The splint bones are two thin, sliver-like bones that run along the inside (medial) and outside (lateral) back of the cannon bones in both front and rear limbs. Their thicker "head" make up an important part of the joint between the cannon region (metatarsal behind and metacarpal in front) and carpal and tarsal joints, respectively.

The entire lengths of these bones are squeezed up against the the cannon bone and joined to it with a short, very strong ligament that runs the length of the bone.

Fractures can occur to any part of the splint bone. Fractures to the lower third are usually associated with internal stress from over-extension of the fetlock joint. Suspensory ligament inflammation can also result in swelling causing internal stress and fracture of the lower splint. Upper level (proximal) swellings are usually caused by some external force, like a kick or interference contact from an opposite hoof. In these cases, a wound is usually created also, and in some cases, there is potential for bone infection.

Diagnosis requires veterinary examination and radiography.

Treatment varies depending on the nature of the fracture. In many cases, non-displaced splint fractures heal like splint exostoses. In some cases, the best approach is surgical removal of the lower fragment. Upper fractures near the joint may require surgery as well. In some cases, the remaining splint head may need to be anchored by a surgical implant like a plate in order to keep it from pulling away and to maintain its important function of weight bearing within the joint.

The outside hind limb splint bone is the only one that can be removed completely. This is because it only makes a small contribution to the joint.