Understanding what makes healthy hooves-and what can go wrong-requires knowledge of the hoof from the inside out. Starting with a look at the bones inside the hoof, the short pastern bone connects to the long pastern bone above. The short pastern bone sits halfway in and halfway out of the hoof. Below the short pastern bone is the somewhat hoof-shaped coffin bone. Along the backside, where the coffin bone and short pastern meet, is the tiny whale-tale shaped navicular bone. Connective tissue with a vascular matrix of arteries, called the corium, makes up the spaces between the hoof wall and the bones.
Tendons and ligaments also play an important role inside the horse's hoof. Ligaments help connect bones and hold things in place, while tendons enable the leg and hoof to move by flexing and extending.
On the outside, a healthy, well cared for hoof is symmetrical. This means if you were to pick up the hoof and draw an imaginary line down the middle from toe to heel, one side would mirror the other. The two heel bulbs would also be of equal height and size (heel problems can include contracted heels, low heels and high heels/club feet). In addition, the two front feet should match up, and the two back feet should match up (hind feet tend to be a little skinner than front feet). The coronet or coronary band where hoof and hair meet should also be straight in front and slope evenly toward the heels along the sides.
The pastern axis is also essential to balance. To determine a horse's pastern axis, imagine a line drawn through the middle of the pastern bone to the ground, parallel to the hoof wall. Ideally the front of the hoof wall and the pastern will be at the same angle. Horses that are club footed will have what is known as a broken forward pastern axis (imagine that ideal line broken forward). Horses that have long toe/low heel will often have a broken back pastern axis.
A horse's hoof symmetry and pastern axis are partly determined by conformation and genetics. However, proper diet, a healthy environment, appropriate exercise, and regular trimming and shoeing by a trusted expert can help make the hoof as symmetrical as possible and help bring the pastern axis into better alignment. The more symmetrical the hooves and the better pastern axis, the less prone horses are to hoof and leg problems.
In addition to being as balanced as possible, healthy hooves should not be too dry and brittle, or too wet and soft. They should be free of major cracks, puncture wounds, bruises, discharges or foul odors. In addition, a horse with healthy hooves will not display obvious tenderness or have unusual heat in his hooves. Once again, a proper diet, appropriate exercise, a healthy environment and regular trimming and shoeing from an expert will help keep your horse's hooves as healthy as possible.