The splint bones are two thin, sliver-like bones which 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.
If there is excessive strain on this short ligament, it can tear. The body responds by laying down a bridge of bone. This bump of bone is known as a splint (sometimes called a “true” splint). Splints start as soft to firm, warm, and painful swellings and progress toward hard, cold painless bumps (known as “cold” splints).
Bony bumps associated with the splint bones can also be caused by direct external trauma such as a kick, or contact by another limb. Some call these “false” splints.
True splints occur far more in horses with abnormal conformation at the hock or carpus. Splints are more commonly associated with the inside splint bone. (If the damage occurs with no outward swelling, these are often called “blind” splints.) Conformation that overloads the inside of the lower limb (knock kneed or bench kneed conformation) are commonly associated with splints.
Splints sometimes cause lameness and sometimes do not. Horses that have recently developed a splint are often lame, and the lameness gradually decreases over days to weeks.
Diagnosis requires a veterinary exam. Splints are preliminarily diagnosed by examination of the swelling directly overlying the splint bone (usually in a horse that is conformationally predisposed). Radiographs provide additional confirmation and are useful to rule out splint fractures, which are often managed differently.
Horses with splints gradually recover, usually no matter what we do. Rest and time are the most important treatment. There are many treatments aimed at getting horses back to work more quickly, including local injection of steroids, a variety of topical anti-inflammatories with or without bandaging. Shockwave is also commonly used for these injuries. The question is how much these treatments really help.
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Rest and time takes care of most splints. For performance horses, some therapies may reduce inflammation and swelling, and hasten the return to soundness and work.
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