Hoof Health: Hoof Anatomy Part 1 – The internal structure

To kick off a series of hoof health articles I plan on writing, I thought I would start with the basic anatomy of the horse’s hoof. The picture I’m using is old, but accurate and best of all, free. I don’t consider it worth the time to recreate the image and if you’re looking for even more detail on what the hoof looks like, then there are piles of images on the internet to search out. Just search for “horse hoof anatomy”, and click “images” when using google. This will bring up more images with more detail than you may ever need. The image is great for the most part and will help me start off this series and refer back when I need to.

The hoof of the horse is probably just about the most important part of the horse, if you want to actually use the horse, and without it being in good health, you will likely have no horse to ride. As they say, “No hoof, no horse”. I myself have gone through many complete dissections of a horse’s leg and hoof and these images made more sense after that then ever before and I would recommend anybody to give it a try. Understanding the horse’s hoof, let alone the rest of it’s structure, bones, muscles, tendons etc etc, is an important part of horsemanship as you are the steward of your animal. Obviously when the going gets tough and beyond your knowledge and abilities (and maybe before then), I strongly recommend calling in a vet or farrier, but a good understanding can take you quite a ways.

Looking at the image of the hoof above we can see the external and internal pieces. Starting out to in we have the hoof wall. This protects the whole hoof like armor and wards off sharp objects, bugs, rocks, bacteria and so forth. Without the wall or if you have a bad wall with cracks etc, the internal parts of the hoof would be destroyed. No more horse.

From there we can move to the next line of defense between the outside and inside and we see laminae, insensitive and sensitive. Meaning that there is some on the inside of the hoof wall and some on the outside of the coffin bone, or P3 as it’s the third bone in the pastern of the leg. The laminae are very very very important to the hoof, like all pieces, it’s like a zipper or velcro and it bonds the coffin bone to the hoof and vice versa. A strong and healthy hoof grows from the coronet band (H), straight down the coffin bone and down to the ground. A bulging, dishing or flaring hoof means the laminae have been damaged, are failing or have outright died. This is generally tied to a diet issue.

Moving inwards from the front we have the coffin bone, or P3 bone and just behind there is a navicular bone and above that the P2 or short/small pastern bone and long/large or P1 bone and then on up to the cannon bone (big long one going to the knee). This whole section (p1, p2, p3) is the pastern of the horse. These bones are very strong and maintain the horse from just falling down on limp noodles of spaghetti. They don’t do it alone though, it is imperative that the tendons ,deep digital flexor (N), superficial flexor (underneath N) and extensor tendon (which is on the dorsal or front of the leg) are all healthy and attached. Without the tendons, the bones would just crumble away from each other. There are of course piles of other tendons and ligaments holding bones and muscles and other tendons together but too many to talk about here. Those are the main ones to support the skeletal structure.

Between the bones there are sacks of a greasy substance that allow the bones to move easily, if your horse has issues moving it’s joints, it’s likely because that sack has dried, emptied or something like that or if the bones have somehow become rough and don’t move well over each other. The last leg I worked on was like glass in the joints, so smooth that your finger slid across like air.

Just behind the coffin bone and tendons is the plantar cushion (inaccurately named here in this old picture) and underneath that would be the frog, referred to as the insensitive frog even though it’s anything but insensitive. It’s one and the same thing but we need to refer to it differently for our purposes of explaining all things to do with the hoof. The bottom of the foot is the sole, the back the bulbs and the spot between the hairline and hoof itself is called the coronet.

Simply put, the hoof wall grows down from the coronet mostly and some from inside out. It goes down along the coffin bone due to the attachment of the dermal and epidermal laminae, and to the ground. The sole grows outwards from the frog area generally and the frog grows from the inside out. All of this is supplied blood by hundreds of tiny little arteries and two main ones that come down the leg. I’ve seen it in person the amount of, and detail of, the blood supply provided to the hoof and it’s amazing. I never wondered again how the hoof gets/stays warm. The coolest part of that though is that the horse can turn that off (it’s automatic of course) based on if it wants to heal or not, warm up or not, cool down or not. Nature has done an amazing job and it’s a challenge to work with it as it’s constantly working hard to fix itself. More often than not, due to human interference.

The sole of the hoof protects the underside of the hoof and generally can be quite thick. It’s a hard material, should never be spongy and if it’s thin, you have a problem. Without it the bones would drop right through the hoof (and it happens) and again, no horse. The frog is also incredibly important as it helps the horse displace load and impact and is sensitive to understand what type of ground it is walking on. A wide calloused frog is ideal, any bacterial infections will destroy it and the rest of the hoof if left untreated as it is a direct path to the rest of the internal parts of the hoof. No armor here.

There are a lot of things to discuss about the foot and I will cover many topics as we go on our path of talking about horse health. From bacterial infections, belling, flaring, laminitis, lameness, trimming, shoeing, P3 rotation, diet, heel length, toe length, whiteline disease and so on and so forth. There are a lot of things to talk about.