Splints: Manage Nutrition and Exercise to Lower the Risk for Your Horse

Splint bones, the second and fourth metacarpals (front) or metatarsals (hind), are long, thin bones that lie along both sides of a horse’s cannon bones. They are attached to the cannon by the interosseous ligament in young horses. As the skeleton matures, the splint bones eventually fuse to the cannon by the time the horse is five or six years old. If a young horse’s legs are subjected to too much exercise that twists the legs, these bones can be pulled loose and the ligament can be strained or torn. A kick that lands on the splint bone can also bruise or fracture it.

In either case, the horse will develop a warm, painful, swollen spot over the injury. He may or may not be lame on the injured leg. This “popped splint” will usually resolve over time, leaving a permanent lump somewhere below the horse’s knee. Though splints are far more likely to occur on the front legs, they are occasionally seen on a horse’s hind legs.

The horse should be taken out of work until lameness has disappeared. Hosing with cold water several times a day will reduce mild discomfort, and anti-inflammatory medications may be used for more severe pain. Horses that recover from popped splints usually don’t have long-term problems after the inflammation resolves, though a fractured splint bone may need to be treated surgically to stabilize or remove broken pieces.

It is possible for a young horse to exercise hard enough in the pasture to pop a splint, but the majority of splint problems are caused by work that has progressed too rapidly or has forced the horse to do a lot of circling.

To minimize the risk of splints, keep these suggestions for feeding and exercise in mind:

• Feed young horses for moderate, steady growth. Avoid letting the horse gain too much body weight before the skeleton has developed enough strength to support the load. Remember that adding the weight of a saddle and rider could potentially add another 150 to 175 pounds, challenging the strength and balance of a green horse.
• Have the young horse’s ration evaluated by an equine nutritionist to be sure that all minerals are being provided in the right quantities and proportions. Calcium and phosphorus balance is important for proper skeletal maturation, and the correct ratio can easily be thrown off by a diet that is too high in either mineral. Though an imbalance may not lead directly to splint problems, suitable nutrition will give young horses the best chance to stay sound and develop a strong mature skeleton.
• Begin exercise or conditioning programs with short periods of easy work, building very gradually toward longer and more intense work sessions. Back off at any indication of strain or soreness.
• Avoid working the young horse on very hard footing, uneven surfaces like frozen mud, and areas with rocky or extremely soft ground. An awkward step can throw the horse off balance and increase the strain on joints and ligaments.
• Limit the amount of work that requires the horse to move on a circle. This includes both longeing and riding. Circling repeatedly twists the front legs as they are loaded, putting strain on the knee structure which is partially supported by the splint bones.
• Work with a farrier to keep the horse’s hooves balanced and at the proper length. Especially for horses with conformation faults such as crooked legs or offset knees, regular trimming and resetting of shoes is important in preventing unnecessary strain during exercise.