Anatomy Of The Foot

STEVE: The anatomy of the horse’s lower limb, or foot, essentially is – on the outside, you have the actual hoof wall itself. This structure right here at the juncture of the skin is called a coronary band. You can see it as we pull this up. This is a coronary band, right here. And of course, structurally this is known as the pastern, the fetlock, cannon bone, and suspensory tendon. And then up to the horse’s knee.

Internally, what we’re looking at here is, this is the actual coffin bone itself. It’s called a coffin bone because it’s encased inside the hoof wall itself. And of course, this is a transverse section – meaning that it goes right down through the middle of the foot. And this joint right here is the coffin joint. It attaches the short pastern to the coffin bone itself.

Here is the extensor tendon that attaches right on the front, this pink structure, right here, right below. And along this base of the coffin bone here, this is a deep flexor tendon. It goes down the back. And right here, we have the navicular bone. The navicular bone is a long, flat bone that goes right across the foot, that is right here at the juncture of the pastern and the coffin bone, and it is where the deep flexor tendon runs across here. It’s kind of like a bridge or a junction to this area.

Back here, we go further up. We have the pastern, that’s slightly encased in here as well. The second pastern and the long pastern joint is above here. And then, of course, we have the suspensory ligaments that come along here. The distal sesamoidean ligaments is what they’re called at this juncture. And of course, here’s the suspensory up in here.

And essentially, this area is a large component in lameness, as far as coffin joint arthritis. If you get arthritis in this area, it’s very, very significant. You usually get a big spur here, and a lot of exostosis. So, there’s some extra bony growth here. The navicular itself in this area can be a big problem from a number of different standpoints if the foot becomes contracted or it’s just very, very small…the horse has a big body. It gets a lot of pressure and can deteriorate quite rapidly due to the amount of pressure put onto it from the size of the animal. This is an area of arthritis and chronic lameness problems in a lot of horses as they get older. The coffin joint can be in young horses, especially race horses, early on. And it can happen to any horse at any time.

Pastern joint arthritis is not usually as complicated and doesn’t happen in as many horses. But fetlock arthritis is real complicated and you see it quite a bit, as far as race horses or performance horses are concerned.

ALEX: We hear a lot about ringbone. Where would ringbone fit into this scenario?

STEVE: Ringbone is essentially isolated to the lower two joints in the foot. It’s between the long pastern and the short pastern right here. This area would be an area known as high ringbone. Okay? And if a horse gets some exostosis and/or extra calcium built up where you can see it visibly in the coffin joint and the short pastern, this is low ringbone or coffin joint arthritis. So, pastern arthritis or high ringbone. Coffin joint arthritis is low ringbone. The reason we call it ringbone is because externally you can see an area where the calcium buildup is in this area, so you know it’s high ringbone. Or if it occurs right above the coronary band in this area, it’s called low ringbone.