of the hoof--it specifically affects the part of the hoof that attaches the wall (outside) to the bone inside.

Laminitis vs founder:

Sometimes used interchangeably, there is technically a difference between these two terms. Laminitis refers to the initial acute stages of the disease, where there is significant inflammation inside of the hoof. This can vary in severity, but generally requires veterinary attention (for pain relief and control of inflammation). The acute stages of laminitis can last from a few days to a few weeks, depending on the cause and severity. During this time most horses will have a very hard time walking, walk as if they are "walking on eggshells", and avoid putting weight on the affected hooves (usually both front).

The most challenging part of this disease is often the aftermath, referred to as founder. Founder actually comes from a Latin word that refers to the sinking of a ship. The reason we call it founder today is that it is commonly believed that the coffin bone actually "sinks" and/or rotates inside the hoof capsule. In fact it is a common practice to rate the severity of the founder by measuring the angle of rotation of the coffin bone. 

I'd like to propose a slightly different explanation, however. I believe it would be more accurate if we referred to the angle of rotation of the hoof wall itself, not the coffin bone. You see, the coffin bone cannot and does not actually go anywhere. Logically, as the base of the horses skeletal system, it cannot go anywhere. Let me just show you what I mean. 

If red is the hoof wall and blue is the coffin bone, here is a normal hoof. Note the front lines (a and b) are parallel. The bottom lines (1 and 2) are also parallel. The angle between line a and 1 (or the angle of the hoof wall compared to the ground) is about 55 degrees. The yellow shaded area represents a normal health lamina that is well attached to the hoof wall.

Now lets look at a foundered hoof.

The yellow area has been permanently damaged by inflammation, and the lamina has died, lost its firm attachment, and stretched out. The heels have also gotten longer as the whole foot speeds up its growth in attempts to heal itself. To help understand this concept, I left the coffin bone parallel with the ground in the first picture. But, realistically, our horse is no longer standing on the ground. If he were, he would look like this:

 

And we begin to see why the coffin bone is considered "rotated"... it appears to have taken a literal nosedive.

But realistically, if the heels hadn't grown out, and the toe hadn't stretched out, the coffin bone wouldn't have "gone" anywhere. Drawing in the original hoof wall, here's where we were at before:

Okay... but then what? Is it permanent?

Can it be fixed?

In a word: YES.

In more than one word: it takes a long time, and a lot of corrective trimming.  Once the lamina has been stretched out and essentially killed, it has to regrow entirely, starting at the coronary band (very top of the hoof) and growing all the way to the ground. During this time, which takes approximately one year, the toe must NEVER be allowed to act as a fulcrum on the fragile, newly grown lamina. What does that mean?
The hoof must be trimmed as follows:

The entire toe area in orange must be removed (remember, it is dead now, hence unneeded). This allows the growing lamina the remain firmly attached to the hoof wall. If the toe is left long, every step the horse takes will stretch the hoof wall away from the coffin bone, damaging the fragile new lamina (shaded pink). See how it would act as a fulcrum if left attached?

"BUT WAIT!!!!" You say now.  "If you trim the heels off, and trim the toe back, then the coffin bone goes right back to where it was! It hasn't really rotated at all!"

Precisely, my friend. Precisely.

PS. What causes founder in the first place?!?

By and large, the most common cause is food related. In a world of processed foods, refined sugars, soda, donuts, and diabetes, it seems that not even our four legged friends are immune to the repercussions of our lifestyle. Their bodies are more sensitive to sugars than humans are, and they are easily exposed to this because of the lifestyle we have provided them. (ie. small pastures with grass and alfalfa planted in them, sweetened and processed feeds, etc).
In a nutshell, any onslaught of sugar can send the horse into a sort of toxic level of high blood sugar (sneaking into the feed bin, an entire bucket of sweet feed from uncle Jimmy, too much rich grass all at once in the spring, etc). Horses metabolisms are not designed to cope with this, and it leads to severe inflammation.