The pastern bones are two bones located below the fetlock in the pastern; The long pastern (P1), and the short pastern (P2). Joining these two bones is the pastern joint.

There are strong and intricate supporting ligaments that hold the two bones together and support the low motion pastern joint. P2 joins P3 (coffin bone) to form the coffin joint within the hoof.

Occasionally the pastern bones are fractured from direct impact or torsional forces on the bone. In some cases, the bones literally explode into small fragments. Vets often liken this injury to a "bag of marbles."

In our area, severe pastern fractures occur during the Winter and Spring, on frozen ground, especially when there is a layer of slippery mud covering solidly frozen ground or ice. It happens to horses cantering or galloping on this sort of surface. This injury also happens to performance horses that overload the bone. I have seen it most commonly in rodeo horses. This is always a severe injury.

Major fracture into the coffin or fetlock joint is often cause for euthanasia because of the tendency for the injury to cause arthritis in these joints. Surgery may be performed in some cases.